Annotated ECMAScript 5.1
+
+ 
+‟Ex igne vita”
+ +‟Ex igne vita”
+ ++ SourceCharacter ::See clause 6
++ any + Unicode code unit
++ InputElementDiv ::See clause 7
+
+ WhiteSpace
LineTerminator
Comment
Token
DivPunctuator
+ InputElementRegExp ::See clause 7
+
+ WhiteSpace
LineTerminator
Comment
Token
RegularExpressionLiteral
+ WhiteSpace ::See 7.2
+
+ <TAB>
<VT>
<FF>
<SP>
<#x0a>
<BOM>
<USP>
+ LineTerminator ::See 7.3
+
+ <LF>
<CR>
<LS>
<PS>
+ LineTerminatorSequence ::See 7.3
+
+ <LF>
<CR>
+ [lookahead
+ ∉
+ <LF>
+ ]
<LS>
<PS>
<CR>
+ <LF>
+ Comment ::See 7.4
+
+ MultiLineComment
SingleLineComment
+ MultiLineComment ::See 7.4
+
+ /* MultiLineCommentCharsopt*/
+ MultiLineCommentChars ::See 7.4
+
+ MultiLineNotAsteriskChar
+ MultiLineCommentCharsopt* PostAsteriskCommentCharsopt
+ PostAsteriskCommentChars ::See 7.4
+
+ MultiLineNotForwardSlashOrAsteriskChar
+ MultiLineCommentCharsopt* PostAsteriskCommentCharsopt
+ MultiLineNotAsteriskChar ::See 7.4
+
+ SourceCharacter but
+ not asterisk *
+ MultiLineNotForwardSlashOrAsteriskChar ::See 7.4
+
+ SourceCharacter but
+ not forward-slash /
+ orasterisk *
+ SingleLineComment ::See 7.4
+
+ // SingleLineCommentCharsopt
+ SingleLineCommentChars ::See 7.4
++ SingleLineCommentChar + SingleLineCommentCharsopt
++ SingleLineCommentChar ::See 7.4
++ SourceCharacter + but + not + LineTerminator
++ Token ::See 7.5
+
+ IdentifierName
Punctuator
NumericLiteral
StringLiteral
+ Identifier ::See 7.6
++ IdentifierName but + not ReservedWord
++ IdentifierName ::See 7.6
+
+ IdentifierStart
IdentifierName
+ IdentifierPart
+ IdentifierStart ::See 7.6
+
+ UnicodeLetter$
_\ UnicodeEscapeSequence
+ IdentifierPart ::See 7.6
+
+ IdentifierStart
UnicodeCombiningMark
UnicodeDigit
UnicodeConnectorPunctuation
<ZWNJ>
<ZWJ>
+ UnicodeLetter See 7.6
++ any + character in the Unicode categories “Uppercase letter (Lu)”, + “Lowercase letter (Ll)”, “Titlecase letter (Lt)”, “Modifier + letter (Lm)”, “Other letter (Lo)”, or “Letter number (Nl)”.
++ UnicodeCombiningMark See 7.6
++ any + character in the Unicode categories “Non-spacing mark (Mn)” or + “Combining spacing mark (Mc)”
++ UnicodeDigit See 7.6
++ any + character in the Unicode category “Decimal number (Nd)”
++ UnicodeConnectorPunctuation See 7.6
++ any + character in the Unicode category “Connector punctuation (Pc)”
++ ReservedWord ::See 7.6.1
+
+ Keyword
FutureReservedWord
NullLiteral
BooleanLiteral
+ Keyword :: one + ofSee 7.6.1.1
+|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+ + | +
|
+
+ |
+
+
+ |
+
+
+ |
+ + | +
+ FutureReservedWord + :: + one + ofSee 7.6.1.2
+|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+ + | +
|
+
+ |
+ |||
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+ + | ++ | ++ | +
+ Punctuator :: one + ofSee 7.7
+|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+ + | +
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+ + | +
+ DivPunctuator :: + one + ofSee 7.7
+|
+
+ |
+
+
+ |
+ + | ++ | ++ | ++ | +
+ Literal ::See 7.8
+
+ NullLiteral
BooleanLiteral
NumericLiteral
StringLiteral
RegularExpressionLiteral
+ NullLiteral ::See 7.8.1
+
+ null
+ BooleanLiteral ::See 7.8.2
+
+ true
false
+ NumericLiteral ::See 7.8.3
+
+ DecimalLiteral
HexIntegerLiteral
+ DecimalLiteral ::See 7.8.3
+
+ DecimalIntegerLiteral . DecimalDigitsoptExponentPartopt. DecimalDigits ExponentPartopt
DecimalIntegerLiteral
+ ExponentPartopt
+ DecimalIntegerLiteral ::See 7.8.3
+
+ 0
NonZeroDigit
+ DecimalDigitsopt
+ DecimalDigits ::See 7.8.3
+
+ DecimalDigit
DecimalDigits
+ DecimalDigit
+ DecimalDigit :: + one + ofSee 7.8.3
+
+ 0
+ 1 2 3 4 5 6 7 8 9
+ NonZeroDigit:: + one + ofSee 7.8.3
+
+ 1 2 3 4 5 6 7 8 9
+ ExponentPart:: + See 7.8.3
+ExponentIndicator SignedInteger
++ ExponentIndicator :: + one + ofSee 7.8.3
+
+ e
+ E
+ SignedInteger ::See 7.8.3
+
+ DecimalDigits+ DecimalDigits- DecimalDigits
+ HexIntegerLiteral ::See 7.8.3
+
+ 0x HexDigit0X HexDigit
HexIntegerLiteral HexDigit
+ HexDigit :: + one + ofSee 7.8.3
+
+ 0
+ 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F
+ StringLiteral ::See 7.8.4
+
+ "DoubleStringCharactersopt
+ "'SingleStringCharactersopt'
+ DoubleStringCharacters ::See 7.8.4
++ DoubleStringCharacter + DoubleStringCharactersopt
++ SingleStringCharacters ::See 7.8.4
++ SingleStringCharacter + SingleStringCharactersopt
++ DoubleStringCharacter ::See 7.8.4
+
+ SourceCharacter but
+ not double-quote "
+ or
+ backslash \ or
+ LineTerminator\
+ EscapeSequence
LineContinuation
+ SingleStringCharacter ::See 7.8.4
+
+ SourceCharacter but
+ not single-quote '
+ orbackslash \ or
+ LineTerminator\
+ EscapeSequence
LineContinuation
+ LineContinuation ::See 7.8.4
+
+ \
+ LineTerminatorSequence
+ EscapeSequence ::See 7.8.4
+
+ CharacterEscapeSequence0 [lookahead
+ ∉DecimalDigit]
HexEscapeSequence
UnicodeEscapeSequence
+ CharacterEscapeSequence ::See 7.8.4
+
+ SingleEscapeCharacter
NonEscapeCharacter
+ SingleEscapeCharacter :: one + ofSee 7.8.4
+
+ '
+ " \ b f n r t v
+ NonEscapeCharacter ::See 7.8.4
++ SourceCharacter + but + notEscapeCharacter or + LineTerminator
++ EscapeCharacter ::See 7.8.4
+
+ SingleEscapeCharacter
DecimalDigitxu
+ HexEscapeSequence ::See 7.8.4
+
+ x
+ HexDigit HexDigit
+ UnicodeEscapeSequence ::See 7.8.4
+
+ u HexDigit HexDigit HexDigit HexDigit
+ RegularExpressionLiteral ::See 7.8.5
+
+ / RegularExpressionBody /
+ RegularExpressionFlags
+ RegularExpressionBody ::See 7.8.5
++ RegularExpressionFirstChar + RegularExpressionChars
++ RegularExpressionChars ::See 7.8.5
+
+ [empty]
RegularExpressionChars
+ RegularExpressionChar
+ RegularExpressionFirstChar ::See 7.8.5
+
+ RegularExpressionNonTerminator but
+ not *
+ or
+ \ or
+ /
+ or
+ [
RegularExpressionBackslashSequence
RegularExpressionClass
+ RegularExpressionChar ::See 7.8.5
+
+ RegularExpressionNonTerminator but
+ not \
+ or
+ /
+ or
+ [
RegularExpressionBackslashSequence
RegularExpressionClass
+ RegularExpressionBackslashSequence ::See 7.8.5
+
+ \ RegularExpressionNonTerminator
+ RegularExpressionNonTerminator ::See 7.8.5
++ SourceCharacter but + not + LineTerminator
++ RegularExpressionClass ::See 7.8.5
+
+ [
+ RegularExpressionClassChars
+ ]
+ RegularExpressionClassChars
+ ::See 7.8.5
+ [empty]
RegularExpressionClassChars
+ RegularExpressionClassChar
+ RegularExpressionClassChar
+ ::See 7.8.5
+ RegularExpressionNonTerminator
+ but
+ not ]
+ or
+ \
RegularExpressionBackslashSequence
+ RegularExpressionFlags ::See 7.8.5
+
+ [empty]
RegularExpressionFlags
+ IdentifierPart
+ StringNumericLiteral :::See 9.3.1
+
+ StrWhiteSpaceopt
StrWhiteSpaceoptStrNumericLiteral StrWhiteSpaceopt
+ StrWhiteSpace :::See 9.3.1
++ StrWhiteSpaceChar + StrWhiteSpaceopt
++ StrWhiteSpaceChar :::See 9.3.1
+
+ WhiteSpace
LineTerminator
+ StrNumericLiteral :::See 9.3.1
+
+ StrDecimalLiteral
HexIntegerLiteral
+ StrDecimalLiteral :::See 9.3.1
+
+ StrUnsignedDecimalLiteral+
+ StrUnsignedDecimalLiteral-
+ StrUnsignedDecimalLiteral
+ StrUnsignedDecimalLiteral :::See 9.3.1
+
+ Infinity
DecimalDigits . DecimalDigitsoptExponentPartopt. DecimalDigits ExponentPartopt
DecimalDigits
+ ExponentPartopt
+ DecimalDigits :::See 9.3.1
+
+ DecimalDigit
DecimalDigits
+ DecimalDigit
+ DecimalDigit ::: one + ofSee 9.3.1
+
+ 0
+ 1 2 3 4 5 6 7 8 9
+ ExponentPart :::See 9.3.1
++ ExponentIndicator + SignedInteger
++ ExponentIndicator ::: + one + ofSee 9.3.1
+
+ e
+ E
+ SignedInteger :::See 9.3.1
+
+ DecimalDigits+
+ DecimalDigits-
+ DecimalDigits
+ HexIntegerLiteral :::See 9.3.1
+
+ 0x HexDigit0X HexDigit
HexIntegerLiteral HexDigit
+ HexDigit ::: + one + ofSee 9.3.1
+
+ 0
+ 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F
+ PrimaryExpression :See 11.1
+
+ this
Identifier
Literal
ArrayLiteral
ObjectLiteral( Expression )
+ ArrayLiteral :See 11.1.4
+
+ [
+ Elisionopt
+ ] ElementList
[
+
+ ] ElementList ,
+ Elisionopt
[
+
+ ]
+ ElementList :See 11.1.4
+
+ Elisionopt
+ AssignmentExpression
ElementList
+ ,
+ Elisionopt
+ AssignmentExpression
+ Elision :See 11.1.4
+
+ ,
Elision
+ ,
+ ObjectLiteral :See 11.1.5
+
+ {
+ } {
+ PropertyNameAndValueList
+ } PropertyNameAndValueList
{
+
+ , }
+ PropertyNameAndValueList :See 11.1.5
+
+ PropertyAssignment
PropertyNameAndValueList
+ , PropertyAssignment
+ PropertyAssignment :See 11.1.5
+
+ PropertyName
+ :
+ AssignmentExpressionget
+ PropertyName()
+ { FunctionBody } PropertyName
set
+ (
+ PropertySetParameterList
+ ) { FunctionBody }
+ PropertyName :See 11.1.5
+
+ IdentifierName
StringLiteral
NumericLiteral
+ PropertySetParameterList :See 11.1.5
++ Identifier
++ MemberExpression :See 11.2
+
+ PrimaryExpression
FunctionExpression
MemberExpression [ Expression ] MemberExpression . IdentifierNamenew MemberExpression
+ Arguments
+ NewExpression :See 11.2
+
+ MemberExpression
new
+ CallExpression :See 11.2
+
+ MemberExpression
+ Arguments
+ Arguments[ Expression ] CallExpression . IdentifierName
+ Arguments :See 11.2
+
+ ( ) ArgumentList
()
+ ArgumentList :See 11.2
+
+ AssignmentExpression
ArgumentList , AssignmentExpression
+ LeftHandSideExpression :See 11.2
+
+ NewExpression
CallExpression
+ PostfixExpression :See 11.3
+
+ LeftHandSideExpression
LeftHandSideExpression
+ [noLineTerminator here]
+ ++
LeftHandSideExpression
+ [noLineTerminator here]
+ --
+ UnaryExpression :See 11.4
+
+ PostfixExpression
delete
+ void
+ UnaryExpressiontypeof
+ UnaryExpression
++-- UnaryExpression+ UnaryExpression- UnaryExpression~ UnaryExpression! UnaryExpression
+ MultiplicativeExpression :See 11.5
+
+ UnaryExpression
MultiplicativeExpression * UnaryExpression
MultiplicativeExpression / UnaryExpression
MultiplicativeExpression % UnaryExpression
+ AdditiveExpression :See 11.6
+
+ MultiplicativeExpression
AdditiveExpression + MultiplicativeExpression
AdditiveExpression - MultiplicativeExpression
+ ShiftExpression :See 11.7
+
+ AdditiveExpression
ShiftExpression << AdditiveExpression
ShiftExpression >> AdditiveExpression
ShiftExpression >>> AdditiveExpression
+ RelationalExpression :See 11.8
+
+ ShiftExpression
RelationalExpression < ShiftExpression
RelationalExpression > ShiftExpression
RelationalExpression <= ShiftExpression
RelationalExpression >= ShiftExpression
RelationalExpression instanceof ShiftExpression
RelationalExpression in ShiftExpression
+ RelationalExpressionNoIn :See 11.8
+
+ ShiftExpression
RelationalExpressionNoIn < ShiftExpression
RelationalExpressionNoIn > ShiftExpression
RelationalExpressionNoIn <= ShiftExpression
RelationalExpressionNoIn >= ShiftExpression
RelationalExpressionNoIn instanceof ShiftExpression
+ EqualityExpression :See 11.9
+
+ RelationalExpression
EqualityExpression == RelationalExpression
EqualityExpression != RelationalExpression
EqualityExpression === RelationalExpression
EqualityExpression !== RelationalExpression
+ EqualityExpressionNoIn :See 11.9
+
+ RelationalExpressionNoIn
EqualityExpressionNoIn == RelationalExpressionNoIn
EqualityExpressionNoIn != RelationalExpressionNoIn
EqualityExpressionNoIn === RelationalExpressionNoIn
EqualityExpressionNoIn !== RelationalExpressionNoIn
+ BitwiseANDExpression :See 11.10
+
+ EqualityExpression
BitwiseANDExpression & EqualityExpression
+ BitwiseANDExpressionNoIn :See 11.10
+
+ EqualityExpressionNoIn
BitwiseANDExpressionNoIn & EqualityExpressionNoIn
+ BitwiseXORExpression :See 11.10
+
+ BitwiseANDExpression
BitwiseXORExpression ^ BitwiseANDExpression
+ BitwiseXORExpressionNoIn :See 11.10
+
+ BitwiseANDExpressionNoIn
BitwiseXORExpressionNoIn ^ BitwiseANDExpressionNoIn
+ BitwiseORExpression :See 11.10
+
+ BitwiseXORExpression
BitwiseORExpression | BitwiseXORExpression
+ BitwiseORExpressionNoIn :See 11.10
+
+ BitwiseXORExpressionNoIn
BitwiseORExpressionNoIn | BitwiseXORExpressionNoIn
+ LogicalANDExpression :See 11.11
+
+ BitwiseORExpression
LogicalANDExpression && BitwiseORExpression
+ LogicalANDExpressionNoIn :See 11.11
+
+ BitwiseORExpressionNoIn
LogicalANDExpressionNoIn && BitwiseORExpressionNoIn
+ LogicalORExpression :See 11.11
+
+ LogicalANDExpression
LogicalORExpression || LogicalANDExpression
+ LogicalORExpressionNoIn :See 11.11
+
+ LogicalANDExpressionNoIn
LogicalORExpressionNoIn || LogicalANDExpressionNoIn
+ ConditionalExpression :See 11.12
+
+ LogicalORExpression
LogicalORExpression
+ ? AssignmentExpression : AssignmentExpression
+ ConditionalExpressionNoIn :See 11.12
+
+ LogicalORExpressionNoIn
LogicalORExpressionNoIn
+ ? AssignmentExpressionNoIn : AssignmentExpressionNoIn
+ AssignmentExpression :See 11.13
+
+ ConditionalExpression
LeftHandSideExpression
+ AssignmentOperator AssignmentExpression
+ AssignmentExpressionNoIn :See 11.13
+
+ ConditionalExpressionNoIn
LeftHandSideExpression
+ AssignmentOperator AssignmentExpressionNoIn
+ AssignmentOperator : + one + ofSee 11.13
+|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+ Expression :See 11.14
+
+ AssignmentExpression
Expression , AssignmentExpression
+ ExpressionNoIn :See 11.14
+
+ AssignmentExpressionNoIn
ExpressionNoIn , AssignmentExpressionNoIn
+ Statement :See clause 12
+
+ Block
VariableStatement
EmptyStatement
ExpressionStatement
IfStatement
IterationStatement
ContinueStatement
BreakStatement
ReturnStatement
WithStatement
LabelledStatement
SwitchStatement
ThrowStatement
TryStatement
DebuggerStatement
+ Block :See 12.1
+
+ { StatementListopt}
+ StatementList :See 12.1
+
+ Statement
StatementList
+ Statement
+ VariableStatement :See 12.2
+
+ var VariableDeclarationList ;
+ VariableDeclarationList :See 12.2
+
+ VariableDeclaration
VariableDeclarationList , VariableDeclaration
+ VariableDeclarationListNoIn :See 12.2
+
+ VariableDeclarationNoIn
VariableDeclarationListNoIn , VariableDeclarationNoIn
+ VariableDeclaration :See 12.2
++ Identifier + Initialiseropt
++ VariableDeclarationNoIn :See 12.2
++ Identifier + InitialiserNoInopt
++ Initialiser :See 12.2
+
+ = AssignmentExpression
+ InitialiserNoIn :See 12.2
+
+ = AssignmentExpressionNoIn
+ EmptyStatement :See 12.3
+
+ ;
+ ExpressionStatement :See 12.4
+
+ [lookahead
+ ∉
+ {{,
+ function}]Expression ;
+ IfStatement :See 12.5
+
+ if ( Expression ) Statement else Statementif ( Expression ) Statement
+ IterationStatement :See 12.6
+
+ do
+ Statement
+ while ( Expression ); while ( Expression ) Statementfor ( ExpressionNoInopt; Expressionopt; Expressionopt) Statementfor ( var VariableDeclarationListNoIn; Expressionopt; Expressionopt) Statementfor ( LeftHandSideExpression in Expression ) Statementfor ( var VariableDeclarationNoIn in Expression ) Statement
+ ContinueStatement :See 12.7
+
+ continue
+ [noLineTerminator here]Identifieropt;
+ BreakStatement :See 12.8
+
+ break
+ [noLineTerminator here]Identifieropt;
+ ReturnStatement :See 12.9
+
+ return
+ [noLineTerminator here]Expressionopt;
+ WithStatement :See 12.10
+
+ with ( Expression ) Statement
+ SwitchStatement :See 12.11
+
+ switch ( Expression ) CaseBlock
+ CaseBlock :See 12.11
+
+ { CaseClausesopt} { CaseClausesoptDefaultClause CaseClausesopt}
+ CaseClauses :See 12.11
+
+ CaseClause
CaseClauses
+ CaseClause
+ CaseClause :See 12.11
+
+ case Expression : StatementListopt
+ DefaultClause :See 12.11
+
+ default : StatementListopt
+ LabelledStatement :See 12.12
+
+ Identifier : Statement
+ ThrowStatement :See 12.13
+
+ throw
+ [noLineTerminator here]
+ Expression ;
+ TryStatement :See 12.14
+
+ try Block Catchtry Block Finallytry Block Catch Finally
+ Catch :See 12.14
+
+ catch (
+ Identifier ) Block
+ Finally :See 12.14
+
+ finally Block
+ DebuggerStatement :See 12.15
+
+ debugger ;
+ FunctionDeclaration :See clause 13
+
+ function Identifier ( FormalParameterListopt) { FunctionBody }
+ FunctionExpression :See clause 13
+
+ function Identifieropt( FormalParameterListopt) { FunctionBody }
+ FormalParameterList :See clause 13
+
+ Identifier
FormalParameterList , Identifier
+ FunctionBody :See clause 13
++ SourceElementsopt
++ Program :See clause 14
++ SourceElementsopt
++ SourceElements :See clause 14
+
+ SourceElement
SourceElements
+ SourceElement
+ SourceElement :See clause 14
+
+ Statement
FunctionDeclaration
+ uri :::See 15.1.3
++ uriCharactersopt
++ uriCharacters :::See 15.1.3
++ uriCharacter + uriCharactersopt
++ uriCharacter :::See 15.1.3
+
+ uriReserved
uriUnescaped
uriEscaped
+ uriReserved ::: + one + ofSee 15.1.3
+
+ ;
+ / ? : @ & = + $ ,
+ uriUnescaped :::See 15.1.3
+
+ uriAlpha
DecimalDigit
uriMark
+ uriEscaped :::See 15.1.3
+
+ % HexDigit HexDigit
+ uriAlpha ::: + one + ofSee 15.1.3
+
+ a
+ b c d e f g h i j k l m n o p q r s t u v w x
+ y z
A B C D E F G H I J K L M N O P Q R S T
+ U V W X Y Z
+ uriMark ::: + one + ofSee 15.1.3
+
+ -
+ _ . ! ~ * ‘ ( )
+ Pattern ::See 15.10.1
++ Disjunction
++ Disjunction ::See 15.10.1
+
+ Alternative
+ Alternative | Disjunction
+ Alternative ::See 15.10.1
+
+ [empty]
Alternative
+ Term
+ Term ::See 15.10.1
+
+ Assertion
Atom
Atom
+ Quantifier
+ Assertion ::See 15.10.1
+
+ ^ $ \
+ b \
+ B (
+ ?
+ =
+ Disjunction ) (
+ ?
+ !
+ Disjunction )
+ Quantifier ::See 15.10.1
+
+ QuantifierPrefix
QuantifierPrefix
+ ?
+ QuantifierPrefix ::See 15.10.1
+
+ *
+? { DecimalDigits } { DecimalDigits
+ ,
+ } { DecimalDigits
+ , DecimalDigits }
+ Atom ::See 15.10.1
+
+ PatternCharacter.\
+ AtomEscape
CharacterClass
() (
+ ?
+ :
+ Disjunction )
+ PatternCharacter :: SourceCharacter but + not any + of:See 15.10.1
+
+ ^
+ $ \ . * + ? ( ) [ ] { } |
+ AtomEscape ::See 15.10.1
+
+ DecimalEscape
CharacterEscape
CharacterClassEscape
+ CharacterEscape ::See 15.10.1
+
+ ControlEscapec ControlLetter
HexEscapeSequence
UnicodeEscapeSequence
IdentityEscape
+ ControlEscape :: one + ofSee 15.10.1
+
+ f
+ n r t v
+ ControlLetter :: one + ofSee 15.10.1
+
+ a
+ b c d e f g h i j k l m n o p q r s t u v w x
+ y z
A B C D E F G H I J K L M N O P Q R S T
+ U V W X Y Z
+ IdentityEscape ::See 15.10.1
+
+ SourceCharacter but
+ not
+ IdentifierPart
<ZWJ>
<ZWNJ>
+ DecimalEscape ::See 15.10.1
++ DecimalIntegerLiteral [lookahead + ∉ + DecimalDigit]
++
++ CharacterClassEscape :: + one + ofSee 15.10.1
+
+ d
+ D s S w W
+ CharacterClass ::See 15.10.1
+
+ [
+ [lookahead
+ ∉
+ {^}]
+ ClassRanges
+ ] [
+ ^ ClassRanges
+ ]
+ ClassRanges ::See 15.10.1
+
+ [empty]
NonemptyClassRanges
+ NonemptyClassRanges ::See 15.10.1
+
+ ClassAtom
ClassAtom
+ NonemptyClassRangesNoDash
ClassAtom
+ – ClassAtom ClassRanges
+ NonemptyClassRangesNoDash ::See 15.10.1
+
+ ClassAtom
ClassAtomNoDash
+ NonemptyClassRangesNoDash
ClassAtomNoDash
+ – ClassAtom ClassRanges
+ ClassAtom ::See 15.10.1
+
+ -
ClassAtomNoDash
+ ClassAtomNoDash ::See 15.10.1
+
+ SourceCharacter but
+ not one
+ of \ or ]
+ or - \
+ ClassEscape
+ ClassEscape ::See 15.10.1
+
+ DecimalEscapeb
CharacterEscape
+ JSONWhiteSpace ::See 15.12.1.1
+
+ <TAB>
<CR>
<LF>
<SP>
+ JSONString ::See 15.12.1.1
+
+ "
+ JSONStringCharactersopt"
+ JSONStringCharacters ::See 15.12.1.1
++ JSONStringCharacter + JSONStringCharactersopt
++ JSONStringCharacter ::See 15.12.1.1
+
+ SourceCharacter but
+ not double-quote " or backslash \
+ or U+0000 thru
+ U+001F
+ \ JSONEscapeSequence
+ JSONEscapeSequence ::See 15.12.1.1
++ JSONEscapeCharacter
++ UnicodeEscapeSequence +
++ JSONEscapeCharacter :: + one + ofSee 15.12.1.1
+
+ "
+ / \ b f n r t
+ JSONNumber ::See 15.12.1.1
+
+ -optDecimalIntegerLiteral JSONFractionoptExponentPartopt
+ JSONFraction ::See 15.12.1.1
+
+ . DecimalDigits
+ JSONNullLiteral ::See 15.12.1.1
++ NullLiteral
++ JSONBooleanLiteral ::See 15.12.1.1
++ BooleanLiteral
++ JSONText :See 15.12.1.2
++ JSONValue
++ JSONValue :See 15.12.1.2 +
+
+ JSONNullLiteral
JSONBooleanLiteral
JSONObject
JSONArray
JSONString
JSONNumber
+ JSONObject :See 15.12.1.2
+
+ {
+ } { JSONMemberList }
+ JSONMember :See 15.12.1.2
+
+ JSONString : JSONValue
+ JSONMemberList :See 15.12.1.2
+
+ JSONMember
+
JSONMemberList ,
+ JSONMember
+
+ JSONArray :See 15.12.1.2
+
+ [
+ ] [ JSONElementList
+ ]
+ JSONElementList :See 15.12.1.2
+
+ JSONValue
JSONElementList
+ , JSONValue
‟Ex igne vita”
+ ++ Past + editions of ECMAScript have included additional syntax and semantics + for specifying octal literals and octal escape sequences. These have + been removed from this edition of ECMAScript. This non-normative + annex presents uniform syntax and semantics for octal literals and + octal escape sequences for compatibility with some older ECMAScript + programs.
++ The + syntax and semantics of 7.8.3 can be extended as follows except that + this extension is not allowed for strict mode code:
++ Syntax
++ NumericLiteral ::
+
+ DecimalLiteral
HexIntegerLiteral
OctalIntegerLiteral
+ OctalIntegerLiteral ::
+
+ 0 OctalDigit
OctalIntegerLiteral OctalDigit
+ OctalDigit :: one + of
+
+ 0
+ 1
+ 2
+ 3
+ 4
+ 5
+ 6
+ 7
+ Semantics
++ The + MV of NumericLiteral + :: + OctalIntegerLiteral is + the MV of OctalIntegerLiteral.
+
+ The
+ MV of OctalDigit ::
+ 0
+ is 0.
+ The
+ MV of OctalDigit ::
+ 1
+ is 1.
+ The
+ MV of OctalDigit ::
+ 2
+ is 2.
+ The
+ MV of OctalDigit ::
+ 3
+ is 3.
+ The
+ MV of OctalDigit ::
+ 4
+ is 4.
+ The
+ MV of OctalDigit ::
+ 5
+ is 5.
+ The
+ MV of OctalDigit ::
+ 6
+ is 6.
+ The
+ MV of OctalDigit ::
+ 7
+ is 7.
+ The
+ MV of OctalIntegerLiteral ::
+ 0
+ OctalDigit is the MV
+ of OctalDigit.
+ The + MV of OctalIntegerLiteral :: + OctalIntegerLiteral + OctalDigit is (the MV + of OctalIntegerLiteral + times 8) plus the MV of OctalDigit.
++ The + syntax and semantics of 7.8.4 can be extended as follows except that + this extension is not allowed for strict mode code:
++ Syntax
++ EscapeSequence ::
+
+ CharacterEscapeSequence
OctalEscapeSequence
HexEscapeSequence
UnicodeEscapeSequence
+ OctalEscapeSequence ::
+
+ OctalDigit [lookahead
+ ∉
+ DecimalDigit]
ZeroToThree
+ OctalDigit [lookahead
+ ∉DecimalDigit]
FourToSeven
+ OctalDigit
ZeroToThree OctalDigit OctalDigit
+ ZeroToThree :: one + of
+
+ 0
+ 1 2 3
+ FourToSeven :: + one + of
++ 4 + 5 6 7
++ Semantics
++ The + CV of EscapeSequence :: + OctalEscapeSequence + is the CV of the OctalEscapeSequence.
++ The + CV of OctalEscapeSequence + :: + OctalDigit [lookahead + ∉ + DecimalDigit] + is the character whose code unit value is the MV of the + OctalDigit.
++ The + CV of OctalEscapeSequence + :: + ZeroToThree + OctalDigit [lookahead + ∉ + DecimalDigit] + is the character whose code unit value is (8 times the MV of the + ZeroToThree) plus the + MV of the OctalDigit.
++ The + CV of OctalEscapeSequence + :: + FourToSeven + OctalDigit is the + character whose code unit value is (8 times the MV of the + FourToSeven) plus the + MV of the OctalDigit.
++ The + CV of OctalEscapeSequence + :: + ZeroToThree + OctalDigit OctalDigit + is the character whose code unit value is (64 (that is, 82) + times the MV of the ZeroToThree) + plus (8 times the MV of the first OctalDigit) + plus the MV of the second OctalDigit.
+
+ The
+ MV of ZeroToThree ::
+ 0
+ is 0.
+ The
+ MV of ZeroToThree ::
+ 1
+ is 1.
+ The
+ MV of ZeroToThree ::
+ 2
+ is 2.
+ The
+ MV of ZeroToThree ::
+ 3
+ is 3.
+ The
+ MV of FourToSeven ::
+ 4
+ is 4.
+ The
+ MV of FourToSeven ::
+ 5
+ is 5.
+ The
+ MV of FourToSeven ::
+ 6
+ is 6.
+ The
+ MV of FourToSeven ::
+ 7
+ is 7.
+ Some + implementations of ECMAScript have included additional properties + for some of the standard native objects. This non-normative annex + suggests uniform semantics for such properties without making the + properties or their semantics part of this standard.
+
+ The
+ escape function is
+ a property of the global object. It computes a new version of a
+ String value in which certain characters have been replaced by a
+ hexadecimal escape sequence.
+ For
+ those characters being replaced whose code unit value is 0xFF
+ or less, a two-digit escape sequence of the form % xx
+ is used. For those characters being replaced whose code unit value
+ is greater than 0xFF,
+ a four-digit escape sequence of the form %u xxxx
+ is used
+ When
+ the escape
+ function is called with one argument string,
+ the following steps are taken:
+ Call + ToString(string).
++ Compute + the number of characters in Result(1).
++ Let + R be the empty string.
++ Let + k be 0.
++ If + k equals Result(2), return R.
++ Get + the character (represented as a 16-bit unsigned integer) at + position k within Result(1).
+
+ If
+ Result(6) is one of the 69 nonblank
+ characters“ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789@*_+-./”then
+ go to step 13.
+ If + Result(6), is less than 256, go to step 11.
+
+ Let
+ S be a String containing six characters “%u wxyz”
+ where wxyz are four hexadecimal digits encoding the value of
+ Result(6).
+ Go + to step 14.
+
+ Let
+ S be a String containing three characters “% xy”
+ where xy are two hexadecimal digits encoding the value of
+ Result(6).
+ Go + to step 14.
++ Let + S be a String containing the single character Result(6).
++ Let + R be a new String value computed by concatenating the + previous value of R and S.
++ Increase + k by 1.
++ Go + to step 5.
+NOTE The + encoding is partly based on the encoding described in RFC 1738, but + the entire encoding specified in this standard is described above + without regard to the contents of RFC 1738. This encoding does not + reflect changes to RFC 1738 made by RFC 3986.
+ +
+ The
+ unescape function
+ is a property of the global object. It computes a new version of a
+ String value in which each escape sequence of the sort that might be
+ introduced by the escape
+ function is replaced with the character that it represents.
+ When
+ the unescape
+ function is called with one argument string,
+ the following steps are taken:
+ Call + ToString(string).
++ Compute + the number of characters in Result(1).
++ Let + R be the empty String.
++ Let + k be 0.
++ If + k equals Result(2), return R.
++ Let + c be the character at position k within Result(1).
+
+ If
+ c is not %,
+ go to step 18.
+ If + k is greater than Result(2)−6, + go to step 14.
+
+ If
+ the character at position k+1 within Result(1) is not u,
+ go to step 14.
+ If + the four characters at positions k+2, k+3, k+4, + and k+5 within Result(1) are not all hexadecimal digits, go + to step 14.
++ Let + c be the character whose code unit value is the integer + represented by the four hexadecimal digits at positions k+2,k+3, k+4, and k+5 within Result(1).
++ Increase + k by 5.
++ Go + to step 18.
++ If + k is greater than Result(2)−3, + go to step 18.
++ If + the two characters at positions k+1 and k+2 within + Result(1) are not both hexadecimal digits, go to step 18.
++ Let + c be the character whose code unit value is the integer + represented by two zeroes plus the two hexadecimal digits at + positions k+1 and k+2 within Result(1).
++ Increase + k by 2.
++ Let + R be a new String value computed by concatenating the + previous value of R and c.
++ Increase + k by 1.
++ Go + to step 5.
+
+ The
+ substr method
+ takes two arguments, start
+ and length, and
+ returns a substring of the result of converting the this object to a
+ String, starting from character position start
+ and running for length
+ characters (or through the end of the String if length
+ is undefined). If start
+ is negative, it is treated as (sourceLength+start)
+ where sourceLength
+ is the length of the String. The result is a String value, not a
+ String object. The following steps are taken:
+ Call + ToString, giving it the this value as its argument.
++ Call + ToInteger(start).
++ If + length is undefined, use +∞; + otherwise call ToInteger(length).
++ Compute + the number of characters in Result(1).
++ If + Result(2) is positive or zero, use Result(2); else use + max(Result(4)+Result(2),0).
++ Compute + min(max(Result(3),0), Result(4)–Result(5)).
++ If + Result(6) ≤ 0, return the empty + String “”.
++ Return + a String containing Result(6) consecutive characters from Result(1) + beginning with the character at position Result(5).
+
+ The
+ length property of
+ the substr method
+ is 2.
NOTE The
+ substr function is
+ intentionally generic; it does not require that its this
+ value be a String object. Therefore it can be transferred to other
+ kinds of objects for use as a method.
NOTE The
+ getFullYear method
+ is preferred for nearly all purposes, because it avoids the “year
+ 2000 problem.”
+ When + the getYear method is called with no arguments, the following + steps are taken:
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + YearFromTime(LocalTime(t)) − + 1900.
+NOTE The
+ setFullYear method
+ is preferred for nearly all purposes, because it avoids the “year
+ 2000 problem.”
+ When + the setYear method is called with one argument year, + the following steps are taken:
++ Let + t be the result of LocalTime(this time value); but if this time value is NaN, let t be +0.
++ Call + ToNumber(year).
++ If + Result(2) is NaN, set the [[PrimitiveValue]] internal + property of the this value to NaN and return NaN.
++ If + Result(2) is not NaN and 0 ≤ + ToInteger(Result(2)) ≤ 99 then + Result(4) is ToInteger(Result(2)) + 1900. Otherwise, Result(4) + is Result(2).
++ Compute + MakeDay(Result(4), MonthFromTime(t), DateFromTime(t)).
++ Compute + UTC(MakeDate(Result(5), TimeWithinDay(t))).
++ Set + the [[PrimitiveValue]] internal property of the this value + to TimeClip(Result(6)).
++ Return + the value of the [[PrimitiveValue]] internal property of the this + value.
+NOTE The
+ property toUTCString
+ is preferred. The toGMTString
+ property is provided principally for compatibility with old code. It
+ is recommended that the toUTCString
+ property be used in new ECMAScript code.
+ The
+ Function object that is the initial value of
+ Date.prototype.toGMTString
+ is the same Function object that is the initial value of
+ Date.prototype.toUTCString.
‟Ex igne vita”
+ ++ The + strict mode restriction and exceptions
+implements", "interface",
+"let", "package", "private",
+"protected", "public", "static", and
+"yield" are classified as FutureReservedWord tokens
+within strict mode code. (7.6.12 [?]).+ A + conforming implementation, when processing strict mode code, may + not extend the syntax of NumericLiteral + (7.8.3) to include OctalIntegerLiteral + as described in B.1.1.
++ A + conforming implementation, when + processing strict mode code (see 10.1.1), may not extend the syntax + of EscapeSequence to + include OctalEscapeSequence + as described in B.1.2.
+
+ Assignment
+ to an undeclared identifier or otherwise unresolvable reference
+ does not create a property in the global object. When a simple
+ assignment occurs within strict mode code, its LeftHandSide must not evaluate to an
+ unresolvable Reference. If it does a ReferenceError
+ exception is thrown (8.7.2). The LeftHandSide also
+ may not be a reference to a data property with the attribute value
+ {[[Writable]]:false},
+ to an accessor property with the attribute value
+ {[[Set]]:undefined},
+ nor to a non-existent
+ property of an object whose [[Extensible]] internal property has
+ the value false.
+ In these cases a TypeError
+ exception is thrown (11.13.1).
+ The
+ identifier eval
+ or arguments
+ may not appear as the LeftHandSideExpression
+ of an Assignment operator (11.13) or of a PostfixExpression
+ (11.3) or as the UnaryExpression
+ operated upon by a Prefix Increment (11.4.4) or a Prefix Decrement
+ (11.4.5) operator.
+
+ Arguments
+ objects for strict mode functions define non-configurable accessor
+ properties named "caller"
+ and "callee"
+ which throw a TypeError exception on access
+ (10.6).
+ Arguments + objects for strict mode functions do not dynamically share their + array indexed property values with the corresponding formal + parameter bindings of their functions. (10.6).
+
+ For
+ strict mode functions, if an arguments object is created the
+ binding of the local identifier arguments
+ to the arguments object is immutable and hence may not be the
+ target of an assignment expression. (10.5).
+ It + is a SyntaxError + if strict mode code contains an + ObjectLiteral with + more than one definition of any data property (11.1.5).
+
+ It
+ is a SyntaxError
+ if the Identifier
+ "eval"
+ or the Identifier "arguments"
+ occurs as the Identifier
+ in a PropertySetParameterList
+ of a
+ PropertyAssignment
+ that is contained in strict code or
+ if its FunctionBody is
+ strict code (11.1.5).
+ Strict + mode eval code cannot instantiate variables or functions in the + variable environment of the caller to eval. Instead, a new variable + environment is created and that environment is used for declaration + binding instantiation for the eval code (10.4.2).
+
+ If
+ this
+ is evaluated within strict mode code, then the this
+ value is not coerced to
+ an object. A this
+ value of null
+ or undefined
+ is not converted to the global object and primitive values are not
+ converted to wrapper objects. The this
+ value passed via a function call (including calls made using
+ Function.prototype.apply
+ and Function.prototype.call)
+ do not coerce the passed this value to an object (10.4.3, 11.1.1,
+ 15.3.4.3, 15.3.4.4).
+ When
+ a delete
+ operator occurs within strict mode code,
+ a SyntaxError is thrown if its
+ UnaryExpression is a
+ direct reference to a variable, function argument, or function
+ name(11.4.1).
+ When
+ a delete
+ operator occurs within strict mode code, a TypeError
+is thrown if the property to
+ be deleted has the attribute { [[Configurable]]:false
+ } (11.4.1).
+ It
+ is a SyntaxError
+ if a VariableDeclaration
+ or VariableDeclarationNoIn
+ occurs within strict code and its Identifier
+ is eval
+ or
+ arguments
+ (12.2.1).
+ Strict + mode code may not include a WithStatement. + The occurrence of a WithStatement + in such a context is an SyntaxError + (12.10).
+
+ It
+ is a SyntaxError if a TryStatement
+ with a Catch
+ occurs within strict code and the Identifier
+ of the Catch
+ production is eval
+ or arguments
+ (12.14.1)
+ It
+ is a SyntaxError if the identifier eval
+ or arguments
+ appears within a FormalParameterList
+ of a strict mode FunctionDeclaration
+ or FunctionExpression
+ (13.1)
+ A
+ strict mode function may not have two or more formal parameters
+ that have the same name. An attempt to create such a function using
+ a FunctionDeclaration,
+ FunctionExpression, or
+ Function
+ constructor is a SyntaxError
+ (13.1, 15.3.2).
+ An
+ implementation may not extend, beyond that defined in this specification,
+ meanings within strict mode functions of properties named caller
+ or arguments
+ of function instances. ECMAScript code may not create or modify
+ properties with these names on function objects that correspond to
+ strict mode functions
+ (10.6, 13.2, 15.3.4.5.3).
+ It
+ is a SyntaxError
+ to use within strict mode code the identifiers eval
+ or arguments
+ as the Identifier of a
+ FunctionDeclaration or
+ FunctionExpression or
+ as a formal parameter name (13.1). Attempting to dynamically define
+ such a strict mode function using the Function
+ constructor (15.3.2) will throw a SyntaxError
+ exception.
‟Ex igne vita”
+ +
+ Throughout:
+ In the Edition 3 specification the meaning of phrases such as “as
+ if by the expression new
+ Array()” are subject to misinterpretation. In the
+ Edition 5 specification text for all internal references and
+ invocations of standard built-in objects and methods has been
+ clarified by making it explicit that the intent is that the actual
+ built-in object is to be used rather than the current dynamic value
+ of the correspondingly named property.
+
+ 11.8.2, + 11.8.3, 11.8.5: ECMAScript generally uses a left to right evaluation + order, however the Edition 3 specification language for the > and + <= operators resulted in a partial right to left order. The + specification has been corrected for these operators such that it + now specifies a full left to right evaluation order. However, this + change of order is potentially observable if side-effects occur + during the evaluation process.
++ 11.1.4: + Edition 5 clarifies the fact that a trailing comma at the end of an + ArrayInitialiser + does not add to the length of the array. This is not a semantic + change from Edition 3 but some implementations may have previously + misinterpreted this.
++ 11.2.3: + Edition 5 reverses the order of steps 2 and 3 of the algorithm. The + original order as specified in Editions 1 through 3 was incorrectly + specified such that side-effects of evaluating Arguments + could affect the result of evaluating MemberExpression.
+
+ 12.4:
+ In Edition 3, an object is created, as if by new
+ Object()to serve as the scope for resolving the name of
+ the exception parameter passed to a catch
+ clause of a try
+ statement. If the actual exception object is a function and it is
+ called from within the catch
+ clause, the scope object will be passed as the this value of
+ the call. The body of the function can then define new properties on
+ its this value and those property names become visible
+ identifiers bindings within the scope of the catch clause
+ after the function returns. In Edition 5, when an exception
+ parameter is called as a function, undefined is passed as the
+ this value.
+ 13:.
+ In Edition 3, the algorithm for the production FunctionExpression
+ with an Identifier
+ adds an object created as if by new
+ Object() to the scope chain to serve as a scope for
+ looking up the name of the function. The identifier resolution rules
+ (10.1.4 in Edition 3) when applied to such an object will, if
+ necessary, follow the object’s prototype chain when attempting to
+ resolve an identifier. This means all the properties of
+ Object.prototype are visible as identifiers within that scope. In
+ practice most implementations of Edition 3 have not implemented this
+ semantics. Edition 5 changes the specified semantics by using a
+ Declarative Environment Record to bind the name of the function.
+ 14:.
+ In Edition 3, the algorithm for the production SourceElements : SourceElements
+ SourceElement did not correctly propagate statement
+ result values in the same manner as Block.
+ This could result in the eval function producing an incorrect result when evaluating a Program
+ text. In practice most implementations of Edition 3 have implemented
+ the correct propagation rather than what was specified in Edition 3.
+ 15.10.6: + RegExp.prototype is now a RegExp object rather than an instance of + Object. The value of its [[Class]] internal property which is + observable using Object.prototype.toString + is now “RegExp” rather than “Object”.
+ \ No newline at end of file diff --git a/E.html b/E.html new file mode 100644 index 0000000..a14f5ac --- /dev/null +++ b/E.html @@ -0,0 +1,232 @@ + +‟Ex igne vita”
+ ++ 7.1: + Unicode format control characters are no longer stripped from + ECMAScript source text before processing. In Edition 5, if such a + character appears in a StringLiteral + or RegularExpressionLiteral + the character will be incorporated into the literal where in Edition + 3 the character would not be incorporated into the literal.
++ 7.2: + Unicode character <BOM> is now treated as whitespace and its + presence in the middle of what appears to be an identifier could + result in a syntax error which would not have occurred in Edition 3
++ 7.3: + Line terminator characters that are preceded by an escape sequence + are now allowed within a string literal token. In Edition 3 a + syntax error would have been produced.
++ 7.8.5: + Regular expression literals now return a unique object each time the + literal is evaluated. This change is detectable by any programs that + test the object identity of such literal values or that are + sensitive to the shared side effects.
++ 7.8.5: + Edition 5 requires early reporting of any possible RegExp + constructor errors that would be produced when converting a + RegularExpressionLiteral + to a RegExp object. Prior to Edition 5 implementations were + permitted to defer the reporting of such errors until the actual + execution time creation of the object.
++ 7.8.5: + In Edition 5 unescaped “/” characters may appear as a + CharacterClass in + a regular expression literal. In Edition 3 such a character would + have been interpreted as the final character of the literal.
+
+ 10.4.2:
+ In Edition 5, indirect calls to the eval function use the global environment as both the variable environment
+ and lexical environment for the eval code. In Edition 3, the
+ variable and lexical environments of the caller of an indirect eval
+ was used as the environments for the eval code.
+ 15.4.4:
+ In Edition 5 all methods of Array.prototype
+ are intentionally generic. In Edition 3 toString
+ and toLocaleString
+ were not generic and would throw a TypeError
+ exception if applied to objects that were not instances of Array.
+ 10.6: + In Edition 5 the array indexed properties of argument objects that + correspond to actual formal parameters are enumerable. In Edition + 3, such properties were not enumerable.
+
+ 10.6:
+ In Edition 5 the value of the [[Class]] internal property of an
+ arguments object is "Arguments".
+ In Edition 3, it was "Object".
+ This is observable if toString
+ is called as a method of an arguments object.
+
+ 12.6.4:
+ for-in statements no longer throw a TypeError if the in
+ expression evaluates to null or undefined. Instead,
+ the statement behaves as if the value of the expression was an
+ object with no enumerable properties.
+ 15:
+ In Edition 5, the following new properties are defined on built-in
+ objects that exist in Edition 3:
+Object.getPrototypeOf,
+Object.getOwnPropertyDescriptor,
+Object.getOwnPropertyNames,
+Object.create,
+Object.defineProperty,
+ Object.defineProperties,
+ Object.seal,
+ Object.freeze,
+ Object.preventExtensions,
+ Object.isSealed,
+ Object.isFrozen,
+ Object.isExtensible,
+ Object.keys,
+ Function.prototype.bind,
+ Array.prototype.indexOf,
+ Array.prototype.lastIndexOf,
+ Array.prototype.every,
+ Array.prototype.some,
+ Array.prototype.forEach,
+ Array.prototype.map,
+ Array.prototype.filter,
+ Array.prototype.reduce,
+ Array.prototype.reduceRight,
+ String.prototype.trim,
+ Date.now,
+ Date.prototype.toISOString,
+ Date.prototype.toJSON.
+
+ 15: + Implementations are now required to ignore extra arguments to + standard built-in methods unless otherwise explicitly specified. In + Edition 3 the handling of extra arguments was unspecified and + implementations were explicitly allowed to throw a TypeError + exception.
++ 15.1.1: + The value properties NaN, Infinity, and undefined + of the Global Object have been changed to be read-only properties.
++ 15.1.2.1. + Implementations are no longer permitted to restrict the use of eval + in ways that are not a direct call. In addition, any invocation of + eval that is not a direct call uses the global environment as its + variable environment rather than the caller’s variable + environment.
+
+ 15.1.2.2:
+ The specification of the function parseInt
+ no longer allows implementations to treat Strings beginning with a 0
+ character as octal values.
+ 15.3.4.3:
+ In Edition 3, a TypeError is thrown if the second argument
+ passed to Function.prototype.apply
+ is neither an array object nor an arguments object. In Edition 5,
+ the second argument may be any kind of generic array-like object
+ that has a valid length
+ property.
+ 15.3.4.3, 15.3.4.4:
+ In Edition 3 passing undefined or null as the first
+ argument to either Function.prototype.apply
+ or Function.prototype.call
+ causes the global object to be passed to the indirectly invoked
+ target function as the this value. If the first argument is a
+ primitive value the result of calling ToObject on the primitive value is passed as the this value. In Edition 5, these
+ transformations are not performed and the actual first argument
+ value is passed as the this value. This difference will
+ normally be unobservable to existing ECMAScript Edition 3 code
+ because a corresponding transformation takes place upon activation
+ of the target function. However, depending upon the implementation,
+ this difference may be observable by host object functions called
+ using apply or
+ call. In addition,
+ invoking a standard built-in function in this manner with null
+ or undefined passed as the this value will in many cases
+ cause behaviour in Edition 5 implementations that differ from
+ Edition 3 behaviour. In particular, in Edition 5 built-in functions
+ that are specified to actually use the passed this value as
+ an object typically throw a TypeError exception if passed
+ null or undefined as the this value.
+ 15.3.5.2:
+ In Edition 5, the prototype
+ property of Function instances is not enumerable. In Edition 3, this
+ property was enumerable.
+ 15.5.5.2: + In Edition 5, the individual characters of a String object’s + [[PrimitiveValue] may be accessed as array indexed properties of the + String object. These properties are non-writable and + non-configurable and shadow any inherited properties with the same + names. In Edition 3, these properties did not exist and ECMAScript + code could dynamically add and remove writable properties with such + names and could access inherited properties with such names. +
+
+ 15.9.4.2:
+ Date.parse is now
+ required to first attempt to parse its argument as an ISO format
+ string. Programs that use this format but depended upon
+ implementation specific behaviour (including failure) may behave
+ differently.
+ 15.10.2.12:
+ In Edition 5, \s
+ now additionally matches <BOM>.
+ 15.10.4.1:
+ In Edition 3, the exact form of the String value of the source
+ property of an object created by the RegExp
+ constructor is implementation defined. In Edition 5, the String must
+ conform to certain specified requirements and hence may be different
+ from that produced by an Edition 3 implementation.
+ 15.10.6.4:
+ In Edition 3, the result of RegExp.prototype.toString
+ need not be derived from the value of the RegExp object’s source
+ property. In Edition 5 the result must be derived from the source
+ property in a specified manner and hence may be different from the
+ result produced by an Edition 3 implementation.
+ 15.11.2.1,
+ 15.11.4.3: In Edition 5, if an initial value for the message
+ property of an Error object is not specified via the Error
+ constructor the initial value of the property is the empty String.
+ In Edition 3, such an initial value is implementation defined.
+ 15.11.4.4:
+ In Edition 3, the result of Error.prototype.toString
+ is implementation defined. In Edition 5, the result is fully
+ specified and hence may differ from some Edition 3 implementations.
+ 15.12:
+ In Edition 5, the name JSON
+ is defined in the global environment. In Edition 3, testing for the
+ presence of that name will show it to be undefined unless it is
+ defined by the program or implementation.
‟Ex igne vita”
+ ++ ANSI/IEEE + Std 754-1985: IEEE Standard for Binary Floating-Point Arithmetic. + Institute of Electrical and Electronic Engineers, New York (1985)
++ The + Unicode Consortium. The Unicode Standard, Version 3.0, defined by: + The Unicode Standard, Version 3.0 (Boston, MA, Addison-Wesley, + 2000. ISBN 0-201-61635-5)
++ Unicode + Inc. (1998), Unicode Technical Report #15: Unicode Normalization + Forms
+ISO 8601:2004(E) Data elements and interchange +formats – Information interchange -- Representation of dates and times
RFC 1738 “Uniform Resource Locators (URL)”, available at +<http://tools.ietf.org/html/rfc1738>
RFC 2396 “Uniform Resource Identifiers (URI): Generic Syntax”, +available at +<http://tools.ietf.org/html/rfc2396>
RFC 3629 “UTF-8, a transformation format of ISO 10646”, available at +<http://tools.ietf.org/html/rfc3629>
RFC 4627 “The application/json Media Type for JavaScript Object +Notation (JSON)“ , available at +<http://tools.ietf.org/html/rfc4627>
‟Ex igne vita”
+ +toc · single-page version · source
NOTE This is not the normative ECMAScript Language specification.
-The normative ECMAScript specification (ECMA 262) is a PDF file maintained by +
The normative ECMAScript specification (ECMA 262) is a PDF file maintained by ECMA TC39 and is available at the following location:
-http://www.ecma-international.org/publications/standards/Ecma-262.htm
+http://www.ecma-international.org/publications/standards/Ecma-262.htm
This document is an annotated, -hyperlinked, HTML view +hyperlinked, HTML version of Edition 5.1 of the ECMAScript Specification. - It is provided as a means for making annotations to the spec available - online, in HTML and at “point of use”, for the purposes of + It’s provided as a means for making annotations to the spec available + online, in HTML and at “point of use”, for the purposes of explaining the spec and assisting in its implementation that are - allowed for in the spec license. - The complete source for this document is available at:
-https://github.com/es5/es5.github.com
- + allowed for in the spec license. + +This version is maintained by Michael[tm] Smith + <sideshowbarker@gmail.com>
-NOTE Any reuse of the body text from this document - also must adhere to the terms of the license on the normative spec. See - the spec’s +
No copyright is asserted on the front matter of this version (everything + up to and including the Table of Contents). However, any reuse of the body + text from this document (everything following the Table of Contents) must + adhere to the terms of the license on the normative spec. See the spec’s copyright notice and license statement.
- + +The complete source for this version is available at + https://github.com/es5/es5.github.com
To view annotations for a particular section of the present document, follow the hyperlinks - marked Ⓐ, Ⓓ, Ⓡ, Ⓖ, Ⓔ, and ① in + marked Ⓐ, Ⓓ, Ⓡ, Ⓖ, Ⓔ, and ① in the section headings. The different types of annotations provided by each of those are as follows:
-The initial version of this rendering of the spec was already published -before I found out that Jason Orendorff had already put together -another excellent HTML version of the spec. -But after seeing the way that Jason had made that document massively more -useful by adding hyperlinks for terms, etc., I basically just followed that -example to add hyperlinks to this rendering as well. Jason’s version -remains available here:
- - +Jason Orendorff was the first to make a usefully hyperlinked +version of the ECMAScript spec. The hyperlinking here just follows +his example. His version remains available at +http://people.mozilla.org/~jorendorff/es5.html
© Ecma International 2010
+© Ecma International 2010
"DISCLAIMER
This @@ -1168,34667 +910,4 @@This Ecma Standard is based on several originating technologies, the most - well known being JavaScript (Netscape) and JScript (Microsoft). The - language was invented by Brendan Eich at Netscape and first appeared - in that company’s Navigator 2.0 browser. It has appeared in all - subsequent browsers from Netscape and in all browsers from Microsoft - starting with Internet Explorer 3.0.
-- The - development of this Standard started in November 1996. The first - edition of this Ecma Standard was adopted by the Ecma General - Assembly of June 1997.
-- That - Ecma Standard was submitted to ISO/IEC JTC 1 for adoption under the - fast-track procedure, and approved as international standard ISO/IEC - 16262, in April 1998. The Ecma General Assembly of June 1998 - approved the second edition of ECMA-262 to keep it fully aligned - with ISO/IEC 16262. Changes between the first and the second edition - are editorial in nature.
-- The - third edition of the Standard introduced powerful regular - expressions, better string handling, new control statements, - try/catch exception handling, tighter definition of errors, - formatting for numeric output and minor changes in anticipation of - forthcoming internationalisation - facilities and future language growth. The third edition of the - ECMAScript standard was adopted by the Ecma General Assembly of - December 1999 and published as ISO/IEC 16262:2002 in June 2002.
-- Since - publication of the third edition, ECMAScript has achieved massive - adoption in conjunction with the World Wide Web where it has become - the programming language that is supported by essentially all web - browsers. Significant work was done to - develop a fourth edition of ECMAScript. Although that work was not - completed and not published - [1] - - as the fourth edition of ECMAScript, it informs continuing evolution - of the language. The present fifth edition of ECMAScript (published - as ECMA-262 5th - edition) codifies de facto interpretations of the language - specification that have become common among browser implementations - and adds support for new features that have emerged since the - publication of the third edition. Such features include accessor - properties, reflective creation and inspection of objects, program - control of property attributes, additional array manipulation - functions, support for the JSON object encoding format, and a strict - mode that provides enhanced error checking and program security.
-- ECMAScript - is a vibrant language and the evolution of the language is not - complete. Significant technical enhancement will continue with - future editions of this specification.
-1 - Note: Please note that for ECMAScript Edition 4 the Ecma standard - number “ECMA-262 Edition 4” was reserved but not used in the - Ecma publication process. Therefore “ECMA-262 Edition 4” as an - Ecma International publication does not exist.
-- This - Standard defines the ECMAScript scripting language.
-- A - conforming implementation of ECMAScript must provide and support all - the types, values, objects, properties, functions, and program - syntax and semantics described in this specification.
-- A - conforming implementation of this International standard shall - interpret characters in conformance with the Unicode Standard, - Version 3.0 or later and ISO/IEC 10646-1 with either UCS-2 or UTF-16 - as the adopted encoding form, implementation level 3. If the adopted - ISO/IEC 10646-1 subset is not otherwise specified, it is presumed to - be the BMP subset, collection 300. If the adopted encoding form is - not otherwise specified, it presumed to be the UTF-16 encoding form.
-- A - conforming implementation of ECMAScript is permitted to provide - additional types, values, objects, properties, and functions beyond - those described in this specification. In particular, a conforming - implementation of ECMAScript is permitted to provide properties not - described in this specification, and values for those properties, - for objects that are described in this specification.
-- A - conforming implementation of ECMAScript is permitted to support - program and regular expression syntax not described in this - specification. In particular, a conforming implementation of - ECMAScript is permitted to support program syntax that makes use of - the “future reserved words” listed in 7.6.1.2 of this - specification.
-- The - following referenced documents are indispensable for the application - of this document. For dated references, only the edition cited - applies. For undated references, the latest edition of the - referenced document (including any amendments) applies.
-- ISO/IEC 9899:1996, - Programming Languages – C, including amendment 1 and technical - corrigenda 1 and 2
-- ISO/IEC 10646-1:1993, - Information Technology – Universal Multiple-Octet Coded Character - Set (UCS) plus its amendments and corrigenda
-- This - section contains a non-normative overview of the ECMAScript - language.
-- ECMAScript - is an object-oriented programming language for performing - computations and manipulating computational objects within a host - environment. ECMAScript as defined here is not intended to be - computationally self-sufficient; indeed, there are no provisions in - this specification for input of external data or output of computed - results. Instead, it is expected that the computational environment - of an ECMAScript program will provide not only the objects and other - facilities described in this specification but also certain - environment-specific host objects, whose description and - behaviour are beyond the scope of this specification except to - indicate that they may provide certain properties that can be - accessed and certain functions that can be called from an ECMAScript - program.
-- A - scripting language is a programming language that is - used to manipulate, customise, and automate the facilities of an - existing system. In such systems, useful functionality is already - available through a user interface, and the scripting language is a - mechanism for exposing that functionality to program control. In - this way, the existing system is said to provide a host environment - of objects and facilities, which completes the capabilities of the - scripting language. A scripting language is intended for use by both - professional and non-professional programmers.
-- ECMAScript - was originally designed to be a Web scripting language, - providing a mechanism to enliven Web pages in browsers and to - perform server computation as part of a Web-based client-server - architecture. ECMAScript can provide core scripting capabilities for - a variety of host environments, and therefore the core scripting - language is specified in this document apart from any particular - host environment.
-- Some - of the facilities of ECMAScript are similar to those used in other - programming languages; in particular Java™, - Self, and Scheme as described in:
-- Gosling, - James, Bill Joy and Guy Steele. The Java™ - Language Specification. Addison Wesley Publishing Co., 1996.
-- Ungar, - David, and Smith, Randall B. Self: The Power of Simplicity. OOPSLA - '87 Conference Proceedings, pp. 227–241, Orlando, FL, October - 1987.
-- IEEE - Standard for the Scheme Programming Language. IEEE Std 1178-1990.
-- A web - browser provides an ECMAScript host environment for client-side - computation including, for instance, objects that represent windows, - menus, pop-ups, dialog boxes, text areas, anchors, frames, history, - cookies, and input/output. Further, the host environment provides a - means to attach scripting code to events such as change of focus, - page and image loading, unloading, error and abort, selection, form - submission, and mouse actions. Scripting code appears within the - HTML and the displayed page is a combination of user interface - elements and fixed and computed text and images. The scripting code - is reactive to user interaction and there is no need for a main - program.
-- A web - server provides a different host environment for server-side - computation including objects representing requests, clients, and - files; and mechanisms to lock and share data. By using browser-side - and server-side scripting together, it is possible to distribute - computation between the client and server while providing a - customised user interface for a Web-based application.
-- Each - Web browser and server that supports ECMAScript supplies its own - host environment, completing the ECMAScript execution environment.
-- The - following is an informal overview of ECMAScript—not all parts of - the language are described. This overview is not part of the - standard proper.
-- ECMAScript - is object-based: basic language and host facilities are provided by - objects, and an ECMAScript program is a cluster of communicating - objects. An ECMAScript object is a collection of - properties each with zero or more attributes - that determine how each property can be used—for example, when the - Writable attribute for a property is set to false, any - attempt by executed ECMAScript code to change the value of the - property fails. Properties are containers that hold other objects, - primitive values, or functions. A - primitive value is a member of one of the following built-in types: -Undefined, -Null, -Boolean, -Number, -and -String; -an object is a member of the remaining built-in type -Object; and a function is a - callable object. A function that - is associated with an object via a property is a method.
-- ECMAScript - defines a collection of built-in objects that round - out the definition of ECMAScript entities. These built-in objects - include the global object, the Object object, the Function object, the Array object, the String object, the - Boolean object, the Number object, the Math object, the Date object, the RegExp object, the JSON object, and the Error objects Error, EvalError, RangeError, - ReferenceError, SyntaxError, TypeError and URIError.
-- ECMAScript - also defines a set of built-in operators. ECMAScript - operators include various -unary operations, -multiplicative operators, -additive operators, -bitwise shift operators, -relational operators, -equality operators, -binary bitwise operators, -binary logical operators, -assignment operators, and -the comma operator.
-- ECMAScript - syntax intentionally resembles Java syntax. ECMAScript syntax - is relaxed to enable it to serve as an easy-to-use scripting - language. For example, a variable is not required to have its type - declared nor are types associated with properties, and defined - functions are not required to have their declarations appear - textually before calls to them.
-
- ECMAScript
- does not use classes such as those in C++, Smalltalk, or Java.
- Instead objects may be created in various ways including via a
- literal notation or via constructors which create
- objects and then execute code that initialises all or part of them
- by assigning initial values to their properties. Each constructor is
- a function that has a property named “prototype”
- that is used to implement prototype-based inheritance
- and shared properties. Objects are created by using
- constructors in new expressions; for example, new
- Date(2009,11) creates a new Date object. Invoking
- a constructor without using new has consequences that depend
- on the constructor. For example, Date()
- produces a string representation of the current date and time rather
- than an object.
- Every
- object created by a constructor has an implicit reference (called
- the object’s prototype) to the value of its constructor’s
- “prototype”
- property. Furthermore, a prototype may have a non-null implicit
- reference to its prototype, and so on; this is called the prototype
- chain. When a reference is made to a property in an object, that
- reference is to the property of that name in the first object in the
- prototype chain that contains a property of that name. In other
- words, first the object mentioned directly is examined for such a
- property; if that object contains the named property, that is the
- property to which the reference refers; if that object does not
- contain the named property, the prototype for that object is
- examined next; and so on.
Figure 1 — Object/Prototype Relationships
-- In a - class-based object-oriented language, in general, state is carried - by instances, methods are carried by classes, and inheritance is - only of structure and behaviour. In ECMAScript, the state and - methods are carried by objects, and structure, behaviour, and state - are all inherited.
-- All - objects that do not directly contain a particular property that - their prototype contains share that property and its value. Figure 1 - illustrates this:
-
- CF
- is a constructor (and also an object). Five objects have been
- created by using new
- expressions: cf1, cf2,
- cf3, cf4, and cf5.
- Each of these objects contains properties named q1
- and q2. The dashed lines
- represent the implicit prototype relationship; so, for example,
- cf3’s prototype is CFp.
- The constructor, CF, has two properties itself, named P1
- and P2, which are not
- visible to CFp, cf1,
- cf2, cf3, cf4,
- or cf5. The property named CFP1
- in CFp is shared by cf1,
- cf2, cf3, cf4,
- and cf5 (but not by CF), as are any
- properties found in CFp’s implicit
- prototype chain that are not named q1,
- q2, or CFP1.
- Notice that there is no implicit prototype link between CF
- and CFp.
- Unlike - class-based object languages, properties can be added to objects - dynamically by assigning values to them. That is, constructors are - not required to name or assign values to all or any of the - constructed object’s properties. In the above diagram, one could - add a new shared property for cf1, cf2, - cf3, cf4, and cf5 - by assigning a new value to the property in CFp.
-- The - ECMAScript Language recognizes the possibility that some users of - the language may wish to restrict their usage of some features - available in the language. They might do so in the interests of - security, to avoid what they consider to be error-prone features, to - get enhanced error checking, or for other reasons of their choosing. - In support of this possibility, ECMAScript defines a strict variant - of the language. The strict variant of the language excludes some - specific syntactic and semantic features of the regular ECMAScript - language and modifies the detailed semantics of some features. The - strict variant also specifies additional error conditions that must - be reported by throwing error exceptions in situations that are not - specified as errors by the non-strict form of the language.
-- The - strict variant of ECMAScript is commonly referred to as the strict - mode of the language. Strict mode selection and use of the - strict mode syntax and semantics of ECMAScript is explicitly made at - the level of individual ECMAScript code units. Because strict mode - is selected at the level of a syntactic code unit, strict mode only - imposes restrictions that have local effect within such a code unit. - Strict mode does not restrict or modify any aspect of the ECMAScript - semantics that must operate consistently across multiple code units. - A complete ECMAScript program may be composed for both strict mode - and non-strict mode ECMAScript code units. In this case, strict mode - only applies when actually executing code that is defined within a - strict mode code unit. -
-- In - order to conform to this specification, an ECMAScript implementation - must implement both the full unrestricted ECMAScript language and - the strict mode variant of the ECMAScript language as defined by - this specification. In addition, an implementation must support the - combination of unrestricted and strict mode code units into a single - composite program.
-- For - the purposes of this document, the following terms and definitions - apply.
-- set - of data values as defined in Clause 8 of this specification.
-- member - of one of the types Undefined, Null, Boolean, Number, or String as - defined in Clause 8.
-NOTE A - primitive value is a datum that is represented directly at the - lowest level of the language implementation.
-- member - of the type Object.
-NOTE An - object is a collection of properties and has a single prototype - object. The prototype may be the null value.
-- Function - object that creates and initialises objects.
-NOTE The
- value of a constructor’s “prototype”
- property is a prototype object that is used to implement inheritance
- and shared properties.
- object - that provides shared properties for other objects.
-NOTE When
- a constructor creates an object, that object implicitly references
- the constructor’s “prototype”
- property for the purpose of resolving property references. The
- constructor’s “prototype”
- property can be referenced by the program expression
- constructor.prototype,
- and properties added to an object’s prototype are shared, through
- inheritance, by all objects sharing the prototype. Alternatively, a
- new object may be created with an explicitly specified prototype by
- using the Object.create
- built-in function.
- object - in an ECMAScript implementation whose semantics are fully defined by - this specification rather than by the host environment.
-NOTE Standard - native objects are defined in this specification. Some native - objects are built-in; others may be constructed during the course of - execution of an ECMAScript program.
-- object - supplied by an ECMAScript implementation, independent of the host - environment, that is present at the start of the execution of an - ECMAScript program.
-NOTE Standard - built-in objects are defined in this specification, and an - ECMAScript implementation may specify and define others. Every - built-in object is a native object. A built-in constructor - is a built-in object that is also a constructor.
-- object - supplied by the host environment to complete the execution - environment of ECMAScript.
-NOTE Any - object that is not native is a host object.
-- primitive value used when a variable has not been assigned a value.
-- type - whose sole value is the undefined value. -
-- primitive value that represents the intentional absence of any object value.
-- type - whose sole value is the null value.
-- member - of the Boolean type.
-NOTE There - are only two Boolean values, true and false.
-- type - consisting of the primitive values true and false.
-
- member
- of the Object type that is an instance of the standard built-in
- Boolean
- constructor.
NOTE A
- Boolean object is created by using the Boolean
- constructor in a new
- expression, supplying a Boolean value as an argument. The resulting
- object has an internal property whose value is the Boolean value. A
- Boolean object can be coerced to a Boolean value.
- primitive value that is a finite ordered sequence of zero or more 16-bit - unsigned integer. -
-NOTE A - String value is a member of the String type. Each integer value in - the sequence usually represents a single 16-bit unit of UTF-16 text. - However, ECMAScript does not place any restrictions or requirements - on the values except that they must be 16-bit unsigned integers.
-- set - of all possible String values.
-
- member
- of the Object type that is an instance of the standard built-in
- String
- constructor.
NOTE A
- String object is created by using the String
- constructor in a new
- expression, supplying a String value as an argument. The resulting
- object has an internal property whose value is the String value. A
- String object can be coerced to a String value by calling the String
- constructor as a function (15.5.1).
- primitive value corresponding to a double-precision 64-bit binary format IEEE - 754 value.
-NOTE A - Number value is a member of the Number type and is a direct - representation of a number.
-- set - of all possible Number values including the special “Not-a-Number” - (NaN) values, positive infinity, and negative infinity.
-
- member
- of the Object type that is an instance of the standard built-in
- Number
- constructor.
NOTE A
- Number object is created by using the Number
- constructor in a new
- expression, supplying a Number value as an argument. The resulting
- object has an internal property whose value is the Number value. A
- Number object can be coerced to a Number value by calling the Number
- constructor as a function (15.7.1).
- Number - value that is the - positive infinite Number value.
-- Number - value that is a IEEE 754 “Not-a-Number” value.
-
- member
- of the Object type that is an instance of the standard built-in
- Function
- constructor and that may be invoked as a subroutine.
NOTE In - addition to its named properties, a function contains executable - code and state that determine how it behaves when invoked. A - function’s code may or may not be written in ECMAScript.
-- built-in - object that is a function.
-NOTE Examples
- of built-in functions include parseInt
- and Math.exp. An
- implementation may provide implementation-dependent built-in
- functions that are not described in this specification.
-
-
- association - between a name and a value that is a part of an object.
-NOTE Depending - upon the form of the property the value may be represented either - directly as a data value (a primitive value, an object, or a - function object) or indirectly by a pair of accessor functions.
-- function - that is the value of a property.
-NOTE When - a function is called as a method of an object, the object is passed - to the function as its this value.
-- method - that is a built-in function.
-NOTE Standard - built-in methods are defined in this specification, and an - ECMAScript implementation may specify and provide other additional - built-in methods. -
-- internal - value that defines some characteristic of a property.
-- property - that is directly contained by its object.
-- property - of an object that is not an own property but is a property (either - own or inherited) of the object’s prototype.
-- A - context-free grammar consists of a number of productions. - Each production has an abstract symbol called a nonterminal - as its left-hand side, and a sequence of zero or more - nonterminal and terminal symbols as its right-hand side. - For each grammar, the terminal symbols are drawn from a specified - alphabet.
-- Starting - from a sentence consisting of a single distinguished nonterminal, - called the goal symbol, a given context-free grammar - specifies a language, namely, the (perhaps infinite) set of - possible sequences of terminal symbols that can result from - repeatedly replacing any nonterminal in the sequence with a - right-hand side of a production for which the nonterminal is the - left-hand side.
-- A - lexical grammar for ECMAScript is given in clause 7. This - grammar has as its terminal symbols characters (Unicode code units) - that conform to the rules for SourceCharacter - defined in Clause 6. It defines a set of productions, starting from - the goal symbol InputElementDiv - or InputElementRegExp, - that describe how sequences of such characters are translated into a - sequence of input elements.
-
- Input
- elements other than white space and comments form the terminal
- symbols for the syntactic grammar for ECMAScript and are called
- ECMAScript tokens. These tokens are the reserved words,
- identifiers, literals, and punctuators of the ECMAScript language.
- Moreover, line terminators, although not considered to be tokens,
- also become part of the stream of input elements and guide the
- process of automatic semicolon insertion (7.9). Simple white space
- and single-line comments are discarded and do not appear in the
- stream of input elements for the syntactic grammar. A
- MultiLineComment
- (that is, a comment of the form “/*…*/”
- regardless of whether it spans more than one line) is likewise
- simply discarded if it contains no line terminator; but if a
- MultiLineComment
- contains one or more line terminators, then it is replaced by a
- single line terminator, which becomes part of the stream of input
- elements for the syntactic grammar.
- A - RegExp grammar for ECMAScript is given in 15.10. This grammar - also has as its terminal symbols the characters as defined by - SourceCharacter. - It defines a set of productions, starting from the goal symbol - Pattern, that - describe how sequences of characters are translated into regular - expression patterns.
-- Productions - of the lexical and RegExp grammars are distinguished by having two - colons “::” as separating punctuation. The lexical and - RegExp grammars share some productions.
-- Another - grammar is used for translating Strings into numeric values. This - grammar is similar to the part of the lexical grammar having to do - with numeric literals and has as its terminal symbols - SourceCharacter. - This grammar appears in 9.3.1.
-- Productions - of the numeric string grammar are distinguished by having three - colons “:::” as punctuation.
-- The - syntactic grammar for ECMAScript is given in clauses 11, 12, - 13 and 14. This grammar has ECMAScript tokens defined by the lexical - grammar as its terminal symbols (5.1.2). It defines a set of - productions, starting from the goal symbol Program, - that describe how sequences of tokens can form syntactically correct - ECMAScript programs.
-- When - a stream of characters is to be parsed as an ECMAScript program, it - is first converted to a stream of input elements by repeated - application of the lexical grammar; this stream of input elements is - then parsed by a single application of the syntactic grammar. The - program is syntactically in error if the tokens in the stream of - input elements cannot be parsed as a single instance of the goal - nonterminal Program, - with no tokens left over.
-- Productions - of the syntactic grammar are distinguished by having just one colon - “:” as punctuation.
-- The - syntactic grammar as presented in clauses 11, 12, 13 and 14 is - actually not a complete account of which token sequences are - accepted as correct ECMAScript programs. Certain additional token - sequences are also accepted, namely, those that would be described - by the grammar if only semicolons were added to the sequence in - certain places (such as before line terminator characters). - Furthermore, certain token sequences that are described by the - grammar are not considered acceptable if a terminator character - appears in certain “awkward” places.
-- The - JSON grammar is used to translate a String describing a set of - ECMAScript objects into actual objects. The JSON grammar is given in - 15.12.1.
-- The - JSON grammar consists of the JSON lexical grammar and the JSON - syntactic grammar. The JSON lexical grammar is used to translate - character sequences into tokens and is similar to parts of the - ECMAScript lexical grammar. The JSON syntactic grammar describes how - sequences of tokens from the JSON lexical grammar can form - syntactically correct JSON object descriptions.
-- Productions - of the JSON lexical grammar are distinguished by having two colons - “::” as separating punctuation. The JSON lexical grammar - uses some productions from the ECMAScript lexical grammar. The JSON - syntactic grammar is similar to parts of the ECMAScript syntactic - grammar. Productions of the JSON syntactic grammar are distinguished - by using one colon “:” as separating punctuation.
-
- Terminal
- symbols of the lexical and string grammars, and some of the terminal
- symbols of the syntactic grammar, are shown in fixed
- width font, both in the productions of the grammars and
- throughout this specification whenever the text directly refers to
- such a terminal symbol. These are to appear in a program exactly as
- written. All terminal symbol characters specified in this way are to
- be understood as the appropriate Unicode character from the ASCII
- range, as opposed to any similar-looking characters from other
- Unicode ranges.
- Nonterminal - symbols are shown in italic - type. The definition of a nonterminal is introduced by the name of - the nonterminal being defined followed by one or more colons. (The - number of colons indicates to which grammar the production belongs.) - One or more alternative right-hand sides for the nonterminal then - follow on succeeding lines. For example, the syntactic definition:
-- WhileStatement :
-
- while
- (
- Expression )
- Statement
- states
- that the nonterminal WhileStatement
- represents the token while,
- followed by a left parenthesis token, followed by an Expression,
- followed by a right parenthesis token, followed by a Statement.
- The occurrences of Expression
- and Statement are
- themselves nonterminals. As another example, the syntactic
- definition:
- ArgumentList - :
-
- AssignmentExpression
ArgumentList
- , AssignmentExpression
- states - that an ArgumentList - may represent either a single AssignmentExpression - or an ArgumentList, - followed by a comma, followed by an AssignmentExpression. - This definition of ArgumentList - is recursive, that is, it is defined in terms of itself. The result - is that an ArgumentList - may contain any positive number of arguments, separated by commas, - where each argument expression is an AssignmentExpression. - Such recursive definitions of nonterminals are common.
-- The - subscripted suffix “opt”, which may appear after a - terminal or nonterminal, indicates an optional symbol. The - alternative containing the optional symbol actually specifies two - right-hand sides, one that omits the optional element and one that - includes it. This means that:
-- VariableDeclaration - :
-- Identifier - Initialiseropt
-- is a - convenient abbreviation for:
-- VariableDeclaration - :
-
- Identifier
Identifier
- Initialiser
- and - that:
-- IterationStatement - :
-
- for
- ( ExpressionNoInopt
- ; Expressionopt
- ; Expressionopt
- ) Statement
- is a - convenient abbreviation for:
-- IterationStatement - :
-
- for
- ( ; Expressionopt
- ; Expressionopt
- ) Statement
for
- (
- ; Expressionopt
- ; Expressionopt
- ) Statement
- which - in turn is an abbreviation for:
-- IterationStatement - :
-
- for
- ( ; ; Expressionopt
- ) Statement
for
- ( ;
- ; Expressionopt
- )
- Statement
for
- (
- ; ; Expressionopt
- )
- Statement
for
- (
- ; Expression
- ; Expressionopt
- )
- Statement
- which - in turn is an abbreviation for:
-- IterationStatement - :
-
- for
- ( ; ; ) Statementfor
- ( ; ; Expression
- ) Statement
for
- ( ;
- ; ) Statement
for
- ( ;
- ; Expression
- ) Statement
for
- (;
- ; ) Statement
for
- (;
- ; Expression
- ) Statement
for
- (;
- Expression
- ; ) Statement
for
- (;
- Expression
- ; Expression
- ) Statement
- so - the nonterminal IterationStatement - actually has eight alternative right-hand sides.
-- If - the phrase “[empty]” - appears as the right-hand side of a production, it indicates that - the production's right-hand side contains no terminals or - nonterminals.
-- If - the phrase - “[lookahead ∉ set]” - appears in the right-hand side of a production, it indicates that - the production may not be used if the immediately following input - token is a member of the given set. - The set can be - written as a list of terminals enclosed in curly braces. For - convenience, the set can also be written as a nonterminal, in which - case it represents the set of all terminals to which that - nonterminal could expand. For example, given the definitions
-- DecimalDigit :: - one - of
-
- 0
- 1 2 3 4 5 6 7 8 9
- DecimalDigits - ::
-
- DecimalDigit
DecimalDigits
- DecimalDigit
- the - definition
-- LookaheadExample - ::
-
- n
- [lookahead
- ∉
- {1 , 3 , 5 , 7 , 9}]DecimalDigits
DecimalDigit [lookahead
- ∉
- DecimalDigit ]
- matches
- either the letter n
- followed by one or more decimal digits the first of which is even,
- or a decimal digit not followed by another decimal digit.
- If the phrase “[no LineTerminator here]” appears in the right-hand side of a production of - the syntactic grammar, it indicates that the production is a restricted production: it may not be used if a LineTerminator - occurs in the input stream at the indicated position. For example, - the production:
-- ReturnStatement - :
-
- return
- [no LineTerminator here]
- Expressionopt ;
- indicates
- that the production may not be used if a LineTerminator
- occurs in the program between the return
- token and the Expression.
- Unless - the presence of a LineTerminator - is forbidden by a restricted production, any number of occurrences - of LineTerminator - may appear between any two consecutive tokens in the stream of input - elements without affecting the syntactic acceptability of the - program.
-- When - the words “one of” follow the colon(s) in a grammar - definition, they signify that each of the terminal symbols on the - following line or lines is an alternative definition. For example, - the lexical grammar for ECMAScript contains the production:
-- NonZeroDigit :: - one - of
-
- 1
- 2 3 4 5 6 7 8 9
- which - is merely a convenient abbreviation for:
-- NonZeroDigit ::
-
- 1
2
3
4
5
6
7
8
9
- When - an alternative in a production of the lexical grammar or the numeric - string grammar appears to be a multi-character token, it represents - the sequence of characters that would make up such a token.
-- The - right-hand side of a production may specify that certain expansions - are not permitted by using the phrase “but not” and then - indicating the expansions to be excluded. For example, the - production:
-- Identifier - ::
-- IdentifierName but - not ReservedWord
-- means - that the nonterminal Identifier - may be replaced by any sequence of characters that could replace - IdentifierName - provided that the same sequence of characters could not replace - ReservedWord.
-- Finally, - a few nonterminal symbols are described by a descriptive phrase in - sans-serif type in cases where it would be impractical to list all - the alternatives:
-- SourceCharacter - ::
-- any - Unicode code unit
-- The - specification often uses a numbered list to specify steps in an - algorithm. These algorithms are used to precisely specify the - required semantics of ECMAScript language constructs. The algorithms - are not intended to imply the use of any specific implementation - technique. In practice, there may be more efficient algorithms - available to implement a given feature.
-- In - order to facilitate their use in multiple parts of this - specification, some algorithms, called abstract operations, - are named and written in parameterized functional form so that they - may be referenced by name from within other algorithms.
-- When - an algorithm is to produce a value as a result, the directive - “return x” - is used to indicate that the result of the algorithm is the value of - x and that the - algorithm should terminate. The notation Result(n) - is used as shorthand for “the result - of step n”. - -
-- For - clarity of expression, algorithm steps may be subdivided into - sequential substeps. Substeps are indented and may themselves be - further divided into indented substeps. Outline numbering - conventions are used to identify substeps with the first level of - substeps labelled with lower case alphabetic characters and the - second level of substeps labelled with lower case roman numerals. - If more than three levels are required these rules repeat with the - fourth level using numeric labels. For example:
-- Top-level - step
-- Substep.
-- Substep - -
-- Subsubstep.
-- Subsubstep.
-- Subsubsubstep
-- Subsubsubsubstep
-- A - step or substep may be written as an “if” predicate that - conditions its substeps. In this case, the substeps are only - applied if the predicate is true. If a step or substep begins with - the word “else”, it is a predicate that is the negation of the - preceding “if” predicate step at the same level.
-- A - step may specify the iterative application of its substeps.
-- Mathematical - operations such as addition, subtraction, negation, multiplication, - division, and the mathematical functions defined later in this - clause should always be understood as computing exact mathematical - results on mathematical real numbers, which do not include - infinities and do not include a negative zero that is distinguished - from positive zero. Algorithms in this standard that model - floating-point arithmetic include explicit steps, where necessary, - to handle infinities and signed zero and to perform rounding. If a - mathematical operation or function is applied to a floating-point - number, it should be understood as being applied to the exact - mathematical value represented by that floating-point number; such a - floating-point number must be finite, and if it is +0 - or −0 - then the corresponding mathematical value is simply 0.
-- The - mathematical function abs(x) - yields the absolute value of x, - which is −x - if x is negative - (less than zero) and otherwise is x - itself.
-- The - mathematical function sign(x) - yields 1 if x - is positive and −1 - if x is negative. - The sign function is not used in this standard for cases when x - is zero.
-- The - notation “x modulo y” (y - must be finite and nonzero) computes a value k - of the same sign as y - (or zero) such that abs(k) - < abs(y) - and x−k = q - × - y for some - integer q.
-- The - mathematical function floor(x) - yields the largest integer (closest to positive infinity) that is - not larger than x.
-NOTE floor(x) - = x−(x - modulo 1).
-- If an - algorithm is defined to “throw an exception”, execution of the - algorithm is terminated and no result is returned. The calling - algorithms are also terminated, until an algorithm step is reached - that explicitly deals with the exception, using terminology such as - “If an exception was thrown…”. Once such an algorithm step has - been encountered the exception is no longer considered to have - occurred.
-- ECMAScript - source text is represented as a sequence of characters in the - Unicode character encoding, version 3.0 or later. The text is - expected to have been normalised to Unicode Normalised Form C - (canonical composition), as described in Unicode Technical Report - #15. Conforming ECMAScript implementations are not required to - perform any normalisation of text, or behave as though they were - performing normalisation of text, themselves. ECMAScript source - text is assumed to be a sequence of 16-bit code units for the - purposes of this specification. Such a source text may include - sequences of 16-bit code units that are not valid UTF-16 character - encodings. If an actual source text is encoded in a form other than - 16-bit code units it must be processed as if it was first convert to - UTF-16.
-- SourceCharacter ::
-- any - Unicode code unit
-- Throughout - the rest of this document, the phrase “code unit” and the word - “character” will be used to refer to a 16-bit unsigned value - used to represent a single 16-bit unit of text. The phrase “Unicode - character” will be used to refer to the abstract linguistic or - typographical unit represented by a single Unicode scalar value - (which may be longer than 16 bits and thus may be represented by - more than one code unit). The phrase “code point” refers to such - a Unicode scalar value. “Unicode character” only refers to - entities represented by single Unicode scalar values: the components - of a combining character sequence are still individual “Unicode - characters,” even though a user might think of the whole sequence - as a single character.
-
- In
- string literals, regular expression literals, and identifiers, any
- character (code unit) may also be expressed as a Unicode escape
- sequence consisting of six characters, namely \u
- plus four hexadecimal digits. Within a comment, such an escape
- sequence is effectively ignored as part of the comment. Within a
- string literal or regular expression literal, the Unicode escape
- sequence contributes one character to the value of the literal.
- Within an identifier, the escape sequence contributes one character
- to the identifier.
NOTE Although - this document sometimes refers to a “transformation” between a - “character” within a “string” and the 16-bit unsigned - integer that is the code unit of that character, there is actually - no transformation because a “character” within a “string” is - actually represented using that 16-bit unsigned value.
-
- ECMAScript
- differs from the Java programming language in the behaviour of
- Unicode escape sequences. In a Java program, if the Unicode escape
- sequence \u000A,
- for example, occurs within a single-line comment, it is interpreted
- as a line terminator (Unicode character 000A
- is line feed) and therefore the next character is not part of the
- comment. Similarly, if the Unicode escape sequence \u000A
- occurs within a string literal in a Java program, it is likewise
- interpreted as a line terminator, which is not allowed within a
- string literal—one must write \n
- instead of \u000A
- to cause a line feed to be part of the string value of a string
- literal. In an ECMAScript program, a Unicode escape sequence
- occurring within a comment is never interpreted and therefore cannot
- contribute to termination of the comment. Similarly, a Unicode
- escape sequence occurring within a string literal in an ECMAScript
- program always contributes a character to the String value of the
- literal and is never interpreted as a line terminator or as a quote
- mark that might terminate the string literal.
- The - source text of an ECMAScript program is first converted into a - sequence of input elements, which are tokens, line terminators, - comments, or white space. The source text is scanned from left to - right, repeatedly taking the longest possible sequence of characters - as the next input element.
-
- There
- are two goal symbols for the lexical grammar. The InputElementDiv
- symbol is used in those syntactic grammar contexts where a leading
- division (/) or
- division-assignment (/=)
- operator is permitted. The InputElementRegExp
- symbol is used in other syntactic grammar contexts.
NOTE There - are no syntactic grammar contexts where both a leading division or - division-assignment, and a leading RegularExpressionLiteral - are permitted. This is not affected by semicolon insertion (see - 7.9); in examples such as the following:
-
- a
- = b
/hi/g.exec(c).map(d);
- where
- the first non-whitespace, non-comment
- character after a LineTerminator
- is slash
- (/)
- and the syntactic context allows division
- or division-assignment, no semicolon is inserted at the
- LineTerminator.
- That is, the above example is interpreted in the same way as:
- a
- = b / hi / g.exec(c).map(d);
- Syntax
-- InputElementDiv ::
-
- WhiteSpace
LineTerminator
Comment
Token
DivPunctuator
-
- InputElementRegExp ::
-
- WhiteSpace
LineTerminator
Comment
Token
RegularExpressionLiteral
- The - Unicode format-control characters (i.e., the characters in category - “Cf” in the Unicode Character Database such as left-to-right - mark or right-to-left - mark) are control codes used to control the formatting of a - range of text in the absence of higher-level protocols for this - (such as mark-up languages).
-- It is - useful to allow format-control characters in source text to - facilitate editing and display. All format control characters may be - used within comments, and within string literals and regular - expression literals.
-- <ZWNJ> - and <ZWJ> are - format-control characters that are used to make necessary - distinctions when forming words or phrases in certain languages. In - ECMAScript source text, <ZWNJ> - and <ZWJ> - may also be used in an identifier after the first character. -
-- <BOM> - is a format-control character used primarily at the start of a text - to mark it as Unicode and to allow detection of the text's encoding - and byte order. <BOM> - characters intended for this purpose can sometimes also appear after - the start of a text, for example as a result of concatenating files. - <BOM> characters are treated as white space characters (see - 7.2). -
-- The - special treatment of certain format-control characters outside of - comments, string literals, and regular expression literals is - summarized in Table 1.
-|
- - Code - Unit Value - |
-
- - Name - |
-
- - Formal - Name - |
-
- - Usage - |
-
|
-
- |
-
- - Zero - width non-joiner - |
-
- - <ZWNJ> - |
-
- - IdentifierPart - |
-
|
-
- |
-
- - Zero - width joiner - |
-
- - <ZWJ> - |
-
- - IdentifierPart - |
-
|
-
- |
-
- - Byte - Order Mark - |
-
- - <BOM> - |
-
- - Whitespace - |
-
- White - space characters are used to improve source text readability and to - separate tokens (indivisible lexical units) from each other, but are - otherwise insignificant. White space characters may occur between - any two tokens and at the start or end of input. White space - characters may also occur within a StringLiteral - or a RegularExpressionLiteral - (where they are considered significant characters forming part of - the literal value) or within a Comment, - but cannot appear within any other kind of token.
-- The - ECMAScript white space characters are listed in Table 2.
-|
- - Code - Unit Value - |
-
- - Name - |
-
- - Formal - Name - |
-
|
-
- |
-
- - Tab - |
-
- - <TAB> - |
-
|
-
- |
-
- - Vertical - Tab - |
-
- - <VT> - |
-
|
-
- |
-
- - Form - Feed - |
-
- - <FF> - |
-
|
-
- |
-
- - Space - |
-
- - <SP> - |
-
|
-
- |
-
- - No-break - space - |
-
- - <#x0a> - |
-
|
-
- - Other - category “Zs” - |
-
- - Byte - Order Mark -- Any - other Unicode “space separator” - |
-
- - <BOM> -- <USP> - |
-
- ECMAScript - implementations must recognize all of the white space characters - defined in Unicode 3.0. Later editions of the Unicode Standard may - define other white space characters. ECMAScript implementations may - recognize white space characters from later editions of the Unicode - Standard.
-- Syntax
-- WhiteSpace - ::
-
- <TAB>
<VT>
<FF>
<SP>
<#x0a>
<BOM>
<USP>
- Like - white space characters, line terminator characters are used to - improve source text readability and to separate tokens (indivisible - lexical units) from each other. However, unlike white space - characters, line terminators have some influence over the behaviour - of the syntactic grammar. In general, line terminators may occur - between any two tokens, but there are a few places where they are - forbidden by the syntactic grammar. Line terminators also affect the - process of automatic semicolon insertion (7.9). A line terminator - cannot occur within any token except a StringLiteral. - Line terminators may only occur within a StringLiteral - token as part of a LineContinuation. - -
-- A - line terminator can occur within a MultiLineComment - (7.4) but cannot occur within a SingleLineComment. - -
-
- Line
- terminators are included in the set of white space characters that
- are matched by the \s
- class in regular expressions.
- The - ECMAScript line terminator characters are listed in Table 3.
-|
- - Code - Unit Value - |
-
- - Name - |
-
- - Formal - Name - |
-
|
-
- |
-
- - Line - Feed - |
-
- - <LF> - |
-
|
-
- |
-
- - Carriage - Return - - |
-
- - <CR> - |
-
|
-
- |
-
- - Line - separator - |
-
- - <LS> - |
-
|
-
- |
-
- - Paragraph - separator - |
-
- - <PS> - |
-
- Only - the characters in Table 3 are treated as line terminators. Other new - line or line breaking characters are treated as white space but not - as line terminators. The character sequence <CR><LF> is - commonly used as a line terminator. It should be considered a single - character for the purpose of reporting line numbers.
-- Syntax
-- LineTerminator ::
-
- <LF>
<CR>
<LS>
<PS>
- LineTerminatorSequence ::
-
- <LF>
<CR>
- [lookahead
- ∉
- <LF>
- ]
<LS>
<PS>
<CR>
- <LF>
- Comments - can be either single or multi-line. Multi-line comments cannot nest.
-
- Because
- a single-line comment can contain any character except a
- LineTerminator
- character, and because of the general rule that a token is always as
- long as possible, a single-line comment always consists of all
- characters from the //
- marker to the end of the line. However, the LineTerminator
- at the end of the line is not considered to be part of the
- single-line comment; it is recognised separately by the lexical
- grammar and becomes part of the stream of input elements for the
- syntactic grammar. This point is very important, because it implies
- that the presence or absence of single-line comments does not affect
- the process of automatic semicolon insertion (see 7.9).
- Comments - behave like white space and are discarded except that, if a - MultiLineComment - contains a line terminator character, then the entire comment is - considered to be a LineTerminator - for purposes of parsing by the syntactic grammar.
-- Syntax
-- Comment ::
-
- MultiLineComment
SingleLineComment
- MultiLineComment ::
-
- /* MultiLineCommentCharsopt */
- MultiLineCommentChars ::
-
- MultiLineNotAsteriskChar
- MultiLineCommentCharsopt* PostAsteriskCommentCharsopt
- PostAsteriskCommentChars ::
-
- MultiLineNotForwardSlashOrAsteriskChar
- MultiLineCommentCharsopt* PostAsteriskCommentCharsopt
- MultiLineNotAsteriskChar - ::
-
- SourceCharacter but
- not asterisk *
- MultiLineNotForwardSlashOrAsteriskChar ::
-
- SourceCharacter
- but
- not forward-slash /
- orasterisk *
- SingleLineComment ::
-
- // SingleLineCommentCharsopt
- SingleLineCommentChars ::
-- SingleLineCommentChar - SingleLineCommentCharsopt
-- SingleLineCommentChar ::
-- SourceCharacter - but - not LineTerminator
-- Syntax
-- Token ::
-
- IdentifierName
Punctuator
NumericLiteral
StringLiteral
-
NOTE The - DivPunctuator and - RegularExpressionLiteral - productions define tokens, but are not included in the Token - production.
-- Identifier - Names are tokens that are interpreted according to the grammar given - in the “Identifiers” section of chapter 5 of the Unicode - standard, with some small modifications. An Identifier - is an IdentifierName - that is not a ReservedWord - (see 7.6.1). The Unicode identifier grammar is based on both - normative and informative character categories specified by the - Unicode Standard. The characters in the specified categories in - version 3.0 of the Unicode standard must be treated as in those - categories by all conforming ECMAScript implementations.
-
- This
- standard specifies specific character additions: The dollar sign ($)
- and the underscore (_)
- are permitted anywhere in an IdentifierName.
- Unicode
- escape sequences are also permitted in an IdentifierName,
- where they contribute a single character to the IdentifierName,
- as computed by the CV of the UnicodeEscapeSequence
- (see 7.8.4). The \
- preceding the UnicodeEscapeSequence
- does not contribute a character to the IdentifierName.
- A UnicodeEscapeSequence
- cannot be used to put a character into an IdentifierName that would otherwise be illegal. In other words, if a \
- UnicodeEscapeSequence
- sequence were replaced by its UnicodeEscapeSequence's
- CV, the result must still be a valid IdentifierName that has the exact same sequence of characters as the
- original IdentifierName.
- All interpretations of identifiers within this specification are
- based upon their actual characters regardless of whether or not an
- escape sequence was used to contribute any particular characters.
- Two - IdentifierName that - are canonically equivalent according to the Unicode standard are not - equal unless they are represented by the exact same sequence of code - units (in other words, conforming ECMAScript implementations are - only required to do bitwise comparison on IdentifierName values). - The intent is that the incoming source text has been converted to - normalised form C before it reaches the compiler.
-- ECMAScript - implementations may recognize identifier characters defined in later - editions of the Unicode Standard. If portability is a concern, - programmers should only employ identifier characters defined in - Unicode 3.0.
-- Syntax
-- Identifier ::
-- IdentifierName but - not ReservedWord
-- IdentifierName - ::
-
- IdentifierStart
IdentifierName
- IdentifierPart
- IdentifierStart ::
-
- UnicodeLetter$
_\
- UnicodeEscapeSequence
- IdentifierPart ::
-
- IdentifierStart
UnicodeCombiningMark
UnicodeDigit
UnicodeConnectorPunctuation
<ZWNJ>
<ZWJ>
- UnicodeLetter
-- any - character in the Unicode categories “Uppercase letter (Lu)”, - “Lowercase letter (Ll)”, “Titlecase letter (Lt)”, “Modifier - letter (Lm)”, “Other letter (Lo)”, or “Letter number (Nl)”.
-- UnicodeCombiningMark
-- any - character in the Unicode categories “Non-spacing mark (Mn)” or - “Combining spacing mark (Mc)”
-- UnicodeDigit
-- any - character in the Unicode category “Decimal number (Nd)”
-- UnicodeConnectorPunctuation
-- any - character in the Unicode category “Connector punctuation (Pc)”
-- UnicodeEscapeSequence
-- see - 7.8.4.
-- A - reserved word is an IdentifierName - that cannot be used as an Identifier.
-- Syntax
-- ReservedWord - ::
-
- Keyword
FutureReservedWord
NullLiteral
BooleanLiteral
- The - following tokens are ECMAScript keywords and may not be used as - Identifiers in - ECMAScript programs.
-- Syntax
-- Keyword :: one - of
-|
-
- |
-
-
- |
-
-
- |
-
-
- |
-
|
-
- |
-
-
- |
-
-
- |
-
-
- |
-
|
-
- |
-
-
- |
-
-
- |
-
-
- |
-
|
-
- |
-
-
- |
-
-
- |
-
-
- |
-
|
-
- |
-
-
- |
-
-
- |
-
-
- |
-
|
-
- |
-
-
- |
-
-
- |
- - | -
|
-
- |
-
-
- |
-
-
- |
- - | -
- The - following words are used as keywords in proposed extensions and are - therefore reserved to allow for the possibility of future adoption - of those extensions.
-- Syntax
-- FutureReservedWord - :: - one - of
-|
-
- |
-
-
- |
-
-
- |
-
-
- |
-
|
-
- |
-
-
- |
-
-
- |
- - | -
- The - following tokens are also considered to be FutureReservedWords - when they occur within strict mode code (see 10.1.1). The - occurrence of any of these tokens within strict mode code in any - context where the occurrence of a FutureReservedWord - would produce an error must also produce an equivalent error:
-|
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
|
-
- |
-
-
- |
-
-
- |
-
-
- |
- - | -
- Syntax
-- Punctuator :: one - of
-|
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
|
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
|
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
- - | -
|
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
|
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
|
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
|
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
|
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
- - | -
- DivPunctuator :: one - of
-|
-
- |
-
-
- |
- - | -- | -- | -- | -
- Syntax
-- Literal ::
-
- NullLiteral
BooleanLiteral
NumericLiteral
StringLiteral
-
RegularExpressionLiteral
- Syntax
-- NullLiteral ::
-
- null
- Semantics
-
- The
- value of the null literal null
- is the sole value of the Null type, namely null.
- Syntax
-- BooleanLiteral ::
-
- true
false
- Semantics
-
- The
- value of the Boolean literal true
- is a value of the Boolean type, namely true.
- The
- value of the Boolean literal false
- is a value of the Boolean type, namely false.
- Syntax
-- NumericLiteral - ::
-
- DecimalLiteral
HexIntegerLiteral
- DecimalLiteral ::
-
- DecimalIntegerLiteral . DecimalDigitsopt
- ExponentPartopt. DecimalDigits ExponentPartopt
DecimalIntegerLiteral
- ExponentPartopt
- DecimalIntegerLiteral - ::
-
- 0
NonZeroDigit
- DecimalDigitsopt
- DecimalDigits ::
-
- DecimalDigit
DecimalDigits
- DecimalDigit
- DecimalDigit :: - one - of
-
- 0
- 1 2 3 4 5 6 7 8 9
- NonZeroDigit :: - one - of
-
- 1
- 2 3 4 5 6 7 8 9
- ExponentPart ::
-- ExponentIndicator - SignedInteger
-- ExponentIndicator :: - one - of
-
- e
- E
- SignedInteger - ::
-
- DecimalDigits+ DecimalDigits- DecimalDigits
- HexIntegerLiteral ::
-
- 0x HexDigit0X HexDigit
HexIntegerLiteral HexDigit
- HexDigit :: one - of
-
- 0
- 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F
- The - source character immediately following a NumericLiteral - must not be an IdentifierStart - or DecimalDigit.
--
NOTE For example:
-3in
is
- an error and not the two input elements 3
- and in.
- Semantics
-- A - numeric literal stands for a value of the Number type. This value is - determined in two steps: first, a mathematical value (MV) is derived - from the literal; second, this mathematical value is rounded as - described below.
-- The - MV of NumericLiteral :: - DecimalLiteral is the MV of - DecimalLiteral.
-- The - MV of NumericLiteral :: - HexIntegerLiteral is the MV - of HexIntegerLiteral.
-
- The
- MV of DecimalLiteral ::
- DecimalIntegerLiteral .
- is the MV of
- DecimalIntegerLiteral.
- The
- MV of DecimalLiteral ::
- DecimalIntegerLiteral . DecimalDigits is
- the MV of DecimalIntegerLiteral plus
- (the MV of DecimalDigits times
- 10–n),
- where n is the
- number of characters in DecimalDigits.
- The
- MV of DecimalLiteral ::
- DecimalIntegerLiteral . ExponentPart is the MV of
- DecimalIntegerLiteral times
- 10e,
- where e is
- the MV of ExponentPart.
- The
- MV of DecimalLiteral ::
- DecimalIntegerLiteral . DecimalDigits ExponentPart is
- (the MV of DecimalIntegerLiteral plus
- (the MV of DecimalDigits times
- 10–n))
- times 10e,
- where n is the
- number of characters in DecimalDigits and
- e is the MV of
- ExponentPart.
- The
- MV of DecimalLiteral ::. DecimalDigits is the MV of
- DecimalDigits times
- 10–n,
- where n is the
- number of characters in DecimalDigits.
- The
- MV
- of DecimalLiteral ::. DecimalDigits ExponentPart is
- the MV of DecimalDigits times
- 10e–n,
- where n is the
- number of characters in DecimalDigits and
- e is the MV of
- ExponentPart.
- The - MV of DecimalLiteral :: - DecimalIntegerLiteral is - the MV of DecimalIntegerLiteral.
-- The - MV of DecimalLiteral :: - DecimalIntegerLiteral ExponentPart is - the MV of DecimalIntegerLiteral times - 10e, - where e is the MV of - ExponentPart.
-
- The
- MV of DecimalIntegerLiteral ::
- 0 is 0.
- The - MV of DecimalIntegerLiteral :: - NonZeroDigit DecimalDigits is - (the MV of NonZeroDigit times - 10n) plus - the MV of DecimalDigits, - where n - is the number of characters in DecimalDigits.
-- The - MV of DecimalDigits :: - DecimalDigit is the MV of - DecimalDigit.
-- The - MV of DecimalDigits :: - DecimalDigits DecimalDigit is - (the MV of DecimalDigits times - 10) plus the MV of DecimalDigit.
-- The - MV of ExponentPart :: - ExponentIndicator SignedInteger is - the MV of SignedInteger.
-- The - MV of SignedInteger :: - DecimalDigits is - the MV of DecimalDigits.
-
- The
- MV of SignedInteger ::
- + DecimalDigits is
- the MV of DecimalDigits.
- The
- MV of SignedInteger ::
- - DecimalDigits is
- the negative of the MV of DecimalDigits.
- The
- MV of DecimalDigit ::
- 0 or
- of HexDigit ::
- 0 is
- 0.
- The
- MV of DecimalDigit ::
- 1 or
- of NonZeroDigit ::
- 1 or
- of HexDigit ::
- 1 is
- 1.
- The
- MV of DecimalDigit ::
- 2 or
- of NonZeroDigit ::
- 2 or
- of HexDigit ::
- 2 is
- 2.
- The
- MV of DecimalDigit ::
- 3 or
- of NonZeroDigit ::
- 3 or
- of HexDigit ::
- 3 is
- 3.
- The
- MV of DecimalDigit ::
- 4 or
- of NonZeroDigit ::
- 4 or
- of HexDigit ::
- 4 is
- 4.
- The
- MV of DecimalDigit ::
- 5 or
- of NonZeroDigit ::
- 5 or
- of HexDigit ::
- 5 is
- 5.
- The
- MV of DecimalDigit ::
- 6 or
- of NonZeroDigit ::
- 6 or
- of HexDigit ::
- 6 is
- 6.
- The
- MV of DecimalDigit ::
- 7 or
- of NonZeroDigit ::
- 7 or
- of HexDigit ::
- 7 is
- 7.
- The
- MV of DecimalDigit ::
- 8 or
- of NonZeroDigit ::
- 8 or
- of HexDigit ::
- 8 is
- 8.
- The
- MV of DecimalDigit ::
- 9 or
- of NonZeroDigit ::
- 9 or
- of HexDigit ::
- 9 is
- 9.
- The
- MV of HexDigit ::
- a or
- of HexDigit ::
- A is
- 10.
- The
- MV of HexDigit ::
- b or
- of HexDigit ::
- B is
- 11.
- The
- MV of HexDigit ::
- c or
- of HexDigit ::
- C is
- 12.
- The
- MV of HexDigit ::
- d or
- of HexDigit ::
- D is
- 13.
- The
- MV of HexDigit ::
- e or
- of HexDigit ::
- E is
- 14.
- The
- MV of HexDigit ::
- f or
- of HexDigit ::
- F is
- 15.
- The
- MV of HexIntegerLiteral ::
- 0x HexDigit
- is the MV of HexDigit.
- The
- MV of HexIntegerLiteral ::
- 0X HexDigit
- is the MV of HexDigit.
- The - MV of HexIntegerLiteral :: - HexIntegerLiteral HexDigit is - (the MV of HexIntegerLiteral times - 16) plus the MV of - HexDigit.
-
- Once
- the exact MV for a numeric literal has been determined, it is then
- rounded to a value of the Number type. If the MV is 0, then the
- rounded value is +0;
- otherwise, the rounded value must be the Number value for the
- MV (as specified in 8.5), unless the literal is a DecimalLiteral
- and the literal has more than 20 significant digits, in which case
- the Number value may be either the Number value for the MV of a
- literal produced by replacing each significant digit after the 20th
- with a 0 digit or
- the Number value for the MV of a literal produced by replacing each
- significant digit after the 20th with a 0
- digit and then incrementing the literal at the 20th significant
- digit position. A digit is significant if it is not part of
- an ExponentPart
- and
- it
- is not 0;
- or
- there - is a nonzero digit to its left and there is a nonzero digit, not - in the ExponentPart, - to its right.
-- A - conforming implementation, when processing strict mode code (see - 10.1.1), must not extend the syntax of NumericLiteral - to include OctalIntegerLiteral - as described in B.1.1.
-- A - string literal is zero or more characters enclosed in single or - double quotes. Each character may be represented by an escape - sequence. All characters may appear literally in a string literal - except for the closing quote character, backslash, carriage return, - line separator, paragraph separator, and line feed. Any character - may appear in the form of an escape sequence.
-- Syntax
-- StringLiteral ::
-
- " DoubleStringCharactersopt
- " SingleStringCharactersopt
-
''
- DoubleStringCharacters ::
-- DoubleStringCharacter - DoubleStringCharactersopt
-- SingleStringCharacters ::
-- SingleStringCharacter - SingleStringCharactersopt
-- DoubleStringCharacter ::
-
- SourceCharacter but
- not double-quote "
- or
- backslash \ or
- LineTerminator\
- EscapeSequence
LineContinuation
- SingleStringCharacter ::
-
- SourceCharacter but
- not single-quote '
- orbackslash \ or
- LineTerminator\
- EscapeSequence
LineContinuation
- LineContinuation ::
-
- \
- LineTerminatorSequence
- EscapeSequence ::
-
- CharacterEscapeSequence0 [lookahead
- ∉
- DecimalDigit]
HexEscapeSequence
UnicodeEscapeSequence
- CharacterEscapeSequence ::
-
- SingleEscapeCharacter
NonEscapeCharacter
- SingleEscapeCharacter :: - one - of
-
- '
- " \ b f n r t v
- NonEscapeCharacter - ::
-- SourceCharacter - but - not EscapeCharacter or - LineTerminator
-- EscapeCharacter ::
-
- SingleEscapeCharacter
DecimalDigitx u
- HexEscapeSequence ::
-
- x
- HexDigit HexDigit
- UnicodeEscapeSequence ::
-
- u HexDigit HexDigit HexDigit HexDigit
- The - definitions of the nonterminal HexDigit - is given in 7.6. SourceCharacter - is defined in clause 6.
-- Semantics
-- A - string literal stands for a value of the String type. The String - value (SV) of the literal is described in terms of character values - (CV) contributed by the various parts of the string literal. As part - of this process, some characters within the string literal are - interpreted as having a mathematical value (MV), as described below - or in 7.8.3.
-
- The
- SV of StringLiteral ::
- "" is
- the empty character sequence.
- The
- SV of StringLiteral ::
- '' is
- the empty character sequence.
- The
- SV of StringLiteral ::
- "
- DoubleStringCharacters "
- is the SV of
- DoubleStringCharacters.
- The
- SV of StringLiteral ::
- '
- SingleStringCharacters '
- is the SV of
- SingleStringCharacters.
- The - SV of DoubleStringCharacters :: - DoubleStringCharacter is a - sequence of one character, the CV of DoubleStringCharacter.
-- The - SV of DoubleStringCharacters :: - DoubleStringCharacter DoubleStringCharacters is - a sequence of the CV of DoubleStringCharacter - followed by all the characters in - the SV of DoubleStringCharacters - in order.
-- The - SV of SingleStringCharacters :: - SingleStringCharacter is a - sequence of one character, the CV of - SingleStringCharacter.
-- The - SV of SingleStringCharacters :: - SingleStringCharacter SingleStringCharacters - is a sequence of the CV of SingleStringCharacter - followed by all the characters in - the SV of SingleStringCharacters in - order.
-
- The
- SV of LineContinuation ::
- \
- LineTerminatorSequence is
- the empty character sequence.
- The
- CV of DoubleStringCharacter ::
- SourceCharacter but not
- double-quote "
- or backslash
- \ or
- LineTerminator is theSourceCharacter character
- itself.
- The
- CV of DoubleStringCharacter ::
- \
- EscapeSequence is
- the CV of the EscapeSequence.
The -CV of DoubleStringCharacter :: -LineContinuation is the -empty character sequence.
- The
- CV of SingleStringCharacter ::
- SourceCharacter but not
- single-quote '
- or backslash
- \ or
- LineTerminator is theSourceCharacter character
- itself.
- The
- CV of SingleStringCharacter ::
- \
- EscapeSequence is
- the CV of the EscapeSequence.
The -CV of SingleStringCharacter :: -LineContinuation is -the empty character sequence.
- The - CV of EscapeSequence :: - CharacterEscapeSequence is - the CV of the CharacterEscapeSequence.
-
- The
- CV of EscapeSequence ::
- 0 [lookahead
- ∉
- DecimalDigit]
- is a <NUL>
- character (Unicode value 0000).
- The - CV of EscapeSequence :: - HexEscapeSequence is the CV - of the HexEscapeSequence.
-- The - CV of EscapeSequence :: - UnicodeEscapeSequence is - the CV of the UnicodeEscapeSequence.
-- The CV of CharacterEscapeSequence ::SingleEscapeCharacter is the - character whose code unit value is determined by theSingleEscapeCharacter according - to Table 4:
-|
- - Escape - Sequence - |
-
- - Code - Unit Value - |
-
- - Name - |
-
- - Symbol - |
-
|
-
- |
-
-
- |
-
- - backspace - |
-
- - <BS> - |
-
|
-
- |
-
-
- |
-
- - horizontal - tab - |
-
- - <HT> - |
-
|
-
- |
-
-
- |
-
- - line - feed (new line) - |
-
- - <LF> - |
-
|
-
- |
-
-
- |
-
- - vertical - tab - |
-
- - <VT> - |
-
|
-
- |
-
-
- |
-
- - form - feed - |
-
- - <FF> - |
-
|
-
- |
-
-
- |
-
- - carriage - return - |
-
- - <CR> - |
-
|
-
- |
-
-
- |
-
- - double - quote - |
-
-
- |
-
|
-
- |
-
-
- |
-
- - single - quote - |
-
-
- |
-
|
-
- |
-
-
- |
-
- - backslash - |
-
-
- |
-
- The - CV of CharacterEscapeSequence :: - NonEscapeCharacter is the - CV of the NonEscapeCharacter.
-- The - CV of NonEscapeCharacter :: - SourceCharacter but - not EscapeCharacter or - LineTerminator is the - SourceCharacter character - itself.
-
- The
- CV of HexEscapeSequence ::
- x HexDigit
- HexDigit is the character
- whose code unit value is (16
- times the MV of the first HexDigit)
- plus the MV of the second HexDigit.
- The
- CV of UnicodeEscapeSequence ::
- u HexDigit
- HexDigit HexDigit HexDigit is the
- character whose code unit value is (4096
- times the MV of the first HexDigit)
- plus (256 times the MV of
- the second HexDigit)
- plus (16 times the MV of
- the third HexDigit)
- plus the MV of the fourth HexDigit.
- A - conforming implementation, when processing strict mode code (see - 10.1.1), may not extend the syntax of EscapeSequence - to include OctalEscapeSequence - as described in B.1.2.
--
NOTE A line
- terminator character cannot appear in a string literal, except as
- part of a LineContinuation
- to produce the empty character sequence. The correct way to cause a
- line terminator character to be part of the String value of a string
- literal is to use an escape sequence such as \n
- or \u000A.
- A
- regular expression literal is an input element that is converted to
- a RegExp object (see 15.10) each time the literal is evaluated. Two
- regular expression literals in a program evaluate to regular
- expression objects that never compare as ===
- to each other even if the two literals' contents are identical. A
- RegExp object may also be created at runtime by new
- RegExp (see 15.10.4) or calling the RegExp
- constructor as a function (15.10.3).
- The - productions below describe the syntax for a regular expression - literal and are used by the input element scanner to find the end of - the regular expression literal. The Strings of characters comprising - the RegularExpressionBody - and the RegularExpressionFlags - are passed uninterpreted to the regular expression constructor, - which interprets them according to its own, more stringent grammar. - An implementation may extend the regular expression constructor's - grammar, but it must not extend the RegularExpressionBody - and RegularExpressionFlags - productions or the productions used by these productions.
-- Syntax
-- RegularExpressionLiteral ::
-
- / RegularExpressionBody /
- RegularExpressionFlags
- RegularExpressionBody - ::
-- RegularExpressionFirstChar - RegularExpressionChars
-- RegularExpressionChars ::
-
- [empty]
RegularExpressionChars
- RegularExpressionChar
- RegularExpressionFirstChar ::
-
- RegularExpressionNonTerminator but
- not *
- or
- \ or
- /
- or
- [
RegularExpressionBackslashSequence
RegularExpressionClass
- RegularExpressionChar ::
-
- RegularExpressionNonTerminator
- but
- not \
- or
- /
- or
- [
RegularExpressionBackslashSequence
RegularExpressionClass
- RegularExpressionBackslashSequence ::
-
- \ RegularExpressionNonTerminator
- RegularExpressionNonTerminator ::
-- SourceCharacter - but - not LineTerminator
-- RegularExpressionClass ::
-
- [
- RegularExpressionClassChars
- ]
- RegularExpressionClassChars
- ::
- [empty]
RegularExpressionClassChars
- RegularExpressionClassChar
- RegularExpressionClassChar
- ::
- RegularExpressionNonTerminator
- but
- not ]
- or
- \
RegularExpressionBackslashSequence
- RegularExpressionFlags - ::
-
- [empty]
RegularExpressionFlags
- IdentifierPart
NOTE Regular
- expression literals may not be empty; instead of representing an
- empty regular expression literal, the characters //
- start a single-line comment. To specify an empty regular expression,
- use: /(?:)/.
- Semantics
-
- A
- regular expression literal evaluates to a value of the Object type
- that is an instance of the standard built-in constructor RegExp.
- This value is determined in two steps: first, the characters
- comprising the regular expression's RegularExpressionBody
- and RegularExpressionFlags
- production expansions are collected uninterpreted into two Strings
- Pattern and Flags, respectively. Then each time the literal is
- evaluated, a new object is created as if by the expression new
- RegExp(Pattern,
- Flags)
- where RegExp is the standard built-in constructor with that name.
- The newly constructed object becomes the value of the
- RegularExpressionLiteral.
- If the call to new RegExp
- would generate an error as specified in 15.10.4.1, the error must be
- treated as an early error (Clause 16).
- Certain
- ECMAScript statements (empty statement, variable statement,
- expression statement, do-while
- statement, continue
- statement, break
- statement, return
- statement, and throw
- statement) must be terminated with semicolons. Such semicolons may
- always appear explicitly in the source text. For convenience,
- however, such semicolons may be omitted from the source text in
- certain situations. These situations are described by saying that
- semicolons are automatically inserted into the source code token
- stream in those situations.
- There - are three basic rules of semicolon insertion:
-- When, - as the program is parsed from left to right, a token (called the - offending token) - is encountered that is not allowed by any production of the - grammar, then a semicolon is automatically inserted before the - offending token if one or more of the following conditions is - true:
-- The - offending token is separated from the previous token by at least - one LineTerminator.
-
- The
- offending token is }.
- When, - as the program is parsed from left to right, the end of the input - stream of tokens is encountered and the parser is unable to parse - the input token stream as a single complete ECMAScript Program, - then a semicolon is automatically inserted at the end of the - input stream.
-- When, - as the program is parsed from left to right, a token is - encountered that is allowed by some production of the grammar, - but the production is a restricted - production and the - token would be the first token for a terminal or nonterminal - immediately following the annotation “[no LineTerminator here]” - within the restricted production - (and therefore such a token is called a restricted token), and - the restricted token is separated from the previous token by at - least one LineTerminator, - then a semicolon is automatically inserted before the restricted - token.
-
- However,
- there is an additional overriding condition on the preceding rules:
- a semicolon is never inserted automatically if the semicolon would
- then be parsed as an empty statement or if that semicolon would
- become one of the two semicolons in the header of a for
- statement (see 12.6.3).
- -
NOTE The following - are the only restricted productions in the grammar:
-- PostfixExpression :
-
- LeftHandSideExpression
- [no LineTerminator here]
- ++
LeftHandSideExpression
- [no LineTerminator here]
- --
- ContinueStatement :
-
- continue [no LineTerminator here] Identifier;
- BreakStatement :
-
- break [no LineTerminator here] Identifier;
- ReturnStatement :
-
- return [no LineTerminator here] Expression;
- ThrowStatement - :
-
- throw [no LineTerminator here] Expression;
- The - practical effect of these restricted productions is as follows:
-
- When
- a ++
- or --
- token is encountered where the parser would treat it as a postfix
- operator, and at least one LineTerminator
- occurred between the preceding token and the ++
- or --
- token, then a semicolon is automatically inserted before the ++
- or --
- token.
- When
- a continue,
- break,
- return,
- or throw
- token is encountered and a LineTerminator
- is encountered before the next token, a semicolon is automatically
- inserted after the continue,
- break,
- return,
- or throw
- token.
- The - resulting practical advice to ECMAScript programmers is:
-
- A
- postfix ++
- or --
- operator should appear on the same line as its operand.
- An
- Expression
- in a return
- or throw
- statement should start on the same line as the return
- or throw
- token.
- A
- Identifier
- in a break
- or continue
- statement should be on the same line as the break
- or continue
- token.
- The - source
-
- {
- 1 2 } 3
is - not a valid sentence in the ECMAScript grammar, even with the - automatic semicolon insertion rules. In contrast, the source
-
- {
- 1
2 } 3
is - also not a valid ECMAScript sentence, but is transformed by - automatic semicolon insertion into the following:
-
- {
- 1
;2 ;} 3;
- which - is a valid ECMAScript sentence.
-The - source
-
- for
- (a; b
)
- is
- not a valid ECMAScript sentence and is not altered by automatic
- semicolon insertion because the semicolon is needed for the header
- of a for
- statement. Automatic semicolon insertion never inserts one of the
- two semicolons in the header of a for
- statement.
The - source
-return
a
- + b
is - transformed by automatic semicolon insertion into the following:
-
- return;
a
- + b;
NOTE The
- expression a + b
- is not treated as a value to be returned by the return
- statement, because a LineTerminator
- separates it from the token return.
The - source
-
- a
- = b
++c
is - transformed by automatic semicolon insertion into the following:
-
- a
- = b;
++c;
NOTE The
- token ++ is not
- treated as a postfix operator applying to the variable b,
- because a LineTerminator
- occurs between b
- and ++.
The - source
-
- if
- (a > b)
else c = d
- is
- not a valid ECMAScript sentence and is not altered by automatic
- semicolon insertion before the else
- token, even though no production of the grammar applies at that
- point, because an automatically inserted semicolon would then be
- parsed as an empty statement.
The - source
-
- a
- = b + c
(d + e).print()
is - not transformed by automatic semicolon insertion, because the - parenthesised expression that begins the second line can be - interpreted as an argument list for a function call:
-
- a
- = b + c(d + e).print()
- In - the circumstance that an assignment statement must begin with a left - parenthesis, it is a good idea for the programmer to provide an - explicit semicolon at the end of the preceding statement rather than - to rely on automatic semicolon insertion.
-- Algorithms - within this specification manipulate values each of which has an - associated type. The possible value types are exactly those defined - in this clause. Types are further subclassified into ECMAScript - language types and specification types.
-- An - ECMAScript language type corresponds to values that are directly - manipulated by an ECMAScript programmer using the ECMAScript - language. The ECMAScript language types are -Undefined, -Null, -Boolean, -String, -Number, -and -Object.
-- A - specification type corresponds to meta-values that are used within - algorithms to describe the semantics of ECMAScript language - constructs and ECMAScript language types. The specification types - are -Reference, -List, -Completion, -Property Descriptor, -Property Identifier, -Lexical Environment, -and -Environment Record. - Specification type values are specification artefacts that do not - necessarily correspond to any specific entity within an ECMAScript - implementation. Specification type values may be used to describe - intermediate results of ECMAScript expression evaluation but such - values cannot be stored as properties of objects or values of - ECMAScript language variables.
-- Within - this specification, the notation “Type(x)” - is used as shorthand for “the - type of x” - where “type” refers - to the ECMAScript language and specification types defined in this - clause.
-- The - Undefined type has exactly one value, called undefined. Any - variable that has not been assigned a value has the value undefined.
-- The - Null type has exactly one value, called null.
-- The - Boolean type represents a logical entity having two values, called - true and false.
-- The - String type is the set of all finite ordered sequences of zero or - more 16-bit unsigned integer values (“elements”). The String - type is generally used to represent textual data in a running - ECMAScript program, in which case each element in the String is - treated as a code unit value (see Clause 6). Each element is - regarded as occupying a position within the sequence. These - positions are indexed with nonnegative integers. The first element - (if any) is at position 0, the next element (if any) at position 1, - and so on. The length of a String is the number of elements (i.e., - 16-bit values) within it. The empty String has length zero and - therefore contains no elements.
-- When - a String contains actual textual data, each element is considered to - be a single UTF-16 code unit. Whether or not this is the actual - storage format of a String, the characters within a String are - numbered by their initial code unit element position as though they - were represented using UTF-16. All operations on Strings (except as - otherwise stated) treat them as sequences of undifferentiated 16-bit - unsigned integers; they do not ensure the resulting String is in - normalised form, nor do they ensure language-sensitive results.
-NOTE The - rationale behind this design was to keep the implementation of - Strings as simple and high-performing as possible. The intent is - that textual data coming into the execution environment from outside - (e.g., user input, text read from a file or received over the - network, etc.) be converted to Unicode Normalised Form C before the - running program sees it. Usually this would occur at the same time - incoming text is converted from its original character encoding to - Unicode (and would impose no additional overhead). Since it is - recommended that ECMAScript source code be in Normalised Form C, - string literals are guaranteed to be normalised (if source text is - guaranteed to be normalised), as long as they do not contain any - Unicode escape sequences.
-
- The
- Number type has exactly 18437736874454810627
- (that is, 264−253+3)
- values, representing the double-precision 64-bit format IEEE 754
- values as specified in the IEEE Standard for Binary Floating-Point
- Arithmetic, except that the 9007199254740990
- (that is, 253−2)
- distinct “Not-a-Number” values of the IEEE Standard are
- represented in ECMAScript as a single special NaN value.
- (Note that the NaN value is produced by the program
- expression NaN.)
- In some implementations, external code might be able to detect a
- difference between various Not-a-Number values, but such behaviour
- is implementation-dependent; to ECMAScript code, all NaN values are
- indistinguishable from each other.
- There
- are two other special values, called positive Infinity and
- negative Infinity. For brevity, these values are also
- referred to for expository purposes by the symbols +∞
- and −∞, respectively.
- (Note that these two infinite Number values are produced by the
- program expressions +Infinity
- (or simply Infinity)
- and -Infinity.)
- The - other 18437736874454810624 - (that is, 264−253) - values are called the finite numbers. Half of these are positive - numbers and half are negative numbers; for every finite positive - Number value there is a corresponding negative value having the same - magnitude.
-
- Note
- that there is both a positive zero and a negative zero.
- For brevity, these values are also referred to for expository
- purposes by the symbols +0
- and −0,
- respectively. (Note that these two different zero Number values are
- produced by the program expressions +0
- (or simply 0) and
- -0.)
- The - 18437736874454810622 - (that is, 264−253−2) - finite nonzero values are of two kinds:
-- 18428729675200069632 - (that is, 264−254) - of them are normalised, having the form
-- s - × m × - 2e
-- where - s is +1 - or −1, - m is a positive - integer less than 253 - but not less than 252, - and e is an - integer ranging from −1074 - to 971, inclusive.
-- The - remaining 9007199254740990 - (that is, 253−2) - values are denormalised, having the form
-- s - × m × - 2e
-- where - s - is +1 or −1, - m is a positive - integer less than 252, - and e is −1074.
-
- Note
- that all the positive and negative integers whose magnitude is no
- greater than 253
- are representable in the Number type (indeed, the integer 0
- has two representations, +0
- and -0).
- A - finite number has an odd significand if it is nonzero and the - integer m used to - express it (in one of the two forms shown above) is odd. Otherwise, - it has an even significand.
-- In - this specification, the phrase “the - Number value for x” - where x represents - an exact nonzero real mathematical quantity (which might even be an - irrational number such as π) - means a Number value chosen in the following manner. Consider the - set of all finite values of the Number type, with −0 - removed and with two additional values added to it that are not - representable in the Number type, namely 21024 - (which is +1 × - 253 - × - 2971) - and −21024 - (which is −1 - × - 253 - × - 2971). - Choose the member of this set that is closest in value to x. - If two values of the set are equally close, then the one with an - even significand is chosen; for this purpose, the two extra values - 21024 - and −21024 - are considered to have even significands. Finally, if 21024 - was chosen, replace it with +∞; - if −21024 - was chosen, replace it with −∞; - if +0 was chosen, - replace it with −0 - if and only if x - is less than zero; any other chosen value is used unchanged. The - result is the Number value for x. - (This procedure corresponds exactly to the behaviour of the IEEE 754 - “round to nearest” mode.)
-- Some - ECMAScript operators deal only with integers in the range −231 - through 231−1, - inclusive, or in the range 0 - through 232−1, - inclusive. These operators accept any value of the Number type but - first convert each such value to one of 232 - integer values. See the descriptions of the ToInt32 and ToUint32 - operators in 9.5 and 9.6, respectively.
-- An - Object is a collection of properties. Each property is either - a named data property, a named accessor property, or an internal - property:
-- A - named data property associates a name with an ECMAScript - language value and a set of Boolean attributes.
-- A - named accessor property associates a name with one or two - accessor functions, and a set of Boolean attributes. The accessor - functions are used to store or retrieve an ECMAScript language - value that is associated with the property. -
-- An - internal property has no name and is not directly accessible - via ECMAScript language operators. Internal properties exist purely - for specification purposes. -
-- There - are two kinds of access for named (non-internal) properties: get and put, corresponding to retrieval and assignment, - respectively.
-- Attributes - are used in this specification to define and explain the state of - named properties. A named data property associates a name with the - attributes listed in Table 5
-|
- - Attribute - Name - |
-
- - Value - Domain - |
-
- - Description - |
-
|
- - [[Value]] - - - |
-
- - Any - ECMAScript language type - |
-
- - The - value retrieved by reading the property. - |
-
|
- - [[Writable]] - - - |
-
- - Boolean - |
-
- - If - false, attempts by ECMAScript code to change the - property’s [[Value]] attribute using [[Put]] will not succeed. - |
-
|
- - [[Enumerable]] - |
-
- - Boolean - |
-
- - If - true, the property will be enumerated by a for-in - enumeration (see 12.6.4). Otherwise, the property is said to be - non-enumerable. - |
-
|
- - [[Configurable]] - |
-
- - Boolean - |
-
- - If - false, attempts to delete the property, change the - property to be an accessor property, or change its attributes - (other than [[Value]]) will fail. - |
-
- A - named accessor property associates a name with the attributes listed - in Table 6.
-|
- - Attribute - Name - |
-
- - Value - Domain - |
-
- - Description - |
-
|
- - [[Get]] - |
-
- - Object - or Undefined - |
-
- - If - the value is an Object it must be a function Object. The - function’s [[Call]] internal method (8.6.2) is called with an - empty arguments list to return the property value each time a - get access of the property is performed. - |
-
|
- - [[Set]] - |
-
- - Object - or Undefined - |
-
- - If - the value is an Object it must be a function Object. The - function’s [[Call]] internal method (8.6.2) is called with an - arguments list containing the assigned value as its sole - argument each time a set access of the property is performed. - The effect of a property's [[Set]] internal method may, but is - not required to, have an effect on the value returned by - subsequent calls to the property's [[Get]] internal method. - |
-
|
- - [[Enumerable]] - |
-
- - Boolean - |
-
- - If - true, the property is to be enumerated by a for-in - enumeration (see 12.6.4). Otherwise, the property is said to be - non-enumerable. - |
-
|
- - [[Configurable]] - |
-
- - Boolean - |
-
- - If - false, attempts to delete the property, change the - property to be a data property, or change its attributes will - fail. - |
-
- If - the value of an attribute is not explicitly specified by this - specification for a named property, the default value defined in - Table 7 is used.
-|
- - Attribute - Name - |
-
- - Default - Value - |
-
|
- - [[Value]] - |
-
- - undefined - |
-
|
- - [[Get]] - |
-
- - undefined - |
-
|
- - [[Set]] - |
-
- - undefined - |
-
|
- - [[Writable]] - |
-
- - false - |
-
|
- - [[Enumerable]] - |
-
- - false - |
-
|
- - [[Configurable]] - |
-
- - false - |
-
- This - specification uses various internal properties to define the - semantics of object values. These internal properties are not part - of the ECMAScript language. They are defined by this specification - purely for expository purposes. An implementation of ECMAScript must - behave as if it produced and operated upon internal properties in - the manner described here. The names of internal properties are - enclosed in double square brackets [[ ]]. When an algorithm uses an - internal property of an object and the object does not implement the - indicated internal property, a TypeError exception is thrown.
-- The - Table 8 summarises the internal properties used by this - specification that are applicable to all ECMAScript objects. The - Table 9 summarises the internal properties used by this - specification that are only applicable to some ECMAScript objects. - The descriptions in these tables indicates their behaviour for - native ECMAScript objects, unless stated otherwise in this document - for particular kinds of native ECMAScript objects. Host objects may - support these internal properties with any implementation-dependent - behaviour as long as it is consistent with the specific host object - restrictions stated in this document.
-- The - “Value Type Domain” columns of the following tables define the - types of values associated with internal properties. The type names - refer to the types defined in Clause 8 augmented by the following - additional names. “any” means the value may be any - ECMAScript language type. “primitive” means Undefined, - Null, Boolean, String, or Number. “SpecOp” means the - internal property is an internal method, an implementation provided - procedure defined by an abstract operation specification. “SpecOp” - is followed by a list of descriptive parameter names. If a parameter - name is the same as a type name then the name describes the type of - the parameter. If a “SpecOp” returns a value, its parameter list - is followed by the symbol “→” and the type of the returned - value.
-|
- - Internal - Property - |
-
- - Value - Type Domain - |
-
- - Description - |
-
|
- - [[Prototype]] - |
-
- - Object - or Null - |
-
- - The - prototype of this object. - |
-
|
- - [[Class]] - |
-
- - String - |
-
- - A - String value indicating a specification defined classification - of objects. - |
-
|
- - [[Extensible]] - |
-
- - Boolean - |
-
- - If - true, own properties may be added to the object. - |
-
|
- - [[Get]] - |
-
- - SpecOp(propertyName) - → any - |
-
- - Returns - the value of the named property. - |
-
|
- - [[GetOwnProperty]] - |
-
- - SpecOp - (propertyName) → -- Undefinedor - Property Descriptor - |
-
- - Returns - the Property Descriptor of the named own property of this - object, or undefined if absent. - |
-
|
- - [[GetProperty]] - |
-
- - SpecOp - (propertyName) → -- Undefinedor - Property Descriptor - |
-
- - Returns - the fully populated Property Descriptor of the named property of - this object, or undefined if absent. - |
-
|
- - [[Put]] - |
-
- - SpecOp - (propertyName, any, Boolean) - |
-
- - Sets - the specified named property to the value of the second - parameter. The flag controls failure handling. - |
-
|
- - [[CanPut]] - |
-
- - SpecOp - (propertyName) → - Boolean - |
-
- - Returns - a Boolean value indicating whether a [[Put]] operation with - PropertyName can be performed. - |
-
|
- - [[HasProperty]] - |
-
- - SpecOp - (propertyName) → - Boolean - |
-
- - Returns - a Boolean value indicating whether the object already has a - property with the given name. - |
-
|
- - [[Delete]] - |
-
- - SpecOp - (propertyName, Boolean) → - Boolean - |
-
- - Removes - the specified named own property from the object. The flag - controls failure handling. - |
-
|
- - [[DefaultValue]] - |
-
- - SpecOp - (Hint) → - primitive - |
-
- - Hint - is a String. Returns a default value for the object. - |
-
|
- - [[DefineOwnProperty]] - |
-
- - SpecOp - (propertyName, PropertyDescriptor, Boolean) - → Boolean - |
-
- - Creates - or alters the named own property to have the state described by - a Property Descriptor. The flag controls failure handling. - |
-
- Every - object (including host objects) must implement all of the internal - properties listed in Table 8. However, the [[DefaultValue]] internal - method may, for some objects, simply throw a TypeError - exception.
-- All - objects have an internal property called [[Prototype]]. The value of - this property is either null or an object and is used for - implementing inheritance. Whether or not a native object can have a - host object as its [[Prototype]] depends on the implementation. - Every [[Prototype]] chain must have finite length (that is, starting - from any object, recursively accessing the [[Prototype]] internal - property must eventually lead to a null value). Named data - properties of the [[Prototype]] object are inherited (are visible as - properties of the child object) for the purposes of get access, but - not for put access. Named accessor properties are inherited for both - get access and put access.
-- Every - ECMAScript object has a Boolean-valued [[Extensible]] internal - property that controls whether or not named properties may be added - to the object. If the value of the [[Extensible]] internal property - is false then additional named properties may not be added to - the object. In addition, if [[Extensible]] is false the - value of the [[Class]] and [[Prototype]] internal properties of the - object may not be modified. Once the value of an [[Extensible]] - internal property has been set to false it may not be - subsequently changed to true.
-NOTE This - specification defines no ECMAScript language operators or built-in - functions that permit a program to modify an object’s [[Class]] or - [[Prototype]] internal properties or to change the value of - [[Extensible]] from false to true. Implementation - specific extensions that modify [[Class]], [[Prototype]] or - [[Extensible]] must not violate the invariants defined in the - preceding paragraph.
-
- The
- value of the [[Class]] internal property is defined by this
- specification for every kind of built-in object. The value of the
- [[Class]] internal property of a host object may be any String value
- except one of "Arguments",
- "Array",
- "Boolean",
- "Date",
- "Error",
- "Function",
- "JSON",
- "Math",
- "Number",
- "Object",
- "RegExp",
- and "String".
- The value of a [[Class]] internal property is used internally to
- distinguish different kinds of objects. Note that this specification
- does not provide any means for a program to access that value except
- through Object.prototype.toString
- (see 15.2.4.2).
- Unless - otherwise specified, the common internal methods of native - ECMAScript objects behave as described in 8.12. Array objects have a - slightly different implementation of the [[DefineOwnProperty]] - internal method (see 15.4.5.1) and String objects have a slightly - different implementation of the [[GetOwnProperty]] internal method - (see 15.5.5.2). Arguments objects (10.6) have different - implementations of [[Get]], [[GetOwnProperty]], - [[DefineOwnProperty]], and [[Delete]]. Function objects (15.3) have - a different implementation of [[Get]].
-- Host - objects may implement these internal methods in any manner unless - specified otherwise; for example, one possibility is that [[Get]] - and [[Put]] for a particular host object indeed fetch and store - property values but [[HasProperty]] always generates false. - However, if any specified manipulation of a host object's internal - properties is not supported by an implementation, that manipulation - must throw a TypeError exception when attempted.
-- The - [[GetOwnProperty]] internal method of a host object must conform to - the following invariants for each property of the host object:
-- If a - property is described as a data property and it may return - different values over time, then either or both of the [[Writable]] - and [[Configurable] attributes must be true even if no - mechanism to change the value is exposed via the other internal - methods.
-- If a - property is described as a data property and its [[Writable]] and - [[Configurable]] are both false, then the SameValue - (according to 9.12) must be returned for the [[Value]] attribute of - the property on all calls to [[GetOwnProperty]].
-- If - the attributes other than [[Writable]] may change over time or if - the property might disappear, then the [[Configurable]] attribute - must be true.
-- If - the [[Writable]] attribute may change from false to true, - then the [[Configurable]] attribute must be true.
-- If - the value of the host object’s [[Extensible]] internal property - is has been observed by ECMAScript code to be false, then if - a call to [[GetOwnProperty]] describes a property as non-existent - all subsequent calls must also describe that property as - non-existent.
-- The - [[DefineOwnProperty]] internal method of a host object must not - permit the addition of a new property to a host object if the - [[Extensible]] internal property of that host object has been - observed by ECMAScript code to be false. -
-- If - the [[Extensible]] internal property of that host object has been - observed by ECMAScript code to be false then it must not - subsequently become true.
-|
- - Internal - Property - |
-
- - Value - Type Domain - |
-
- - Description - |
-
|
- - [[PrimitiveValue]] - |
-
- - primitive - |
-
- - Internal - state information associated with this object. Of the standard - built-in ECMAScript objects, only Boolean, Date, Number, and - String objects implement [[PrimitiveValue]]. - |
-
|
- - [[Construct]] - |
- - - | -
-
- Creates
- an object. Invoked via the |
-
|
- - [[Call]] - |
- - - | -
- - Executes - code associated with the object. Invoked via a function call - expression. The arguments to the SpecOp are a this object and a - list containing the arguments passed to the function call - expression. Objects that implement this internal method are - callable. Only callable objects that are host objects may - return Reference values. - |
-
|
- - [[HasInstance]] - |
-
- - SpecOp(any) - → - Boolean - |
-
- - Returns - a Boolean value indicating whether the argument is likely an - Object that was constructed by this object. Of the standard - built-in ECMAScript objects, only Function objects implement - [[HasInstance]]. - |
-
|
- - [[Scope]] - |
- - - | -
- - A - lexical environment that defines the environment in which a - Function object is executed. Of the standard built-in ECMAScript - objects, only Function objects implement [[Scope]]. - |
-
|
- - [[FormalParameters]] - |
-
- - List - of Strings - |
-
- - A - possibly empty List containing the identifier Strings of a - Function’s FormalParameterList. - Of the standard built-in ECMAScript objects, only Function - objects implement [[FormalParameterList]]. - |
-
|
- - [[Code]] - |
-
- - ECMAScript - code - |
-
- - The - ECMAScript code of a function. Of the standard built-in - ECMAScript objects, only Function objects implement [[Code]]. - |
-
|
- - [[TargetFunction]] - |
-
- - Object - |
-
- - The - target function of a function object created using the standard - built-in Function.prototype.bind method. Only ECMAScript objects - created using Function.prototype.bind have a [[TargetFunction]] - internal property. - |
-
|
- - [[BoundThis]] - |
-
- - any - |
-
- - The - pre-bound this value of a function Object created using the - standard built-in Function.prototype.bind method. Only - ECMAScript objects created using Function.prototype.bind have a - [[BoundThis]] internal property. - |
-
|
- - [[BoundArguments]] - |
-
- - List - of any - |
-
- - The - pre-bound argument values of a function Object created using the - standard built-in Function.prototype.bind method. Only - ECMAScript objects created using Function.prototype.bind have a - [[BoundArguments]] internal property. - |
-
|
- - [[Match]] - |
-
- - SpecOp(String, - index) → - MatchResult - |
-
- - Tests - for a regular expression match and returns a MatchResult value - (see 15.10.2.1). Of the standard built-in ECMAScript objects, - only RegExp objects implement [[Match]]. - |
-
|
- - [[ParameterMap]] - |
-
- - Object - |
-
- - Provides - a mapping between the properties of an arguments object (see - 10.6) and the formal parameters of the associated function. Only - ECMAScript objects that are arguments objects have a - [[ParameterMap]] internal property. - |
-
- The
- Reference type is used to explain the behaviour of such operators as
- delete, typeof,
- and the assignment operators. For example, the left-hand operand of
- an assignment is expected to produce a reference. The behaviour of
- assignment could, instead, be explained entirely in terms of a case
- analysis on the syntactic form of the left-hand operand of an
- assignment operator, but for one difficulty: function calls are
- permitted to return references. This possibility is admitted purely
- for the sake of host objects. No built-in ECMAScript function
- defined by this specification returns a reference and there is no
- provision for a user-defined function to return a reference.
- (Another reason not to use a syntactic case analysis is that it
- would be lengthy and awkward, affecting many parts of the
- specification.)
- A - Reference is a resolved name binding. A Reference consists of - three components, the base value, the referenced - name and the Boolean valued strict - reference flag. The base value is either undefined, - an Object, a Boolean, a String, a Number, or an environment record - (10.2.1). A base value of undefined indicates that the - reference could not be resolved to a binding. The referenced name is - a String.
-- The - following abstract operations are used in this specification to - access the components of references:
-GetBase(V). - Returns the base value component of the reference V.
-GetReferencedName(V). - Returns the referenced name component of the reference V.
-IsStrictReference(V). - Returns the strict reference component of the reference V.
-HasPrimitiveBase(V). - Returns true if the base value is a Boolean, String, or - Number.
-IsPropertyReference(V). - Returns true if either the base value is an object or - HasPrimitiveBase(V) is true; otherwise returns false.
-IsUnresolvableReference(V). - Returns true if the base value is undefined and false - otherwise.
-- The - following abstract operations are used in this specification to - operate on references:
-- Let - base be the result of calling GetBase(V).
-- If - IsUnresolvableReference(V), throw a ReferenceError - exception.
-- If - IsPropertyReference(V), then
-- If - HasPrimitiveBase(V) is false, then let get be - the [[Get]] internal method of base, otherwise let get - be the special [[Get]] internal method defined below.
-- Return - the result of calling the get internal method using base as its this value, and passing GetReferencedName(V) - for the argument.
-- Else, - base must be an environment record.
-- Return - the result of calling the GetBindingValue (see 10.2.1) concrete - method of base passing GetReferencedName(V) and - IsStrictReference(V) as arguments.
-- The - following [[Get]] internal method is used by GetValue when V - is a property reference with a primitive base value. It is called - using base as its - this value and with property P - as its argument. The following steps are taken:
-- Let - O be ToObject(base).
-- Let - desc be the result of calling the [[GetProperty]] internal - method of O with property name P.
-- If - desc is undefined, return undefined.
-- If - IsDataDescriptor(desc) is true, return - desc.[[Value]].
-- Otherwise, - IsAccessorDescriptor(desc) must be true so, let - getter be desc.[[Get]].
-- If - getter is undefined, return undefined.
-- Return - the result calling the [[Call]] internal method of getter providing base as the this value and providing no - arguments.
-NOTE The - object that may be created in step 1 is not accessible outside of - the above method. An implementation might choose to avoid the actual - creation of the object. The only situation where such an actual - property access that uses this internal method can have visible - effect is when it invokes an accessor function.
-- If - Type(V) is not Reference, - throw a ReferenceError - exception.
-- Let - base be the result of calling GetBase(V).
-- If - IsUnresolvableReference(V), then
-- If - IsStrictReference(V) is true, then
-- Throw - ReferenceError exception.
-- Call - the [[Put]] internal method of the global object, passing - GetReferencedName(V) for the property name, W for - the value, and false for the Throw flag.
-- Else - if IsPropertyReference(V), then
-- If - HasPrimitiveBase(V) is false, then let put be - the [[Put]] internal method of base, otherwise let put - be the special [[Put]] internal method defined below.
-- Call - the put internal method using base as its this - value, and passing GetReferencedName(V) for the - property name, W for the value, and IsStrictReference(V) - for the Throw flag.
-- Else - base must be a reference whose base is an environment record. So,
-- Call - the SetMutableBinding (10.2.1) concrete method of base, - passing GetReferencedName(V), W, and - IsStrictReference(V) as arguments.
-- Return.
-- The - following [[Put]] internal method is used by PutValue when V - is a property reference with a primitive base value. It is called - using base as its - this value and with property P, - value W, and - Boolean flag Throw - as arguments. The following steps are taken:
-- Let - O be ToObject(base).
-- If - the result of calling the [[CanPut]] internal method of O - with argument P is false, then
-- If - Throw is true, then throw a TypeError - exception.
-- Else - return.
-- Let - ownDesc be the result of calling the [[GetOwnProperty]] - internal method of O with argument P.
-- If - IsDataDescriptor(ownDesc) is true, then
-- If - Throw is true, then throw a TypeError - exception.
-- Else - Return.
-- Let - desc be the result of calling the [[GetProperty]] internal - method of O with argument P. This may be either an - own or inherited accessor property descriptor - or an inherited data property descriptor.
-- If - IsAccessorDescriptor(desc) is true, then
-- Let - setter be desc.[[Set]] which cannot be undefined.
-- Call - the [[Call]] internal method of setter providing base - as the this value and an argument list containing only W.
-- Else, - this is a request to create an own property on the transient object - O
-- If - Throw is true, then throw a TypeError - exception.
-- Return.
-NOTE The - object that may be created in step 1 is not accessible outside of - the above method. An implementation might choose to avoid the - actual creation of that transient object. The only situations where - such an actual property assignment that uses this internal method - can have visible effect are when it either invokes an accessor - function or is in violation of a Throw - predicated error check. When Throw - is true any property assignment that would create a new - property on the transient object throws an error.
-
- The
- List type is used to explain the evaluation of argument lists (see
- 11.2.4) in new
- expressions, in function calls, and in other algorithms where a
- simple list of values is needed. Values of the List type are simply
- ordered sequences of values. These sequences may be of any length.
- The
- Completion type is used to explain the behaviour of statements
- (break, continue,
- return and throw)
- that perform nonlocal transfers of control. Values of the Completion
- type are triples of the form (type, value, target),
- where type is one of normal, break, continue,
- return, or throw, value is any ECMAScript
- language value or empty, and target is any ECMAScript
- identifier or empty.
- The - term “abrupt completion” refers to any completion with a type - other than normal.
-- The - Property Descriptor type is used to explain the manipulation and - reification of named property attributes. Values of the Property - Descriptor type are records composed of named fields where each - field’s name is an attribute name and its value is a corresponding - attribute value as specified in 8.6.1. In addition, any field may be - present or absent.
-- Property - Descriptor values may be further classified as data property - descriptors and accessor property descriptors based upon the - existence or use of certain fields. A data property descriptor is - one that includes any fields named either [[Value]] or [[Writable]]. - An accessor property descriptor is one that includes any fields - named either [[Get]] or [[Set]]. Any property descriptor may have - fields named [[Enumerable]] and [[Configurable]]. A Property - Descriptor value may not be both a data property descriptor and an - accessor property descriptor; however, it may be neither. A generic - property descriptor is a Property Descriptor value that is neither a - data property descriptor nor an accessor property descriptor. - A fully populated property descriptor is one that is either an - accessor property descriptor or a data property descriptor and that - has all of the fields that correspond to the property attributes - defined in either 8.6.1 Table 5 or Table 6.
-- For - notational convenience within this specification, an object - literal-like syntax can be used to define a property descriptor - value. For example, Property Descriptor {[[Value]]: 42, - [[Writable]]: false, [[Configurable]]: true} defines a - data property descriptor. Field name order is not significant. Any - fields that are not explicitly listed are considered to be absent.
-- In - specification text and algorithms, dot notation may be used to refer - to a specific field of a Property Descriptor. For example, if D is a - property descriptor then D.[[Value]] is shorthand for “the field - of D named [[Value]]”.
-- The - Property Identifier type is used to associate a property name with a - Property Descriptor. Values of the Property Identifier type are - pairs of the form (name, descriptor), where name is a String and - descriptor is a Property Descriptor value. -
-- The - following abstract operations are used in this specification to - operate upon Property Descriptor values:
-- When - the abstract operation IsAccessorDescriptor is called with property descriptor Desc, - the following steps are taken:
-- If - Desc - is undefined, - then return false.
-- If - both Desc.[[Get]] - and Desc.[[Set]] - are absent, then return false.
-- Return - true.
-- When - the abstract operation IsDataDescriptor is called with property descriptor Desc, - the following steps are taken:
-- If - Desc - is undefined, - then return false.
-- If - both Desc.[[Value]] - and Desc.[[Writable]] - are absent, then return false.
-- Return - true.
-- When - the abstract operation IsGenericDescriptor is called with property descriptor Desc, - the following steps are taken:
-- If - Desc - is undefined, - then return false.
-- If - IsAccessorDescriptor(Desc) - and IsDataDescriptor(Desc) - are both false, - then return true.
-- Return - false.
-- When - the abstract operation FromPropertyDescriptor is called with - property descriptor Desc, - the following steps are taken:
-- The - following algorithm assumes that Desc is a fully populated Property Descriptor, such as that - returned from [[GetOwnProperty]] (see 8.12.1).
-- If - Desc - is undefined, - then return undefined.
-- Let - obj be - the result of creating a new object as if by the expression new - Object() where - Object is the - standard built-in constructor with that name.
-- If - IsDataDescriptor(Desc) - is true, - then -
-
- Call
- the [[DefineOwnProperty]] internal method of obj
- with arguments "value",
- Property Descriptor {[[Value]]: Desc.[[Value]],
- [[Writable]]: true,
- [[Enumerable]]: true,
- [[Configurable]]: true},
- and false.
-
-
- Call
- the [[DefineOwnProperty]] internal method of obj
- with arguments "writable",
- Property Descriptor {[[Value]]: Desc.[[Writable]],
- [[Writable]]: true,
- [[Enumerable]]: true,
- [[Configurable]]: true},
- and false.
-
-
- Else, - IsAccessorDescriptor(Desc) - must be true, - so
-
- Call
- the [[DefineOwnProperty]] internal method of obj
- with arguments "get",
- Property Descriptor {[[Value]]: Desc.[[Get]],
- [[Writable]]: true,
- [[Enumerable]]: true,
- [[Configurable]]: true},
- and false.
- Call
- the [[DefineOwnProperty]] internal method of obj
- with arguments "set",
- Property Descriptor {[[Value]]: Desc.[[Set]],
- [[Writable]]: true,
- [[Enumerable]]: true,
- [[Configurable]]: true},
- and false.
-
-
- Call
- the [[DefineOwnProperty]] internal method of obj
- with arguments "enumerable",
- Property Descriptor {[[Value]]: Desc.[[Enumerable]],
- [[Writable]]: true,
- [[Enumerable]]: true,
- [[Configurable]]: true},
- and false.
-
-
- Call
- the [[DefineOwnProperty]] internal method of obj
- with arguments "configurable",
- Property Descriptor {[[Value]]: Desc.[[Configurable]],
- [[Writable]]: true,
- [[Enumerable]]: true,
- [[Configurable]]: true},
- and false.
-
-
- Return - obj.
-- When - the abstract operation ToPropertyDescriptor is called with object - Desc, the - following steps are taken:
-- If - Type(Obj) is not Object throw a TypeError exception.
-- Let - desc be the result of creating a new Property Descriptor - that initially has no fields.
-
- If
- the result of calling the [[HasProperty]] internal method of Obj
- with argument "enumerable"
- is true, then
- Let
- enum be the result of calling the [[Get]] internal method
- of Obj with "enumerable".
- Set - the [[Enumerable]] field of desc to ToBoolean(enum).
-
- If
- the result of calling the [[HasProperty]] internal method of Obj
- with argument "configurable"
- is true, then
- Let
- conf be the result of calling the [[Get]] internal method
- of Obj with argument "configurable".
- Set - the [[Configurable]] field of desc to ToBoolean(conf).
-
- If
- the result of calling the [[HasProperty]] internal method of Obj
- with argument "value"
- is true, then
- Let
- value be the result of calling the [[Get]] internal method
- of Obj with argument “value”.
- Set - the [[Value]] field of desc to value.
-
- If
- the result of calling the [[HasProperty]] internal method of Obj
- with argument "writable"
- is true, then
- Let
- writable be the result of calling the [[Get]] internal
- method of Obj with argument "writable".
- Set - the [[Writable]] field of desc to ToBoolean(writable).
-
- If
- the result of calling the [[HasProperty]] internal method of Obj
- with argument "get"
- is true, then
- Let
- getter be the result of calling the [[Get]] internal method
- of Obj with argument "get".
- If - IsCallable(getter) is false and getter is not - undefined, then throw a TypeError exception.
-- Set - the [[Get]] field of desc to getter.
-
- If
- the result of calling the [[HasProperty]] internal method of Obj
- with argument "set"
- is true, then
- Let
- setter be the result of calling the [[Get]] internal method
- of Obj with argument "set".
- If - IsCallable(setter) is false and setter is not - undefined, then throw a TypeError exception.
-- Set - the [[Set]] field of desc to setter.
-- If - either desc.[[Get]] or desc.[[Set]] are present, then
-- If - either desc.[[Value]] or desc.[[Writable]] are - present, then throw a TypeError exception.
-- Return - desc.
-- The - Lexical Environment and Environment Record types are used to explain - the behaviour of name resolution in nested functions and blocks. - These types and the operations upon them are defined in Clause 10.
-- In - the following algorithm descriptions, assume O - is a native ECMAScript object, P - is a String, Desc - is a Property Description record, and Throw - is a Boolean flag.
-- When - the [[GetOwnProperty]] internal method of O - is called with property name P, - the following steps are taken:
-- If - O doesn’t have an own property with name P, return - undefined.
-- Let - D be a newly created Property Descriptor with no fields.
-- Let - X be O’s own property named P.
-- If - X is a data property, then
-- Set - D.[[Value]] to the value of X’s [[Value]] - attribute.
-- Set - D.[[Writable]] to the value of X’s [[Writable]] - attribute
-- Else - X is an accessor property, so
-- Set - D.[[Get]] to the value of X’s [[Get]] attribute.
-- Set - D.[[Set]] to the value of X’s [[Set]] attribute.
-- Set - D.[[Enumerable]] to the value of X’s [[Enumerable]] - attribute.
-- Set - D.[[Configurable]] to the value of X’s - [[Configurable]] attribute.
-- Return - D.
-- However, - if O is a String - object it has a more elaborate [[GetOwnProperty]] internal method - defined in 15.5.5.2.
-- When - the [[GetProperty]] internal method of O - is called with property name P, - the following steps are taken:
-- Let - prop be the result of calling the [[GetOwnProperty]] - internal method of O with property name P.
-- If - prop is not undefined, return prop.
-- Let - proto be the value of the [[Prototype]] internal property of - O.
-- If - proto is null, return undefined.
-- Return - the result of calling the [[GetProperty]] internal method of proto - with argument P.
-- When - the [[Get]] internal method of O - is called with property name P, - the following steps are taken:
-- Let - desc be the result of calling the [[GetProperty]] internal - method of O with property name P.
-- If - desc is undefined, return undefined.
-- If - IsDataDescriptor(desc) is true, return - desc.[[Value]].
-- Otherwise, - IsAccessorDescriptor(desc) must be true so, let getter - be desc.[[Get]].
-- If - getter is undefined, return undefined.
-- Return - the result calling the [[Call]] internal method of getter providing O as the this value and providing no - arguments.
-- When - the [[CanPut]] internal method of O is called with property name P, - the following steps are taken:
-- Let - desc be the result of calling the [[GetOwnProperty]] - internal method of O with argument P.
-- If - desc is not undefined, then
-- If - IsAccessorDescriptor(desc) is true, then
-- If - desc.[[Set]] is undefined, then return false.
-- Else - return true.
-- Else, - desc must be a DataDescriptor so return the value of - desc.[[Writable]].
-- Let - proto be the [[Prototype]] internal property of O.
-- If - proto is null, then return the value of the - [[Extensible]] internal property of O.
-- Let - inherited be the result of calling the [[GetProperty]] - internal method of proto with property name P.
-- If - inherited is undefined, return the value of the - [[Extensible]] internal property of O.
-- If - IsAccessorDescriptor(inherited) is true, then
-- If - inherited.[[Set]] is undefined, then return false.
-- Else - return true.
-- Else, - inherited must be a DataDescriptor
-- If - the [[Extensible]] internal property of O is false, - return false.
-- Else - return the value of inherited.[[Writable]].
-Host - objects may define additional constraints upon [[Put]] operations. - If possible, host objects should not allow [[Put]] operations in - situations where this definition of [[CanPut]] returns false.
-- When - the [[Put]] internal method of O - is called with property P, - value V, and - Boolean flag Throw, - the following steps are taken:
-- If - the result of calling the [[CanPut]] internal method of O with - argument P is false, then
-- If - Throw is true, then throw a TypeError exception.
-- Else - return.
-- Let - ownDesc be the result of calling the [[GetOwnProperty]] - internal method of O with argument P.
-- If - IsDataDescriptor(ownDesc) is true, then
-- Let - valueDesc be the Property Descriptor {[[Value]]: V}.
-- Call - the [[DefineOwnProperty]] internal method of O passing P, - valueDesc, and Throw as arguments.
-- Return.
-- Let - desc be the result of calling the [[GetProperty]] internal - method of O with argument P. This may be either an - own or inherited accessor property descriptor - or an inherited data property descriptor.
-- If - IsAccessorDescriptor(desc) is true, then
-- Let - setter be desc.[[Set]] which cannot be undefined.
-- Call - the [[Call]] internal method of setter providing O as - the this value and providing V as the sole argument.
-- Else, - create a named data property named P on object O as - follows
-
- Let
- newDesc be the Property Descriptor
{[[Value]]: V,
- [[Writable]]: true, [[Enumerable]]: true,
- [[Configurable]]: true}.
- Call - the [[DefineOwnProperty]] internal method of O passing P, - newDesc, and Throw as arguments.
-- Return.
-- When - the [[HasProperty]] internal method of O - is called with property name P, - the following steps are taken:
-- Let - desc be the result of calling the [[GetProperty]] internal - method of O with property name P.
-- If - desc is undefined, then return false.
-- Else - return true.
-- When - the [[Delete]] internal method of O - is called with property name P and the Boolean flag Throw, - the following steps are taken:
-- Let - desc be the result of calling the [[GetOwnProperty]] - internal method of O with property name P.
-- If - desc is undefined, then return true.
-- If - desc.[[Configurable]] is true, then
-- Remove - the own property with name P from O.
-- Return - true.
-- Else - if Throw, then throw a TypeError exception.
-- Return - false.
-- When - the [[DefaultValue]] internal method of O - is called with hint String, the following steps are taken:
-
- Let
- toString be the result of calling the [[Get]] internal
- method of object O with argument "toString".
- If - IsCallable(toString) is true then,
-- Let - str be the result of calling the [[Call]] internal method - of toString, with O as the this value and an - empty argument list.
-- If - str is a primitive value, return str.
-
- Let
- valueOf be the result of calling the [[Get]] internal method
- of object O with argument "valueOf".
- If - IsCallable(valueOf) is true then, -
-- Let - val be the result of calling the [[Call]] internal method - of valueOf, with O as the this value and an empty - argument list.
-- If - val is a primitive value, return val.
-- Throw - a TypeError exception.
-- When - the [[DefaultValue]] internal method of O - is called with hint Number, the following steps are taken:
-
- Let
- valueOf be the result of calling the [[Get]] internal method
- of object O with argument "valueOf".
- If - IsCallable(valueOf) is true then,
-- Let - val be the result of calling the [[Call]] internal method - of valueOf, with O as the this value and an - empty argument list.
-- If - val is a primitive value, return val.
-
- Let
- toString be the result of calling the [[Get]] internal
- method of object O with argument "toString".
- If - IsCallable(toString) is true then,
-- Let - str be the result of calling the [[Call]] internal method - of toString, with O as the this value and an empty - argument list.
-- If - str is a primitive value, return str.
-- Throw - a TypeError exception.
-- When - the [[DefaultValue]] internal method of O - is called with no hint, then it behaves as if the hint were Number, - unless O is a Date - object (see 15.9.6), in which case it behaves as if the hint were - String.
-- The - above specification of [[DefaultValue]] for native objects can - return only primitive values. If a host object implements its own - [[DefaultValue]] internal method, it must ensure that its - [[DefaultValue]] internal method can return only primitive values.
-- In - the following algorithm, the term “Reject” means “If Throw - is true, then throw a TypeError exception, otherwise - return false”. The algorithm contains steps that test - various fields of the Property Descriptor Desc - for specific values. The fields that are tested in this manner need - not actually exist in Desc. - If a field is absent then its value is considered to be false.
-- When - the [[DefineOwnProperty]] internal method of O - is called with property name P, - property descriptor Desc, - and Boolean flag Throw, - the following steps are taken:
-- Let - current be the result of calling the [[GetOwnProperty]] - internal method of O with property name P.
-- Let - extensible be the value of the [[Extensible]] internal - property of O.
-- If - current is undefined and extensible is false, - then Reject.
-- If - current is undefined and extensible is true, - then
-- If - IsGenericDescriptor(Desc) or IsDataDescriptor(Desc) - is true, then
-- Create - an own data property named P of object O whose - [[Value]], [[Writable]], [[Enumerable]] and [[Configurable]] - attribute values are described by Desc. If the value of an - attribute field of Desc is absent, the attribute of the - newly created property is set to its default value.
-- Else, - Desc must be an - accessor Property Descriptor so,
-- Create - an own accessor property named P of object O whose - [[Get]], [[Set]], [[Enumerable]] and [[Configurable]] attribute - values are described by Desc. If the value of an attribute - field of Desc is absent, the attribute of the newly - created property is set to its default value.
-- Return - true.
-- Return - true, if every field in Desc is absent.
-- Return - true, if every field in Desc also occurs in current - and the value of every field in Desc is the same value as - the corresponding field in current when compared using the - SameValue algorithm (9.12).
-- If - the [[Configurable]] field of current is false then
- -- If - IsGenericDescriptor(Desc) is true, then no further - validation is required.
-- Else, - if IsDataDescriptor(current) and IsDataDescriptor(Desc) - have different results, then
-- Reject, - if the [[Configurable]] field of current is false. -
-- If - IsDataDescriptor(current) is true, then
-- Convert - the property named P of object O from a data - property to an accessor property. Preserve the existing values of - the converted property’s [[Configurable]] and [[Enumerable]] - attributes and set the rest of the property’s attributes to - their default values.
-- Else,
-- Convert - the property named P of object O from an accessor - property to a data property. Preserve the existing values of the - converted property’s [[Configurable]] and [[Enumerable]] - attributes and set the rest of the property’s attributes to - their default values.
-- Else, - if IsDataDescriptor(current) and IsDataDescriptor(Desc) - are both true, then
-- If - the [[Configurable]] field of current is false, then
- -- else, - the [[Configurable]] field of current is true, so - any change is acceptable.
-- Else, - IsAccessorDescriptor(current) and IsAccessorDescriptor(Desc) - are both true so,
- -- For - each attribute field of Desc that is present, set the - correspondingly named attribute of the property named P of - object O to the value of the field.
-- Return - true.
-- However, - if O is an Array - object, it has a more elaborate [[DefineOwnProperty]] internal - method defined in 15.4.5.1.
-NOTE Step - 10.b allows any field of Desc to be different from the corresponding - field of current if current’s [[Configurable]] field is true. - This even permits changing the [[Value]] of a property whose - [[Writable]] attribute is false. This is allowed because a - true [[Configurable]] attribute would permit an equivalent - sequence of calls where [[Writable]] is first set to true, a - new [[Value]] is set, and then [[Writable]] is set to false.
-- The - ECMAScript runtime system performs automatic type conversion as - needed. To clarify the semantics of certain constructs it is useful - to define a set of conversion abstract operations. These abstract - operations are not a part of the language; they are defined here to - aid the specification of the semantics of the language. The - conversion abstract operations are polymorphic; that is, they can - accept a value of any ECMAScript language type, but not of - specification types.
-- The - abstract operation ToPrimitive takes an input - argument and an optional argument PreferredType. - The abstract operation ToPrimitive converts its input - argument to a non-Object type. If an object is capable of converting - to more than one primitive type, it may use the optional hint - PreferredType to - favour that type. Conversion occurs according to Table 10:
-|
- - Input - Type - |
-
- - Result - |
-
|
- - Undefined - |
-
- - The - result equals the input - argument (no conversion). - |
-
|
- - Null - |
-
- - The - result equals the input - argument (no conversion). - |
-
|
- - Boolean - |
-
- - The - result equals the input - argument (no conversion). - |
-
|
- - Number - |
-
- - The - result equals the input - argument (no conversion). - |
-
|
- - String - |
-
- - The - result equals the input - argument (no conversion). - |
-
|
- - Object - |
-
- - Return - a default value for the Object. The default value of an object - is retrieved by calling the [[DefaultValue]] internal method of - the object, passing the optional hint PreferredType. - The behaviour of the [[DefaultValue]] internal method is defined - by this specification for all native ECMAScript objects in - 8.12.8. - |
-
- The - abstract operation ToBoolean converts its argument to a value of - type Boolean according to Table 11:
-|
- - Argument - Type - |
-
- - Result - |
-
|
- - Undefined - |
-
- - false - |
-
|
- - Null - |
-
- - false - |
-
|
- - Boolean - |
-
- - The - result equals the input argument (no conversion). - |
-
|
- - Number - |
-
- - The - result is false if the argument is +0, −0, - or NaN; otherwise the result is true. - - |
-
|
- - String - |
-
- - The - result is false if the argument is the empty String (its - length is zero); otherwise the result is true. - |
-
|
- Object - |
-
- true - |
-
- The - abstract operation ToNumber converts its argument to a value of type - Number according to Table 12:
-|
- - Argument - Type - |
-
- - Result - |
-
|
- - Undefined - |
-
- - NaN - |
-
|
- - Null - |
-
- - +0 - |
-
|
- - Boolean - |
-
- - The - result is 1 if the argument is true. The result is - +0 if the argument is false. - |
-
|
- - Number - |
-
- - The - result equals the input argument (no conversion). - |
-
|
- - String - |
-
- - See - grammar and note below. - |
-
|
- - Object - |
-
- - Apply - the following steps: -
|
-
- ToNumber - applied to Strings applies the following grammar to the input - String. If the grammar cannot interpret the String as an expansion - of StringNumericLiteral, - then the result of ToNumber is NaN.
-- StringNumericLiteral :::
-
- StrWhiteSpaceopt
StrWhiteSpaceoptStrNumericLiteral StrWhiteSpaceopt
- StrWhiteSpace :::
-- StrWhiteSpaceChar - StrWhiteSpaceopt
-- StrWhiteSpaceChar :::
-
- WhiteSpace
LineTerminator
- StrNumericLiteral :::
-
- StrDecimalLiteral
HexIntegerLiteral
- StrDecimalLiteral :::
-
- StrUnsignedDecimalLiteral+
- StrUnsignedDecimalLiteral-
- StrUnsignedDecimalLiteral
- StrUnsignedDecimalLiteral :::
-
- Infinity
- DecimalDigits . DecimalDigitsopt
- ExponentPartopt. DecimalDigits ExponentPartopt
DecimalDigits
- ExponentPartopt
- DecimalDigits :::
-
- DecimalDigit
DecimalDigits
- DecimalDigit
- DecimalDigit ::: - one - of
-
- 0
- 1 2 3 4 5 6 7 8 9
- ExponentPart :::
-- ExponentIndicator - SignedInteger
-- ExponentIndicator ::: - one - of
-
- e
- E
- SignedInteger :::
-
- DecimalDigits+
- DecimalDigits-
- DecimalDigits
- HexIntegerLiteral :::
-
- 0x HexDigit0X HexDigit
HexIntegerLiteral HexDigit
- HexDigit ::: one - of
-
- 0
- 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F
- Some - differences should be noted between the syntax of a - StringNumericLiteral - and a NumericLiteral - (see 7.8.3):
-- A - StringNumericLiteral - may be preceded and/or followed by white space and/or line - terminators.
-
- A
- StringNumericLiteral
- that is decimal may have any number of leading 0
- digits.
- A
- StringNumericLiteral
- that is decimal may be preceded by +
- or - to indicate
- its sign.
- A - StringNumericLiteral - that is empty or contains only white space is converted to +0.
-- The - conversion of a String to a Number value is similar overall to the - determination of the Number value for a numeric literal (see 7.8.3), - but some of the details are different, so the process for converting - a String numeric literal to a value of Number type is given here in - full. This value is determined in two steps: first, a mathematical - value (MV) is derived from the String numeric literal; second, this - mathematical value is rounded as described below.
-- The - MV of StringNumericLiteral - ::: [empty] - is 0.
-- The - MV of StringNumericLiteral - ::: StrWhiteSpace - is 0.
-- The - MV of StringNumericLiteral - ::: StrWhiteSpaceopt - StrNumericLiteral - StrWhiteSpaceopt - is the MV of StrNumericLiteral, - no matter whether white space is present or not.
-- The - MV of StrNumericLiteral - ::: StrDecimalLiteral - is the MV of StrDecimalLiteral.
-- The - MV of StrNumericLiteral - ::: HexIntegerLiteral - is the MV of HexIntegerLiteral.
-- The - MV of StrDecimalLiteral - ::: StrUnsignedDecimalLiteral - is the MV of StrUnsignedDecimalLiteral.
-
- The
- MV of StrDecimalLiteral
- ::: +
- StrUnsignedDecimalLiteral
- is the MV of StrUnsignedDecimalLiteral.
- The
- MV of StrDecimalLiteral
- ::: -
- StrUnsignedDecimalLiteral
- is the negative of the MV of StrUnsignedDecimalLiteral.
- (Note that if the MV of StrUnsignedDecimalLiteral
- is 0, the negative of this MV is also 0. The rounding rule
- described below handles the conversion of this signless
- mathematical zero to a floating-point +0 or −0
- as appropriate.)
- The
- MV of StrUnsignedDecimalLiteral:::
- Infinity
- is 1010000
- (a value so large that it will round to +∞).
- The
- MV of StrUnsignedDecimalLiteral:::
- DecimalDigits.
- is the MV of DecimalDigits.
- The
- MV of StrUnsignedDecimalLiteral:::
- DecimalDigits . DecimalDigits
- is the MV of the first DecimalDigits
- plus (the MV of the second DecimalDigits
- times 10−n),
- where n is the
- number of characters in the second DecimalDigits.
- The
- MV of StrUnsignedDecimalLiteral::: DecimalDigits. ExponentPart is the MV of
- DecimalDigits times 10e, where e
- is the MV of ExponentPart.
- The
- MV of StrUnsignedDecimalLiteral::: DecimalDigits. DecimalDigits ExponentPart is (the MV of the first
- DecimalDigits plus (the MV of the second DecimalDigits
- times 10−n))
- times 10e, where n is the number of
- characters in the second DecimalDigits and e is
- the MV of ExponentPart.
- The
- MV of StrUnsignedDecimalLiteral:::. DecimalDigits is the MV of
- DecimalDigits times 10−n,
- where n is the number of characters in DecimalDigits.
- The
- MV of StrUnsignedDecimalLiteral:::. DecimalDigits ExponentPart is
- the MV of DecimalDigits times 10e−n,
- where n is the number of characters in DecimalDigits
- and e is the MV of
- ExponentPart.
- The - MV of StrUnsignedDecimalLiteral::: DecimalDigits - is the MV of DecimalDigits.
-- The - MV of StrUnsignedDecimalLiteral::: DecimalDigits - ExponentPart is the MV of - DecimalDigits times 10e, where e - is the MV of ExponentPart.
-- The - MV of DecimalDigits ::: DecimalDigit is - the MV of DecimalDigit.
-- The - MV of DecimalDigits ::: DecimalDigits - DecimalDigit is (the MV of DecimalDigits times 10) - plus the MV of DecimalDigit.
-- The - MV of ExponentPart ::: ExponentIndicator - SignedInteger is - the MV of SignedInteger.
-- The - MV of SignedInteger ::: DecimalDigits - is the MV of DecimalDigits.
-
- The
- MV of SignedInteger ::: + DecimalDigits is
- the MV of DecimalDigits.
- The
- MV of SignedInteger ::: - DecimalDigits is the negative of the MV of
- DecimalDigits.
- The
- MV of DecimalDigit ::: 0
- or of HexDigit :::
- 0 is 0.
- The
- MV of DecimalDigit ::: 1
- or of HexDigit :::
- 1 is 1.
- The
- MV of DecimalDigit ::: 2
- or of HexDigit :::
- 2 is 2.
- The
- MV of DecimalDigit ::: 3
- or of HexDigit :::
- 3 is 3.
- The
- MV of DecimalDigit ::: 4
- or of HexDigit :::
- 4 is 4.
- The
- MV of DecimalDigit ::: 5
- or of HexDigit :::
- 5 is 5.
- The
- MV of DecimalDigit ::: 6
- or of HexDigit :::
- 6 is 6.
- The
- MV of DecimalDigit ::: 7
- or of HexDigit :::
- 7 is 7.
- The
- MV of DecimalDigit ::: 8
- or of HexDigit :::
- 8 is 8.
- The
- MV of DecimalDigit ::: 9
- or of HexDigit :::
- 9 is 9.
- The
- MV of HexDigit ::: a
- or of HexDigit :::
- A is 10.
- The
- MV of HexDigit ::: b
- or of HexDigit :::
- B is 11.
- The
- MV of HexDigit ::: c
- or of HexDigit :::
- C is 12.
- The
- MV of HexDigit ::: d
- or of HexDigit :::
- D is 13.
- The
- MV of HexDigit ::: e
- or of HexDigit :::
- E is 14.
- The
- MV of HexDigit ::: f
- or of HexDigit :::
- F is 15.
- The
- MV of HexIntegerLiteral ::: 0x
- HexDigit is the MV of
- HexDigit.
- The
- MV of HexIntegerLiteral ::: 0X
- HexDigit is the MV of
- HexDigit.
- The - MV of HexIntegerLiteral ::: HexIntegerLiteral - HexDigit is (the MV of HexIntegerLiteral times 16) - plus the MV of HexDigit.
-
- Once
- the exact MV for a String numeric literal has been determined, it is
- then rounded to a value of the Number type. If the MV is 0, then the
- rounded value is +0 unless the first non white space character in
- the String numeric literal is ‘-’,
- in which case the rounded value is −0.
- Otherwise, the rounded value must be the Number value for the MV (in
- the sense defined in 8.5), unless the literal includes a
- StrUnsignedDecimalLiteral
- and the literal has more than 20 significant digits, in which case
- the Number value may be either the Number value for the MV of a
- literal produced by replacing each significant digit after the 20th
- with a 0 digit or the Number value for the MV of a literal produced
- by replacing each significant digit after the 20th with a 0 digit
- and then incrementing the literal at the 20th digit position. A
- digit is significant if it is not part of an ExponentPart
- and
- it - is not 0; - or
-- there - is a nonzero digit to its left and there is a nonzero digit, not in - the ExponentPart, - to its right.
-- The - abstract operation ToInteger converts its argument to an integral - numeric value. This abstract operation functions as follows:
-- Let - number be the result of calling ToNumber on the input - argument.
-- If - number is NaN, return +0.
-- If - number is +0, −0, - +∞, or −∞, - return number.
-- Return - the result of computing sign(number) * floor(abs(number)).
-- The - abstract operation ToInt32 converts its argument to one of 232 - integer values in the range −231 - through 231−1, - inclusive. This abstract operation functions as follows:
-- Let - number be the result of calling ToNumber on the input - argument.
-- If - number is NaN, +0, −0, - +∞, or −∞, - return +0.
-- Let - int32bit be posInt modulo 232; that is, a - finite integer value k of Number type with positive sign and less - than 232 in magnitude such that the mathematical - difference of posInt and k is mathematically an integer - multiple of 232.
-- If - int32bit is greater than or equal to 231, return - int32bit − 232, - otherwise return int32bit.
--
NOTE Given the above definition of ToInt32:
-- The ToInt32 - abstract operation is idempotent: if applied to a result that it - produced, the second application leaves that value unchanged.
-- ToInt32(ToUint32(x)) - is equal to ToInt32(x) - for all values of x. - (It is to preserve this latter property that +∞ - and −∞ - are mapped to +0.)
-- ToInt32 maps −0 - to +0.
-- The - abstract operation ToUint32 converts its argument to one of 232 - integer values in the range 0 - through 232−1, - inclusive. This abstraction operation functions as follows:
-- Let - number be the result of calling ToNumber on the input - argument.
-- If - number is NaN, +0, −0, - +∞, or −∞, - return +0.
-- Let - int32bit be posInt modulo 232; that is, a - finite integer value k of Number type with positive sign and less - than 232 in magnitude such that the mathematical - difference of posInt and k is mathematically an integer - multiple of 232.
-- Return - int32bit.
--
NOTE Given the above definition of ToUInt32:
-- Step 5 is the - only difference between ToUint32 and ToInt32.
-- The ToUint32 - abstract operation is idempotent: if applied to a result that it - produced, the second application leaves that value unchanged.
-- ToUint32(ToInt32(x)) - is equal to ToUint32(x) - for all values of x. - (It is to preserve this latter property that +∞ - and −∞ are mapped to - +0.)
-- ToUint32 maps −0 - to +0.
-- The - abstract operation ToUint16 converts its argument to one of 216 - integer values in the range 0 - through 216−1, - inclusive. This abstract operation functions as follows:
-- Let - number be the result of calling ToNumber on the input - argument.
-- If - number is NaN, +0, −0, - +∞, or −∞, - return +0.
-- Let - int16bit be posInt modulo 216; that is, a - finite integer value k of Number type with positive sign and - less than 216 in magnitude such that the mathematical - difference of posInt and k is mathematically an - integer multiple of 216.
-- Return - int16bit.
--
NOTE Given the above definition of ToUint16:
-- The substitution - of 216 - for 232 - in step 4 is the only difference between ToUint32 and ToUint16.
-- ToUint16 maps −0 - to +0.
-- The - abstract operation ToString converts its argument to a value of type - String according to Table 13:
-|
- - Argument - Type - |
-
- - Result - |
-
|
- - Undefined - |
-
-
|
-
|
- - Null - |
-
-
|
-
|
- - Boolean - |
-
- If
- the argument is true, then the result is If
- the argument is false, then the result is |
-
|
- - Number - |
-
- See - 9.8.1. - |
-
|
- - String - |
-
- Return - the input argument (no conversion) - |
-
|
- - Object - |
-
- Apply - the following steps: -- 1. - Let primValue - be ToPrimitive(input argument, hint String). -- 2. - Return ToString(primValue). - |
-
- The - abstract operation ToString converts a Number m - to String format as follows:
-
- If
- m is NaN, return the String "NaN".
- If
- m is +0 or −0,
- return the String "0".
- If
- m is less than zero, return the String concatenation of the
- String "-"
- and ToString(−m).
- If
- m is infinity, return the String "Infinity".
- Otherwise, - let n, k, and s be integers such that k - ≥ 1, 10k−1 - ≤ s < 10k, - the Number value for s × - 10n−k - is m, and k is as small as possible. Note that k - is the number of digits in the decimal representation of s, - that s is not divisible by 10, and that the least - significant digit of s is not necessarily uniquely - determined by these criteria.
-
- If
- k ≤ n ≤
- 21, return the String consisting of the k digits of the
- decimal representation of s (in order, with no leading zeroes),
- followed by n−k
- occurrences of the character ‘0’.
- If
- 0 < n ≤ 21, return the
- String consisting of the most significant n digits of the
- decimal representation of s, followed by a decimal point
- ‘.’, followed
- by the remaining k−n
- digits of the decimal representation of s.
- If
- −6 < n ≤
- 0, return the String consisting of the character ‘0’,
- followed by a decimal point ‘.’,
- followed by −n
- occurrences of the character ‘0’,
- followed by the k digits of the decimal representation of s.
- Otherwise,
- if k = 1, return the String consisting of the single digit
- of s, followed by lowercase character ‘e’,
- followed by a plus sign ‘+’
- or minus sign ‘−’
- according to whether n−1
- is positive or negative, followed by the decimal representation of
- the integer abs(n−1)
- (with no leading zeros).
- Return - the String consisting of the most significant digit of the decimal - representation of s, followed by a decimal point ‘.’, followed - by the remaining k−1 digits of - the decimal representation of s, followed by the lowercase - character ‘e’, followed by a plus sign ‘+’ or minus sign - ‘−’ according to whether - n−1 is positive or negative, - followed by the decimal representation of the integer abs(n−1) - (with no leading zeros).
-NOTE 1 The following observations may be useful as guidelines for - implementations, but are not part of the normative requirements of - this Standard:
-- If x is any - Number value other than −0, - then ToNumber(ToString(x)) is exactly the same Number value as x.
-- The least - significant digit of s is not always uniquely determined by the - requirements listed in step 5.
-NOTE 2 For implementations that provide more accurate conversions than - required by the rules above, it is recommended that the following - alternative version of step 5 be used as a guideline:
-- Otherwise, - let n, - k, - and s - be integers such that k - ≥ - 1, 10k−1 - ≤ - s - < 10k, - the Number value for s - × - 10n−k - is m, - and k - is as small as possible. If there are multiple possibilities for s, - choose the value of s - for which s - × - 10n−k - is closest in value to m. - If there are two such possible values of s, - choose the one that is even. Note that k - is the number of digits in the decimal representation of s - and that s - is not divisible by 10.
-NOTE 3 Implementers of ECMAScript may find useful the paper and code - written by David M. Gay for binary-to-decimal conversion of - floating-point numbers:
-
- Gay, David M.
- Correctly Rounded Binary-Decimal and Decimal-Binary Conversions.
- Numerical Analysis, Manuscript 90-10. AT&T Bell Laboratories
- (Murray Hill, New Jersey). November 30, 1990. Available
- as
-
http://cm.bell-labs.com/cm/cs/doc/90/4-10.ps.gz.
- Associated code available
- as
-
http://cm.bell-labs.com/netlib/fp/dtoa.c.gz
- and as
-
http://cm.bell-labs.com/netlib/fp/g_fmt.c.gz
- and may also be found at the various netlib
- mirror sites.
- The - abstract operation ToObject converts its argument to a value of type - Object according to Table 14:
-|
- - Argument - Type - |
-
- - Result - |
-
|
- - Undefined - |
-
- - Throw - a TypeError exception. - |
-
|
- - Null - |
-
- - Throw - a TypeError exception. - |
-
|
- - Boolean - |
-
- - Create - a new Boolean object whose [[PrimitiveValue]] internal property - is set to the value of the argument. See 15.6 for a description - of Boolean objects. - |
-
|
- - Number - |
-
- - Create - a new Number object whose [[PrimitiveValue]] internal property - is set to the value of the argument. See 15.7 for a description - of Number objects. - |
-
|
- - String - |
-
- - Create - a new String object whose [[PrimitiveValue]] internal property - is set to the value of the argument. See 15.5 for a description - of String objects. - |
-
|
- Object - |
-
- The - result is the input argument (no conversion). - |
-
- The - abstract operation CheckObjectCoercible throws an error if its - argument is a value that cannot be converted to an Object using - ToObject. It is defined by Table 15:
-|
- - Argument - Type - |
-
- - Result - |
-
|
- - Undefined - |
-
- - Throw - a TypeError exception. - |
-
|
- - Null - |
-
- - Throw - a TypeError exception. - |
-
|
- - Boolean - |
-
- - Return - |
-
|
- - Number - |
-
- - Return - |
-
|
- - String - |
-
- - Return - |
-
|
- Object - |
-
- Return - |
-
- The - abstract operation IsCallable determines if its argument, which must - be an ECMAScript language value, is a callable function Object - according to Table 16:
-|
- - Argument - Type - |
-
- - Result - |
-
|
- - Undefined - |
-
- - Return - false. - |
-
|
- - Null - |
-
- - Return - false. - |
-
|
- - Boolean - |
-
- - Return - false. - |
-
|
- - Number - |
-
- - Return - false. - |
-
|
- - String - |
-
- - Return - false. - |
-
|
- Object - |
-
- If - the argument object has an [[Call]] internal method, then return - true, otherwise return false. - |
-
- The - internal comparison abstract operation SameValue(x, - y), where x - and y are - ECMAScript language values, produces true or false. - Such a comparison is performed as follows:
-- If - Type(x) is Undefined, return true.
-- If - Type(x) is Null, return true.
-- If - Type(x) is Number, then.
-- If - x is NaN and y is NaN, return true.
-- If - x is +0 and y is -0, return false.
-- If - x is -0 and y is +0, return false.
-- If - x is the same Number value as y, return true.
-- Return - false.
-- If - Type(x) is String, then return true if x and y - are exactly the same sequence of characters (same length and same - characters in corresponding positions); otherwise, return false.
-- If - Type(x) is Boolean, return true if x and y - are both true or both false; otherwise, return false.
-- Return - true if x and y refer to the same object. Otherwise, - return false.
-- There - are three types of ECMAScript executable code:
-Global code is source text that - is treated as an ECMAScript Program. - The global code of a particular Program - does not include any source text that is parsed as part of a - FunctionBody.
-Eval code is the source text
- supplied to the built-in eval function. More precisely, if the parameter to the built-in eval function is a String, it is treated as an ECMAScript Program.
- The eval code for a particular invocation of eval
- is the global code portion of that Program.
Function code is source text that
- is parsed as part of a FunctionBody.
- The function code
- of a particular FunctionBody
- does not include any source text that is parsed as part of a nested
- FunctionBody. Function
- code also denotes the
- source text supplied when using the built-in Function object as a constructor. More precisely, the last parameter
- provided to the Function
- constructor is converted to a String and treated as the
- FunctionBody. If more
- than one parameter is provided to the Function
- constructor, all parameters except the last one are converted to
- Strings and concatenated together, separated by commas. The
- resulting String is interpreted as the FormalParameterList
- for the FunctionBody
- defined by the last parameter. The function code for a particular
- instantiation of a Function
- does not include any source text that is parsed as part of a nested
- FunctionBody.
- An - ECMAScript Program - syntactic unit may be processed using either unrestricted or strict - mode syntax and semantics. When processed using strict mode the - three types of ECMAScript code are referred to as strict global - code, strict eval code, and strict function code. Code is - interpreted as strict mode code in the following situations:
-- Global code is strict global code if it begins with a Directive Prologue - that contains a Use Strict Directive (see 14.1).
-- Eval code is strict eval code if it begins with a Directive Prologue - that contains a Use Strict Directive or if the call to eval is a - direct call (see 15.1.2.1.1) to the eval function that is contained - in strict mode code. -
-- Function code that is part of a FunctionDeclaration, - FunctionExpression, - or accessor PropertyAssignment - is strict function code if its FunctionDeclaration, - FunctionExpression, - or PropertyAssignment - is contained in strict mode code or if the function code begins - with a Directive Prologue that contains a Use Strict Directive.
-- Function code that is supplied as the last argument to the built-in Function - constructor is strict function code if the last argument is a - String that when processed as a FunctionBody - begins with a Directive Prologue that contains a Use Strict - Directive.
-- A - Lexical Environment is a specification type used to define - the association of Identifiers - to specific variables and functions based upon the lexical nesting - structure of ECMAScript code. A Lexical Environment consists of an - Environment Record and a possibly null reference to an outer - Lexical Environment. Usually a Lexical Environment is associated - with some specific syntactic structure of ECMAScript code such as a - FunctionDeclaration, - a WithStatement, - or a Catch clause - of a TryStatement - and a new Lexical Environment is created each time such code is - evaluated.
-- An - Environment Record records the identifier bindings that are - created within the scope of its associated Lexical Environment.
-- The - outer environment reference is used to model the logical nesting of - Lexical Environment values. The outer reference of a (inner) Lexical - Environment is a reference to the Lexical Environment that logically - surrounds the inner Lexical Environment. An outer Lexical - Environment may, of course, have its own outer Lexical Environment. - A Lexical Environment may serve as the outer environment for - multiple inner Lexical Environments. For example, if a - FunctionDeclaration - contains two nested FunctionDeclarations - then the Lexical Environments of each of the nested functions will - have as their outer Lexical Environment the Lexical Environment of - the current execution of the surrounding function.
-- Lexical - Environments and Environment Record values are purely specification - mechanisms and need not correspond to any specific artefact of an - ECMAScript implementation. It is impossible for an ECMAScript - program to directly access or manipulate such values.
-- There - are two kinds of Environment Record values used in this - specification: declarative environment records and object - environment records. Declarative environment records are used - to define the effect of ECMAScript language syntactic elements such - as FunctionDeclarations, - VariableDeclarations, - and Catch clauses - that directly associate identifier bindings with ECMAScript - language values. Object environment records are used to define the - effect of ECMAScript elements such as Program - and WithStatement - that associate identifier bindings with the properties of - some object.
-- For - specification purposes Environment Record values can be thought of - as existing in a simple object-oriented hierarchy where Environment - Record is an abstract class with two concrete subclasses, - declarative environment record - and object environment record. The - abstract class includes the abstract specification methods defined - in Table 17. These abstract methods have distinct concrete - algorithms for each of the concrete subclasses. -
-|
- - Method - |
-
- - Purpose - |
-
|
- - HasBinding(N) - |
-
- - Determine - if an environment record has a binding for an identifier. Return - true if it - does and false - if it does not. The String value N - is the text of the identifier. - |
-
|
- - CreateMutableBinding(N, - D) - |
-
- - Create - a new mutable binding in an environment record. The String value - N is the text - of the bound name. If the optional Boolean argument D - is true the binding is may be subsequently deleted. - - |
-
|
- - SetMutableBinding(N,V, - S) - |
-
- - Set - the value of an already existing mutable binding in an - environment record. The String value N - is the text of the bound name. V - is the value for the binding and may be a value of any - ECMAScript language type. S - is a Boolean flag. If S - is true and - the binding cannot be set throw a TypeError exception. S - is used to identify strict mode references. - |
-
|
- - GetBindingValue(N,S) - |
-
- - Returns - the value of an already existing binding from an environment - record. The String value N - is the text of the bound name. S - is used to identify strict mode references. If S - is true and - the binding does not exist or is uninitialized throw a - ReferenceError exception. - - |
-
|
- - DeleteBinding(N) - |
-
- - Delete - a binding from an environment record. The String value N - is the text of the bound name If a binding for N - exists, remove the binding and return true. If the - binding exists but cannot be removed return false. If the - binding does not exist return true. - |
-
|
- ImplicitThisValue() - |
-
- Returns - the value to use as the this value on calls to function - objects that are obtained as binding values from this - environment record. - - |
-
- Each - declarative environment record is associated with an ECMAScript - program scope containing variable and/or function declarations. A - declarative environment record binds the set of identifiers defined - by the declarations contained within its scope.
-- In - addition to the mutable bindings supported by all Environment - Records, declarative environment records also provide for immutable - bindings. An immutable binding is one where the association between - an identifier and a value may not be modified once it has been - established. Creation and initialization of immutable binding are - distinct steps so it is possible for such bindings to exist in - either an initialized or uninitialized state. Declarative - environment records support the methods listed in Table 18 in - addition to the Environment Record abstract specification methods:
-|
- - Method - |
-
- - Purpose - |
-
| - - | -
- - Create - a new but uninitialized immutable binding in an environment - record. The String value N - is the text of the bound name. - |
-
| - - | -
- Set - the value of an already existing but uninitialized immutable binding in an environment record. The String value N - is the text of the bound name. V - is the value for the binding and is a value of any ECMAScript - language type. - - |
-
- The - behaviour of the concrete specification methods for Declarative - Environment Records are defined by the following algorithms.
-- The - concrete environment record method HasBinding for declarative - environment records simply determines if the argument identifier is - one of the identifiers bound by the record:
-- Let - envRec be the declarative environment record for which the - method was invoked.
-- If - envRec has a binding for the name that is the value of N, - return true.
-- If - it does not have such a binding, return false
-- The - concrete Environment Record method CreateMutableBinding for - declarative environment records creates a new mutable binding for - the name N that is - initialized to the value undefined. A binding must not - already exist in this Environment Record for N. - If Boolean argument D - is provided and has the value true the new binding is marked - as being subject to deletion.
-- Let - envRec be the declarative environment record for which the - method was invoked.
-- Assert: - envRec does not already have a binding for N.
-- Create - a mutable binding in envRec for N and set its bound - value to undefined. If D is true record that the - newly created binding may be deleted by a subsequent DeleteBinding - call.
-- The - concrete Environment Record method SetMutableBinding for declarative - environment records attempts to change the bound value of the - current binding of the identifier whose name is the value of the - argument N to the - value of argument V. - A binding for N - must already exist. If the binding is an immutable binding, a - TypeError is - thrown - if S is true. -
- -- Let - envRec be the declarative environment record for which the - method was invoked.
-- Assert: - envRec must have a binding for N.
-- If - the binding for N in envRec is a mutable binding, - change its bound value to V.
-- Else - this must be an attempt to change the value of an immutable binding - so - if S is true - throw a - TypeError - exception.
-- The - concrete Environment Record method GetBindingValue for declarative - environment records simply returns the value of its bound identifier - whose name is the value of the argument N. - The binding must already exist. If S - is true and the binding is an uninitialized immutable binding - throw a ReferenceError exception.
-- Let - envRec be the declarative environment record for which the - method was invoked.
-- Assert: - envRec has a binding for N.
-- If - the binding for N in envRec is an uninitialized - immutable binding, then
-- If - S is false, return the value undefined, - otherwise throw a ReferenceError exception.
-- Else, - return the value currently bound to N in envRec.
-- The - concrete Environment Record method DeleteBinding for declarative - environment records can only delete bindings that have been - explicitly designated as being subject to deletion.
-- Let - envRec be the declarative environment record for which the - method was invoked.
-- If - envRec does not have a binding for the name that is the - value of N, return true.
-- If - the binding for N in envRec is cannot be deleted, - return false.
-- Remove - the binding for N from envRec.
-- Return - true.
-- Declarative - Environment Records always return undefined as their - ImplicitThisValue.
-- Return - undefined.
-- The - concrete Environment Record method CreateImmutableBinding for - declarative environment records creates a new immutable binding for - the name N that is - initialized to the value undefined. A binding must not - already exist in this environment record for N.
-- Let - envRec be the declarative environment record for which the - method was invoked.
-- Assert: - envRec does not already have a binding for N.
-- Create - an immutable binding in envRec for N and record that - it is uninitialized.
-- The - concrete Environment Record method InitializeImmutableBinding for - declarative environment records is used to set the bound value of - the current binding of the identifier whose name is the value of the - argument N to the - value of argument V. - An uninitialized immutable binding for N - must already exist. -
-- Let - envRec be the declarative environment record for which the - method was invoked.
-- Assert: - envRec must have an uninitialized immutable binding for N.
-- Set - the bound value for N in envRec to V.
-- Record - that the immutable binding for N in envRec has been - initialized.
-- Each - object environment record is associated with an object called its - binding object. An object environment record binds the set of - identifier names that directly correspond to the property names of - its binding object. Property names that are not an IdentifierName are not included in the set of bound identifiers. Both - own and inherited properties are included in the set regardless of - the setting of their [[Enumerable]] attribute. Because properties - can be dynamically added and deleted from objects, the set of - identifiers bound by an object environment record may potentially - change as a side-effect of any operation that adds or deletes - properties. Any bindings that are created as a result of such a - side-effect are considered to be a mutable binding even if the - Writable attribute of the corresponding property has the value - false. Immutable bindings do not exist for object environment - records.
-- Object - environment records can be configured to provide their binding - object as an implicit this value for use in function calls. This - capability is used to specify the behaviour of With Statement - (12.10) induced bindings. The capability is controlled by a - provideThis - Boolean value that is associated with each object environment - record. By default, the value of provideThis - is false for any object environment record.
-- The - behaviour of the concrete specification methods for Object - Environment Records is defined by the following algorithms.
-- The - concrete Environment Record method HasBinding for object environment - records determines if its associated binding object has a property - whose name is the value of the argument N:
-- Let - envRec be the object environment record for which the method - was invoked.
-- Let - bindings be the binding object for envRec.
-- Return - the result of calling the [[HasProperty]] internal method of - bindings, passing N as the property name.
-- The - concrete Environment Record method CreateMutableBinding for object - environment records creates in an environment record’s associated - binding object a property whose name is the String value and - initializes it to the value undefined. A property named N - must not already exist in the binding object. If Boolean argument D - is provided and has the value true the new property’s - [[Configurable]] attribute is set to true, otherwise it is - set to false.
-- Let - envRec be the object environment record for which the method - was invoked.
-- Let - bindings be the binding object for envRec.
-- Assert: - The result of calling the [[HasProperty]] internal method of - bindings, passing N as the property name, is false.
-- If - D is true then let configValue be true - otherwise let configValue be false.
-- Call - the [[DefineOwnProperty]] internal method of bindings, - passing N, Property Descriptor {[[Value]]:undefined, - [[Writable]]: true, [[Enumerable]]: true , - [[Configurable]]: configValue}, and - true - as - arguments.
-- The - concrete Environment Record method SetMutableBinding for object - environment records attempts to set the value of the environment - record’s associated binding object’s property whose name is the - value of the argument N - to the value of argument V. - A property named N - should already exist but if it does not or is not currently - writable, error handling is determined by the value of the Boolean - argument S.
-- Let - envRec be the object environment record for which the method - was invoked.
-- Let - bindings be the binding object for envRec.
-- Call - the [[Put]] internal method of bindings with arguments N, - V, and S.
-- The - concrete Environment Record method GetBindingValue for object - environment records returns the value of its associated binding object’s property whose name is the String value of the argument - identifier N. The - property should already exist but if it does not the result depends - upon the value of the S - argument:
-- Let - envRec be the object environment record for which the method - was invoked.
-- Let - bindings be the binding object for envRec.
-- Let - value be the result of calling the [[HasProperty]] internal - method of bindings, passing N as the property name.
-- If - value is false, then
-- If - S is false, return the value undefined, - otherwise throw a ReferenceError exception.
-- Return - the result of calling the [[Get]] internal method of bindings, - passing N for the argument.
-- The - concrete Environment Record method DeleteBinding for object - environment records can only delete bindings that correspond to - properties of the environment object whose [[Configurable]] - attribute have the value true.
-- Let - envRec be the object environment record for which the method - was invoked.
-- Let - bindings be the binding object for envRec.
-- Return - the result of calling the [[Delete]] internal method of bindings, - passing N and false as arguments.
-- Object - Environment Records return undefined as their - ImplicitThisValue unless their provideThis - flag is true.
-- Let - envRec be the object environment record for which the method - was invoked.
-- If - the provideThis flag of envRec is true, return - the binding object for envRec.
-- Otherwise, - return undefined.
-- The - following abstract operations are used in this specification to - operate upon lexical environments:
-- The - abstract operation GetIdentifierReference is called with a Lexical Environment lex, - an identifier String name, - and a Boolean flag strict. The value of lex may be null. When called, the following steps are - performed:
-- If - lex is the value null, then
-- Return - a value of type Reference whose base value is undefined, - whose referenced name is name, and whose strict mode flag - is strict.
-- Let - envRec be lex’s environment record.
-- Let - exists be the result of calling the HasBinding(N) - concrete method of envRec passing name as the - argument N.
-
- If
- exists is true,
- then
- Return - a value of type Reference whose base value is envRec, whose - referenced name is name, and whose strict mode flag is - strict.
-- Else
-- Let - outer be the value of lex’s outer environment reference.
-- Return - the result of calling GetIdentifierReference passing outer, - name, and strict as arguments.
-- When - the abstract operation NewDeclarativeEnvironment is called with - either a Lexical Environment or null as argument E the following steps are performed:
-- Let - env be a new Lexical Environment.
-- Let - envRec be a new declarative environment record containing no - bindings.
-- Set - env’s environment record to be envRec.
-- Set - the outer lexical environment reference of env to E.
-- Return - env.
-- When - the abstract operation NewObjectEnvironmentis called with an Object - O and a Lexical Environment E (or - null) as arguments, the following steps are performed:
-- Let - env be a new Lexical Environment.
-- Let - envRec be a new object environment record containing O - as the binding object.
-- Set - env’s environment record to be envRec.
-- Set - the outer lexical environment reference of env to E.
-- Return - env.
-- The - global environment is a unique Lexical Environment which is - created before any ECMAScript code is executed. The global - environment’s Environment Record is an object environment record - whose binding object is the global object (15.1). The global - environment’s outer environment reference is null.
-- As - ECMAScript code is executed, additional properties may be added to - the global object and the initial properties may be modified. - -
-- When - control is transferred to ECMAScript executable code, control is - entering an execution context. Active execution contexts - logically form a stack. The top execution context on this logical - stack is the running execution context. A new execution context is - created whenever control is transferred from the executable code - associated with the currently running execution context to - executable code that is not associated with that execution context. - The newly created execution context is pushed onto the stack and - becomes the running execution context.
-- An - execution context contains whatever state is necessary to track the - execution progress of its associated code. In addition, each - execution context has the state components listed in Table 19.
-|
- - Component - |
-
- - Purpose - |
-
|
- - LexicalEnvironment - |
-
- - Identifies - the Lexical Environment used to resolve identifier references - made by code within this execution context. - |
-
|
- - VariableEnvironment - |
-
- - Identifies - the Lexical Environment whose environment record holds bindings - created by VariableStatements - and FunctionDeclarations - within this execution context. - |
-
|
- ThisBinding - |
-
- The
- value associated with the |
-
- The - LexicalEnvironment and VariableEnvironment components of an - execution context are always Lexical Environments. When an execution - context is created its LexicalEnvironment and VariableEnvironment - components initially have the same value. The value of the - VariableEnvironment component never changes while the value of the - LexicalEnvironment component may change during execution of code - within an execution context.
-- In - most situations only the running execution context (the top of the - execution context stack) is directly manipulated by algorithms - within this specification. Hence when the terms - “LexicalEnvironment”, “VariableEnvironment” and - “ThisBinding” are used without qualification they are in - reference to those components of the running execution context.
-- An - execution context is purely a specification mechanism and need not - correspond to any particular artefact of an ECMAScript - implementation. It is impossible for an ECMAScript program to - access an execution context. -
-- Identifier - resolution is the process of determining the binding of an - Identifier using - the LexicalEnvironment of the running execution context. During - execution of ECMAScript code, the syntactic production - PrimaryExpression - : - Identifier is - evaluated using the following algorithm:
-- Let - env be the running execution context’s LexicalEnvironment.
-- If - the syntactic production that is being evaluated is contained in a - strict mode code, then let strict be true, else let - strict be false.
-- Return - the result of calling GetIdentifierReference function passing env, - Identifier, and strict as arguments.
-- The - result of evaluating an identifier is always a value of type - Reference with its referenced name component equal to the Identifier - String.
-- Evaluation - of global code or code using the eval function (15.1.2.1) - establishes and enters a new execution context. Every invocation of - an ECMAScript code function (13.2.1) also establishes and enters a - new execution context, even if a function is calling itself - recursively. Every return exits an execution context. A thrown - exception may also exit one or more execution contexts.
-- When - control enters an execution context, the execution context’s - ThisBinding is set, its VariableEnvironment and initial - LexicalEnvironment are defined, and declaration binding - instantiation (10.5) is performed. The exact manner in which these - actions occur depend on the type of code being entered.
-- The - following steps are performed when control enters the execution - context for global code:
-- Initialize - the execution context using the global code as described in - 10.4.1.1.
-- Perform - Declaration Binding Instantiation as described in 10.5 using the - global code.
-- The - following steps are performed to initialize a global execution - context for ECMAScript code C:
-- Set - the VariableEnvironment to the Global Environment.
-- Set - the LexicalEnvironment to the Global Environment.
-- Set - the ThisBinding to the global object.
-- The - following steps are performed when control enters the execution - context for eval code:
-- If - there is no calling context or if the eval code is not being - evaluated by a direct call (15.1.2.1.1) to the eval function then,
- -- Else,
-- Set - the ThisBinding to the same value as the ThisBinding of the - calling execution context.
-- Set - the LexicalEnvironment to the same value as the LexicalEnvironment - of the calling execution context.
-- Set - the VariableEnvironment to the same value as the - VariableEnvironment of the calling execution context.
-- If - the eval code is strict code, then
-- Let - strictVarEnv be the result of calling - NewDeclarativeEnvironment passing the LexicalEnvironment as the - argument.
-- Set - the LexicalEnvironment to strictVarEnv.
-- Set - the VariableEnvironment to strictVarEnv.
-- Perform - Declaration Binding Instantiation as described in 10.5 using the - eval code.
-- The - eval code cannot instantiate variable or function bindings in the - variable environment of the calling context that invoked the eval if - either the code of the calling context or the eval code is strict code. Instead such bindings are instantiated in a new - VariableEnvironment that is only accessible to the eval code.
-- The - following steps are performed when control enters the execution - context for function code contained in function object F, - a caller provided thisArg, - and a caller provided argumentsList:
-- If - the function code is strict code, set the ThisBinding to thisArg.
-- Else - if thisArg is null or undefined, set the - ThisBinding to the global object.
-- Else - if Type(thisArg) is not Object, set the ThisBinding to - ToObject(thisArg).
-- Else - set the ThisBinding to thisArg.
-- Let - localEnv be the result of calling NewDeclarativeEnvironment - passing the value of the [[Scope]] internal property of F as - the argument.
-- Set - the LexicalEnvironment to localEnv.
-- Set - the VariableEnvironment to localEnv.
-- Let - code be the value of F’s [[Code]] internal - property.
-- Perform - Declaration Binding Instantiation using the function code code - and argumentList as described in 10.5.
-- Every - execution context has an associated VariableEnvironment. Variables - and functions declared in ECMAScript code evaluated in an execution - context are added as bindings in that VariableEnvironment’s - Environment Record. For function code, parameters are also added as - bindings to that Environment Record.
-- Which - Environment Record is used to bind a declaration and its kind - depends upon the type of ECMAScript code executed by the execution - context, but the remainder of the behaviour is generic. On entering - an execution context, bindings are created in the - VariableEnvironment as follows using the caller provided code and, if it is function code, argument List args:
-- Let - env be the environment record component of the running - execution context’s VariableEnvironment.
-- If - code is eval code, then let configurableBindings be - true else let configurableBindings be false.
-- If - code is strict mode code, then let strict be true - else let strict be false.
-- If - code is function code, then
-- Let - func be the function whose [[Call]] internal method - initiated execution of code. Let names be the value - of func’s [[FormalParameters]] internal property. -
-- Let - argCount be the number of elements in args.
-- Let - n be the number 0.
-- For - each String argName in names, in list order do
-- Let - n be the current value of n plus 1.
-- If - n is greater than argCount, let v be - undefined otherwise let v be the value of the n’th - element of args.
-- Let - argAlreadyDeclared be the result of calling env’s - HasBinding concrete method passing argName as the - argument.
-- If - argAlreadyDeclared is false, call env’s - CreateMutableBinding concrete method passing argName as - the argument.
-- Call - env’s SetMutableBinding concrete method passing argName, - v, and strict as the arguments.
-- For each - FunctionDeclaration f in code, in source text - order do
-Let - fn be the Identifier in FunctionDeclaration - f.
-Let - fo be the result of instantiating FunctionDeclaration f - as described in Clause 13.
-Let - funcAlreadyDeclared be the result of calling env’s - HasBinding concrete method passing fn as the argument.
-If - funcAlreadyDeclared is false, call env’s - CreateMutableBinding concrete method passing fn and - configurableBindings as the arguments.
-Else - if env - is the environment record component of the global environment then
-Let - go - be the global object.
-Let - existingProp - be the resulting of calling the [[GetProperty]] internal method - of go - with argument fn.
-If - existingProp - .[[Configurable]] is true, - then
-Call - the [[DefineOwnProperty]] internal method of go, - passing fn, - Property Descriptor {[[Value]]: - undefined, - [[Writable]]: true, - [[Enumerable]]: true - , [[Configurable]]: configurableBindings - }, and true - as arguments.
-Else - if IsAccessorDescrptor(existingProp) - or existingProp - does not have attribute values {[[Writable]]: true, - [[Enumerable]]: true}, - then
-Throw - a TypeError exception.
-Call - env’s SetMutableBinding concrete method passing fn, - fo, and strict as the arguments.
-
- Let
- argumentsAlreadyDeclared be the result of calling env’s
- HasBinding concrete method passing "arguments"
- as the argument
- If - code is function code and argumentsAlreadyDeclared is - false, then
-- Let - argsObj be the result of calling the abstract operation - CreateArgumentsObject (10.6) passing func, names, args, - env and strict as arguments.
-- If - strict is true, then -
-
- Call
- env’s CreateImmutableBinding concrete method passing the
- String "arguments"
- as the argument.
- Call
- env’s InitializeImmutableBinding concrete method passing
- "arguments"
- and argsObj as arguments.
- Else,
-
- Call
- env’s CreateMutableBinding concrete method passing the
- String "arguments"
- as the argument.
- Call
- env’s SetMutableBinding concrete method passing
- "arguments",
- argsObj, and false as arguments.
- For - each VariableDeclaration and VariableDeclarationNoIn - d in code, in source text order do
-- Let - dn be the Identifier in d.
-- Let - varAlreadyDeclared be the result of calling env’s - HasBinding concrete method passing dn as the argument.
-- If - varAlreadyDeclared is false, then
-- Call - env’s CreateMutableBinding concrete method passing dn and configurableBindings as the arguments.
-- Call - env’s SetMutableBinding concrete method passing dn, - undefined, and strict as the arguments.
-
- When
- control enters an execution context for function code, an arguments
- object is created unless (as specified in 10.5) the identifier
- arguments occurs
- as an Identifier
- in the function’s FormalParameterList
- or occurs as the Identifier
- of a VariableDeclaration
- or FunctionDeclaration
- contained in the function code.
- The - arguments object is created by calling the abstract operation - CreateArgumentsObject with arguments func - the function object whose code is to be evaluated, - names a List containing the function’s formal parameter - names, args the - actual arguments passed to the [[Call]] internal method, env the variable environment for the function code, and - strict a Boolean - that indicates whether or not the function code is strict code. When - CreateArgumentsObject is called the following steps are performed:
-- Let - len be the number of elements in args.
-- Let - obj be the result of creating a new ECMAScript object.
-- Set - all the internal methods of obj as specified in 8.12.
-
- Set
- the [[Class]] internal property of obj to "Arguments".
- Let - Object be the standard built-in Object constructor (15.2.2).
-- Set - the [[Prototype]] internal property of obj to the standard - built-in Object prototype object (15.2.4).
-
- Call
- the [[DefineOwnProperty]] internal method on obj passing
- "length",
- the Property Descriptor {[[Value]]: len, [[Writable]]: true,
- [[Enumerable]]: false, [[Configurable]]: true}, and
- false as arguments.
- Let
- map be the result of creating a new object as if by the
- expression new Object()
- where Object is
- the standard built-in constructor with that name
- Let - mappedNames be an empty List.
-- Let - indx = len - 1.
-- Repeat - while indx >= 0, -
-- Let - val be the element of args at 0-origined list - position indx.
-- Call - the [[DefineOwnProperty]] internal method on obj passing - ToString(indx), the property descriptor {[[Value]]: val, - [[Writable]]: true, [[Enumerable]]: true, - [[Configurable]]: true}, and false as arguments.
-- If - indx is less than the number of elements in names, - then
-- Let - name be the element of names at 0-origined list - position indx.
-- If - strict is false and name is not an element - of mappedNames, then
-- Add - name as an element of the list mappedNames.
-- Let - g be the result of calling the MakeArgGetter - abstract operation with arguments name and env.
-- Let - p be the result of calling the MakeArgSetter - abstract operation with arguments name and env.
-- Call - the [[DefineOwnProperty]] internal method of map passing - ToString(indx), the Property Descriptor {[[Set]]: p, - [[Get]]: g, [[Configurable]]: true}, and false - as arguments.
-- Let - indx = indx - 1
-- If - mappedNames is not empty, then
-- Set - the [[ParameterMap]] internal property of obj to map.
-- Set - the [[Get]], [[GetOwnProperty]], [[DefineOwnProperty]], and - [[Delete]] internal methods of obj to the definitions - provided below.
-- If - strict is false, then
-
- Call
- the [[DefineOwnProperty]] internal method on obj passing
- "callee",
- the property descriptor {[[Value]]: func, [[Writable]]:
- true, [[Enumerable]]: false, [[Configurable]]:
- true}, and false as arguments.
- Else, - strict is true so
-- Let - thrower be the [[ThrowTypeError]] function Object (13.2.3).
-
- Call
- the [[DefineOwnProperty]] internal method of obj with
- arguments "caller",
- PropertyDescriptor {[[Get]]: thrower, [[Set]]: thrower,
- [[Enumerable]]: false, [[Configurable]]: false}, and
- false.
- Call
- the [[DefineOwnProperty]] internal method of obj with
- arguments "callee",
- PropertyDescriptor {[[Get]]: thrower, [[Set]]: thrower,
- [[Enumerable]]: false, [[Configurable]]: false}, and
- false.
- Return - obj
-- The - abstract operation MakeArgGetter called with String name - and environment record env - creates a function object that when executed returns the value bound - for name in env. - It performs the following steps:
-
- Let
- body be the result of concatenating the Strings "return
- ", name, and ";"
- Return - the result of creating a function object as described in 13.2 using - no FormalParameterList, body for FunctionBody, - env as Scope, and true for Strict.
-- The - abstract operation MakeArgSetter called with String name - and environment record env - creates a function object that when executed sets the value bound - for name in env. - It performs the following steps:
-
- Let
- param be the String name concatenated with the String
- "_arg"
- Let
- body be the String "<name> =
- <param>;"
- with <name> replaced by the value of name and
- <param> replaced by the value of param.
- Return - the result of creating a function object as described in 13.2 using - a List containing the single String param as - FormalParameterList, body for FunctionBody, - env as Scope, and true for Strict.
-- The - [[Get]] internal method of an arguments object for a non-strict mode - function with formal parameters when called with a property name P - performs the following steps:
-- Let - map be the value of the [[ParameterMap]] internal property - of the arguments object.
-- Let - isMapped be the result of calling the [[GetOwnProperty]] - internal method of map passing P as the argument.
-- If - the value of isMapped is undefined, then
- -- Else, - map contains a formal parameter mapping for P so, -
-- Return - the result of calling the [[Get]] internal method of map - passing P as the argument.
-- The - [[GetOwnProperty]] internal method of an arguments object for a - non-strict mode function with formal parameters when called with a - property name P - performs the following steps:
-- Let - desc be the result of calling the default [[GetOwnProperty]] - internal method (8.12.1) on the arguments object passing P - as the argument.
-- If - desc is undefined then return desc.
-- Let - map be the value of the [[ParameterMap]] internal property - of the arguments object.
-- Let - isMapped be the result of calling the [[GetOwnProperty]] - internal method of map passing P as the argument.
-- If - the value of isMapped is not undefined, then
-- Set - desc.[[Value]] to the result of calling the [[Get]] - internal method of map passing P as the argument.
-- Return - desc. -
-- The - [[DefineOwnProperty]] internal method of an arguments object for a - non-strict mode function with formal parameters when called with a - property name P, - Property Descriptor Desc, - and Boolean flag Throw - performs the following steps:
-- Let - map be the value of the [[ParameterMap]] internal property - of the arguments object.
-- Let - isMapped be the result of calling the [[GetOwnProperty]] - internal method of map passing P as the argument.
-- Let - allowed be the result of calling the default - [[DefineOwnProperty]] internal method (8.12.9) on the arguments - object passing P, Desc, and false as the - arguments.
-- If - allowed is false, then
-- If - Throw is true then throw a TypeError exception, - otherwise return false.
-- If - the value of isMapped is not undefined, then
-- If - IsAccessorDescriptor(Desc) is true, then
-- Call - the [[Delete]] internal method of map passing P, - and false as the arguments.
-- Else
-- If - Desc.[[Value]] is present, then
-- Call - the [[Put]] internal method of map passing P, - Desc.[[Value]], and Throw as the arguments.
-- If - Desc.[[Writable]] is present and its value is false, - then
-- Call - the [[Delete]] internal method of map passing P and - false as arguments.
-- Return - true.
-- The - [[Delete]] internal method of an arguments object for a non-strict - mode function with formal parameters when called with a property - name P and Boolean - flag Throw - performs the following steps:
-- Let - map be the value of the [[ParameterMap]] internal property - of the arguments object.
-- Let - isMapped be the result of calling the [[GetOwnProperty]] - internal method of map passing P as the argument.
-- Let - result be the result of calling the default [[Delete]] - internal method (8.12.7) on the arguments object passing P and - Throw as the arguments.
-- If - result is true and the value of isMapped is - not undefined, then
-- Call - the [[Delete]] internal method of map passing P, and - false as the arguments.
-- Return - result.
-NOTE 1 For non-strict mode functions the array index (defined in 15.4) - named data properties of an arguments object whose numeric name - values are less than the number of formal parameters of the - corresponding function object initially share their values with the - corresponding argument bindings in the function’s execution - context. This means that changing the property changes the - corresponding value of the argument binding and vice-versa. This - correspondence is broken if such a property is deleted and then - redefined or if the property is changed into an accessor property. - For strict mode functions, the values of the arguments object‘s - properties are simply a copy of the arguments passed to the function - and there is no dynamic linkage between the property values and the - formal parameter values.
-NOTE 2 The ParameterMap object and its property values are used as a - device for specifying the arguments object correspondence to - argument bindings. The ParameterMap object and the objects that are - the values of its properties are not directly accessible from - ECMAScript code. An ECMAScript implementation does not need to - actually create or use such objects to implement the specified - semantics.
-NOTE 3 Arguments objects for strict mode functions define
- non-configurable accessor properties named "caller"
- and "callee"
- which throw a TypeError exception on access. The "callee"
- property has a more specific meaning for non-strict mode functions
- and a "caller"
- property has historically been provided as an implementation-defined
- extension by some ECMAScript implementations. The strict mode
- definition of these properties exists to ensure that neither of them
- is defined in any other manner by conforming ECMAScript
- implementations.
- Syntax - -
-- PrimaryExpression :
-
- this
Identifier
Literal
ArrayLiteral
ObjectLiteral( Expression )
- The
- this keyword
- evaluates to the value of the ThisBinding of the current execution
- context.
- An - Identifier is - evaluated by performing Identifier Resolution as specified in - 10.3.1. The result of evaluating an Identifier - is always a value of type Reference.
-- A - Literal is - evaluated as described in 7.8.
-- An - array initialiser is an expression describing the initialisation of - an Array object, written in a form of a literal. It is a list of - zero or more expressions, each of which represents an array element, - enclosed in square brackets. The elements need not be literals; they - are evaluated each time the array initialiser is evaluated.
-- Array elements may be elided at the beginning, middle or end of the - element list. Whenever a comma in the element list is not preceded - by an AssignmentExpression - (i.e., a comma at the beginning or after another comma), the missing - array element contributes to the length of the Array and increases - the index of subsequent elements. Elided array elements are not - defined. If an element is elided at the end of an array, that - element does not contribute to the length of the Array.
-- Syntax
-- ArrayLiteral :
-
- [
- Elisionopt
- ] ElementList
[
-
- ] ElementList , Elisionopt
[
-
- ]
- ElementList :
-
- Elisionopt
- AssignmentExpression
ElementList , Elisionopt
- AssignmentExpression
- Elision :
-
- ,
Elision ,
- Semantics
-
- The
- production ArrayLiteral
- : [ Elisionopt
- ] is
- evaluated as follows:
- Let
- array be the result of creating a new object as if by the
- expression new Array() where
- Array is the standard built-in constructor with that
- name.
- Let - pad be the result of evaluating Elision; if not - present, use the numeric value zero.
-
- Call
- the [[Put]] internal method of array with arguments
- "length",
- pad, and false.
- Return - array.
-
- The
- production ArrayLiteral
- : [ ElementList
- ] is
- evaluated as follows:
- Return - the result of evaluating ElementList.
-
- The
- production ArrayLiteral
- : [ ElementList
- , Elisionopt
- ] is
- evaluated as follows:
- Let - array be the result of evaluating ElementList.
-- Let - pad be the result of evaluating Elision; if not - present, use the numeric value zero.
-
- Let
- len be the result of calling the [[Get]] internal method of
- array with argument "length".
- Call
- the [[Put]] internal method of array with arguments
- "length",
- ToUint32(pad+len), and false.
- Return - array.
-
- The
- production ElementList
- : Elisionopt
- AssignmentExpression
- is evaluated as follows:
- Let
- array be the result of creating a new object as if by the
- expression new Array() where
- Array is the standard built-in constructor with that
- name.
- Let - firstIndex be the result of evaluating Elision; if - not present, use the numeric value zero.
-- Let - initResult be the result of evaluating AssignmentExpression.
-- Let - initValue be GetValue(initResult).
-- Call - the [[DefineOwnProperty]] internal method of array with - arguments ToString(firstIndex), the Property Descriptor { - [[Value]]: initValue, [[Writable]]: true, - [[Enumerable]]: true, [[Configurable]]: true}, and - false.
-- Return - array.
-
- The
- production ElementList
- : ElementList
- , Elisionopt
- AssignmentExpression
- is evaluated as follows:
- Let - array be the result of evaluating ElementList.
-- Let - pad be the result of evaluating Elision; if not - present, use the numeric value zero.
-- Let - initResult be the result of evaluating AssignmentExpression.
-- Let - initValue be GetValue(initResult).
-
- Let
- len be the result of calling the [[Get]] internal method of
- array with argument "length".
- Call - the [[DefineOwnProperty]] internal method of array with - arguments ToString(ToUint32((pad+len)) and the - Property Descriptor { [[Value]]: initValue, [[Writable]]: - true, [[Enumerable]]: true, [[Configurable]]: true}, - and false.
-- Return - array.
-- The - production Elision - : , is evaluated as follows:
-- Return - the numeric value 1.
-- The - production Elision - : Elision - , is evaluated as follows:
-- Let - preceding be the result of evaluating Elision.
-- Return - preceding+1.
--
NOTE - [[DefineOwnProperty]] is used to ensure that own properties are - defined for the array even if the standard built-in Array prototype - object has been modified in a manner that would preclude the - creation of new own properties using [[Put]].
-- An - object initialiser is an expression describing the initialisation of - an Object, written in a form resembling a literal. It is a list of - zero or more pairs of property names and associated values, enclosed - in curly braces. The values need not be literals; they are evaluated - each time the object initialiser is evaluated.
-- Syntax
-- ObjectLiteral :
-
- {
- } {
- PropertyNameAndValueList
- } PropertyNameAndValueList
{
-
- , }
- PropertyNameAndValueList :
-
- PropertyAssignment
PropertyNameAndValueList
- ,
- PropertyAssignment
- PropertyAssignment - :
-
- PropertyName : AssignmentExpressionget
- PropertyName (
- ) { FunctionBody } set
- PropertyName (
- PropertySetParameterList )
- { FunctionBody }
- PropertyName :
-
- IdentifierName
StringLiteral
NumericLiteral
- PropertySetParameterList - :
-- Identifier
-- Semantics
-
- The
- production ObjectLiteral
- : {
- } is
- evaluated as follows:
- Return
- a new object created as if by the expression new
- Object() where Object
- is the standard built-in constructor with that name.
- The
- productions ObjectLiteral
- : {
- PropertyNameAndValueList
- }
- and
ObjectLiteral
- : {
- PropertyNameAndValueList
- ,}
- are evaluated as follows:
- Return - the result of evaluating PropertyNameAndValueList.
-- The - production PropertyNameAndValueList - : PropertyAssignment - is evaluated as follows:
-
- Let
- obj be the result of creating a new object as if by the
- expression new Object()
- where Object
- is the standard built-in constructor with that name.
- Let - propId be the result of evaluating PropertyAssignment.
-- Call - the [[DefineOwnProperty]] internal method of obj with - arguments propId.name, propId.descriptor, and false.
-- Return - obj.
-
- The
- production
PropertyNameAndValueList
- : PropertyNameAndValueList
- , PropertyAssignment
is
- evaluated as follows:
- Let - obj be the result of evaluating PropertyNameAndValueList.
-- Let - propId be the result of evaluating PropertyAssignment.
-- Let - previous be the result of calling the [[GetOwnProperty]] - internal method of obj with argument propId.name.
-- If - previous is not undefined then throw a SyntaxError - exception if any of the following conditions are true
-- This - production is contained in strict code and - IsDataDescriptor(previous) is true and - IsDataDescriptor(propId.descriptor) is true.
-- IsDataDescriptor(previous) - is true and IsAccessorDescriptor(propId.descriptor) - is true.
-- IsAccessorDescriptor(previous) - is true and IsDataDescriptor(propId.descriptor) is - true.
-- IsAccessorDescriptor(previous) - is true and IsAccessorDescriptor(propId.descriptor) - is true and either both previous and - propId.descriptor have [[Get]] fields or both previous - and propId.descriptor have [[Set]] fields
-- Call - the [[DefineOwnProperty]] internal method of obj with - arguments propId.name, propId.descriptor, and false.
-- Return - obj.
-- If - the above steps would throw a SyntaxError then an - implementation must treat the error as an early error (Clause 16).
-
- The
- production PropertyAssignment
- : PropertyName
- :
- AssignmentExpression
- is evaluated as follows:
- Let - propName be the result of evaluating PropertyName.
-- Let - exprValue be the result of evaluating AssignmentExpression.
-- Let - propValue be GetValue(exprValue).
-- Let - desc be the Property Descriptor{[[Value]]: propValue, - [[Writable]]: true, [[Enumerable]]: true, - [[Configurable]]: true}
-- Return - Property Identifier (propName, desc).
-
- The
- production PropertyAssignment
- : get
- PropertyName (
- ) { FunctionBody
- } is
- evaluated as follows:
- Let - propName be the result of evaluating PropertyName.
-- Let - closure be the result of creating a new Function object as - specified in 13.2 with an empty parameter list and body specified - by FunctionBody. Pass in the LexicalEnvironment of the - running execution context as the Scope. Pass in true - as the Strict flag if the PropertyAssignment - is contained in strict code or if its FunctionBody is strict code.
-- Let - desc be the Property Descriptor{[[Get]]: closure, - [[Enumerable]]: true, [[Configurable]]: true}
-- Return - Property Identifier (propName, desc).
-
- The
- production PropertyAssignment
- : set
- PropertyName (
- PropertySetParameterList
- ) {
- FunctionBody
- } is evaluated as
- follows:
- Let - propName be the result of evaluating PropertyName.
-- Let - closure be the result of creating a new Function object as - specified in 13.2 with parameters specified by - PropertySetParameterList and body specified by FunctionBody. - Pass in the LexicalEnvironment of the running execution context as - the Scope. Pass in true as the Strict flag if - the PropertyAssignment - is contained in strict code or if its FunctionBody is strict code.
-- Let - desc be the Property Descriptor{[[Set]]: closure, - [[Enumerable]]: true, [[Configurable]]: true}
-- Return - Property Identifier (propName, desc).
-
- It is
- a SyntaxError if the Identifier
- "eval"
- or the Identifier "arguments"
- occurs as the Identifier
- in a PropertySetParameterList
- of a
- PropertyAssignment
- that is contained in strict code
- or if its FunctionBody
- is strict code.
- The - production PropertyName - : IdentifierName - is evaluated as follows:
-- Return - the String value containing the same sequence of characters as the - IdentifierName.
-- The - production PropertyName - : StringLiteral - is evaluated as follows:
-- Return - the SV of the StringLiteral.
-- The - production PropertyName - : NumericLiteral - is evaluated as follows:
-- Let - nbr be the result of forming the value of the - NumericLiteral.
-- Return - ToString(nbr).
-
- The
- production PrimaryExpression
- : (
- Expression )
- is evaluated as follows:
- Return - the result of evaluating Expression. This may be of type - Reference.
--
NOTE This
- algorithm does not apply GetValue to the result of evaluating
- Expression. The principal motivation for this is so that operators
- such as delete and
- typeof may be
- applied to parenthesised expressions.
- Syntax
-- MemberExpression :
-
- PrimaryExpression
FunctionExpression
MemberExpression [ Expression ] MemberExpression . IdentifierNamenew MemberExpression
- Arguments
- NewExpression :
-
- MemberExpression
new
- CallExpression :
-
- MemberExpression
- Arguments
- Arguments[ Expression ] CallExpression . IdentifierName
- Arguments :
-
- ( ) ArgumentList
()
- ArgumentList :
-
- AssignmentExpression
ArgumentList , AssignmentExpression
- LeftHandSideExpression :
-
- NewExpression
CallExpression
- Properties - are accessed by name, using either the dot notation:
-
- MemberExpression . IdentifierName
CallExpression . IdentifierName
- or - the bracket notation:
-
- MemberExpression [ Expression ]
CallExpression [ Expression ]
- The - dot notation is explained by the following syntactic conversion:
-
- MemberExpression . IdentifierName
- is - identical in its behaviour to
-
- MemberExpression [ <identifier-name-string> ]
- and - similarly
-
- CallExpression . IdentifierName
- is - identical in its behaviour to
-
- CallExpression [ <identifier-name-string> ]
- where - <identifier-name-string> - is a string literal containing the same sequence of characters after - processing of Unicode escape sequences as the IdentifierName.
-
- The
- production MemberExpression
- : MemberExpression
- [ Expression
- ] is evaluated as
- follows:
- Let - baseReference be the result of evaluating MemberExpression.
-- Let - baseValue be GetValue(baseReference).
-- Let - propertyNameReference be the result of evaluating - Expression.
-- Let - propertyNameValue be GetValue(propertyNameReference).
-- Call - CheckObjectCoercible(baseValue).
-- Let - propertyNameString be ToString(propertyNameValue).
-- If - the syntactic production that is being evaluated is contained in - strict mode code, let strict be true, else let strict - be false.
-- Return - a value of type Reference whose base value is baseValue and - whose referenced name is propertyNameString, and whose - strict mode flag is strict.
-
- The
- production CallExpression
- : CallExpression [ Expression ] is evaluated
- in exactly the same manner, except that the contained CallExpression
- is evaluated in step 1.
- The
- production NewExpression : new NewExpression is evaluated as follows:
- Let - ref be the result of evaluating NewExpression.
-- Let - constructor be GetValue(ref).
-- If - Type(constructor) is not Object, throw a TypeError - exception.
-- If - constructor does not implement the [[Construct]] internal - method, throw a TypeError exception.
-- Return - the result of calling the [[Construct]] internal method on - constructor, providing no arguments (that is, an empty list - of arguments).
-
- The
- production MemberExpression
- : new
- MemberExpression
- Arguments is
- evaluated as follows:
- Let - ref be the result of evaluating MemberExpression.
-- Let - constructor be GetValue(ref).
-- Let - argList be the result of evaluating Arguments, - producing an internal list of argument values (11.2.4).
-- If - Type(constructor) is not Object, throw a TypeError - exception.
-- If - constructor does not implement the [[Construct]] internal - method, throw a TypeError exception.
-- Return - the result of calling the [[Construct]] internal method on - constructor, providing the list argList as the - argument values.
-- The - production CallExpression - : MemberExpression - Arguments is - evaluated as follows:
-- Let - ref be the result of evaluating MemberExpression.
-- Let - func be GetValue(ref).
-- Let - argList be the result of evaluating Arguments, - producing an internal list of argument values (see 11.2.4).
-- If - Type(func) is not Object, throw a TypeError - exception.
-- If - IsCallable(func) is false, throw a TypeError - exception.
-- If - Type(ref) is Reference, then
-- If - IsPropertyReference(ref) is true, then
-- Let - thisValue be GetBase(ref).
-- Else, - the base of ref is an Environment Record
-- Let - thisValue be the result of calling the ImplicitThisValue - concrete method of GetBase(ref).
-- Else, - Type(ref) is not Reference.
-- Let - thisValue be undefined.
-- Return - the result of calling the [[Call]] internal method on func, - providing thisValue as the this value and providing - the list argList as the argument values.
-- The - production CallExpression - : CallExpression - Arguments is - evaluated in exactly the same manner, except that the contained - CallExpression is - evaluated in step 1.
--
NOTE The returned - result will never be of type Reference if func - is a native ECMAScript object. Whether calling a host object can - return a value of type Reference is implementation-dependent. If a - value of type Reference is returned, it must be a non-strict - Property Reference.
-- The - evaluation of an argument list produces a List of values (see 8.8).
-
- The
- production Arguments :
- ( ) is evaluated
- as follows:
- Return - an empty List.
-
- The
- production Arguments : (
- ArgumentList
- ) is evaluated as follows:
- Return - the result of evaluating ArgumentList.
-
- The
- production ArgumentList :
- AssignmentExpression
- is evaluated as follows:
- Let - ref be the result of evaluating AssignmentExpression.
-- Let - arg be GetValue(ref).
-- Return - a List whose sole item is arg.
-
- The
- production ArgumentList : ArgumentList
- , AssignmentExpression
- is evaluated as follows:
- Let - precedingArgs be the result of evaluating ArgumentList.
-- Let - ref be the result of evaluating AssignmentExpression.
-- Let - arg be GetValue(ref).
-- Return - a List whose length is one greater than the length of precedingArgs - and whose items are the items of precedingArgs, in order, - followed at the end by arg which is the last item of the new - list.
-- The - production MemberExpression - : FunctionExpression - is evaluated as follows:
-- Return - the result of evaluating FunctionExpression.
-- Syntax
-- PostfixExpression :
-
- LeftHandSideExpression
LeftHandSideExpression
- [no LineTerminator here]
- ++
LeftHandSideExpression
- [no LineTerminator here]
- --
- The
- production PostfixExpression
- : LeftHandSideExpression
- [no LineTerminator here] ++
- is evaluated as follows:
- Let - lhs be the result of evaluating LeftHandSideExpression.
-- Throw - a SyntaxError exception if the following conditions are all - true:
-- IsStrictReference(lhs) - is true
-- Type(GetBase(lhs)) - is Environment Record
-
- GetReferencedName(lhs)
- is either "eval"
- or "arguments"
- Let
- newValue be the result of adding the value 1
- to oldValue, using the same rules as for the +
- operator (see 11.6.3).
- Call - PutValue(lhs, newValue).
-- Return - oldValue.
-
- The
- production PostfixExpression
- : LeftHandSideExpression
- [no LineTerminator here]
- -- is
- evaluated as follows:
- Let - lhs be the result of evaluating LeftHandSideExpression.
-- Throw - a SyntaxError exception if the following conditions are all - true:
-- IsStrictReference(lhs) - is true
-- Type(GetBase(lhs)) - is Environment Record
-
- GetReferencedName(lhs)
- is either "eval"
- or "arguments"
- Let
- newValue be the result of subtracting the value 1
- from oldValue, using the same rules as for the -
- operator (11.6.3).
- Call - PutValue(lhs, newValue).
-- Return - oldValue.
-- Syntax
-- UnaryExpression :
-
- PostfixExpression
delete
- void
- UnaryExpressiontypeof
- UnaryExpression
++-- UnaryExpression+ UnaryExpression- UnaryExpression~ UnaryExpression! UnaryExpression
- The
- production UnaryExpression
- : delete UnaryExpression is evaluated as follows:
- Let - ref be the result of evaluating UnaryExpression.
-- If - IsUnresolvableReference(ref) then,
-- If - IsStrictReference(ref) is true, throw a SyntaxError - exception.
-- Else, - return true.
-- If - IsPropertyReference(ref) is true, then
-- Return - the result of calling the [[Delete]] internal method on - ToObject(GetBase(ref)) providing GetReferencedName(ref) - and IsStrictReference(ref) as the arguments.
-- Else, - ref is a Reference to an Environment Record binding, so
-- If - IsStrictReference(ref) is true, throw a SyntaxError - exception.
-- Let - bindings be GetBase(ref).
-- Return - the result of calling the DeleteBinding concrete method of - bindings, providing GetReferencedName(ref) as the - argument.
-NOTE When
- a delete operator
- occurs within strict mode code, a SyntaxError exception is
- thrown if its UnaryExpression
- is a direct reference to a variable, function argument, or function
- name. In addition, if a delete
- operator occurs within strict mode code and the property to be
- deleted has the attribute { [[Configurable]]: false }, a
- TypeError exception is thrown.
- The
- production UnaryExpression
- : void
- UnaryExpression is
- evaluated as follows:
- Let - expr be the result of evaluating UnaryExpression.
-- Call - GetValue(expr).
-- Return - undefined.
-NOTE GetValue - must be called even though its value is not used because it may have - observable side-effects.
-
- The
- production UnaryExpression
- : typeof UnaryExpression
- is evaluated as follows:
- Let - val be the result of evaluating UnaryExpression.
-- If - Type(val) is Reference, then
-
- If
- IsUnresolvableReference(val) is true, return
- "undefined".
- Let - val be GetValue(val).
-- Return - a String determined by Type(val) according to Table 20.
-|
- - Type - of val - |
-
- - Result - |
-
|
- - Undefined - |
-
-
- |
-
|
- - Null - |
-
-
- |
-
|
- - Boolean - |
-
-
- |
-
|
- - Number - |
-
-
- |
-
|
- - String - |
-
-
- |
-
|
- - Object - (native and does not implement [[Call]]) - |
-
-
- |
-
|
- Object - (native or host and does implement [[Call]]) - |
-
-
|
-
|
- Object - (host and does not implement [[Call]]) - |
-
-
- Implementation-defined
- except may not be |
-
- The
- production UnaryExpression : ++
- UnaryExpression
- is evaluated as follows:
- Let - expr be the result of evaluating UnaryExpression.
-- Throw - a SyntaxError exception if the following conditions are all - true:
-- IsStrictReference(expr) - is true
-- Type(GetBase(expr)) - is Environment Record
-
- GetReferencedName(expr)
- is either "eval"
- or "arguments"
- Let
- newValue be the result of adding the value 1
- to oldValue, using the same rules as for the +
- operator (see 11.6.3).
- Call - PutValue(expr, newValue).
-- Return - newValue.
-
- The
- production UnaryExpression : --
- UnaryExpression
- is evaluated as follows:
- Let - expr be the result of evaluating UnaryExpression.
-- Throw - a SyntaxError exception if the following conditions are all - true:
-- IsStrictReference(expr) - is true
-- Type(GetBase(expr)) - is Environment Record
-
- GetReferencedName(expr)
- is either "eval"
- or "arguments"
- Let
- newValue be the result of subtracting the value 1
- from oldValue, using the same rules as for the -
- operator (see 11.6.3).
- Call - PutValue(expr, newValue).
-- Return - newValue.
-- The - unary + operator converts its operand to Number type.
-
- The
- production UnaryExpression : +
- UnaryExpression is
- evaluated as follows:
- Let - expr be the result of evaluating UnaryExpression.
-
- The
- unary - operator
- converts its operand to Number type and then negates it. Note that
- negating +0 produces −0,
- and negating −0
- produces +0.
- The
- production UnaryExpression : -
- UnaryExpression is
- evaluated as follows:
- Let - expr be the result of evaluating UnaryExpression.
-- If - oldValue is NaN, return NaN.
-- Return - the result of negating oldValue; that is, compute a Number - with the same magnitude but opposite sign.
-
- The
- production UnaryExpression : ~
- UnaryExpression is
- evaluated as follows:
- Let - expr be the result of evaluating UnaryExpression.
-- Return - the result of applying bitwise complement to oldValue. The - result is a signed 32-bit integer.
-
- The
- production UnaryExpression : !
- UnaryExpression is
- evaluated as follows:
- Let - expr be the result of evaluating UnaryExpression.
-- If - oldValue is true, return false.
-- Return - true.
-- Syntax
-- MultiplicativeExpression :
-
- UnaryExpression
MultiplicativeExpression * UnaryExpression
MultiplicativeExpression / UnaryExpression
MultiplicativeExpression % UnaryExpression
- Semantics
-- The - production MultiplicativeExpression : MultiplicativeExpression@ UnaryExpression, - where @ stands for one of the operators in the above definitions, is - evaluated as follows:
-- Let - left be the result of evaluating MultiplicativeExpression.
-- Let - leftValue be GetValue(left).
-- Let - right be the result of evaluating UnaryExpression.
-- Let - rightValue be GetValue(right).
-- Let - leftNum be ToNumber(leftValue).
-- Let - rightNum be ToNumber(rightValue).
-- Return - the result of applying the specified operation (*, /, or %) to - leftNum and rightNum. See the Notes below 11.5.1, - 11.5.2, 11.5.3.
-
- The *
- operator performs multiplication, producing the product of its
- operands. Multiplication is commutative. Multiplication is not
- always associative in ECMAScript, because of finite precision.
The - result of a floating-point multiplication is governed by the rules - of IEEE 754 binary double-precision arithmetic:
-- If - either operand is NaN, - the result is NaN.
-- The - sign of the result is positive if both operands have the same - sign, negative if the operands have different signs.
-- Multiplication - of an infinity by a zero results in NaN.
-- Multiplication - of an infinity by an infinity results in an infinity. The sign is - determined by the rule already stated above.
-- Multiplication - of an infinity by a finite non-zero value results in a signed - infinity. The sign is determined by the rule already stated above.
-- In - the remaining cases, where neither an infinity or NaN is involved, - the product is computed and rounded to the nearest representable - value using IEEE 754 round-to-nearest mode. If the magnitude is - too large to represent, the result is then an infinity of - appropriate sign. If the magnitude is too small to represent, the - result is then a zero of appropriate sign. The ECMAScript language - requires support of gradual underflow as defined by IEEE 754.
-The
- / operator
- performs division, producing the quotient of its operands. The left
- operand is the dividend and the right operand is the divisor.
- ECMAScript does not perform integer division. The operands and
- result of all division operations are double-precision
- floating-point numbers. The result of division is determined by the
- specification of IEEE 754 arithmetic:
- If - either operand is NaN, - the result is NaN.
-- The - sign of the result is positive if both operands have the same - sign, negative if the operands have different signs.
-- Division - of an infinity by an infinity results in NaN.
-- Division - of an infinity by a zero results in an infinity. The sign is - determined by the rule already stated above.
-- Division - of an infinity by a non-zero finite value results in a signed - infinity. The sign is determined by the rule already stated above.
-- Division - of a finite value by an infinity results in zero. The sign is - determined by the rule already stated above.
-- Division - of a zero by a zero results in NaN; - division of zero by any other finite value results in zero, with - the sign determined by the rule already stated above.
-- Division - of a non-zero finite value by a zero results in a signed infinity. - The sign is determined by the rule already stated above.
-- In - the remaining cases, where neither an infinity, nor a zero, nor - NaN - is involved, the quotient is computed and rounded to the nearest - representable value using IEEE 754 round-to-nearest mode. If the - magnitude is too large to represent, the operation overflows; the - result is then an infinity of appropriate sign. If the magnitude - is too small to represent, the operation underflows and the result - is a zero of the appropriate sign. The ECMAScript language - requires support of gradual underflow as defined by IEEE 754.
-
- The %
- operator yields the remainder of its operands from an implied
- division; the left operand is the dividend and the right operand is
- the divisor.
NOTE In - C and C++, the remainder operator accepts only integral operands; in - ECMAScript, it also accepts floating-point operands.
-
- The
- result of a floating-point remainder operation as computed by the %
- operator is not the same as the “remainder” operation defined by
- IEEE 754. The IEEE 754 “remainder” operation computes the
- remainder from a rounding division, not a truncating division, and
- so its behaviour is not analogous to that of the usual integer
- remainder operator. Instead the ECMAScript language defines %
- on floating-point operations to behave in a manner analogous to that
- of the Java integer remainder operator; this may be compared with
- the C library function fmod.
The - result of an ECMAScript floating-point remainder operation is - determined by the rules of IEEE arithmetic:
-- If - either operand is NaN, - the result is NaN.
-- The - sign of the result equals the sign of the dividend.
-- If - the dividend is an infinity, or the divisor is a zero, or both, - the result is NaN.
-- If - the dividend is finite and the divisor is an infinity, the result - equals the dividend.
-- If - the dividend is a zero and the divisor is finite, the result is - the same as the dividend.
-- In - the remaining cases, where neither an infinity, nor a zero, nor - NaN - is involved, the floating-point remainder r from a dividend n and - a divisor d is defined by the mathematical relation r = n − - (d * q) where q is an integer that is negative only if n/d is - negative and positive only if n/d is positive, and whose - magnitude is as large as possible without exceeding the magnitude - of the true mathematical quotient of n and d. -r is computed and rounded to the nearest representable value using -IEEE 754 round-to-nearest mode. -
-- Syntax
-- AdditiveExpression :
-
- MultiplicativeExpression
AdditiveExpression + MultiplicativeExpression
AdditiveExpression - MultiplicativeExpression
- The - addition operator either performs string concatenation or numeric - addition.
-
- The
- production AdditiveExpression
- : AdditiveExpression
- +
- MultiplicativeExpression
- is evaluated as follows:
- Let - lref be the result of evaluating AdditiveExpression.
-- Let - lval be GetValue(lref).
-- Let - rref be the result of evaluating MultiplicativeExpression.
-- Let - rval be GetValue(rref).
-- Let - lprim be ToPrimitive(lval).
-- Let - rprim be ToPrimitive(rval).
-- If - Type(lprim) is String or Type(rprim) is String, then -
- -- Return - the result of applying the addition operation to ToNumber(lprim) - and ToNumber(rprim). See the Note below 11.6.3.
-NOTE 1 No hint is provided in the calls to ToPrimitive in steps 5 and 6. - All native ECMAScript objects except Date objects handle the absence - of a hint as if the hint Number were given; Date objects handle the - absence of a hint as if the hint String were given. Host objects may - handle the absence of a hint in some other manner.
-NOTE 2 Step 7 differs from step 3 of the comparison algorithm for the - relational operators (11.8.5), by using the logical-or operation - instead of the logical-and operation.
-
- The
- production AdditiveExpression
- : AdditiveExpression
- -
- MultiplicativeExpression
- is evaluated as follows:
- Let - lref be the result of evaluating AdditiveExpression.
-- Let - lval be GetValue(lref).
-- Let - rref be the result of evaluating MultiplicativeExpression.
-- Let - rval be GetValue(rref).
-- Let - lnum be ToNumber(lval).
-- Let - rnum be ToNumber(rval).
-- Return - the result of applying the subtraction operation to lnum and - rnum. See the note below 11.6.3.
-
- The +
- operator performs addition when applied to two operands of numeric
- type, producing the sum of the operands. The -
- operator performs subtraction, producing the difference of two
- numeric operands.
- Addition - is a commutative operation, but not always associative.
-The - result of an addition is determined using the rules of IEEE 754 - binary double-precision arithmetic:
-- If - either operand is NaN, - the result is NaN.
-- The - sum of two infinities of opposite sign is NaN.
-- The - sum of two infinities of the same sign is the infinity of that - sign.
-- The - sum of an infinity and a finite value is equal to the infinite - operand.
-- The - sum of two negative zeros is −0. - The sum of two positive zeros, or of two zeros of opposite sign, - is +0.
-- The - sum of a zero and a nonzero finite value is equal to the nonzero - operand.
-- The - sum of two nonzero finite values of the same magnitude and - opposite sign is +0.
-- In - the remaining cases, where neither an infinity, nor a zero, nor - NaN is involved, and the operands have the same sign or have - different magnitudes, the sum is computed and rounded to the - nearest representable value using IEEE 754 round-to-nearest mode. - If the magnitude is too large to represent, the operation - overflows and the result is then an infinity of appropriate sign. - The ECMAScript language requires support of gradual underflow as - defined by IEEE 754.
-
- The -
- operator performs subtraction when applied to two operands of
- numeric type, producing the difference of its operands; the left
- operand is the minuend and the right operand is the subtrahend.
- Given numeric operands a
- and b, it is
- always the case that a–b
- produces the same result as a +(–b).
- Syntax
-- ShiftExpression :
-
- AdditiveExpression
ShiftExpression << AdditiveExpression
ShiftExpression >> AdditiveExpression
ShiftExpression >>> AdditiveExpression
- Performs - a bitwise left shift operation on the left operand by the amount - specified by the right operand.
-
- The
- production ShiftExpression
- : ShiftExpression
- <<
- AdditiveExpression
- is evaluated as follows:
- Let - lref be the result of evaluating ShiftExpression.
-- Let - lval be GetValue(lref).
-- Let - rref be the result of evaluating AdditiveExpression.
-- Let - rval be GetValue(rref).
-- Let - lnum be ToInt32(lval).
-- Let - rnum be ToUint32(rval).
-- Let - shiftCount be the result of masking out all but the least - significant 5 bits of rnum, that is, compute rnum & - 0x1F.
-- Return - the result of left shifting lnum by shiftCount bits. - The result is a signed 32-bit integer.
-- Performs - a sign-filling bitwise right shift operation on the left operand by - the amount specified by the right operand.
-
- The
- production ShiftExpression
- : ShiftExpression
- >>
- AdditiveExpression
- is evaluated as follows:
- Let - lref be the result of evaluating ShiftExpression.
-- Let - lval be GetValue(lref).
-- Let - rref be the result of evaluating AdditiveExpression.
-- Let - rval be GetValue(rref).
-- Let - lnum be ToInt32(lval).
-- Let - rnum be ToUint32(rval).
-- Let - shiftCount be the result of masking out all but the least - significant 5 bits of rnum, that is, compute rnum & - 0x1F.
-- Return - the result of performing a sign-extending right shift of lnum - by shiftCount bits. The most significant bit is propagated. - The result is a signed 32-bit integer.
-- Performs - a zero-filling bitwise right shift operation on the left operand by - the amount specified by the right operand.
-
- The
- production ShiftExpression
- : ShiftExpression
- >>>
- AdditiveExpression
- is evaluated as follows:
- Let - lref be the result of evaluating ShiftExpression.
-- Let - lval be GetValue(lref).
-- Let - rref be the result of evaluating AdditiveExpression.
-- Let - rval be GetValue(rref).
-- Let - lnum be ToUint32(lval).
-- Let - rnum be ToUint32(rval).
-- Let - shiftCount be the result of masking out all but the least - significant 5 bits of rnum, that is, compute rnum & - 0x1F.
-- Return - the result of performing a zero-filling right shift of lnum - by shiftCount bits. Vacated bits are filled with zero. The - result is an unsigned 32-bit integer.
-- Syntax
-- RelationalExpression :
-
- ShiftExpression
RelationalExpression < ShiftExpression
RelationalExpression > ShiftExpression
RelationalExpression <= ShiftExpression
RelationalExpression >= ShiftExpression
RelationalExpression instanceof ShiftExpression
RelationalExpression in ShiftExpression
- RelationalExpressionNoIn :
-
- ShiftExpression
RelationalExpressionNoIn < ShiftExpression
RelationalExpressionNoIn > ShiftExpression
RelationalExpressionNoIn <= ShiftExpression
RelationalExpressionNoIn >= ShiftExpression
RelationalExpressionNoIn instanceof ShiftExpression
NOTE The
- “NoIn” variants are needed to avoid confusing the in
- operator in a relational expression with the in
- operator in a for
- statement.
- Semantics
-- The - result of evaluating a relational operator is always of type - Boolean, reflecting whether the relationship named by the operator - holds between its two operands.
-- The - RelationalExpressionNoIn - productions are evaluated in the same manner as the - RelationalExpression - productions except that the contained RelationalExpressionNoIn - is evaluated instead of the contained RelationalExpression.
-
- The
- production RelationalExpression
- : RelationalExpression
- <
- ShiftExpression is
- evaluated as follows:
- Let - lref be the result of evaluating RelationalExpression.
-- Let - lval be GetValue(lref).
-- Let - rref be the result of evaluating ShiftExpression.
-- Let - rval be GetValue(rref).
-- Let - r be the result of performing abstract relational comparison - lval < rval. (see 11.8.5)
-- If - r is undefined, return false. Otherwise, - return r.
-
- The
- production RelationalExpression : RelationalExpression
- >
- ShiftExpression is
- evaluated as follows:
- Let - lref be the result of evaluating RelationalExpression.
-- Let - lval be GetValue(lref).
-- Let - rref be the result of evaluating ShiftExpression.
-- Let - rval be GetValue(rref).
-- Let - r be the result of performing abstract relational comparison - rval < lval with LeftFirst equal to false. - (see 11.8.5).
-- If - r is undefined, return false. Otherwise, - return r.
-
- The
- production RelationalExpression : RelationalExpression
- <=
- ShiftExpression is
- evaluated as follows:
- Let - lref be the result of evaluating RelationalExpression.
-- Let - lval be GetValue(lref).
-- Let - rref be the result of evaluating ShiftExpression.
-- Let - rval be GetValue(rref).
-- Let - r be the result of performing abstract relational comparison - rval < lval with LeftFirst equal to false. - (see 11.8.5).
-- If - r is true or undefined, return false. - Otherwise, return true.
-
- The
- production RelationalExpression : RelationalExpression
- >=
- ShiftExpression is
- evaluated as follows:
- Let - lref be the result of evaluating RelationalExpression.
-- Let - lval be GetValue(lref).
-- Let - rref be the result of evaluating ShiftExpression.
-- Let - rval be GetValue(rref).
-- Let - r be the result of performing abstract relational comparison - lval < rval. (see 11.8.5)
-- If - r is true or undefined, return false. - Otherwise, return true.
-- The - comparison x < - y, where x - and y are values, - produces true, false, or undefined (which - indicates that at least one operand is NaN). In addition to x - and y the - algorithm takes a Boolean flag named LeftFirst - as a parameter. The flag is used to control the order in which - operations with potentially visible side-effects are performed upon - x and y. - It is necessary because ECMAScript specifies left to right - evaluation of expressions. The default value of LeftFirst - is true and indicates that the x - parameter corresponds to an expression that occurs to the left of - the y parameter’s - corresponding expression. If LeftFirst is false, the reverse is the case and operations - must be performed upon y before x. - Such a comparison is performed as follows:
-- If - the LeftFirst flag is true, then
-- Let - px be the result of calling ToPrimitive(x, hint - Number).
-- Let - py be the result of calling ToPrimitive(y, hint - Number).
-- Else - the order of evaluation needs to be reversed to preserve left to - right evaluation
-- Let - py be the result of calling ToPrimitive(y, hint - Number).
-- Let - px be the result of calling ToPrimitive(x, hint - Number).
-- If - it is not the case that both Type(px) is String and Type(py) - is String, then -
-- Let - nx be the result of calling ToNumber(px). Because px and py are primitive values evaluation order is not - important.
-- Let - ny be the result of calling ToNumber(py).
-- If - nx is NaN, return undefined.
-- If - ny is NaN, return undefined.
-- If - nx and ny are the same Number value, return false.
-- If - nx is +0 and ny is −0, - return false.
-- If - nx is −0 - and ny is +0, return false.
-- If - nx is +∞, - return false.
-- If - ny is +∞, - return true.
-- If - ny is −∞, - return false.
-- If - nx is −∞, - return true.
-- If - the mathematical value of nx is less than the mathematical - value of ny —note that these mathematical values are both - finite and not both zero—return true. Otherwise, return - false.
-- Else, - both px and py are Strings
-- If - py is a prefix of px, return false. (A String - value p is a prefix of String value q if q - can be the result of concatenating p and some other String - r. Note that any String is a prefix of itself, because r - may be the empty String.)
-- If - px is a prefix of py, return true.
-- Let - k be the smallest nonnegative integer such that the - character at position k within px is different from - the character at position k within py. (There must - be such a k, for neither String is a prefix of the other.)
-- Let - m be the integer that is the code unit value for the - character at position k within px.
-- Let - n be the integer that is the code unit value for the - character at position k within py.
-- If - m < n, return true. Otherwise, return - false.
-NOTE 1 Step 3 differs from step 7 in the algorithm for the addition
- operator +
- (11.6.1) in using and instead of or.
NOTE 2 The comparison of Strings uses a simple lexicographic ordering on - sequences of code unit values. There is no attempt to use the more - complex, semantically oriented definitions of character or string - equality and collating order defined in the Unicode specification. - Therefore String values that are canonically equal according to the - Unicode standard could test as unequal. In effect this algorithm - assumes that both Strings are already in normalised form. - Also, note that for strings containing supplementary characters, - lexicographic ordering on sequences of UTF-16 code unit values - differs from that on sequences of code point values.
-
- The
- production RelationalExpression:
- RelationalExpression
- instanceof
- ShiftExpression is
- evaluated as follows:
- Let - lref be the result of evaluating RelationalExpression.
-- Let - lval be GetValue(lref).
-- Let - rref be the result of evaluating ShiftExpression.
-- Let - rval be GetValue(rref).
-- If - Type(rval) is not Object, throw a TypeError - exception.
-- If - rval does not have a [[HasInstance]] internal method, throw - a TypeError exception.
-- Return - the result of calling the [[HasInstance]] internal method of rval - with argument lval.
-
- The
- production RelationalExpression
- : RelationalExpression
- in ShiftExpression
- is evaluated as follows:
- Let - lref be the result of evaluating RelationalExpression.
-- Let - lval be GetValue(lref).
-- Let - rref be the result of evaluating ShiftExpression.
-- Let - rval be GetValue(rref).
-- If - Type(rval) is not Object, throw a TypeError - exception.
-- Return - the result of calling the [[HasProperty]] internal method of rval - with argument ToString(lval).
-- Syntax
-- EqualityExpression :
-
- RelationalExpression
EqualityExpression == RelationalExpression
EqualityExpression != RelationalExpression
EqualityExpression === RelationalExpression
EqualityExpression !== RelationalExpression
- EqualityExpressionNoIn :
-
- RelationalExpressionNoIn
EqualityExpressionNoIn == RelationalExpressionNoIn
EqualityExpressionNoIn != RelationalExpressionNoIn
EqualityExpressionNoIn === RelationalExpressionNoIn
EqualityExpressionNoIn !== RelationalExpressionNoIn
- Semantics
-- The - result of evaluating an equality operator is always of type Boolean, - reflecting whether the relationship named by the operator holds - between its two operands.
-- The - EqualityExpressionNoIn - productions are evaluated in the same manner as the - EqualityExpression - productions except that the contained EqualityExpressionNoIn - and RelationalExpressionNoIn - are evaluated instead of the contained EqualityExpression - and RelationalExpression, - respectively.
-
- The
- production EqualityExpression : EqualityExpression
- ==
- RelationalExpression
- is evaluated as follows:
- Let - lref be the result of evaluating EqualityExpression.
-- Let - lval be GetValue(lref).
-- Let - rref be the result of evaluating RelationalExpression.
-- Let - rval be GetValue(rref).
-- Return - the result of performing abstract equality comparison rval - == lval. (see 11.9.3).
-
- The
- production EqualityExpression : EqualityExpression
- !=
- RelationalExpression
- is evaluated as follows:
- Let - lref be the result of evaluating EqualityExpression.
-- Let - lval be GetValue(lref).
-- Let - rref be the result of evaluating RelationalExpression.
-- Let - rval be GetValue(rref).
-- Let - r be the result of performing abstract equality comparison - rval == lval. (see 11.9.3).
-- If - r is true, return false. Otherwise, return - true.
-- The - comparison x == y, - where x and y - are values, produces true or false. Such a comparison - is performed as follows:
-- If - Type(x) is the same as Type(y), then
-- If - Type(x) is Undefined, return true.
-- If - Type(x) is Null, return true.
-- If - Type(x) is Number, then
-- If - x is NaN, return false.
-- If - y is NaN, return false.
-- If - x is the same Number value as y, return true.
-- If - x is +0 and y is −0, - return true.
-- If - x is −0 - and y is +0, return true.
-- Return - false.
-- If - Type(x) is String, then return true if x and - y are exactly the same sequence of characters (same length - and same characters in corresponding positions). Otherwise, return - false.
-- If - Type(x) is Boolean, return true if x and y are both true or both false. Otherwise, return - false.
-- Return - true if x and y refer to the same object. - Otherwise, return false.
-- If - x is null and y is undefined, return - true.
-- If - x is undefined and y is null, return - true.
-
- If
- Type(x) is Number and Type(y) is String,
return
- the result of the comparison x == ToNumber(y).
- If
- Type(x) is String and Type(y) is Number,
return
- the result of the comparison ToNumber(x) == y.
- If - Type(x) is Boolean, return the result of the comparison - ToNumber(x) == y.
-- If - Type(y) is Boolean, return the result of the comparison x - == ToNumber(y).
-
- If
- Type(x) is either String or Number and Type(y) is
- Object,
return the result of the comparison x ==
- ToPrimitive(y).
- If
- Type(x) is Object and Type(y) is either String or
- Number,
return the result of the comparison ToPrimitive(x)
- == y.
- Return - false.
-NOTE 1 Given the above definition of equality:
-
- String
- comparison can be forced by:
- ""
- + a == "" + b.
- Numeric
- comparison can be forced by:
- +a
- == +b.
- Boolean
- comparison can be forced by:
- !a
- == !b.
NOTE 2 The equality operators maintain the following invariants:
-
- A
- !=
- B
- is
- equivalent to
- !(A
- ==
- B).
- A
- ==
- B
- is
- equivalent to B
- ==
- A,
- except in the order of evaluation of
- A
- and
- B.
NOTE 3 The
- equality operator is not always transitive. For example, there might
- be two distinct String objects, each representing the same String
- value; each String object would be considered equal to the String
- value by the ==
- operator, but the two String objects would not be equal to each
- other.
NOTE 4 Comparison of Strings uses a simple equality test on sequences of - code unit values. There is no attempt to use the more complex, - semantically oriented definitions of character or string equality - and collating order defined in the Unicode specification. Therefore - Strings values that are canonically equal according to the Unicode - standard could test as unequal. In effect this algorithm assumes - that both Strings are already in normalised form.
-
- The
- production EqualityExpression : EqualityExpression
- ===
- RelationalExpression
- is evaluated as follows:
- Let - lref be the result of evaluating EqualityExpression.
-- Let - lval be GetValue(lref).
-- Let - rref be the result of evaluating RelationalExpression.
-- Let - rval be GetValue(rref).
-- Return - the result of performing the strict equality comparison rval - === lval. (See 11.9.6)
-
- The
- production EqualityExpression : EqualityExpression
- !==
- RelationalExpression
- is evaluated as follows:
- Let - lref be the result of evaluating EqualityExpression.
-- Let - lval be GetValue(lref).
-- Let - rref be the result of evaluating RelationalExpression.
-- Let - rval be GetValue(rref).
-- Let - r be the result of performing strict equality comparison - rval === lval. (See 11.9.6)
-- If - r is true, return false. Otherwise, return - true.
-- The - comparison x === - y, where x - and y are values, - produces true or false. Such a comparison is performed - as follows:
-- If - Type(x) is Undefined, return true.
-- If - Type(x) is Null, return true.
-- If - Type(x) is Number, then
-- If - x is NaN, return false.
-- If - y is NaN, return false.
-- If - x is the same Number value as y, return true.
-- If - x is +0 and y is −0, - return true.
-- If - x is −0 - and y is +0, return true.
-- Return - false.
-- If - Type(x) is String, then return true if x and y - are exactly the same sequence of characters (same length and same - characters in corresponding positions); otherwise, return false.
-- If - Type(x) is Boolean, return true if x and y - are both true or both false; otherwise, return false.
-- Return - true if x and y refer to the same object. - Otherwise, return false.
-NOTE This - algorithm differs from the SameValue Algorithm (9.12) in its - treatment of signed zeroes and NaNs.
-- Syntax
-- BitwiseANDExpression :
-
- EqualityExpression
BitwiseANDExpression & EqualityExpression
- BitwiseANDExpressionNoIn :
-
- EqualityExpressionNoIn
BitwiseANDExpressionNoIn & EqualityExpressionNoIn
- BitwiseXORExpression :
-
- BitwiseANDExpression
BitwiseXORExpression ^ BitwiseANDExpression
- BitwiseXORExpressionNoIn :
-
- BitwiseANDExpressionNoIn
BitwiseXORExpressionNoIn ^ BitwiseANDExpressionNoIn
- BitwiseORExpression :
-
- BitwiseXORExpression
BitwiseORExpression | BitwiseXORExpression
- BitwiseORExpressionNoIn :
-
- BitwiseXORExpressionNoIn
BitwiseORExpressionNoIn | BitwiseXORExpressionNoIn
- Semantics
-- The - production A : A @ B, - where @ is one of the bitwise operators in the productions above, is - evaluated as follows:
-- Let - lref be the result of evaluating A.
-- Let - lval be GetValue(lref).
-- Let - rref be the result of evaluating B.
-- Let - rval be GetValue(rref).
-- Let - lnum be ToInt32(lval).
-- Let - rnum be ToInt32(rval).
-- Return - the result of applying the bitwise operator @ to lnum and - rnum. The result is a signed 32 bit integer.
-- Syntax
-- LogicalANDExpression :
-
- BitwiseORExpression
LogicalANDExpression && BitwiseORExpression
- LogicalANDExpressionNoIn :
-
- BitwiseORExpressionNoIn
LogicalANDExpressionNoIn && BitwiseORExpressionNoIn
- LogicalORExpression :
-
- LogicalANDExpression
LogicalORExpression || LogicalANDExpression
- LogicalORExpressionNoIn :
-
- LogicalANDExpressionNoIn
LogicalORExpressionNoIn || LogicalANDExpressionNoIn
- Semantics
-
- The
- production LogicalANDExpression
- : LogicalANDExpression
- &&
- BitwiseORExpression
- is evaluated as follows:
- Let - lref be the result of evaluating LogicalANDExpression.
-- Let - lval be GetValue(lref).
-- If - ToBoolean(lval) is false, return lval.
-- Let - rref be the result of evaluating BitwiseORExpression.
-- Return - GetValue(rref).
-
- The
- production LogicalORExpression
- : LogicalORExpression
- ||
- LogicalANDExpression
- is evaluated as follows:
- Let - lref be the result of evaluating LogicalORExpression.
-- Let - lval be GetValue(lref).
-- If - ToBoolean(lval) is true, return lval.
-- Let - rref be the result of evaluating LogicalANDExpression.
-- Return - GetValue(rref).
-- The - LogicalANDExpressionNoIn - and LogicalORExpressionNoIn - productions are evaluated in the same manner as the - LogicalANDExpression - and LogicalORExpression - productions except that the contained LogicalANDExpressionNoIn, - BitwiseORExpressionNoIn - and LogicalORExpressionNoIn - are evaluated instead of the contained LogicalANDExpression, - BitwiseORExpression - and LogicalORExpression, - respectively.
-NOTE The
- value produced by a &&
- or || operator is
- not necessarily of type Boolean. The value produced will always be
- the value of one of the two operand expressions.
- Syntax
-- ConditionalExpression :
-
- LogicalORExpression
LogicalORExpression
- ? AssignmentExpression : AssignmentExpression
- ConditionalExpressionNoIn :
-
- LogicalORExpressionNoIn
LogicalORExpressionNoIn
- ? AssignmentExpression : AssignmentExpressionNoIn
- Semantics
-
- The
- production ConditionalExpression
- :
- LogicalORExpression
- ?
- AssignmentExpression
- :
- AssignmentExpression
- is evaluated as follows:
- Let - lref be the result of evaluating LogicalORExpression.
-- If - ToBoolean(GetValue(lref)) is true, then
-- Let - trueRef be the result of evaluating the first - AssignmentExpression.
-- Return - GetValue(trueRef).
-- Else
-- Let - falseRef be the result of evaluating the second - AssignmentExpression.
-- Return - GetValue(falseRef).
-- The - ConditionalExpressionNoIn - production is evaluated in the same manner as the - ConditionalExpression - production except that the contained LogicalORExpressionNoIn, - AssignmentExpression - and AssignmentExpressionNoIn - are evaluated instead of the contained LogicalORExpression, - first AssignmentExpression - and second AssignmentExpression, - respectively.
--
NOTE The grammar - for a ConditionalExpression in ECMAScript is a little bit different - from that in C and Java, which each allow the second subexpression - to be an Expression but restrict the third expression to be a - ConditionalExpression. The motivation for this difference in - ECMAScript is to allow an assignment expression to be governed by - either arm of a conditional and to eliminate the confusing and - fairly useless case of a comma expression as the centre expression.
-- Syntax
-- AssignmentExpression :
-
- ConditionalExpression
LeftHandSideExpression
- AssignmentOperator AssignmentExpression
- AssignmentExpressionNoIn :
-
- ConditionalExpressionNoIn
LeftHandSideExpression
- AssignmentOperator AssignmentExpressionNoIn
- AssignmentOperator : - one - of
-|
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
- Semantics
-- The - AssignmentExpressionNoIn - productions are evaluated in the same manner as the - AssignmentExpression - productions except that the contained ConditionalExpressionNoIn andAssignmentExpressionNoIn are evaluated instead of the - contained ConditionalExpression - and AssignmentExpression, - respectively.
-
- The
- production AssignmentExpression
- : LeftHandSideExpression
- =
- AssignmentExpression
- is evaluated as follows:
- Let - lref be the result of evaluating LeftHandSideExpression.
-- Let - rref be the result of evaluating AssignmentExpression.
-- Let - rval be GetValue(rref).
-- Throw - a SyntaxError exception if the following conditions are all - true:
-- IsStrictReference(lref) - is true
-- Type(GetBase(lref)) - is Environment Record
-
- GetReferencedName(lref)
- is either "eval"
- or "arguments"
- Call - PutValue(lref, rval).
-- Return - rval.
-NOTE When - an assignment occurs within strict mode code, its LeftHandSide - must not evaluate to an unresolvable reference. If it does a - ReferenceError exception is thrown upon assignment. The - LeftHandSide also - may not be a reference to a data property with the attribute value - {[[Writable]]:false}, - to an accessor property with the attribute value - {[[Set]]:undefined}, - nor to a non-existent property of an object whose [[Extensible]] - internal property has the value false. In these cases a - TypeError exception is thrown.
-
- The
- production AssignmentExpression : LeftHandSideExpression@ = AssignmentExpression,
- where @ represents one of the operators indicated above, is
- evaluated as follows:
- Let - lref be the result of evaluating LeftHandSideExpression.
-- Let - lval be GetValue(lref).
-- Let - rref be the result of evaluating AssignmentExpression.
-- Let - rval be GetValue(rref).
-- Let - r be the result of applying operator @ to lval and - rval.
-- Throw - a SyntaxError exception if the following conditions are all - true:
-- IsStrictReference(lref) - is true
-- Type(GetBase(lref)) - is Environment Record
-
- GetReferencedName(lref)
- is either "eval"
- or "arguments"
- Call - PutValue(lref, r).
-- Return - r.
-NOTE See - NOTE 11.13.1.
-- Syntax
-- Expression :
-
- AssignmentExpression
Expression , AssignmentExpression
- ExpressionNoIn :
-
- AssignmentExpressionNoIn
ExpressionNoIn , AssignmentExpressionNoIn
- Semantics
-
- The
- production Expression
- : Expression
- ,
- AssignmentExpression
- is evaluated as follows:
- Let - lref be the result of evaluating Expression.
-- Call - GetValue(lref).
-- Let - rref be the result of evaluating AssignmentExpression.
-- Return - GetValue(rref).
-- The - ExpressionNoIn - production is evaluated in the same manner as the Expression - production except that the contained ExpressionNoIn - and AssignmentExpressionNoIn - are evaluated instead of the contained Expression - and AssignmentExpression, - respectively.
--
NOTE GetValue must - be called even though its value is not used because it may have - observable side-effects.
-- Syntax
-- Statement :
-
- Block
VariableStatement
EmptyStatement
ExpressionStatement
IfStatement
IterationStatement
ContinueStatement
BreakStatement
ReturnStatement
WithStatement
LabelledStatement
SwitchStatement
ThrowStatement
TryStatement
DebuggerStatement
- Semantics
-- A - Statement can be - part of a LabelledStatement, - which itself can be part of a LabelledStatement, - and so on. The labels introduced this way are collectively referred - to as the “current label set” when describing the semantics of - individual statements. A LabelledStatement - has no semantic meaning other than the introduction of a label to a - label set. The label set of an IterationStatement - or a SwitchStatement - initially contains the single element empty. The label set of - any other statement is initially empty.
-NOTE Several - widely used implementations of ECMAScript are known to support the - use of FunctionDeclaration - as a Statement. However - there are significant and irreconcilable variations among the - implementations in the semantics applied to such - FunctionDeclarations. - Because of these irreconcilable difference, the use of a - FunctionDeclaration - as a Statement - results in code that is not reliably portable among implementations. - It is recommended that ECMAScript implementations either disallow - this usage of FunctionDeclaration - or issue a warning when such a usage is encountered. Future editions - of ECMAScript may define alternative portable means for declaring - functions in a Statement - context.
-- Syntax
-- Block :
-
- { StatementListopt }
- StatementList :
-
- Statement
StatementList
- Statement
- Semantics
-
- The
- production Block : { }
- is evaluated as follows:
- Return - (normal, empty, empty).
-
- The
- production Block : {
- StatementList }is
- evaluated as follows:
- Return - the result of evaluating StatementList.
-- The - production StatementList :Statement is evaluated as follows:
-- Let - s be the result of evaluating Statement.
-- If - an exception was thrown, return (throw, - V, empty) where V - is the exception. (Execution now proceeds as if no exception were - thrown.)
-- Return - s.
-- The - production StatementList :StatementList Statement is evaluated as follows:
-- Let - sl be the result of evaluating StatementList.
-- If - sl is an abrupt completion, return sl.
-- Let - s be the result of evaluating Statement.
-- If - an exception was thrown, return (throw, - V, empty) where V - is the exception. (Execution now proceeds as if no exception were - thrown.)
-- If - s.value is empty, let - V = sl.value, otherwise let V = s.value.
-- Return - (s.type, V, s.target).
-- Syntax
-- VariableStatement :
-
- var VariableDeclarationList ;
- VariableDeclarationList :
-
- VariableDeclaration
VariableDeclarationList , VariableDeclaration
- VariableDeclarationListNoIn :
-
- VariableDeclarationNoIn
VariableDeclarationListNoIn , VariableDeclarationNoIn
- VariableDeclaration :
-- Identifier - Initialiseropt
-- VariableDeclarationNoIn :
-- Identifier - InitialiserNoInopt
-- Initialiser :
-
- = AssignmentExpression
- InitialiserNoIn :
-
- = AssignmentExpressionNoIn
- A - variable statement declares variables that are created as defined in - 10.5. Variables are initialised to undefined when created. A - variable with an Initialiser - is assigned the value of its AssignmentExpression - when the VariableStatement - is executed, not when the variable is created.
-- Semantics
-
- The
- production VariableStatement : var VariableDeclarationList ;
- is evaluated as follows:
- Evaluate - VariableDeclarationList.
-- Return - (normal, empty, - empty).
-- The - production VariableDeclarationList - : VariableDeclaration - is evaluated as follows:
-- Evaluate - VariableDeclaration.
-
- The
- production VariableDeclarationList
- : VariableDeclarationList
- ,
- VariableDeclaration
- is evaluated as follows:
- Evaluate - VariableDeclarationList.
-- Evaluate - VariableDeclaration.
-- The - production VariableDeclaration : Identifier is evaluated as follows:
-- Return - a String value containing the same sequence of characters as in the - Identifier.
-- The - production VariableDeclaration - : Identifier - Initialiser is evaluated as follows:
-- Let - lhs be the result of evaluating Identifier as - described in 11.1.2.
-- Let - rhs be the result of evaluating Initialiser.
-- Let - value be GetValue(rhs).
-- Call - PutValue(lhs, value).
-- Return - a String value containing the same sequence of characters as in the - Identifier.
-NOTE The - String value of a VariableDeclaration - is used in the evaluation of for-in statements (12.6.4).
-- If a - VariableDeclaration - is nested within a with statement and the Identifier in the - VariableDeclaration - is the same as a property name of the binding object of the with - statement’s object environment record, then step 4 will assign - value to the property instead of to the VariableEnvironment binding - of the Identifier.
-
- The
- production Initialiser : = AssignmentExpression is evaluated as follows:
- Return - the result of evaluating AssignmentExpression.
-- The - VariableDeclarationListNoIn, - VariableDeclarationNoIn - and InitialiserNoIn - productions are evaluated in the same manner as the - VariableDeclarationList, - VariableDeclaration - and Initialiser - productions except that the contained VariableDeclarationListNoIn, - VariableDeclarationNoIn, - InitialiserNoIn - and AssignmentExpressionNoIn - are evaluated instead of the contained VariableDeclarationList, - VariableDeclaration, - Initialiser and - AssignmentExpression, - respectively.
-
- It is
- a SyntaxError if a VariableDeclaration
- or VariableDeclarationNoIn
- occurs within strict code and its Identifier
- is either "eval"
- or "arguments".
- Syntax
-- EmptyStatement :
-- ;
-- Semantics
-
- The
- production EmptyStatement : ; is
- evaluated as follows:
- Return - (normal, - empty, empty).
-- Syntax
-- ExpressionStatement :
-
- [lookahead
- ∉
- {{,
- function}] Expression ;
NOTE An
- ExpressionStatement
- cannot start with an opening curly brace because that might make it
- ambiguous with a Block.
- Also, an ExpressionStatement
- cannot start with the function
- keyword because that might make it ambiguous with a
- FunctionDeclaration.
- Semantics
-
- The
- production ExpressionStatement : [lookahead ∉
- {{,
- function}]Expression;
- is evaluated as follows:
- Let - exprRef be the result of evaluating Expression.
-- Return - (normal, GetValue(exprRef), - empty).
-- Syntax
-- IfStatement :
-
- if ( Expression ) Statement else Statementif ( Expression ) Statement
- Each
- else for which the
- choice of associated if
- is ambiguous shall be associated with the nearest possible if
- that would otherwise have no corresponding else.
- Semantics
-
- The
- production IfStatement : if ( Expression ) Statement else Statement is evaluated as follows:
- Let - exprRef be the result of evaluating Expression.
-- If - ToBoolean(GetValue(exprRef)) is true, then
-- Return - the result of evaluating the first Statement.
-- Else,
-- Return - the result of evaluating the second Statement.
-
- The
- production IfStatement : if ( Expression ) Statement is evaluated as follows:
- Let - exprRef be the result of evaluating Expression.
-- If - ToBoolean(GetValue(exprRef)) is false, return - (normal, empty, - empty).
-- Return - the result of evaluating Statement.
-- Syntax
-- IterationStatement :
-
- do
- Statement
- while ( Expression ); while ( Expression ) Statementfor ( ExpressionNoInopt; Expressionopt ; Expressionopt ) Statementfor ( var VariableDeclarationListNoIn; Expressionopt ; Expressionopt ) Statementfor ( LeftHandSideExpression in Expression ) Statementfor ( var VariableDeclarationNoIn in Expression ) Statement
- The
- production do Statement while ( Expression );
- is evaluated as follows:
- Let - V = empty.
-- Let - iterating be true.
-- Repeat, - while iterating is true
-- Let - stmt be the result of evaluating Statement.
-- If - stmt.value is not empty, - let V = stmt.value.
-- If - stmt.type is not continue - || stmt.target is not in the current label set, then
-- If - stmt.type is break - and stmt.target is in the current label set, return - (normal, V, empty).
-- If - stmt is an abrupt completion, return stmt.
-- Let - exprRef be the result of evaluating Expression.
-- If - ToBoolean(GetValue(exprRef)) is false, set iterating - to false.
-- Return - (normal, V, empty);
-
- The
- production IterationStatement : while ( Expression ) Statement is evaluated as follows:
- Let - V = empty.
-- Repeat
-- Let - exprRef be the result of evaluating Expression.
-- If - ToBoolean(GetValue(exprRef)) is false, return - (normal, V, empty).
-- Let - stmt be the result of evaluating Statement.
-- If - stmt.value is not empty, - let V = stmt.value.
-- If - stmt.type is not continue - || stmt.target is not in the current label set, then
-- If - stmt.type is break - and stmt.target is in the current label set, then
-- Return - (normal, V, empty).
-- If - stmt is an abrupt completion, return stmt.
-
- The
- production
IterationStatement
- : for
- ( ExpressionNoInopt
- ; Expressionopt
- ; Expressionopt)
- Statement
is
- evaluated as follows:
- If - ExpressionNoIn is present, then.
-- Let - exprRef be the result of evaluating ExpressionNoIn.
-- Call - GetValue(exprRef). (This value is not used.)
-- Let - V = empty.
-- Repeat
-- If - the first Expression is present, then
- -- Let - stmt be the result of evaluating Statement.
-- If - stmt.value is not empty, - let V = stmt.value
-- If - stmt.type is break - and stmt.target is in the current label set, return - (normal, V, empty).
-- If - stmt.type is not continue - || stmt.target is not in the current label set, then
-- If - stmt is an abrupt completion, return stmt.
-- If - the second Expression is present, then
-- Let - incExprRef be the result of evaluating the second - Expression.
-- Call - GetValue(incExprRef). (This value is not used.)
-
- The
- production
IterationStatement
- : for (
- var
- VariableDeclarationListNoIn
- ; Expressionopt ;
- Expressionopt ) Statement
is
- evaluated as follows:
- Evaluate - VariableDeclarationListNoIn.
-- Let - V = empty.
-- Repeat
-- If - the first Expression is present, then
- -- Let - stmt be the result of evaluating Statement.
-- If - stmt.value is not empty, - let V = stmt.value.
-- If - stmt.type is break - and stmt.target is in the current label set, return - (normal, V, empty).
-- If - stmt.type is not continue - || stmt.target is not in the current label set, then
-- If - stmt is an abrupt completion, return stmt.
-- If - the second Expression is present, then.
-- Let - incExprRef be the result of evaluating the second - Expression.
-- Call - GetValue(incExprRef). (This value is not used.)
-
- The
- production IterationStatement
- : for (
- LeftHandSideExpression
- in Expression
- ) Statement
- is evaluated as follows:
- Let - exprRef be the result of evaluating the Expression.
-- Let - experValue be GetValue(exprRef).
-- If - experValue is null or undefined, return - (normal, empty, - empty).
-- Let - obj be ToObject(experValue).
-- Let - V = empty.
-- Repeat
-- Let - P be the name of the next property of obj whose - [[Enumerable]] attribute is true. If there is no such - property, return (normal, V, - empty).
-- Let - lhsRef be the result of evaluating the - LeftHandSideExpression ( it may be evaluated repeatedly).
-- Call - PutValue(lhsRef, P).
-- Let - stmt be the result of evaluating Statement.
-- If - stmt.value is not empty, - let V = stmt.value.
-- If - stmt.type is break - and stmt.target is in the current label set, return - (normal, V, empty).
-- If - stmt.type is not continue || stmt.target is - not in the current label set, then
-- If - stmt is an abrupt completion, return stmt.
-
- The
- production
IterationStatement
- : for (
- var
- VariableDeclarationNoIn
- in Expression
- ) Statement
is
- evaluated as follows:
- Let - varName be the result of evaluating VariableDeclarationNoIn.
-- Let - exprRef be the result of evaluating the Expression.
-- Let - experValue be GetValue(exprRef).
-- If - experValue is null or undefined, return - (normal, empty, - empty).
-- Let - obj be ToObject(experValue).
-- Let - V = empty.
-- Repeat
-- Let - P be the name of the next property of obj whose - [[Enumerable]] attribute is true. If there is no such - property, return (normal, V, - empty).
-- Let - varRef be the result of evaluating varName as if it - were an Identifier Reference (11.1.2); it may be evaluated - repeatedly.
-- Call - PutValue(varRef, P).
-- Let - stmt be the result of evaluating Statement.
-- If - stmt.value is not empty, - let V = stmt.value.
-- If - stmt.type is break - and stmt.target is in the current label set, return - (normal, V, empty).
-- If - stmt.type is not continue - || stmt.target is not in the current label set, then
-- If - stmt is an abrupt completion, return stmt.
-- The - mechanics and order of enumerating the properties (step 6.a in the - first algorithm, step 7.a in the second) is not specified. - Properties of the object being enumerated may be deleted during - enumeration. If a property that has not yet been visited during - enumeration is deleted, then it will not be visited. If new - properties are added to the object being enumerated during - enumeration, the newly added properties are not guaranteed to be - visited in the active enumeration. - A property name must not be visited more than once in any enumeration. -
- -- Enumerating - the properties of an object includes enumerating properties of its - prototype, and the prototype of the prototype, and so on, - recursively; but a property of a prototype is not enumerated if it - is “shadowed” because some previous object in the prototype - chain has a property with the same name. - The values of [[Enumerable]] attributes are not considered when - determining if a property of a prototype object is shadowed by a previous - object on the prototype chain.
- -NOTE See - NOTE 11.13.1.
-- Syntax
- -- ContinueStatement :
-
- continue ;
- continue
- [no LineTerminator here] Identifier;
- Semantics
-- A - program is considered syntactically incorrect if either of the - following is true:
-
- The
- program contains a continue
- statement without the optional Identifier,
- which is not nested, directly or indirectly (but not crossing
- function boundaries), within an IterationStatement.
- The
- program contains a continue
- statement with the optional Identifier,
- where Identifier does
- not appear in the label set of an enclosing (but not crossing
- function boundaries) IterationStatement.
- A - ContinueStatement - without an Identifier - is evaluated as follows:
-- Return - (continue, empty, - empty).
-- A - ContinueStatement - with the optional Identifier - is evaluated as follows:
-- Return - (continue, empty, - Identifier).
-- Syntax
-- BreakStatement :
-
- break ;
- break
- [no LineTerminator here] Identifier ;
- Semantics
-- A - program is considered syntactically incorrect if either of the - following is true:
-
- The
- program contains a break
- statement without the optional Identifier,
- which is not nested, directly or indirectly (but not crossing
- function boundaries), within an IterationStatement
- or a SwitchStatement.
- The
- program contains a break
- statement with the optional Identifier,
- where Identifier does
- not appear in the label set of an enclosing (but not crossing
- function boundaries) Statement.
- A - BreakStatement - without an Identifier - is evaluated as follows:
-- Return - (break, empty, - empty).
-- A - BreakStatement - with an Identifier - is evaluated as follows:
-- Return - (break, empty,Identifier).
-- Syntax
-- ReturnStatement :
-
- return ;
- return
- [no LineTerminator here] Expression ;
- Semantics
-
- An
- ECMAScript program is considered syntactically incorrect if it
- contains a return
- statement that is not within a FunctionBody.
- A return statement
- causes a function to cease execution and return a value to the
- caller. If Expression
- is omitted, the return value is undefined. Otherwise, the
- return value is the value of Expression.
- The
- production ReturnStatement
- : return
- [no LineTerminator here]
- Expressionopt
- ; is
- evaluated as:
- If - the Expression is not present, return (return, - undefined, empty).
-- Let - exprRef be the result of evaluating Expression.
-- Return - (return, GetValue(exprRef), - empty).
-- Syntax
-- WithStatement :
-
- with ( Expression ) Statement
- The
- with statement
- adds an object environment record for a computed object to the
- lexical environment of the current execution context. It then
- executes a statement using this augmented lexical environment.
- Finally, it restores the original lexical environment.
- Semantics
-
- The
- production WithStatement : with ( Expression ) Statement is evaluated as follows:
- Let - val be the result of evaluating Expression.
-- Let - oldEnv be the running execution context’s - LexicalEnvironment.
-- Let - newEnv be the result of calling NewObjectEnvironment passing - obj and oldEnv as the arguments
-- Set - the provideThis flag of newEnv to true.
-- Set - the running execution context’s LexicalEnvironment to newEnv.
-- Let - C be the result of evaluating Statement but if an - exception is thrown during the evaluation, let C be (throw, - V, empty), where V - is the exception. (Execution now proceeds as if no exception were - thrown.)
-- Set - the running execution context’s Lexical Environment to oldEnv.
-- Return - C.
--
NOTE No matter how - control leaves the embedded Statement, - whether normally or by some form of abrupt completion or exception, - the LexicalEnvironment is always restored to its former state.
-- Strict - mode code may not include a WithStatement. - The occurrence of a WithStatement - in such a context is treated as a SyntaxError.
-- Syntax
-- SwitchStatement :
-
- switch ( Expression ) CaseBlock
- CaseBlock :
-
- { CaseClausesopt } { CaseClausesoptDefaultClause CaseClausesopt }
- CaseClauses :
-
- CaseClause
CaseClauses
- CaseClause
- CaseClause :
-
- case Expression : StatementListopt
- DefaultClause :
-
- default : StatementListopt
- Semantics
-
- The
- production SwitchStatement : switch ( Expression ) CaseBlock is evaluated as follows:
- Let - exprRef be the result of evaluating Expression.
-- Let - R be the result of evaluating CaseBlock, passing it - GetValue(exprRef) as a parameter.
-- If - R.type is break and - R.target is in the current label set, return (normal, - R.value, empty).
-- Return - R.
-
- The
- production CaseBlock
- : {
- CaseClausesopt
- }
- is given an input parameter, input,
- and is evaluated as follows:
- Let - V - = empty.
-- Let - A - be the list of CaseClause - items in source text order.
-- Let - searching - be true.
-- Repeat, - while searching - is true
-- Let - C - be the next CaseClause - in A. - If there is no such CaseClause, - return (normal, - V, - empty).
-- Let - clauseSelector - be the result of evaluating C.
-
- If
- input
- is equal to clauseSelector
- as defined by the ===
- operator, then
- Set - searching - to false.
-- IfC - has a StatementList, - then -
-- EvaluateC’s - StatementList - and letR - be the result.
-- IfR - is an abrupt completion, then returnR.
-- LetV - =R.value.
-- Repeat
-- LetC - be the next CaseClause - inA. - If there is no such CaseClause, - return (normal,V, - empty).
-- IfC - has a StatementList, - then -
-- EvaluateC’s - StatementList - and letR - be the result.
-- IfR.value - is not - empty, - then letV - =R.value.
-- IfR - is an abrupt completion, then return (R.type,V,R.target).
-
- The
- production CaseBlock
- : {
- CaseClausesoptDefaultClause CaseClausesopt
- }
- is given an input parameter, input,
- and is evaluated as follows:
- Let - V - = empty.
-- Let - A - be the list of CaseClause - items in the first CaseClauses, - in source text order.
-- Let - B - be the list of CaseClause items in the second CaseClauses, in - source text order.
-- Let - found - be false.
-- Repeat - letting C - be in order each CaseClause - in A
-- If - found - is false, - then
-- Let - clauseSelector - be the result of evaluating C.
-
- If
- input
- is equal to clauseSelector
- as defined by the ===
- operator, then set found
- to true.
- If - found - is true, - then
-- If - C - has a StatementList, then
-- Evaluate - C’s - StatementList - and let R - be the result.
-- IfR.value - is not - empty, - then letV - =R.value.
-- R - is an abrupt completion, then return (R.type,V,R.target).
-- Let - foundInB - be false.
-- If - found - is false, - then -
-- Repeat, - while foundInB - is false - and all elements of B - have not been processed
-- Let - C - be the next CaseClause - in B. - -
-- Let - clauseSelector - be the result of evaluating C.
-
- If
- input
- is equal to clauseSelector
- as defined by the ===
- operator, then
- Set - foundInB - to true.
-- IfC - has a StatementList, - then
-- Evaluate - C’s - StatementList - and let R - be the result.
-- IfR.value - is not - empty, - then letV - =R.value.
-- R - is an abrupt completion, then return (R.type,V,R.target).
-- If - foundInB - is false - and the DefaultClause - has a StatementList, - then
-- Evaluate - the DefaultClause’s - StatementList - and let R - be the result.
-- If - R.value - is not empty, - then let V - = R.value.
-- If - R - is an abrupt completion, then return (R.type, - V, - R.target).
-- Repeat - (Note that if step 7.a.i has been performed this loop does not - start at the beginning of B)
-- Let - C - be the next CaseClause - in B. - If there is no such CaseClause, - return (normal, - V, - empty).
-- If - C - has a StatementList, then -
-- Evaluate - C’s - StatementList and let R - be the result.
-- If - R.value - is not empty, - then let V - = R.value.
-- If - R - is an abrupt completion, then return (R.type, - V, - R.target).
-
- The
- production CaseClause
- : case Expression : StatementListopt is evaluated as follows:
- Let - exprRef be the result of evaluating Expression.
-- Return - GetValue(exprRef).
-NOTE Evaluating - CaseClause does - not execute the associated StatementList. - It simply evaluates the Expression - and returns the value, which the CaseBlock - algorithm uses to determine which StatementList - to start executing.
-- Syntax
-- LabelledStatement :
-
- Identifier : Statement
- Semantics
-
- A
- Statement may be
- prefixed by a label. Labelled statements are only used in
- conjunction with labelled break
- and continue
- statements. ECMAScript has no goto
- statement.
- An - ECMAScript program is considered syntactically incorrect if it - contains a LabelledStatement - that is enclosed by a LabelledStatement - with the same Identifier - as label. This does not apply to labels appearing within the body of - a FunctionDeclaration - that is nested, directly or indirectly, within a labelled statement.
-
- The
- production Identifier : Statement is evaluated by adding Identifier
- to the label set of Statement
- and then evaluating Statement.
- If the LabelledStatement
- itself has a non-empty label set, these labels are also added to the
- label set of Statement
- before evaluating it. If the result of evaluating Statement
- is (break, V,
- L) where L
- is equal to Identifier,
- the production results in (normal, V,
- empty).
- Prior - to the evaluation of a LabelledStatement, - the contained Statement - is regarded as possessing an empty label set, unless it is an - IterationStatement - or a SwitchStatement, - in which case it is regarded as possessing a label set consisting of - the single element, empty.
-- Syntax
-- ThrowStatement - :
-
- throw
- [no LineTerminator here] Expression ;
- Semantics
-
- The
- production ThrowStatement
- : throw
- [no LineTerminator here]
- Expression
- ; is evaluated as:
- Let - exprRef be the result of evaluating Expression.
-- Return - (throw, GetValue(exprRef), - empty).
-- Syntax
-- TryStatement :
-
- try Block Catchtry Block Finallytry Block Catch Finally
- Catch :
-
- catch (
- Identifier
- ) Block
- Finally :
-
- finally Block
- The
- try statement
- encloses a block of code in which an exceptional condition can
- occur, such as a runtime error or a throw
- statement. The catch
- clause provides the exception-handling code. When a catch clause
- catches an exception, its Identifier
- is bound to that exception.
- Semantics
-
- The
- production TryStatement
- : try Block
- Catch is evaluated
- as follows:
- Let - B be the result of evaluating Block.
-- If - B.type is not throw, - return B.
-- Return - the result of evaluating Catch with parameter B.
-
- The
- production TryStatement
- : try Block
- Finally is
- evaluated as follows:
- Let - B be the result of evaluating Block.
-- Let - F be the result of evaluating Finally.
-- If - F.type is normal, - return B.
-- Return - F.
-
- The
- production TryStatement
- : try Block
- Catch Finally
- is evaluated as follows:
- Let - B be the result of evaluating Block.
-- If - B.type is throw, then
-- Let - C be the result of evaluating Catch with parameter - B.
-- Else, - B.type is not throw,
-- Let - C be B.
-- Let - F be the result of evaluating Finally.
-- If - F.type is normal, - return C.
-- Return - F.
-
- The
- production Catch :
- catch (
- Identifier
- ) Block
- is evaluated as follows:
- Let - C be the parameter that has been passed to this production.
-- Let - oldEnv be the running execution context’s - LexicalEnvironment.
-- Let - catchEnv be the result of calling NewDeclarativeEnvironment - passing oldEnv as the argument. -
-- Call - the CreateMutableBinding concrete method of catchEnv passing - the Identifier String value as the argument.
-- Call - the SetMutableBinding concrete method of catchEnv passing - the Identifier, C, and false as arguments. - Note that the last argument is immaterial in this situation.
-- Set - the running execution context’s LexicalEnvironment to catchEnv.
-- Let - B be the result of evaluating Block.
-- Set - the running execution context’s LexicalEnvironment to oldEnv.
-- Return - B.
-NOTE No - matter how control leaves the Block - the LexicalEnvironment is always restored to its former state.
-
- The
- production Finally
- : finally Block
- is evaluated as follows:
- Return - the result of evaluating Block.
-
- It is
- an SyntaxError if a TryStatement
- with a Catch
- occurs within strict code and the Identifier
- of the Catch
- production is either "eval"
- or "arguments".
- Syntax
-- DebuggerStatement :
-
- debugger ;
- Semantics
-- Evaluating - the DebuggerStatement production may allow an implementation to cause a - breakpoint when run under a debugger. If a debugger is not present - or active this statement has no observable effect.
-
- The
- production DebuggerStatement : debugger
- ; is evaluated as follows:
- If - an implementation defined debugging facility is available and - enabled, then
-- Perform - an implementation defined debugging action.
-- Let - result be an implementation defined Completion value. -
-- Else
-- Let - result be (normal, - empty, empty).
-- Return - result.
-- Syntax
-- FunctionDeclaration :
-
- function Identifier ( FormalParameterListopt ) { FunctionBody }
- FunctionExpression :
-
- function Identifieropt ( FormalParameterListopt ) { FunctionBody }
- FormalParameterList :
-
- Identifier
FormalParameterList , Identifier
- FunctionBody :
-- SourceElementsopt
-- Semantics
-
- The
- production
FunctionDeclaration : function
- Identifier ( FormalParameterListopt ) {
- FunctionBody }
is
- instantiated as follows during Declaration Binding instantiation
- (10.5):
- Return - the result of creating a new Function object as specified in 13.2 - with parameters specified by FormalParameterListopt, - and body specified by FunctionBody. - Pass in the VariableEnvironment of the running execution context as - the Scope. - Pass in true - as the Strict - flag if the FunctionDeclaration - is contained in strict code or if its FunctionBody - is strict code.
-
- The
- production
FunctionExpression : function
- ( FormalParameterListopt ) {
- FunctionBody }
-
is evaluated as follows:
- Return - the result of creating a new Function object as specified in 13.2 - with parameters specified by FormalParameterListopt - and body specified by FunctionBody. - Pass in the LexicalEnvironment of the running execution context as - the Scope. - Pass in true - as the Strict - flag if the FunctionExpression - is contained in strict code or if its FunctionBody - is strict code.
-
- The
- production
FunctionExpression
- : function
- Identifier (
- FormalParameterListopt
- ) {
- FunctionBody }
is
- evaluated as follows:
- Let - funcEnv be - the result of calling NewDeclarativeEnvironment passing the running - execution context’s Lexical Environment as the argument
-- Let - envRec be - funcEnv’s environment record.
-- Call - the CreateImmutableBinding(N) concrete method of envRec passing the String - value of Identifier - as the argument.
-- Let - closure be - the result of creating a new Function object as specified in 13.2 - with parameters specified by FormalParameterListopt - and body specified by FunctionBody. - Pass in funcEnv as - the Scope. - Pass in true - as the Strict - flag if the FunctionExpression - is contained in strict code or if its FunctionBody - is strict code.
-- Call - the InitializeImmutableBinding(N,V) - concrete method of envRec passing the String - value of Identifier and closure as the arguments.
-- Return - closure.
-NOTE The - Identifier in a FunctionExpression - can be referenced from inside the FunctionExpression's - FunctionBody to - allow the function to call itself recursively. However, unlike in a - FunctionDeclaration, - the Identifier in - a FunctionExpression - cannot be referenced from and does not affect the scope enclosing - the FunctionExpression.
-- The - production FunctionBody :SourceElementsopt is evaluated as follows:
-- The - code of this FunctionBody is strict mode code - if it is part of a FunctionDeclaration - or FunctionExpression - that is contained in strict mode code or if the Directive Prologue - (14.1) of its SourceElements - contains a Use Strict Directive or if any of the conditions in - 10.1.1 apply. If the code of this FunctionBody is strict mode code, - SourceElements - is evaluated in the following steps as strict mode code. Otherwise, - SourceElements - is evaluated in the following steps as non-strict mode code.
-- If - SourceElements - is present return the result of evaluating SourceElements.
-- Else - return (normal, - undefined, - empty).
-- It is - a SyntaxError if any Identifier - value occurs more than once within a FormalParameterList - of a strict mode FunctionDeclaration - or FunctionExpression.
-
- It is
- a SyntaxError if the Identifier
- "eval"
- or the Identifier "arguments"
- occurs within a FormalParameterList
- of a strict mode FunctionDeclaration
- or FunctionExpression.
- It is
- a SyntaxError if the Identifier
- "eval"
- or the Identifier "arguments"
- occurs as the Identifier
- of a strict mode FunctionDeclaration
- or FunctionExpression.
- Given - an optional parameter list specified by FormalParameterList, - a body specified by FunctionBody, - a Lexical Environment specified by Scope, - and a Boolean flag Strict, - a Function object is constructed as follows:
-- Create - a new native ECMAScript object and let F - be that object.
-- Set - all the internal methods, except for [[Get]], of F - as described in 8.12.
-
- Set
- the [[Class]] internal property of F
- to "Function".
- Set - the [[Prototype]] internal property of F - to the standard built-in Function prototype object as specified in - 15.3.3.1.
-- Set - the [[Get]] internal property of F - as described in 15.3.5.4.
-- Set - the [[Call]] internal property of F - as described in 13.2.1.
-- Set - the [[Construct]] internal property of F - as described in 13.2.2.
-- Set - the [[HasInstance]] internal property of F - as described in 15.3.5.3.
-- Set - the [[Scope]] internal property of F - to the value of Scope.
-- Let - names be - a List containing, in left to right textual order, the Strings - corresponding to the identifiers of FormalParameterList.
-- Set - the [[FormalParameters]] internal property of F to names.
-- Set - the [[Code]] internal property of F to FunctionBody.
-- Set - the [[Extensible]] internal property of F to true.
-- Let - len - be the number of formal parameters specified in - FormalParameterList. - If no parameters are specified, let len - be 0.
-
- Call
- the [[DefineOwnProperty]] internal method of F
- with arguments "length",
- Property Descriptor {[[Value]]: len,
- [[Writable]]: false,
- [[Enumerable]]: false,
- [[Configurable]]: false},
- and false.
-
-
- Let
- proto
- be the result of creating a new object as would be constructed by
- the expression new
- Object()where Object
- is the standard built-in constructor with that name.
- Call
- the [[DefineOwnProperty]] internal method of proto
- with arguments "constructor",
- Property Descriptor {[[Value]]: F,
- { [[Writable]]: true,
- [[Enumerable]]: false,
- [[Configurable]]: true},
- and false.
- Call
- the [[DefineOwnProperty]] internal method of F
- with arguments "prototype",
- Property Descriptor {[[Value]]: proto,
- { [[Writable]]: true,
- [[Enumerable]]: false,
- [[Configurable]]: false},
- and false.
- If - Strict - is true, - then
-- Let - thrower - be the [[ThrowTypeError]] function Object (13.2.3).
-
- Call
- the [[DefineOwnProperty]] internal method of F
- with arguments "caller",
- PropertyDescriptor {[[Get]]: thrower,
- [[Set]]: thrower,
- [[Enumerable]]: false,
- [[Configurable]]: false},
- and false.
- Call
- the [[DefineOwnProperty]] internal method of F
- with arguments "arguments",
- PropertyDescriptor {[[Get]]: thrower,
- [[Set]]: thrower,
- [[Enumerable]]: false,
- [[Configurable]]: false},
- and false.
- Return - F.
-NOTE A
- prototype
- property is automatically created for every function, to allow for
- the possibility that the function will be used as a constructor.
- When - the [[Call]] internal method for a Function object F - is called with a this value and a list of arguments, the following - steps are taken:
-- Let - funcCtx be the result of establishing a new execution - context for function code using the value of F's - [[FormalParameters]] internal property, the passed arguments List - args, and the this value as described in 10.4.3.
-- Let - result be the result of evaluating the FunctionBody - that is the value of F's [[Code]] internal property. If F - does not have a [[Code]] internal property or if its value is an - empty FunctionBody, then result is (normal, - undefined, empty).
-- Exit - the execution context funcCtx, restoring the previous - execution context.
-- If - result.type is throw - then throw result.value.
-- If - result.type is return - then return result.value.
-- Otherwise - result.type must be normal. - Return undefined.
-- When - the [[Construct]] internal method for a Function object F - is called with a possibly empty list of arguments, the following - steps are taken:
-- Let - obj be - a newly created native ECMAScript object.
-- Set - all the internal methods of obj - as specified in 8.12.
-
- Set
- the [[Class]] internal property of obj to "Object".
- Set - the [[Extensible]] internal property of obj to true.
-
- Let
- proto be
- the value of calling the [[Get]] internal property of F
- with argument "prototype".
- If - Type(proto) is Object, set the - [[Prototype]] internal property of obj to proto.
-- If - Type(proto) is not Object, set - the [[Prototype]] internal property of obj to the standard - built-in Object prototype object as described in 15.2.4.
-- Let - result be - the result of calling the [[Call]] internal property of F, - providing obj as - the this - value and providing the argument list passed into [[Construct]] as - args.
-- If - Type(result) - is Object then return result.
-- Return - obj.
-- The - [[ThrowTypeError]] object is a unique function object that is - defined once as follows:
-- Create - a new native ECMAScript object and let F - be that object.
-- Set - all the internal methods of F - as described in 8.12.
-
- Set
- the [[Class]] internal property of F
- to "Function".
- Set - the [[Prototype]] internal property of F - to the standard built-in Function prototype object as specified in - 15.3.3.1.
-- Set - the [[Call]] internal property of F - as described in 13.2.1.
-- Set - the [[Scope]] internal property of F - to the Global Environment.
-- Set - the [[FormalParameters]] internal property of F to an empty List.
-- Set - the [[Code]] internal property of F to be a FunctionBody - that unconditionally throws a TypeError - exception and performs no other action.
-
- Call
- the [[DefineOwnProperty]] internal method of F
- with arguments "length",
- Property Descriptor {[[Value]]: 0,
- [[Writable]]: false,
- [[Enumerable]]: false,
- [[Configurable]]: false},
- and false.
-
-
- Set - the [[Extensible]] internal property of F to false.
-- Let - [[ThrowTypeError]] be F.
-- Syntax
-- Program :
-- SourceElementsopt
-- SourceElements :
-
- SourceElement
SourceElements
- SourceElement
- SourceElement :
-
- Statement
FunctionDeclaration
- Semantics
-
- The
- production Program :SourceElementsopt
- is evaluated as follows:
- The - code of this Program is strict mode code if the Directive - Prologue (14.1) of its SourceElements contains a Use Strict - Directive or if any of the conditions of 10.1.1 apply. If the code - of this Program is strict mode code, SourceElements - is evaluated in the following steps as strict mode code. Otherwise - SourceElements is evaluated in the following steps as - non-strict mode code.
-- If - SourceElements is not present, return (normal, - empty, empty).
-- Let - progCxt be a new execution context for global code as - described in 10.4.1. -
-- Let - result be the result of evaluating SourceElements.
-- Exit - the execution context progCxt.
-- Return - result.
-NOTE The - processes for initiating the evaluation of a Program - and for dealing with the result of such an evaluation are defined by - an ECMAScript implementation and not by this specification.
-- The - production SourceElements - : SourceElements - SourceElement is - evaluated as follows:
-- Let - headResult be the result of evaluating SourceElements.
-- If - headResult is an abrupt completion, return headResult
-- Let - tailResult be result of evaluating SourceElement.
-- If - tailResult.value is empty, - let V = headResult.value, otherwise let V = - tailResult.value.
-- Return - (tailResult.type, V, tailResult.target) -
-- The - production SourceElement :Statement is evaluated as follows:
-- Return - the result of evaluating Statement.
-- The - production SourceElement :FunctionDeclaration is evaluated as follows:
-- Return - (normal, empty, - empty).
-- A - Directive Prologue is the longest sequence of ExpressionStatement productions occurring as the initial SourceElement - productions of a Program - or FunctionBody - and where each ExpressionStatement in the sequence - consists entirely of a StringLiteral - token followed a semicolon. - The semicolon may appear explicitly or may be inserted by -automatic semicolon insertion. A Directive Prologue may be an empty sequence.
-
- A Use
- Strict Directive is an ExpressionStatement
- in a Directive Prologue whose StringLiteral
- is either the exact character sequences "use strict"
- or 'use strict'.
- A Use Strict Directive may not contain an EscapeSequence
- or LineContinuation.
- A - Directive Prologue may contain more than one Use Strict Directive. - However, an implementation may issue a warning if this occurs.
-NOTE The - ExpressionStatement - productions of a Directive Prologue are evaluated normally during - evaluation of the containing SourceElements - production. Implementations may define implementation specific - meanings for ExpressionStatement - productions which are not a Use Strict Directive and which occur in - a Directive Prologue. If an appropriate notification mechanism - exists, an implementation should issue a warning if it encounters in - a Directive Prologue an ExpressionStatement - that is not a Use Strict Directive or which does not have a meaning - defined by the implementation.
-- There - are certain built-in objects available whenever an ECMAScript - program begins execution. One, the global object, is part of the - lexical environment of the executing program. Others are accessible - as initial properties of the global object.
-
- Unless
- specified otherwise, the [[Class]] internal property of a built-in
- object is "Function"
- if that built-in object has a [[Call]] internal property, or
- "Object"
- if that built-in object does not have a [[Call]] internal property.
- Unless specified otherwise, the [[Extensible]] internal property of
- a built-in object initially has the value true.
- Many
- built-in objects are functions: they can be invoked with arguments.
- Some of them furthermore are constructors: they are functions
- intended for use with the new
- operator. For each built-in function, this specification describes
- the arguments required by that function and properties of the
- Function object. For each built-in constructor, this specification
- furthermore describes properties of the prototype object of that
- constructor and properties of specific object instances returned by
- a new expression
- that invokes that constructor.
- Unless - otherwise specified in the description of a particular function, if - a function or constructor described in this clause is given fewer - arguments than the function is specified to require, the function or - constructor shall behave exactly as if it had been given sufficient - additional arguments, each such argument being the undefined - value.
-- Unless - otherwise specified in the description of a particular function, if - a function or constructor described in this clause is given more - arguments than the function is specified to allow, the extra - arguments are evaluated by the call and then ignored by the - function. However, an implementation may define implementation - specific behaviour relating to such arguments as long as the - behaviour is not the throwing of a TypeError exception that - is predicated simply on the presence of an extra argument.
-NOTE Implementations - that add additional capabilities to the set of built-in functions - are encouraged to do so by adding new functions rather than adding - new parameters to existing functions.
-
- Every
- built-in function and every built-in constructor has the
- Function prototype object, which is the initial value of the expression
- Function.prototype
- (15.3.4), as the value of its [[Prototype]] internal property.
- Unless
- otherwise specified every built-in prototype object has the
- Object prototype object, which is the initial value of the expression
- Object.prototype
- (15.2.4), as the value of its [[Prototype]] internal property,
- except the Object prototype object itself.
- None
- of the built-in functions described in this clause that are not
- constructors shall implement the [[Construct]] internal method
- unless otherwise specified in the description of a particular
- function. None of the built-in functions described in this clause
- shall have a prototype
- property unless otherwise specified in the description of a
- particular function.
- This - clause generally describes distinct behaviours for when a - constructor is “called as a function” and for when it is “called - as part of a new expression”. The “called as a function” - behaviour corresponds to the invocation of the constructor’s - [[Call]] internal method and the “called as part of a new - expression” behaviour corresponds to the invocation of the - constructor’s [[Construct]] internal method. -
-
- Every
- built-in Function object described in this clause—whether as a
- constructor, an ordinary function, or both—has a length
- property whose value is an integer. Unless otherwise specified, this
- value is equal to the largest number of named arguments shown in the
- subclause headings for the function description, including optional
- parameters.
NOTE For
- example, the Function object that is the initial value of the slice
- property of the String prototype object is described under the
- subclause heading “String.prototype.slice (start, end)” which
- shows the two named arguments start and end; therefore the value of
- the length property of
- that Function object is 2.
- In
- every case, the length
- property of a built-in Function object described in this clause has
- the attributes { [[Writable]]: false, [[Enumerable]]:
- false, [[Configurable]]: false }. Every other property
- described in this clause has the attributes { [[Writable]]: true,
- [[Enumerable]]: false, [[Configurable]]: true } unless
- otherwise specified.
- The - unique global object is created before control enters any - execution context. -
-- Unless - otherwise specified, the standard built-in properties of the global - object have attributes {[[Writable]]: true, [[Enumerable]]: - false, [[Configurable]]: true}.
-
- The
- global object does not have a [[Construct]] internal property; it is
- not possible to use the global object as a constructor with the new
- operator.
- The - global object does not have a [[Call]] internal property; it is not - possible to invoke the global object as a function.
-- The - values of the [[Prototype]] and [[Class]] internal properties of the - global object are implementation-dependent.
-
- In
- addition to the properties defined in this specification the global
- object may have additional host defined properties. This may include
- a property whose value is the global object itself; for example, in
- the HTML document object model the window
- property of the global object is the global object itself.
- The
- value of NaN is
- NaN (see 8.5). This property has the attributes {
- [[Writable]]: false, [[Enumerable]]: false,
- [[Configurable]]: false }.
- The
- value of Infinity
- is +∞ (see 8.5).
- This property has the attributes { [[Writable]]: false,
- [[Enumerable]]: false, [[Configurable]]: false }.
- The
- value of undefined
- is undefined (see 8.1). This property has the attributes {
- [[Writable]]: false, [[Enumerable]]: false,
- [[Configurable]]: false }.
- When
- the eval function
- is called with one argument x,
- the following steps are taken:
- If - Type(x) - is not String, return x.
-- Let - prog be - the ECMAScript code that is the result of parsing x as a Program. - If the parse fails, throw a SyntaxError - exception (but see also clause 16).
-- Let - evalCtx be - the result of establishing a new execution context (10.4.2) for the - eval code prog.
-- Let - result be - the result of evaluating the program prog.
-- Exit - the running execution context evalCtx, restoring the previous - execution context.
-- If - result.type - is normal and its - completion value is a value V, - then return the value V.
-- If - result.type - is normal and its - completion value is empty, - then return the value undefined.
-- Otherwise, - result.type - must be throw. Throw - result.value - as an exception.
-- A - direct call to the eval function is one that is expressed as a - CallExpression - that meets the following two conditions:
-
- The
- Reference that is the result of evaluating the MemberExpression
- in the CallExpression
- has an environment record as its base value and its reference name
- is "eval".
- The - result of calling the abstract operation GetValue with that - Reference as the argument is the standard built-in function defined - in 15.1.2.1.
-
- The
- parseInt function
- produces an integer value dictated by interpretation of the contents
- of the string
- argument according to the specified radix.
- Leading white space in string
- is ignored. If radix
- is undefined or 0, it is assumed to be 10
- except when the number begins with the character pairs 0x
- or 0X, in which
- case a radix of 16 is assumed. If radix
- is 16, number may also
- optionally begin with the character pairs 0x
- or 0X.
- When
- the parseInt
- function is called, the following steps are taken:
- Let - inputString be ToString(string).
-- Let - S be a newly created substring of inputString - consisting of the first character that is not a StrWhiteSpaceChar - and all characters following that character. (In other words, - remove leading white space.) -If inputString does not contain any such characters, let S be the -empty string.
-- Let - sign be 1.
-
- If
- S is not empty and the first character of S is a
- minus sign -, let
- sign be −1.
- If
- S is not empty and the first character of S is a plus
- sign + or a minus
- sign -, then
- remove the first character from S.
- Let - R = ToInt32(radix).
-- Let - stripPrefix be true.
-- If - R ≠ 0, then
-- If - R < 2 or R > 36, then return NaN.
-- If - R ≠ 16, let stripPrefix - be false.
-- Else, - R = 0
-- Let - R = 10.
-- If - stripPrefix is true, then
-
- If
- the length of S is at least 2 and the first two characters
- of S are either “0x”
- or “0X”,
- then remove the first two characters from S and let R
- = 16.
- If - S contains any character that is not a radix-R digit, - then let Z be the substring of S consisting of all - characters before the first such character; otherwise, let Z - be S.
-- If - Z is empty, return NaN.
-
- Let
- mathInt be the mathematical integer value that is
- represented by Z in radix-R notation, using the
- letters A-Z
- and a-z
- for digits with values 10 through 35. (However, if R is 10
- and Z contains more than 20 significant digits, every
- significant digit after the 20th may be replaced by a 0
- digit, at the option of the implementation; and if R
- is not 2, 4, 8, 10, 16, or 32, then mathInt may be an
- implementation-dependent approximation to the mathematical integer
- value that is represented by Z in radix-R notation.)
- Let - number be the Number value for mathInt.
-- Return - sign × number.
-NOTE parseInt
- may interpret only a leading portion of string
- as an integer value; it ignores any characters that cannot be
- interpreted as part of the notation of an integer, and no indication
- is given that any such characters were ignored.
- The
- parseFloat
- function produces a Number value dictated by interpretation of the
- contents of the string
- argument as a decimal literal.
- When
- the parseFloat
- function is called, the following steps are taken:
- Let - inputString be ToString(string).
-- Let - trimmedString be a substring of inputString - consisting of the leftmost character that is not a - StrWhiteSpaceChar and all characters to the right of that - character. (In other words, remove leading white space.) -If inputString does not contain any such characters, let -trimmedString be the empty string.
-- If - neither trimmedString nor any prefix of trimmedString - satisfies the syntax of a StrDecimalLiteral (see 9.3.1), - return NaN.
-- Let - numberString be the longest prefix of trimmedString, - which might be trimmedString itself, that satisfies the - syntax of a StrDecimalLiteral.
-- Return - the Number value for the MV of numberString.
-NOTE parseFloat
- may interpret only a leading portion of string
- as a Number value; it ignores any characters that cannot be
- interpreted as part of the notation of an decimal literal, and no
- indication is given that any such characters were ignored.
- Returns - true if the argument coerces to NaN, and otherwise - returns false.
-- If - ToNumber(number) is NaN, return true.
-- Otherwise, - return false.
-NOTE A
- reliable way for ECMAScript code to test if a value X
- is a NaN is an expression of the form X
- !== X. The result will be true if and only if X
- is a NaN.
- Returns - false if the argument coerces to NaN, +∞, - or −∞, and otherwise - returns true.
-- If - ToNumber(number) is NaN, +∞, - or −∞, return false.
-- Otherwise, - return true.
-- Uniform - Resource Identifiers, or URIs, are Strings that identify resources - (e.g. web pages or files) and transport protocols by which to access - them (e.g. HTTP or FTP) on the Internet. The ECMAScript language - itself does not provide any support for using URIs except for - functions that encode and decode URIs as described in 15.1.3.1, - 15.1.3.2, 15.1.3.3 and 15.1.3.4.
-NOTE Many - implementations of ECMAScript provide additional functions and - methods that manipulate web pages; these functions are beyond the - scope of this standard.
-- A URI - is composed of a sequence of components separated by component - separators. The general form is:
-
- Scheme
- :
- First
- /
- Second
- ;
- Third
- ?
- Fourth
- where
- the italicised names represent components and the “:”,
- “/”, “;”
- and “?” are
- reserved characters used as separators. The encodeURI
- and decodeURI
- functions are intended to work with complete URIs; they assume that
- any reserved characters in the URI are intended to have special
- meaning and so are not encoded. The encodeURIComponent
- and decodeURIComponent
- functions are intended to work with the individual
- component parts of a URI; they assume that any reserved characters
- represent text and so must be encoded so that they are not
- interpreted as reserved characters when the component is part of a
- complete URI.
- The - following lexical grammar specifies the form of encoded URIs.
-- uri :::
-- uriCharactersopt
-- uriCharacters :::
-- uriCharacter - uriCharactersopt
-- uriCharacter :::
-
- uriReserved
uriUnescaped
uriEscaped
- uriReserved ::: one - of
-
- ;
- / ? : @ & = + $ ,
- uriUnescaped :::
-
- uriAlpha
DecimalDigit
uriMark
- uriEscaped :::
-
- % HexDigit HexDigit
- uriAlpha ::: one - of
-
- a
- b c d e f g h i j k l m n o p q r s t u v w x
- y z
A B C D E F G H I J K L M N O P Q R S T
- U V W X Y Z
- uriMark ::: one - of
-
- -
- _ . ! ~ * ' ( )
NOTE The above syntax is based upon RFC 2396 - and does not reflect changes introduced by the more recent RFC 3986.
- -
- When
- a character to be included in a URI is not listed above or is not
- intended to have the special meaning sometimes given to the reserved
- characters, that character must be encoded. The character is
- transformed into its UTF-8 encoding, with surrogate pairs first
- converted from UTF-16 to the corresponding code point value. (Note
- that for code units in the range [0,127] this results in a single
- octet with the same value.) The resulting sequence of octets is then
- transformed into a String with each octet represented by an escape
- sequence of the form “%xx”.
- The - encoding and escaping process is described by the abstract operation - Encode taking two String arguments string - and unescapedSet.
-- Let - strLen be the number of characters in string.
-- Let - R be the empty String.
-- Let - k be 0.
-- Repeat
-- If - k equals strLen, return R.
-- Let - C be the character at position k within string.
-- If - C is in unescapedSet, then
-- Let - S be a String containing only the character C.
-- Let - R be a new String value computed by concatenating the - previous value of R and S.
-- Else, - C is not in unescapedSet
-- If - the code unit value of C is not less than 0xDC00 and not - greater than 0xDFFF, throw a URIError exception.
-- If - the code unit value of C is less than 0xD800 or greater - than 0xDBFF, then
-- Let - V be the code unit value of C.
-- Else, - -
-- Increase - k by 1.
-- If - k equals strLen, throw a URIError - exception.
-- Let - kChar be the code unit value of the character at position - k within string.
-- If - kChar is less than 0xDC00 or greater than 0xDFFF, throw a - URIError exception.
-- Let - V be (((the code unit value of C) – 0xD800) * - 0x400 + (kChar – 0xDC00) + 0x10000).
-- Let - Octets be the array of octets resulting by applying the - UTF-8 transformation to V, and let L be the array - size.
-- Let - j be 0.
-- Repeat, - while j < L
-- Let - jOctet be the value at position j within Octets.
-
- Let
- S be a String containing three characters “%XY”
- where XY are two uppercase hexadecimal digits encoding
- the value of jOctet.
- Let - R be a new String value computed by concatenating the - previous value of R and S.
-- Increase - j by 1.
-- Increase - k by 1.
-- The - unescaping and decoding process is described by the abstract - operation Decode taking two String arguments string - and reservedSet.
-- Let - strLen be the number of characters in string.
-- Let - R be the empty String.
-- Let - k be 0.
-- Repeat
-- If - k equals strLen, return R.
-- Let - C be the character at position k within string.
-
- If
- C is not ‘%’,
- then
- Let - S be the String containing only the character C.
-
- Else,
- C is ‘%’
- Let - start be k.
-- If - k + 2 is greater than or equal to strLen, throw a - URIError exception.
-- If - the characters at position (k+1) and (k + 2) within - string do not represent hexadecimal digits, throw a - URIError exception.
-- Let - B be the 8-bit value represented by the two hexadecimal - digits at position (k + 1) and (k + 2).
-- Increment - k by 2.
-- If - the most significant bit in B is 0, then
-- Let - C be the character with code unit value B.
-- If - C is not in reservedSet, then
-- Let - S be the String containing only the character C.
-- Else, - C is in reservedSet
-- Let - S be the substring of string from position start - to position k included.
-- Else, - the most significant bit in B is 1
-- Let - n be the smallest non-negative number such that (B - << n) & 0x80 is equal to 0.
-- If - n equals 1 or n is greater than 4, throw a - URIError exception.
-- Let - Octets be an array of 8-bit integers of size n.
-- Put - B into Octets at position 0.
-- If - k + (3 * (n – 1)) is greater than or equal to - strLen, throw a URIError exception.
-- Let - j be 1.
-- Repeat, - while j < n
-- Increment - k by 1.
-- If - the character at position k is not ‘%’, throw a - URIError exception.
-- If - the characters at position (k +1) and (k + 2) - within string do not represent hexadecimal digits, throw - a URIError exception.
-- Let - B be the 8-bit value represented by the two hexadecimal - digits at position (k + 1) and (k + 2).
-- If - the two most significant bits in B are not 10, throw a - URIError exception.
-- Increment - k by 2.
-- Put - B into Octets at position j.
-- Increment - j by 1.
-- Let - V be the value obtained by applying the UTF-8 - transformation to Octets, that is, from an array of - octets into a 32-bit value. If Octets does not contain a - valid UTF-8 encoding of a Unicode code point throw a URIError - exception.
-- If - V is less than 0x10000, then
-- Let - C be the character with code unit value V.
-- If - C is not in reservedSet, then
-- Let - S be the String containing only the character C.
-- Else, - C is in reservedSet
-- Let - S be the substring of string from position start - to position k included.
-- Else, - V is ≥ 0x10000
-- Let - L be (((V – 0x10000) & 0x3FF) + 0xDC00).
-- Let - H be ((((V – 0x10000) >> 10) & 0x3FF) - + 0xD800).
-- Let - S be the String containing the two characters with code - unit values H and L.
-- Let - R be a new String value computed by concatenating the - previous value of R and S.
-- Increase - k by 1.
-NOTE The - syntax of Uniform Resource Identifiers is given in RFC 2396 and - does not reflect the more recent RFC 3986 which replaces RFC 2396. A - formal description and implementation of UTF-8 is given in RFC 3629.
- -- In - UTF-8, characters are encoded using sequences of 1 to 6 octets. The - only octet of a "sequence" of one has the higher-order bit - set to 0, the remaining 7 bits being used to encode the character - value. In a sequence of n octets, n>1, the initial octet has the - n higher-order bits set to 1, followed by a bit set to 0. The - remaining bits of that octet contain bits from the value of the - character to be encoded. The following octets all have the - higher-order bit set to 1 and the following bit set to 0, leaving 6 - bits in each to contain bits from the character to be encoded. The - possible UTF-8 encodings of ECMAScript characters are specified in - Table 21.
-|
- - Code - Unit Value - |
-
- - Representation - |
-
- - 1st - Octet - |
-
- - 2nd - Octet - |
-
- - 3rd - Octet - |
-
- - 4th - Octet - |
-
|
-
- |
-
-
- |
-
-
- |
- - | -- | -- | -
|
-
- |
-
-
- |
-
-
- |
-
-
- |
- - | -- | -
|
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
- - | -
|
-
- - followed - by -
- |
-
-
- - followed - by -
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
|
-
- - not - followed by -
- |
-
-
- |
- - | -- | -- | -- | -
|
-
- |
-
-
- |
- - | -- | -- | -- | -
|
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
- - | -
- Where
-
- uuuuu
- =
- vvvv +
- 1
- to - account for the addition of 0x10000 as in Surrogates, section 3.7, - of the Unicode Standard.
-- The - range of code unit values 0xD800-0xDFFF is used to encode surrogate - pairs; the above transformation combines a UTF-16 surrogate pair - into a UTF-32 representation and encodes the resulting 21-bit value - in UTF-8. Decoding reconstructs the surrogate pair.
-- RFC - 3629 prohibits the decoding of invalid UTF-8 octet sequences. For - example, the invalid sequence C0 80 must not decode into the - character U+0000. Implementations of the Decode algorithm are - required to throw a URIError - when encountering such invalid sequences.
-
- The
- decodeURI function
- computes a new version of a URI in which each escape sequence and
- UTF-8 encoding of the sort that might be introduced by the encodeURI
- function is replaced with the character that it represents. Escape
- sequences that could not have been introduced by encodeURI
- are not replaced.
- When
- the decodeURI
- function is called with one argument encodedURI,
- the following steps are taken:
- Let - uriString be ToString(encodedURI).
-
- Let
- reservedURISet be a String containing one instance of each
- character valid in uriReserved plus “#”.
- Return - the result of calling Decode(uriString, reservedURISet)
-NOTE The
- character “#”
- is not decoded from escape sequences even though it is not a
- reserved URI character.
- The
- decodeURIComponent
- function computes a new version of a URI in which each escape
- sequence and UTF-8 encoding of the sort that might be introduced by
- the encodeURIComponent
- function is replaced with the character that it represents.
- When
- the decodeURIComponent
- function is called with one argument encodedURIComponent,
- the following steps are taken:
- Let - componentString be ToString(encodedURIComponent).
-- Let - reservedURIComponentSet be the empty String.
-- Return - the result of calling Decode(componentString, - reservedURIComponentSet)
-
- The
- encodeURI function
- computes a new version of a URI in which each instance of certain
- characters is replaced by one, two or three escape sequences
- representing the UTF-8 encoding of the character.
- When
- the encodeURI
- function is called with one argument uri,
- the following steps are taken:
- Let - uriString be ToString(uri).
-
- Let
- unescapedURISet be a String containing one instance of each
- character valid in uriReserved and uriUnescaped plus
- “#”.
- Return - the result of calling Encode(uriString, unescapedURISet)
-NOTE The
- character “#”
- is not encoded to an escape sequence even though it is not a
- reserved or unescaped URI character.
- The
- encodeURIComponent
- function computes a new version of a URI in which each instance of
- certain characters is replaced by one, two or three escape sequences
- representing the UTF-8 encoding of the character.
- When
- the encodeURIComponent
- function is called with one argument uriComponent,
- the following steps are taken:
- Let - componentString be ToString(uriComponent).
-- Let - unescapedURIComponentSet be a String containing one instance - of each character valid in uriUnescaped.
-- Return - the result of calling Encode(componentString, - unescapedURIComponentSet)
-- See - 15.9.2.
-- See - 15.11.6.1.
-- See - 15.11.6.2.
-- See - 15.11.6.3.
-- See - 15.11.6.4.
-- See - 15.11.6.5.
-- See - 15.11.6.6.
-- See - 15.8.
-- See - 15.12.
-
- When
- Object is called
- as a function rather than as a constructor, it performs a type
- conversion.
- When
- the Object
- function is called with no arguments or with one argument value,
- the following steps are taken:
- If - value is null, undefined or not supplied, - create and return a new Object object exactly as if the standard - built-in Object constructor had been called with the same arguments - (15.2.2.1).
-- Return - ToObject(value).
-
- When
- Object is called
- as part of a new
- expression, it is a constructor that may create an object.
- When
- the Object
- constructor is called with no arguments or with one argument value,
- the following steps are taken:
- If - value is supplied, then
-- If - Type(value) is Object, then
-- If - the value is a native ECMAScript object, do not create a - new object but simply return value.
-- If - the value is a host object, then actions are taken and a - result is returned in an implementation-dependent manner that may - depend on the host object.
-- Asset: - The argument value was not supplied or its type was Null or - Undefined. -
-- Let - obj be a newly created native ECMAScript object.
-- Set - the [[Prototype]] internal property of obj t to the standard - built-in Object prototype object (15.2.4).
-
- Set
- the [[Class]] internal property of obj to "Object".
- Set - the [[Extensible]] internal property of obj to true.
-- Set - the all the internal methods of obj as specified in 8.12
-- Return - obj.
-- The - value of the [[Prototype]] internal property of the Object - constructor is the standard built-in Function prototype object.
-
- Besides
- the internal properties and the length
- property (whose value is 1), the Object constructor has the
- following properties:
- The
- initial value of Object.prototype
- is the standard built-in Object prototype object (15.2.4).
- This - property has the attributes {[[Writable]]: false, [[Enumerable]]: - false, [[Configurable]]: false }.
-
- When
- the getPrototypeOf
- function is called with argument O,
- the following steps are taken:
- If - Type(O) is not Object throw a TypeError exception.
-- Return - the value of the [[Prototype]] internal property of O.
-- When - the getOwnPropertyDescriptor function is called, the - following steps are taken:
-- If - Type(O) is not Object throw a TypeError exception.
-- Let - name be ToString(P).
-- Let - desc be the result of calling the [[GetOwnProperty]] - internal method of O with argument name.
-- Return - the result of calling FromPropertyDescriptor(desc) (8.10.4). -
-- When - the getOwnPropertyNames function is called, the following - steps are taken:
-- If - Type(O) is not Object throw a TypeError exception.
-
- Let
- array be the result of creating a new object as if by the
- expression new Array ()
- where Array is
- the standard built-in constructor with that name.
- Let - n be 0.
-- For - each named own property P of O
-- Let - name be the String value that is the name of P.
-- Call - the [[DefineOwnProperty]] internal method of array with - arguments ToString(n), the PropertyDescriptor {[[Value]]: - name, [[Writable]]: true, [[Enumerable]]: true, - [[Configurable]]: true}, and false.
-- Increment - n by 1.
-- Return - array.
-NOTE If - O is a String - instance, the set of own properties processed in step 4 includes the - implicit properties defined in 15.5.5.2 that correspond to character - positions within the object’s [[PrimitiveValue]] String.
-- The - create function creates a new object with a specified - prototype. When the create function is called, the following - steps are taken:
-- If - Type(O) is not Object or Null throw a TypeError - exception.
-- Let - obj be the result of creating a new object as if by the - expression new Object() where Object is the standard built-in - constructor with that name
-- Set - the [[Prototype]] internal property of obj to O.
-
- If
- the argument Properties is present and not undefined,
- add own properties to obj as if by calling the standard
- built-in function Object.defineProperties
-with arguments obj and Properties.
- Return - obj.
-- The - defineProperty function is used to add an own property and/or - update the attributes of an existing own property of an object. When - the defineProperty function is called, the following steps - are taken:
-- If - Type(O) is not Object throw a TypeError exception.
-- Let - name be ToString(P).
-- Let - desc be the result of calling ToPropertyDescriptor with - Attributes as the argument.
-- Call - the [[DefineOwnProperty]] internal method of O with - arguments name, desc, and true.
-- Return - O.
-- The - defineProperties function is used to add own properties - and/or update the attributes of existing own properties of an - object. When the defineProperties function is called, the - following steps are taken:
-- Let - props be ToObject(Properties).
-- Let - names be an internal list containing the names of each - enumerable own property of props.
-- Let - descriptors be an empty internal List.
-- For - each element P of names in list order,
-- Let - descObj be the result of calling the [[Get]] internal - method of props with P as the argument.
-- Let - desc be the result of calling ToPropertyDescriptor with - descObj as the argument.
-- Append - desc to the end of descriptors.
-For - each element desc of descriptors in list order,
-Call the [[DefineOwnProperty]] internal method of O with - arguments P, desc, and true.
Return O
-- If an - implementation defines a specific order of enumeration for the - for-in statement, that same enumeration order must be used to order - the list elements in step 3 of this algorithm.
-- When - the seal function is called, the following steps are taken:
-- If - Type(O) is not Object throw a TypeError exception.
-- For - each named own property name P of O,
-- Let - desc be the result of calling the [[GetOwnProperty]] - internal method of O with P.
-- If - desc.[[Configurable]] is true, set - desc.[[Configurable]] to false.
-- Call - the [[DefineOwnProperty]] internal method of O with P, - desc, and true as arguments.
-- Set - the [[Extensible]] internal property of O to false.
-- Return - O.
-- When - the freeze function is called, the following steps are taken:
-- If - Type(O) is not Object throw a TypeError exception.
-- For - each named own property name P of O,
-- Let - desc be the result of calling the [[GetOwnProperty]] - internal method of O with P.
-- If - IsDataDescriptor(desc) is true, then
-- If - desc.[[Writable]] is true, set desc.[[Writable]] - to false.
-- If - desc.[[Configurable]] is true, set - desc.[[Configurable]] to false.
-- Call - the [[DefineOwnProperty]] internal method of O with P, - desc, and true as arguments.
-- Set - the [[Extensible]] internal property of O to false.
-- Return - O.
-- When - the preventExtensions function is called, the following steps - are taken:
-- If - Type(O) is not Object throw a TypeError exception.
-- Set - the [[Extensible]] internal property of O to false.
-- Return - O.
-- When - the isSealed function is called with argument O, - the following steps are taken:
-- If - Type(O) is not Object throw a TypeError exception.
-- For - each named own property name P of O,
-- Let - desc be the result of calling the [[GetOwnProperty]] - internal method of O with P.
-- If - desc.[[Configurable]] is true, then return false.
-- If - the [[Extensible]] internal property of O is false, - then return true.
-- Otherwise, - return false.
-- When - the isFrozen function is called with argument O, - the following steps are taken:
-- If - Type(O) is not Object throw a TypeError exception.
-- For - each named own property name P of O,
-- Let - desc be the result of calling the [[GetOwnProperty]] - internal method of O with P.
-- If - IsDataDescriptor(desc) is true then
-- If - desc.[[Writable]] is true, return false.
-- If - desc.[[Configurable]] is true, then return false.
-- If - the [[Extensible]] internal property of O is false, - then return true.
-- Otherwise, - return false.
-- When - the isExtensible function is called with argument O, - the following steps are taken:
-- If - Type(O) is not Object throw a TypeError exception.
-- Return - the Boolean value of the [[Extensible]] internal property of O.
-- When - the keys function is called with argument O, - the following steps are taken:
-- If - the Type(O) is not Object, throw a TypeError - exception.
-- Let - n be the number of own enumerable properties of O
-
- Let
- array be the result of creating a new Object as if by the
- expression new Array(n)
- where Array
- is the standard built-in constructor with that name.
- Let - index be 0.
-- For - each own enumerable property of O whose name String is P - -
-- Call - the [[DefineOwnProperty]] internal method of array with - arguments ToString(index), the PropertyDescriptor - {[[Value]]: P, [[Writable]]: true, [[Enumerable]]: - true, [[Configurable]]: true}, and false.
-- Increment - index by 1.
-- Return - array.
-- If an - implementation defines a specific order of enumeration for the - for-in statement, that same enumeration order must be used in step 5 - of this algorithm.
-
- The
- value of the [[Prototype]] internal property of the Object prototype
- object is null, the value of the [[Class]] internal property
- is "Object",
- and the initial value of the [[Extensible]] internal property is
- true.
- The
- initial value of Object.prototype.constructor
- is the standard built-in Object
- constructor.
- When
- the toString
- method is called, the following steps are taken:
If - the this - value is undefined, - return "[object Undefined]".
If - the this - value is null, - return "[object Null]".
Let - O be the result of calling ToObject passing the this value - as the argument.
Let - class be the value of the [[Class]] internal property of O.
Return - the String value that is the result of concatenating the three - Strings "[object ", - class, and "]".
- When - the toLocaleString method is called, the following steps are - taken:
-- Let - O be the result of calling ToObject passing the this - value as the argument.
-- Let - toString be the result of calling the [[Get]] internal - method of O passing "toString" as the - argument.
-- If - IsCallable(toString) is false, throw a TypeError - exception.
-- Return - the result of calling the [[Call]] internal method of toString - passing O as the this value and no arguments.
-NOTE 1 This function is provided to give all Objects a generic
- toLocaleString
- interface, even though not all may use it. Currently, Array,
- Number, and Date
- provide their own locale-sensitive toLocaleString
- methods.
NOTE 2 The first parameter to this function is likely to be used in a - future version of this standard; it is recommended that - implementations do not use this parameter position for anything - else.
-- When - the valueOf method is called, the following steps are taken: -
-- Let - O be the result of calling ToObject passing the this - value as the argument.
-- If - O is the result of calling the Object constructor with a - host object (15.2.2.1), then
-- Return - either O or another value such as the host object - originally passed to the constructor. The specific result that is - returned is implementation-defined.
-- Return - O.
-
- When
- the hasOwnProperty
- method is called with argument V,
- the following steps are taken:
- Let - P be ToString(V).
-- Let - O be the result of calling ToObject passing the this - value as the argument.
-- Let - desc be the result of calling the [[GetOwnProperty]] - internal method of O passing P as the argument.
-- If - desc is undefined, return false.
-- Return - true.
-NOTE 1 Unlike [[HasProperty]] (8.12.6), this method does not consider - objects in the prototype chain.
-NOTE 2 The ordering of steps 1 and 2 is chosen to ensure that any - exception that would have been thrown by step 1 in previous editions - of this specification will continue to be thrown even if the this - value is undefined or null.
-
- When
- the isPrototypeOf
- method is called with argument V,
- the following steps are taken:
- If - V is not an object, return false.
-- Let - O be the result of calling ToObject passing the this - value as the argument.
-- Repeat
-- Let - V be the value of the [[Prototype]] internal property of V.
-- if - V is null, return false
-- If - O and V refer to the same object, return true.
-NOTE The - ordering of steps 1 and 2 is chosen to preserve the behaviour - specified by previous editions of this specification for the case - where V is not an object and the this value is undefined or null.
-
- When
- the propertyIsEnumerable
- method is called with argument V,
- the following steps are taken:
- Let - P be ToString(V).
-- Let - O be the result of calling ToObject passing the this - value as the argument.
-- Let - desc be the result of calling the [[GetOwnProperty]] - internal method of O passing P as the argument.
-- If - desc is undefined, return false.
-- Return - the value of desc.[[Enumerable]].
-NOTE 1 This method does not consider objects in the prototype chain.
-NOTE 2 The ordering of steps 1 and 2 is chosen to ensure that any - exception that would have been thrown by step 1 in previous editions - of this specification will continue to be thrown even if the this - value is undefined or null.
-- Object - instances have no special properties beyond those inherited from the - Object prototype object.
-
- When
- Function is called
- as a function rather than as a constructor, it creates and
- initialises a new Function object. Thus the function call
- Function(…)
- is equivalent to the object creation expression new
- Function(…)
- with the same arguments.
- When
- the Function
- function is called with some arguments p1,
- p2, … , pn,
- body (where n
- might be 0, that is,
- there are no “p”
- arguments, and where body
- might also not be provided), the following steps are taken:
- Create - and return a new Function object as if the standard built-in - constructor Function was used in a new expression with the - same arguments (15.3.2.1).
-
- When
- Function is called
- as part of a new
- expression, it is a constructor: it initialises the newly created
- object.
- The - last argument specifies the body (executable code) of a function; - any preceding arguments specify formal parameters.
-
- When
- the Function
- constructor is called with some arguments p1,
- p2, … , pn,
- body (where n
- might be 0, that is,
- there are no “p”
- arguments, and where body
- might also not be provided), the following steps are taken:
- Let - argCount be the total number of arguments passed to this - function invocation.
-- Let - P be the empty String.
-- If - argCount = 0, let body be the empty String.
-- Else - if argCount = 1, let body be that argument.
-- Else, - argCount > 1
-- Let - firstArg be the first argument.
-- Let - P be ToString(firstArg).
-- Let - k be 2.
-- Repeat, - while k < argCount
-- Let - nextArg be the k’th argument.
-
- Let
- P be the result of concatenating the previous value of P,
- the String ","
- (a comma), and ToString(nextArg).
- Increase - k by 1.
-- Let - body be the k’th argument.
-- Let - body be ToString(body).
-- If - P is not parsable as a FormalParameterListopt - then throw a SyntaxError exception.
-- If - body is not parsable as FunctionBody then throw a - SyntaxError exception.
-- Ifbody is strict mode code (see 10.1.1) then let strict be - true, else let strict be false.
-- If - strict is true, throw any exceptions specified in - 13.1 that apply. -
-- Return - a new Function object created as specified in 13.2 passing P - as the FormalParameterList and body as the - FunctionBody. Pass in the Global Environment as the Scope - parameter and strict as the Strict flag.
-
- A
- prototype property
- is automatically created for every function, to provide for the
- possibility that the function will be used as a constructor.
-
NOTE It - is permissible but not necessary to have one argument for each - formal parameter to be specified. For example, all three of the - following expressions produce the same result:
-
- new
- Function("a", "b", "c", "return
- a+b+c")
- new
- Function("a, b, c", "return a+b+c")
- new
- Function("a,b", "c", "return a+b+c")
- The
- Function constructor is itself a Function object and its [[Class]]
- is "Function".
- The value of the [[Prototype]] internal property of the Function
- constructor is the standard built-in Function prototype object
- (15.3.4).
- The - value of the [[Extensible]] internal property of the Function - constructor is true.
-- The - Function constructor has the following properties:
-
- The
- initial value of Function.prototype
- is the standard built-in Function prototype object (15.3.4).
- This - property has the attributes { [[Writable]]: false, - [[Enumerable]]: false, [[Configurable]]: false }.
-- This - is a data property with a value of 1. This property has the - attributes { [[Writable]]: false, [[Enumerable]]: false, - [[Configurable]]: false }.
-
- The
- Function prototype object is itself a Function object (its [[Class]]
- is "Function")
- that, when invoked, accepts any arguments and returns undefined.
- The - value of the [[Prototype]] internal property of the Function - prototype object is the standard built-in Object prototype object - (15.2.4). The initial value of the [[Extensible]] internal property - of the Function prototype object is true.
-
- The
- Function prototype object does not have a valueOf
- property of its own; however, it inherits the valueOf
- property from the Object prototype Object.
- The
- length property of
- the Function prototype object is 0.
- The
- initial value of Function.prototype.constructor
- is the built-in Function
- constructor.
- An - implementation-dependent representation of the function is returned. - This representation has the syntax of a FunctionDeclaration. - Note in particular that the use and placement of white space, line - terminators, and semicolons within the representation String is - implementation-dependent.
-
- The
- toString function
- is not generic; it throws a TypeError exception if its this
- value is not a Function object. Therefore, it cannot be transferred
- to other kinds of objects for use as a method.
- When
- the apply method
- is called on an object func
- with arguments thisArg
- and argArray, the
- following steps are taken:
-
- If - IsCallable(func) is false, then throw a TypeError - exception.
-- If - argArray is null or undefined, then
-- Return - the result of calling the [[Call]] internal method of func, - providing thisArg as the this value and an empty - list of arguments.
-- If - Type(argArray) is not Object, then throw a TypeError - exception.
-
- Let
- len be the result of calling the [[Get]] internal method of
- argArray with argument "length".
- Let - n be ToUint32(len).
-- Let - argList be an empty List.
-- Let - index be 0.
-- Repeat - while index < n
-- Let - indexName be ToString(index).
-- Let - nextArg be the result of calling the [[Get]] internal - method of argArray with indexName as the argument.
-- Append - nextArg as the last element of argList.
-- Set - index to index + 1.
-- Return - the result of calling the [[Call]] internal method of func, - providing thisArg as the this value and argList - as the list of arguments.
-
- The
- length property of
- the apply method
- is 2.
NOTE The - thisArg value is passed without modification as the this - value. This is a change from Edition 3, where a undefined or - null thisArg is replaced with the global object and ToObject - is applied to all other values and that result is passed as the this - value.
-
- When
- the call method is
- called on an object func
- with argument thisArg
- and optional arguments arg1,
- arg2 etc, the
- following steps are taken:
- If - IsCallable(func) is false, then throw a TypeError - exception.
-- Let - argList be an empty List.
-- If - this method was called with more than one argument then in left to - right order starting with arg1 append each argument as the - last element of argList
-- Return - the result of calling the [[Call]] internal method of func, - providing thisArg as the this value and argList - as the list of arguments.
-
- The
- length property of
- the call method is
- 1.
NOTE The - thisArg value is passed without modification as the this - value. This is a change from Edition 3, where a undefined or - null thisArg is replaced with the global object and ToObject - is applied to all other values and that result is passed as the this - value.
-- The - bind method takes one or more arguments, thisArg - and (optionally) arg1, - arg2, etc, and - returns a new function object by performing the following steps:
-- Let - Target be the this value.
-- If - IsCallable(Target) is false, throw a TypeError - exception.
-- Let - A be a new (possibly empty) internal list of all of the - argument values provided after thisArg (arg1, arg2 - etc), in order.
-- Let - F be a new native ECMAScript object .
-- Set - all the internal methods, except for [[Get]], of F as - specified in 8.12.
-- Set - the [[Get]] internal property of F as specified in 15.3.5.4.
-- Set - the [[TargetFunction]] internal property of F to Target.
-- Set - the [[BoundThis]] internal property of F to the value of - thisArg.
-- Set - the [[BoundArgs]] internal property of F to A.
-- Set - the [[Class]] internal property of F to "Function".
-- Set - the [[Prototype]] internal property of F to the standard - built-in Function prototype object as specified in 15.3.3.1.
-- Set - the [[Call]] internal property of F as described in - 15.3.4.5.1.
-- Set - the [[Construct]] internal property of F as described in - 15.3.4.5.2.
-- Set - the [[HasInstance]] internal property of F as described in - 15.3.4.5.3.
-- If - the [[Class]] internal property of Target is "Function", - then
-- Let - L be the length property of Target minus the - length of A.
-- Set - the length own property of F to either 0 or - L, whichever is larger. -
-- Else - set the length own property of F to 0.
-- Set - the attributes of the length own property of F to - the values specified in 15.3.5.1.
-- Set - the [[Extensible]] internal property of F to true.
-- Let - thrower be the [[ThrowTypeError]] function Object (13.2.3).
-
- Call
- the [[DefineOwnProperty]] internal method of F with
- arguments "caller",
- PropertyDescriptor {[[Get]]: thrower, [[Set]]: thrower,
- [[Enumerable]]: false, [[Configurable]]: false}, and
- false.
- Call
- the [[DefineOwnProperty]] internal method of F with
- arguments "arguments",
- PropertyDescriptor {[[Get]]: thrower, [[Set]]: thrower,
- [[Enumerable]]: false, [[Configurable]]: false}, and
- false.
- Return - F.
-
- The
- length property of
- the bind method is
- 1.
NOTE Function
- objects created using Function.prototype.bind
- do not have a prototype
- property or the [[Code]], [[FormalParameters]], and [[Scope]]
- internal properties.
- When - the [[Call]] internal method of a function object, F, - which was created using the bind function is called with a this - value and a list of arguments ExtraArgs, - the following steps are taken:
-- Let - boundArgs be the value of F’s [[BoundArgs]] - internal property.
-- Let - boundThis be the value of F’s [[BoundThis]] - internal property.
-- Let - target be the value of F’s [[TargetFunction]] - internal property.
-- Let - args be a new list containing the same values as the list - boundArgs in the same order followed by the same values as - the list ExtraArgs in the same order.
-- Return - the result of calling the [[Call]] internal method of target - providing boundThis as the this value and providing - args as the arguments.
-- When - the [[Construct]] internal method of a function object, F - that was created using the bind function is called with a list of - arguments ExtraArgs, - the following steps are taken:
-- Let - target be the value of F’s [[TargetFunction]] - internal property.
-- If - target has no [[Construct]] internal method, a TypeError - exception is thrown.
-- Let - boundArgs be the value of F’s [[BoundArgs]] - internal property.
-- Let - args be a new list containing the same values as the list - boundArgs in the same order followed by the same values as - the list ExtraArgs in the same order.
-- Return - the result of calling the [[Construct]] internal method oftarget providing args as the arguments.
-- When - the [[HasInstance]] internal method of a function object F, - that was created using the bind function is called with argument V, - the following steps are taken:
-- Let - target be the value of F’s [[TargetFunction]] - internal property.
-- If - target has no [[HasInstance]] internal method, a TypeError - exception is thrown.
-- Return - the result of calling the [[HasInstance]] internal method oftarget providing V as the argument.
-- In - addition to the required internal properties, every function - instance has a [[Call]] internal property and in most cases use a - different version of the [[Get]] internal property. Depending on how - they are created (see 8.6.2 ,13.2, 15, and 15.3.4.5), function - instances may have a [[HasInstance]] internal property, a [[Scope]] - internal property, a [[Construct]] internal property, a - [[FormalParameters]] internal property, a [[Code]] internal - property, a [[TargetFunction]] internal property, a [[BoundThis]] - internal property, and a [[BoundArgs]] internal property.
-- The - value of the [[Class]] internal property is "Function".
-- Function - instances that correspond to strict mode functions (13.2) and - function instances created using the Function.prototype.bind - method (15.3.4.5) have properties named “caller” and - “arguments” that throw a TypeError exception. An - ECMAScript implementation must not associate any implementation - specific behaviour with accesses of these properties from strict - mode function code. -
-
- The
- value of the length
- property is an integer that indicates the “typical” number of
- arguments expected by the function. However, the language permits
- the function to be invoked with some other number of arguments. The
- behaviour of a function when invoked on a number of arguments other
- than the number specified by its length
- property depends on the function. This property has the attributes
- { [[Writable]]: false,
- [[Enumerable]]: false,
- [[Configurable]]: false }.
- The
- value of the prototype
- property is used to initialise the [[Prototype]] internal property
- of a newly created object before the Function object is invoked as a
- constructor for that newly created object. This property has the
- attribute { [[Writable]]: true,
- [[Enumerable]]: false,
- [[Configurable]]: false
- }.
NOTE Function
- objects created using Function.prototype.bind
- do not have a prototype
- property.
- Assume - F is a Function - object.
-- When - the [[HasInstance]] internal method of F - is called with value V, - the following steps are taken:
-- If - V is not an object, return false.
-
- Let
- O be the result of calling the [[Get]] internal method of F
- with property name "prototype".
- Repeat
-- Let - V be the value of the [[Prototype]] internal property of V.
-
- If
- V is null,
- return false.
- If - O and V refer to the same object, return true.
--
NOTE Function
- objects created using Function.prototype.bind
- have a different implementation of [[HasInstance]] defined in
- 15.3.4.5.3.
- Function - objects use a variation of the [[Get]] internal method used for - other native ECMAScript objects (8.12.3).
-- Assume - F is a Function - object. When the [[Get]] internal method of F - is called with property name P, - the following steps are taken:
-- Let - v be the result of calling the default [[Get]] internal - method (8.12.3) on F passing P as the property name - argument.
-
- If
- P is "caller"
- and v is a strict mode Function object, throw a
- TypeError exception.
-
- Return - v.
-NOTE Function
- objects created using Function.prototype.bind
- use the default [[Get]] internal method.
- Array
- objects give special treatment to a certain class of property names.
- A property name P
- (in the form of a String value) is an array index if and only
- if ToString(ToUint32(P))
- is equal to P and
- ToUint32(P)
- is not equal to 232−1.
- A property whose property name is an array index is also called an
- element. Every Array object has a length
- property whose value is always a nonnegative integer less than 232.
- The value of the length
- property is numerically greater than the name of every property
- whose name is an array index; whenever a property of an Array object
- is created or changed, other properties are adjusted as necessary to
- maintain this invariant. Specifically, whenever a property is added
- whose name is an array index, the length
- property is changed, if necessary, to be one more than the numeric
- value of that array index; and whenever the length
- property is changed, every property whose name is an array index
- whose value is not smaller than the new length is automatically
- deleted. This constraint applies only to own properties of an Array
- object and is unaffected by length
- or array index properties that may be inherited from its prototypes.
- An - object, O, is - said to be sparse if the following algorithm returns true:
-- Let - len - be the result of calling the [[Get]] internal method of O - with argument "length".
-- For - each integer i - in the range 0≤i<ToUint32(len)
-- Let - elem - be the result of calling the [[GetOwnProperty]] internal method of - O - with argument ToString(i).
-- If - elem - is undefined, - return true.
-- Return - false.
-
- When
- Array is called as
- a function rather than as a constructor, it creates and initialises
- a new Array object. Thus the function call Array(…)
- is equivalent to the object creation expression new Array(…)
- with the same arguments.
- When
- the Array function
- is called the following steps are taken:
- Create
- and return a new Array object exactly as if the standard built-in
- constructor Array
- was used in a new
- expression with the same arguments (15.4.2).
- When
- Array is called as
- part of a new
- expression, it is a constructor: it initialises the newly created
- object.
- This - description applies if and only if the Array constructor is given no - arguments or at least two arguments.
-
- The
- [[Prototype]] internal property of the newly constructed object is
- set to the original Array prototype object, the one that is the
- initial value of Array.prototype
- (15.4.3.1).
- The
- [[Class]] internal property of the newly constructed object is set
- to "Array".
- The - [[Extensible]] internal property of the newly constructed object is - set to true.
-
- The
- length property of
- the newly constructed object is set to the number of arguments.
- The 0
- property of the newly constructed object is set to item0
- (if supplied); the 1
- property of the newly constructed object is set to item1
- (if supplied); and, in general, for as many arguments as there are,
- the k property of
- the newly constructed object is set to argument k,
- where the first argument is considered to be argument number 0.
- These properties all have the attributes {[[Writable]]: true,
- [[Enumerable]]: true, [[Configurable]]: true}.
- The
- [[Prototype]] internal property of the newly constructed object is
- set to the original Array prototype object, the one that is the
- initial value of Array.prototype
- (15.4.3.1). The [[Class]] internal property of the newly constructed
- object is set to "Array".
- The [[Extensible]] internal property of the newly constructed object
- is set to true.
- If
- the argument len
- is a Number and ToUint32(len)
- is equal to len,
- then the length
- property of the newly constructed object is set to ToUint32(len).
- If the argument len
- is a Number and ToUint32(len)
- is not equal to len,
- a RangeError exception is thrown.
- If
- the argument len
- is not a Number, then the length
- property of the newly constructed object is set to 1
- and the 0 property
- of the newly constructed object is set to len
- with attributes {[[Writable]]: true, [[Enumerable]]: true,
- [[Configurable]]: true}..
- The - value of the [[Prototype]] internal property of the Array - constructor is the Function prototype object (15.3.4).
-
- Besides
- the internal properties and the length
- property (whose value is 1), the Array constructor has the
- following properties:
- The
- initial value of Array.prototype
- is the Array prototype object (15.4.4).
- This - property has the attributes { [[Writable]]: false, - [[Enumerable]]: false, [[Configurable]]: false }.
-
- The
- isArray function takes one argument arg,
- and returns the Boolean value true if the argument is an
- object whose class internal property is "Array";
- otherwise it returns false. The following steps are taken:
- If - Type(arg) is not Object, return false.
-
- If
- the value of the [[Class]] internal property of arg is
- "Array",
- then return true.
- Return - false.
-- The - value of the [[Prototype]] internal property of the Array prototype - object is the standard built-in Object prototype object (15.2.4).
-
- The
- Array prototype object is itself an array; its [[Class]] is "Array",
- and it has a length
- property (whose initial value is +0) and the special
- [[DefineOwnProperty]] internal method described in 15.4.5.1.
- In
- following descriptions of functions that are properties of the Array
- prototype object, the phrase “this object” refers to the object
- that is the this value for the invocation of the function. It
- is permitted for the this to be an object for which the value
- of the [[Class]] internal property is not "Array".
NOTE The
- Array prototype object does not have a valueOf
- property of its own; however, it inherits the valueOf
- property from the standard built-in Object prototype Object.
- The
- initial value of Array.prototype.constructor
- is the standard built-in Array
- constructor.
- When
- the toString
- method is called, the following steps are taken:
- Let - array be the result of calling ToObject on the this - value.
-
- Let
- func be the result of calling the [[Get]] internal method of
- array with argument "join".
- If - IsCallable(func) is false, then let func be - the standard built-in method Object.prototype.toString (15.2.4.2).
-- Return - the result of calling the [[Call]] internal method of func - providing array as the this value and an empty - arguments list.
--
NOTE The toString
- function is intentionally generic; it does not require that its this
- value be an Array object. Therefore it can be transferred to other
- kinds of objects for use as a method. Whether the toString
- function can be applied successfully to a host object is
- implementation-dependent.
- The
- elements of the array are converted to Strings using their
- toLocaleString
- methods, and these Strings are then concatenated, separated by
- occurrences of a separator String that has been derived in an
- implementation-defined locale-specific way. The result of calling
- this function is intended to be analogous to the result of toString,
- except that the result of this function is intended to be
- locale-specific.
- The - result is calculated as follows:
-- Let - O be the result of calling ToObject passing the this - value as the argument.
-
- Let
- arrayLen be the result of calling the [[Get]] internal
- method of array with argument "length".
- Let - len be ToUint32(arrayLen).
-- Let - separator be the String value for the list-separator String - appropriate for the host environment’s current locale (this is - derived in an implementation-defined way).
-- If - len is zero, return the empty String.
-
- Let
- firstElement be the result of calling the [[Get]] internal
- method of array with argument "0".
- If - firstElement is undefined or null, then
-- Let - R be the empty String.
-- Else - -
-- Let - elementObj be ToObject(firstElement).
-
- Let
- func be the result of calling the [[Get]] internal method
- of elementObj with argument "toLocaleString".
- If - IsCallable(func) is false, throw a TypeError - exception.
-- Let - R be the result of calling the [[Call]] internal method of - func providing elementObj as the this value - and an empty arguments list. -
-
- Let
- k be 1.
- Repeat, - while k < len
-- Let - S be a String value produced by concatenating R and - separator.
-- Let - nextElement be the result of calling the [[Get]] internal - method of array with argument ToString(k).
-- If - nextElement is undefined or null, then
-- Let - R be the empty String.
-- Else - -
-- Let - elementObj be ToObject(nextElement).
-
- Let
- func be the result of calling the [[Get]] internal method
- of elementObj with argument "toLocaleString".
- If - IsCallable(func) is false, throw a TypeError - exception.
-- Let - R be the result of calling the [[Call]] internal method of - func providing elementObj as the this value - and an empty arguments list. -
-- Let - R be a String value produced by concatenating S and - R.
-- Increase - k by 1.
-- Return - R.
-NOTE 1 The first parameter to this function is likely to be used in a - future version of this standard; it is recommended that - implementations do not use this parameter position for anything - else.
-NOTE 2 The toLocaleString
- function is intentionally generic; it does not require that its this
- value be an Array object. Therefore it can be transferred to other
- kinds of objects for use as a method. Whether the toLocaleString
- function can be applied successfully to a host object is
- implementation-dependent.
- When
- the concat method
- is called with zero or more arguments item1,
- item2, etc., it
- returns an array containing the array elements of the object
- followed by the array elements of each argument in order.
- The - following steps are taken:
-- Let - O be the result of calling ToObject passing the this - value as the argument.
-
- Let
- A be a new array created as if by the expression new
- Array() where Array
- is the standard built-in constructor with that name.
- Let - n be 0.
-- Let - items be an internal List whose first element is O - and whose subsequent elements are, in left to right order, the - arguments that were passed to this function invocation.
-- Repeat, - while items is not empty
-- Remove - the first element from items and let E be the value - of the element.
-
- If
- the value of the [[Class]] internal property of E is
- "Array",
- then
- Let - k be 0.
-
- Let
- len be the result of calling the [[Get]] internal method
- of E with argument "length".
- Repeat, - while k < len
-- Let - P be ToString(k).
-- Let - exists be the result of calling the [[HasProperty]] - internal method of E with P.
-- If - exists is true, then
-- Let - subElement be the result of calling the [[Get]] internal - method of E with argument P.
-- Call - the [[DefineOwnProperty]] internal method of A with - arguments ToString(n), Property Descriptor {[[Value]]: - subElement, [[Writable]]: true, [[Enumerable]]: - true, [[Configurable]]: true}, and false.
-- Increase - n by 1.
-- Increase - k by 1.
-- Else, - E is not an Array
-- Call - the [[DefineOwnProperty]] internal method of A with - arguments ToString(n), Property Descriptor {[[Value]]: E, - [[Writable]]: true, [[Enumerable]]: true, - [[Configurable]]: true}, and false.
-- Increase - n by 1.
-- Return - A.
-
- The
- length property of
- the concat method
- is 1.
NOTE The
- concat function is
- intentionally generic; it does not require that its this
- value be an Array object. Therefore it can be transferred to other
- kinds of objects for use as a method. Whether the concat
- function can be applied successfully to a host object is
- implementation-dependent.
- The - elements of the array are converted to Strings, and these Strings - are then concatenated, separated by occurrences of the separator. - If no separator is provided, a single comma is used as the - separator.
-
- The
- join method takes
- one argument, separator,
- and performs the following steps:
- Let - O be the result of calling ToObject passing the this - value as the argument.
-
- Let
- lenVal be the result of calling the [[Get]] internal method
- of O with argument "length".
- Let - len be ToUint32(lenVal).
-
- If
- separator is undefined, let separator be the
- single-character String ",".
- Let - sep be ToString(separator).
-- If - len is zero, return the empty String.
-
- Let
- element0 be the result of calling the [[Get]] internal
- method of O with argument "0".
- If - element0 is undefined or null, let R be - the empty String; otherwise, Let R be ToString(element0).
-
- Let
- k be 1.
- Repeat, - while k < len
-- Let - S be the String value produced by concatenating R - and sep.
-- Let - element be the result of calling the [[Get]] internal - method of O with argument ToString(k).
-- If - element is undefined or null, Let next - be the empty String; otherwise, let next be - ToString(element).
-- Let - R be a String value produced by concatenating S and - next.
-- Increase - k by 1.
-- Return - R.
-
- The
- length property of
- the join method is
- 1.
NOTE The
- join function is
- intentionally generic; it does not require that its this
- value be an Array object. Therefore, it can be transferred to other
- kinds of objects for use as a method. Whether the join
- function can be applied successfully to a host object is
- implementation-dependent.
- The - last element of the array is removed from the array and returned.
-- Let - O be the result of calling ToObject passing the this - value as the argument.
-
- Let
- lenVal be the result of calling the [[Get]] internal method
- of O with argument "length".
- Let - len be ToUint32(lenVal).
-- If - len is zero, -
-
- Call
- the [[Put]] internal method of O with arguments "length",
- 0, and true.
- Return - undefined.
-- Else, - len > 0
-- Let - indx be ToString(len–1).
-- Let - element be the result of calling the [[Get]] internal - method of O with argument indx.
-- Call - the [[Delete]] internal method of O with arguments indx - and true.
-
- Call
- the [[Put]] internal method of O with arguments "length",
- indx, and true.
- Return - element.
-NOTE The
- pop function is
- intentionally generic; it does not require that its this
- value be an Array object. Therefore it can be transferred to other
- kinds of objects for use as a method. Whether the pop
- function can be applied successfully to a host object is
- implementation-dependent.
- The - arguments are appended to the end of the array, in the order in - which they appear. The new length of the array is returned as the - result of the call.
-
- When
- the push method is
- called with zero or more arguments item1,item2, etc., the following steps are taken:
- Let - O be the result of calling ToObject passing the this - value as the argument.
-
- Let
- lenVal be the result of calling the [[Get]] internal method
- of O with argument "length".
- Let - n be ToUint32(lenVal).
-- Let - items be an internal List whose elements are, in left to - right order, the arguments that were passed to this function - invocation.
-- Repeat, - while items is not empty
-- Remove - the first element from items and let E be the value - of the element.
-- Call - the [[Put]] internal method of O with arguments - ToString(n), E, and true.
-- Increase - n by 1.
-
- Call
- the [[Put]] internal method of O with arguments "length",
- n, and true.
- Return - n.
-
- The
- length property of
- the push method is
- 1.
NOTE The
- push function is
- intentionally generic; it does not require that its this
- value be an Array object. Therefore it can be transferred to other
- kinds of objects for use as a method. Whether the push
- function can be applied successfully to a host object is
- implementation-dependent.
- The - elements of the array are rearranged so as to reverse their order. - The object is returned as the result of the call.
-- Let - O be the result of calling ToObject passing the this - value as the argument.
-
- Let
- lenVal be the result of calling the [[Get]] internal method
- of O with argument "length".
- Let - len be ToUint32(lenVal).
-- Let - middle be floor(len/2).
-- Letlower be 0.
-- Repeat, - while lower ≠ middle
-- Let - upper be len−lower −1.
-- Let - upperP be ToString(upper).
-- Let - lowerP be ToString(lower).
-- Let - lowerValue be the result of calling the [[Get]] internal - method of O with argument lowerP.
-- Let - upperValue be the result of calling the [[Get]] internal - method of O with argument upperP .
-- Let - lowerExists be the result of calling the [[HasProperty]] - internal method of O with argument lowerP.
-- Let - upperExists be the result of calling the [[HasProperty]] - internal method of O with argument upperP.
-- If - lowerExists is true and upperExists is true, - then
-- Call - the [[Put]] internal method of O with arguments lowerP, - upperValue, and true .
-- Call - the [[Put]] internal method of O with arguments upperP, - lowerValue, and true .
-- Else - if lowerExists is false and upperExists is - true, then
-- Call - the [[Put]] internal method of O with arguments lowerP, - upperValue, and true .
-- Call - the [[Delete]] internal method of O, with arguments upperP - and true.
-- Else - if lowerExists is true and upperExists is - false, then
-- Call - the [[Delete]] internal method of O, with arguments lowerP - and true .
-- Call - the [[Put]] internal method of O with arguments upperP, - lowerValue, and true .
-- Else, - both lowerExists and upperExists are false
-- No - action is required.
-- Increase - lower by 1.
-- Return - O .
-NOTE The
- reverse function
- is intentionally generic; it does not require that its this
- value be an Array object. Therefore, it can be transferred to other
- kinds of objects for use as a method. Whether the reverse
- function can be applied successfully to a host object is
- implementation-dependent.
- The - first element of the array is removed from the array and returned.
-- Let - O be the result of calling ToObject passing the this - value as the argument.
-
- Let
- lenVal be the result of calling the [[Get]] internal method
- of O with argument "length".
- Let - len be ToUint32(lenVal).
-- If - len is zero, then
-
- Call
- the [[Put]] internal method of O with arguments "length",
- 0, and true.
- Return - undefined.
-
- Let
- first be the result of calling the [[Get]] internal method
- of O with argument "0".
- Let - k be 1.
-- Repeat, - while k < len
-- Let - from be ToString(k).
-- Let - to be ToString(k–1).
-- Let - fromPresent be the result of calling the [[HasProperty]] - internal method of O with argument from.
-- If - fromPresent is true, then
-- Let - fromVal be the result of calling the [[Get]] internal - method of O with argument from.
-- Call - the [[Put]] internal method of O with arguments to, - fromVal, and true.
-- Else, - fromPresent is false
-- Call - the [[Delete]] internal method of O with arguments to - and true.
-- Increase - k by 1.
-- Call - the [[Delete]] internal method of O with arguments - ToString(len–1) and true.
-
- Call
- the [[Put]] internal method of O with arguments "length",
- (len–1) , and true.
- Return - first.
-NOTE The
- shift function is
- intentionally generic; it does not require that its this
- value be an Array object. Therefore it can be transferred to other
- kinds of objects for use as a method. Whether the shift
- function can be applied successfully to a host object is
- implementation-dependent.
- The
- slice method takes
- two arguments, start
- and end, and
- returns an array containing the elements of the array from element
- start up to, but
- not including, element end
- (or through the end of the array if end
- is undefined). If start
- is negative, it is treated as length+start
- where length is
- the length of the array. If end
- is negative, it is treated as length+end
- where length
- is the length of the array. The following steps are taken:
- Let - O be the result of calling ToObject passing the this - value as the argument.
-
- Let
- A be a new array created as if by the expression new
- Array() where Array
- is the standard built-in constructor with that name.
- Let
- lenVal be the result of calling the [[Get]] internal method
- of O with argument "length".
- Let - len be ToUint32(lenVal).
-- Let - relativeStart be ToInteger(start).
-- If - relativeStart is negative, let k be max((len +relativeStart),0); else let k be min(relativeStart,len).
-- If - end is undefined, let relativeEnd be len; - else let relativeEnd be ToInteger(end).
-- If - relativeEnd is negative, let final be max((len - + relativeEnd),0); else let final be min(relativeEnd,len).
-- Let - n be 0.
-- Repeat, - while k < final
-- Let - Pk be ToString(k).
-- Let - kPresent be the result of calling the [[HasProperty]] - internal method of O with argument Pk.
-- If - kPresent is true, then
-- Let - kValue be the result of calling the [[Get]] internal - method of O with argument Pk.
-- Call - the [[DefineOwnProperty]] internal method of A with - arguments ToString(n), Property Descriptor {[[Value]]: - kValue, [[Writable]]: true, [[Enumerable]]: true, - [[Configurable]]: true}, and false.
-- Increase - k by 1.
-- Increase - n by 1.
-- Return - A.
-
- The
- length property of
- the slice method
- is 2.
NOTE The
- slice function is
- intentionally generic; it does not require that its this
- value be an Array object. Therefore it can be transferred to other
- kinds of objects for use as a method. Whether the slice
- function can be applied successfully to a host object is
- implementation-dependent.
- The - elements of this array are sorted. The sort is not necessarily - stable (that is, elements that compare equal do not necessarily - remain in their original order). If comparefn - is not undefined, it should be a function that accepts two - arguments x and y - and returns a negative value if x - < y, - zero if x = - y, or a positive - value if x > - y.
-- Let - obj be the result - of calling ToObject passing the this value as the argument.
-
- Let
- len be the result
- of applying Uint32 to the result of calling the [[Get]] internal
- method of obj with
- argument "length".
- If
- comparefn is not
- undefined and is not a consistent comparison function for the
- elements of this array (see below), the behaviour of sort
- is implementation-defined.
- Let
- proto be the value
- of the [[Prototype]] internal property of obj.
- If proto is not
- null and there exists an integer j
- such that all of the conditions below are satisfied then the
- behaviour of sort
- is implementation-defined:
- 0 ≤ - j < len
-- The - result of calling the [[HasProperty]] internal method of proto - with argument ToString(j) - is true.
-
- The
- behaviour of sort
- is also implementation defined if obj is sparse and any of the following conditions are true:
- The - [[Extensible]] internal property of obj - is false.
-- Any - array index property of obj - whose name is a nonnegative integer less than len is a data property whose [[Configurable]] attribute is - false.
-
- The
- behaviour of sort
- is also implementation defined if any array index property of obj
- whose name is a nonnegative integer less than len
- is an accessor property or is a data property whose [[Writable]]
- attribute is false.
- Otherwise, - the following steps are taken.
-- Perform - an implementation-dependent sequence of calls to the [[Get]] , - [[Put]], and [[Delete]] internal methods of obj and to - SortCompare (described below), where the first argument for each - call to [[Get]], [[Put]], or [[Delete]] is a nonnegative integer - less than len and where the arguments for calls to - SortCompare are results of previous calls to the [[Get]] internal - method. The throw argument to the [[Put]] and [[Delete]] internal - methods will be the value true. If obj is not sparse - then [[Delete]] must not be called.
-- Return - obj.
-- The - returned object must have the following two properties.
-
- There
- must be some mathematical permutation π
- of the nonnegative integers less than len,
- such that for every nonnegative integer j
- less than len, if
- property old[j]
- existed, then new[π(j)]
- is exactly the same value as old[j],.
- But if property old[j]
- did not exist, then new[π(j)]
- does not exist.
- Then
- for all nonnegative integers j
- and k, each less
- than len, if
- SortCompare(j,k)
- < 0 (see
- SortCompare below), then π(j)
- < π(k).
- Here - the notation old[j] - is used to refer to the hypothetical result of calling the [[Get]] - internal method of obj - with argument j - before this function is executed, and the notation new[j] - to refer to the hypothetical result of calling the [[Get]] internal - method of obj with - argument j after - this function has been executed.
-- A - function comparefn - is a consistent comparison function for a set of values S - if all of the requirements below are met for all values a, - b, and c - (possibly the same value) in the set S: - The notation a <CF b - means comparefn(a,b) < 0; - a =CF b - means comparefn(a,b) = 0 - (of either sign); and a >CF b - means comparefn(a,b) > 0.
-- Calling - comparefn(a,b) - always returns the same value v - when given a specific pair of values a - and b - as its two arguments. Furthermore, Type(v) - is Number, and v - is not NaN. Note that this implies that exactly one of a <CF b, - a =CF b, - and a >CF b - will be true for a given pair of a - and b.
-- Calling - comparefn(a,b) - does not modify the this - object.
-- a =CF a - (reflexivity)
-- If - a =CF b, - then b =CF a - (symmetry)
-- If - a =CF b - and b =CF c, - then a =CF c - (transitivity of =CF)
-- If - a <CF b - and b <CF c, - then a <CF c - (transitivity of <CF)
-- If - a >CF b - and b >CF c, - then a >CF c - (transitivity of >CF)
-NOTE The - above conditions are necessary and sufficient to ensure that - comparefn divides - the set S into - equivalence classes and that these equivalence classes are totally - ordered.
-- When - the SortCompare abstract operation is called with two arguments j - and k, the - following steps are taken:
-- Let - jString be ToString(j).
-- Let - kString be ToString(k).
-- Let - hasj be the result of calling the [[HasProperty]] internal - method of obj with argument jString.
-- Let - hask be the result of calling the [[HasProperty]] internal - method of obj with argument kString.
-- If - hasj and hask are both false, then - return +0.
-- If - hasj is false, then return 1.
-- If - hask is false, then return –1.
-- Let - x be the result of calling the [[Get]] internal method of - obj with argument jString.
-- Let - y be the result of calling the [[Get]] internal method of - obj with argument kString.
-- If - x and y are both undefined, return +0.
-- If - x is undefined, return 1.
-- If - y is undefined, return −1.
-- If - the argument comparefn is not undefined, then
-- If - IsCallable(comparefn) is false, throw a TypeError - exception.
-- Return - the result of calling the [[Call]] internal method of comparefn - passing undefined as the this value and with - arguments x and y.
-- Let - xString be ToString(x).
-- Let - yString be ToString(y).
-- If - xString < yString, return −1.
-- If - xString > yString, return 1.
-- Return - +0.
-NOTE 1 Because non-existent property values always compare greater than - undefined property values, and undefined always - compares greater than any other value, undefined property values - always sort to the end of the result, followed by non-existent - property values.
-NOTE 2 The sort
- function is intentionally generic; it does not require that its this
- value be an Array object. Therefore, it can be transferred to other
- kinds of objects for use as a method. Whether the sort
- function can be applied successfully to a host object is
- implementation-dependent.
- When
- the splice method
- is called with two or more arguments start,
- deleteCount and
- (optionally) item1,
- item2, etc., the
- deleteCount
- elements of the array starting at array index start
- are replaced by the arguments item1,
- item2, etc. An
- Array object containing the deleted elements (if any) is returned.
- The following steps are taken:
- Let - O be the result of calling ToObject passing the this - value as the argument.
-
- Let
- A be a new array created as if by the expression new
- Array()where Array
- is the standard built-in constructor with that name.
- Let
- lenVal be the result of calling the [[Get]] internal method
- of O with argument "length".
- Let - len be ToUint32(lenVal).
-- Let - relativeStart be ToInteger(start).
-- If - relativeStart is negative, let actualStart be - max((len + relativeStart),0); else let actualStart - be min(relativeStart, len).
-- Let - actualDeleteCount be min(max(ToInteger(deleteCount),0),len – actualStart).
-- Let - k be 0.
-- Repeat, - while k < actualDeleteCount
-- Let - from be ToString(actualStart+k).
-- Let - fromPresent be the result of calling the [[HasProperty]] - internal method of O with argument from.
-- If - fromPresent is true, then
-- Let - fromValue be the result of calling the [[Get]] internal - method of O with argument from.
-- Call - the [[DefineOwnProperty]] internal method of A with - arguments ToString(k), Property Descriptor {[[Value]]: - fromValue, [[Writable]]: true, [[Enumerable]]: - true, [[Configurable]]: true}, and false.
-- Increment - k by 1.
-- Let - items be an internal List whose elements are, in left to - right order, the portion of the actual argument list starting with - item1. The list will be empty if no such items are present.
-- Let - itemCount be the number of elements in items.
-- If - itemCount < actualDeleteCount, then
-- Let - k be actualStart.
-- Repeat, - while k < (len – actualDeleteCount)
-- Let - from be ToString(k+actualDeleteCount).
-- Let - to be ToString(k+itemCount).
-- Let - fromPresent be the result of calling the [[HasProperty]] - internal method of O with argument from.
-- If - fromPresent is true, then
-- Let - fromValue be the result of calling the [[Get]] internal - method of O with argument from.
-- Call - the [[Put]] internal method of O with arguments to, - fromValue, and true.
-- Else, - fromPresent is false
-- Call - the [[Delete]] internal method of O with arguments to - and true.
-- Increase - k by 1.
-- Let - k be len.
-- Repeat, - while k > (len – actualDeleteCount +itemCount) -
-- Call - the [[Delete]] internal method of O with arguments - ToString(k–1) and true.
-- Decrease - k by 1.
-- Else - if itemCount > actualDeleteCount, then
-- Let - k be (len – actualDeleteCount).
-- Repeat, - while k > actualStart
-- Let - from be ToString(k + actualDeleteCount – - 1).
-- Let - to be ToString(k + itemCount – 1)
-- Let - fromPresent be the result of calling the [[HasProperty]] - internal method of O with argument from.
-- If - fromPresent is true, then
-- Let - fromValue be the result of calling the [[Get]] internal - method of O with argument from.
-- Call - the [[Put]] internal method of O with arguments to, - fromValue, and true.
-- Else, - fromPresent is false
-- Call - the [[Delete]] internal method of O with argument to - and true.
-- Decrease - k by 1.
-- Let - k be actualStart.
-- Repeat, - while items is not empty
-- Remove - the first element from items and let E be the value - of that element.
-- Call - the [[Put]] internal method of O with arguments - ToString(k), E, and true.
-- Increase - k by 1.
-
- Call
- the [[Put]] internal method of O with arguments "length",
- (len – actualDeleteCount + itemCount), and
- true.
- Return - A.
-
- The
- length property of
- the splice method
- is 2.
NOTE The
- splice function is
- intentionally generic; it does not require that its this
- value be an Array object. Therefore it can be transferred to other
- kinds of objects for use as a method. Whether the splice
- function can be applied successfully to a host object is
- implementation-dependent.
- The - arguments are prepended to the start of the array, such that their - order within the array is the same as the order in which they appear - in the argument list.
-
- When
- the unshift method
- is called with zero or more arguments item1,item2, etc., the following steps are taken:
- Let - O be the result of calling ToObject passing the this - value as the argument.
-
- Let
- lenVal be the result of calling the [[Get]] internal method
- of O with argument "length".
- Let - len be ToUint32(lenVal).
-- Let - argCount be the number of actual arguments.
-- Let - k be len.
-- Repeat, - while k > 0, -
-- Let - from be ToString(k–1).
-- Let - to be ToString(k+argCount –1).
-- Let - fromPresent be the result of calling the [[HasProperty]] - internal method of O with argument from.
-- If - fromPresent is true, then
-- Let - fromValue be the result of calling the [[Get]] internal - method of O with argument from.
-- Call - the [[Put]] internal method of O with arguments to, - fromValue, and true.
-- Else, - fromPresent is false
-- Call - the [[Delete]] internal method of O with arguments to, - and true.
-- Decrease - k by 1.
-- Let - j be 0.
-- Let - items be an internal List whose elements are, in left to - right order, the arguments that were passed to this function - invocation.
-- Repeat, - while items is not empty
-- Remove - the first element from items and let E be the value - of that element.
-- Call - the [[Put]] internal method of O with arguments - ToString(j), E, and true.
-- Increase - j by 1.
-
- Call
- the [[Put]] internal method of O with arguments "length",
- len+argCount, and true.
- Return - len+argCount.
-
- The
- length property of
- the unshift method
- is 1.
NOTE The
- unshift function
- is intentionally generic; it does not require that its this
- value be an Array object. Therefore it can be transferred to other
- kinds of objects for use as a method. Whether the unshift
- function can be applied successfully to a host object is
- implementation-dependent.
- indexOf
- compares searchElement
- to the elements of the array, in ascending order, using the internal
- Strict Equality Comparison Algorithm (11.9.6), and if found at one
- or more positions, returns the index of the first such position;
- otherwise, -1 is returned.
- The - optional second argument fromIndex - defaults to 0 (i.e. the whole array is searched). If it is greater - than or equal to the length of the array, -1 is returned, i.e. the - array will not be searched. If it is negative, it is used as the - offset from the end of the array to compute fromIndex. - If the computed index is less than 0, the whole array will be - searched.
-
- When
- the indexOf method
- is called with one or two arguments, the following steps are taken:
- Let - O be the result of calling ToObject passing the this - value as the argument.
-
- Let
- lenValue be the result of calling the [[Get]] internal
- method of O with the argument "length".
- Let - len be ToUint32(lenValue).
-- If - len is 0, return -1.
-- If - argument fromIndex was passed let n be - ToInteger(fromIndex); else let n be 0.
-- If - n ≥ len, return -1.
-- If - n ≥ 0, then -
-- Let - k be n.
-- Else, - n<0
-- Let - k be len - abs(n).
-- If - k is less than 0, then let k be 0.
-- Repeat, - while k<len
-- Let - kPresent be the result of calling the [[HasProperty]] - internal method of O with argument ToString(k).
-- If - kPresent is true, then
-- Let - elementK be the result of calling the [[Get]] internal - method of O with the argument ToString(k).
-- Let - same be the result of applying the Strict Equality - Comparison Algorithm to searchElement and elementK.
-- If - same is true, return k.
-- Increase - k by 1.
-- Return - -1.
-
- The
- length property of
- the indexOf method
- is 1.
NOTE The
- indexOf function
- is intentionally generic; it does not require that its this
- value be an Array object. Therefore it can be transferred to other
- kinds of objects for use as a method. Whether the indexOf
- function can be applied successfully to a host object is
- implementation-dependent.
- lastIndexOf
- compares searchElement
- to the elements of the array in descending order using the internal
- Strict Equality Comparison Algorithm (11.9.6), and if found at one
- or more positions, returns the index of the last such position;
- otherwise, -1 is returned.
- The - optional second argument fromIndex - defaults to the array's length minus one (i.e. the whole array is searched). - If it is greater than or equal to the length of the array, the whole - array will be searched. If it is negative, it is used as the offset - from the end of the array to compute fromIndex. - If the computed index is less than 0, -1 is returned.
-
- When
- the lastIndexOf
- method is called with one or two arguments, the following steps are
- taken:
- Let - O be the result of calling ToObject passing the this - value as the argument.
-
- Let
- lenValue be the result of calling the [[Get]] internal
- method of O with the argument "length".
- Let - len be ToUint32(lenValue).
-- If - len is 0, return -1.
-- If - argument fromIndex was passed let n be - ToInteger(fromIndex); else let n be len.
-- If - n ≥ 0, then let k be min(n, len - – 1).
-- Else, - n < 0
-- Let - k be len - abs(n).
-- Repeat, - while k≥ 0
-- Let - kPresent be the result of calling the [[HasProperty]] - internal method of O with argument ToString(k).
-- If - kPresent is true, then
-- Let - elementK be the result of calling the [[Get]] internal - method of O with the argument ToString(k).
-- Let - same be the result of applying the Strict Equality - Comparision Algorithm to searchElement and elementK.
-- If - same is true, return k.
-- Decrease - k by 1.
-- Return - -1.
-
- The
- length property of
- the lastIndexOf
- method is 1.
NOTE The
- lastIndexOf
- function is intentionally generic; it does not require that its this
- value be an Array object. Therefore it can be transferred to other
- kinds of objects for use as a method. Whether the lastIndexOf
- function can be applied successfully to a host object is
- implementation-dependent.
- callbackfn should be a function that accepts three arguments and
- returns a value that is coercible to the Boolean value true
- or false. every
- calls callbackfn
- once for each element present in the array, in ascending order,
- until it finds one where callbackfn
- returns false. If such an element is found, every
- immediately returns false. Otherwise, if callbackfn
- returned true for all elements, every
- will return true. callbackfn
- is called only for elements of the array which actually exist; it is
- not called for missing elements of the array.
- If a - thisArg parameter - is provided, it will be used as the this value for each - invocation of callbackfn. - If it is not provided, undefined is used instead.
-- callbackfn - is called with three arguments: the value of the element, the index - of the element, and the object being traversed.
-
- every
- does not directly mutate the object on which it is called but the
- object may be mutated by the calls to callbackfn.
-
-
- The
- range of elements processed by every
- is set before the first call to callbackfn.
- Elements which are appended to the array after the call to every
- begins will not be visited by callbackfn.
- If existing elements of the array are changed, their value as passed
- to callbackfn will
- be the value at the time every
- visits them; elements that are deleted after the call to every
- begins and before being visited are not visited. every
- acts like the "for all" quantifier in mathematics. In
- particular, for an empty array, it returns true.
- When
- the every method
- is called with one or two arguments, the following steps are taken:
- Let - O be the result of calling ToObject passing the this - value as the argument.
-
- Let
- lenValue be the result of calling the [[Get]] internal
- method of O with the argument "length".
- Let - len be ToUint32(lenValue).
-- If - IsCallable(callbackfn) is false, throw a TypeError - exception.
-- If - thisArg was supplied, let T be thisArg; else - let T be undefined.
-- Let - k be 0.
-- Repeat, - while k < len
-- Let - Pk be ToString(k).
-- Let - kPresent be the result of calling the [[HasProperty]] - internal method of O with argument Pk.
-- If - kPresent is true, then
-- Let - kValue be the result of calling the [[Get]] internal - method of O with argument Pk.
-- Let - testResult be the result of calling the [[Call]] internal - method of callbackfn with T as the this - value and argument list containing kValue, k, and - O.
-- If - ToBoolean(testResult) is false, return false.
-- Increase - k by 1.
-- Return - true.
-
- The
- length property of
- the every method
- is 1.
NOTE The
- every function is
- intentionally generic; it does not require that its this
- value be an Array object. Therefore it can be transferred to other
- kinds of objects for use as a method. Whether the every
- function can be applied successfully to a host object is
- implementation-dependent.
- callbackfn should be a function that accepts three arguments and
- returns a value that is coercible to the Boolean value true
- or false. some
- calls callbackfn
- once for each element present in the array, in ascending order,
- until it finds one where callbackfn
- returns true. If such an element is found, some
- immediately returns true. Otherwise, some
- returns false. callbackfn
- is called only for elements of the array which actually exist; it is
- not called for missing elements of the array.
- If a - thisArg parameter - is provided, it will be used as the this value for each - invocation of callbackfn. - If it is not provided, undefined is used instead.
-- callbackfn - is called with three arguments: the value of the element, the index - of the element, and the object being traversed.
-
- some
- does not directly mutate the object on which it is called but the
- object may be mutated by the calls to callbackfn.
- The
- range of elements processed by some
- is set before the first call to callbackfn.
- Elements that are appended to the array after the call to some
- begins will not be visited by callbackfn.
- If existing elements of the array are changed, their value as passed
- to callbackfn will
- be the value at the time that some
- visits them; elements that are deleted after the call to some
- begins and before being visited are not visited.
- some acts like the "exists" quantifier in
- mathematics. In particular, for an empty array, it returns false.
- When
- the some method is
- called with one or two arguments, the following steps are taken:
- Let - O be the result of calling ToObject passing the this - value as the argument.
-
- Let
- lenValue be the result of calling the [[Get]] internal
- method of O with the argument "length".
- Let - len be ToUint32(lenValue).
-- If - IsCallable(callbackfn) is false, throw a TypeError - exception.
-- If - thisArg was supplied, let T be thisArg; else - let T be undefined.
-- Let - k be 0.
-- Repeat, - while k < len
-- Let - Pk be ToString(k).
-- Let - kPresent be the result of calling the [[HasProperty]] - internal method of O with argument Pk.
-- If - kPresent is true, then
-- Let - kValue be the result of calling the [[Get]] internal - method of O with argument Pk.
-- Let - testResult be the result of calling the [[Call]] internal - method of callbackfn with T as the this - value and argument list containing kValue, k, and - O.
-- If - ToBoolean(testResult) is true, return true.
-- Increase - k by 1.
-- Return - false.
-
- The
- length property of
- the some method is
- 1.
NOTE The
- some function
- is intentionally generic; it does not require that its this
- value be an Array object. Therefore it can be transferred to other
- kinds of objects for use as a method. Whether the some
- function can be applied successfully to a host object is
- implementation-dependent.
- callbackfn should be a function that accepts three arguments.
- forEach calls
- callbackfn once
- for each element present in the array, in ascending order.
- callbackfn is
- called only for elements of the array which actually exist; it is
- not called for missing elements of the array.
- If a - thisArg parameter - is provided, it will be used as the this value for each - invocation of callbackfn. - If it is not provided, undefined is used instead.
-- callbackfn - is called with three arguments: the value of the element, the index - of the element, and the object being traversed. -
-
- forEach
- does not directly mutate the object on which it is called but the
- object may be mutated by the calls to callbackfn.
-
-
- The
- range of elements processed by forEach
- is set before the first call to callbackfn.
- Elements which are appended to the array after the call to forEach
- begins will not be visited by callbackfn.
- If existing elements of the array are changed, their value as passed
- to callback will be the value at the time forEach
- visits them; elements that are deleted after the call to forEach
- begins and before being visited are not visited.
- When
- the forEach method
- is called with one or two arguments, the following steps are taken:
- Let - O be the result of calling ToObject passing the this - value as the argument.
-
- Let
- lenValue be the result of calling the [[Get]] internal
- method of O with the argument "length".
- Let - len be ToUint32(lenValue).
-- If - IsCallable(callbackfn) is false, throw a TypeError - exception.
-- If - thisArg was supplied, let T be thisArg; else - let T be undefined.
-- Let - k be 0.
-- Repeat, - while k < len
-- Let - Pk be ToString(k).
-- Let - kPresent be the result of calling the [[HasProperty]] - internal method of O with argument Pk.
-- If - kPresent is true, then
-- Let - kValue be the result of calling the [[Get]] internal - method of O with argument Pk.
-- Call - the [[Call]] internal method of callbackfn with T - as the this value and argument list containing kValue, - k, and O.
-- Increase - k by 1.
-- Return undefined.
-
- The
- length property of
- the forEach method
- is 1.
NOTE The
- forEach
- function is intentionally generic; it does not require that its
- this value be an Array object. Therefore it can be
- transferred to other kinds of objects for use as a method. Whether
- the forEach
- function can be applied successfully to a host object is
- implementation-dependent.
- callbackfn should be a function that accepts three arguments. map
- calls callbackfn
- once for each element in the array, in ascending order, and
- constructs a new Array from the results. callbackfn
- is called only for elements of the array which actually exist; it is
- not called for missing elements of the array.
- If a - thisArg parameter - is provided, it will be used as the this value for - each invocation of callbackfn. - If it is not provided, undefined is used instead.
-- callbackfn - is called with three arguments: the value of the element, the index - of the element, and the object being traversed.
-
- map
- does not directly mutate the object on which it is called but the
- object may be mutated by the calls to callbackfn.
- The
- range of elements processed by map
- is set before the first call to callbackfn.
- Elements which are appended to the array after the call to map
- begins will not be visited by callbackfn.
- If existing elements of the array are changed, their value as passed
- to callbackfn will
- be the value at the time map
- visits them; elements that are deleted after the call to map
- begins and before being visited are not visited.
- When
- the map method is
- called with one or two arguments, the following steps are taken:
-
- Let - O be the result of calling ToObject passing the this - value as the argument.
-
- Let
- lenValue be the result of calling the [[Get]] internal
- method of O with the argument "length".
- Let - len be ToUint32(lenValue).
-- If - IsCallable(callbackfn) is false, throw a TypeError - exception.
-- If - thisArg was supplied, let T be thisArg; else - let T be undefined.
-
- Let
- A be a new array created as if by the expression new
- Array( len)
- where Array is
- the standard built-in constructor with that name and len is
- the value of len.
- Let - k be 0.
-- Repeat, - while k < len
-- Let - Pk be ToString(k).
-- Let - kPresent be the result of calling the [[HasProperty]] - internal method of O with argument Pk.
-- If - kPresent is true, then
-- Let - kValue be the result of calling the [[Get]] internal - method of O with argument Pk.
-- Let - mappedValue be the result of calling the [[Call]] internal - method of callbackfn with T as the this - value and argument list containing kValue, k, and - O.
-- Call - the [[DefineOwnProperty]] internal method of A with - arguments Pk, Property Descriptor {[[Value]]: mappedValue, - [[Writable]]: true, [[Enumerable]]: true, - [[Configurable]]: true}, and false.
-- Increase - k by 1.
-- Return - A.
-
- The
- length property of
- the map method is
- 1.
NOTE The
- map function
- is intentionally generic; it does not require that its this
- value be an Array object. Therefore it can be transferred to other
- kinds of objects for use as a method. Whether the map
- function can be applied successfully to a host object is
- implementation-dependent.
- callbackfn should be a function that accepts three arguments and
- returns a value that is coercible to the Boolean value true
- or false. filter
- calls callbackfn
- once for each element in the array, in ascending order, and
- constructs a new array of all the values for which callbackfn
- returns true. callbackfn
- is called only for elements of the array which actually exist; it is
- not called for missing elements of the array.
- If a - thisArg parameter - is provided, it will be used as the this value for each - invocation of callbackfn. - If it is not provided, undefined is used instead.
-- callbackfn - is called with three arguments: the value of the element, the index - of the element, and the object being traversed.
-
- filter
- does not directly mutate the object on which it is called but the
- object may be mutated by the calls to callbackfn.
- The
- range of elements processed by filter
- is set before the first call to callbackfn.
- Elements which are appended to the array after the call to filter
- begins will not be visited by callbackfn.
- If existing elements of the array are changed their value as passed
- to callbackfn will
- be the value at the time filter
- visits them; elements that are deleted after the call to filter
- begins and before being visited are not visited.
- When
- the filter method
- is called with one or two arguments, the following steps are taken:
-
- Let - O be the result of calling ToObject passing the this - value as the argument.
-
- Let
- lenValue be the result of calling the [[Get]] internal
- method of O with the argument "length".
- Let - len be ToUint32(lenValue).
-- If - IsCallable(callbackfn) is false, throw a TypeError - exception.
-- If - thisArg was supplied, let T be thisArg; else - let T be undefined.
-
- Let
- A be a new array created as if by the expression new
- Array() where Array
- is the standard built-in constructor with that name.
- Let - k be 0.
-- Let - to be 0.
-- Repeat, - while k < len
-- Let - Pk be ToString(k).
-- Let - kPresent be the result of calling the [[HasProperty]] - internal method of O with argument Pk.
-- If - kPresent is true, then
-- Let - kValue be the result of calling the [[Get]] internal - method of O with argument Pk.
-- Let - selected be the result of calling the [[Call]] internal - method of callbackfn with T as the this - value and argument list containing kValue, k, and - O.
-- If - ToBoolean(selected) is true, then
-- Call - the [[DefineOwnProperty]] internal method of A with - arguments ToString(to), Property Descriptor {[[Value]]: - kValue, [[Writable]]: true, [[Enumerable]]: true, - [[Configurable]]: true}, and false.
-- Increase - to by 1.
-- Increase - k by 1.
-- Return - A.
-
- The
- length property of
- the filter method
- is 1.
NOTE The
- filter function
- is intentionally generic; it does not require that its this
- value be an Array object. Therefore it can be transferred to other
- kinds of objects for use as a method. Whether the filter
- function can be applied successfully to a host object is
- implementation-dependent.
- callbackfn should be a function that takes four arguments. reduce
- calls the callback, as a function, once for each element present in
- the array, in ascending order.
- callbackfn is called with four arguments: the previousValue
- (or value from the previous call to callbackfn),
- the currentValue (value of the current element), the
- currentIndex, and the object being traversed. The first time
- that callback is called, the previousValue and currentValue
- can be one of two values. If an initialValue was provided in the call to reduce,
- then previousValue will be equal to initialValue and currentValue will be equal to the first value
- in the array. If no initialValue was provided, then previousValue will be equal to
- the first value in the array and currentValue will be equal
- to the second. It is a TypeError if the array contains no
- elements and initialValue
- is not provided.
- reduce
- does not directly mutate the object on which it is called but the
- object may be mutated by the calls to callbackfn.
- The
- range of elements processed by reduce
- is set before the first call to callbackfn.
- Elements that are appended to the array after the call to reduce
- begins will not be visited by callbackfn.
- If existing elements of the array are changed, their value as passed
- to callbackfn will
- be the value at the time reduce
- visits them; elements that are deleted after the call to reduce
- begins and before being visited are not visited.
- When
- the reduce method
- is called with one or two arguments, the following steps are taken:
-
- Let - O be the result of calling ToObject passing the this - value as the argument.
-
- Let
- lenValue be the result of calling the [[Get]] internal
- method of O with the argument "length".
- Let - len be ToUint32(lenValue ).
-- If - IsCallable(callbackfn) is false, throw a TypeError - exception.
-- If - len is 0 and initialValue is not present, throw a TypeError - exception.
-- Let - k be 0.
-- If - initialValue is present, then
-- Set - accumulator to initialValue.
-- Else, - initialValue is not present
-- Let - kPresent be false.
-- Repeat, - while kPresent is false and k < len
-- Let - Pk be ToString(k).
-- Let - kPresent be the result of calling the [[HasProperty]] - internal method of O with argument Pk.
-- If - kPresent is true, then
-- Let - accumulator be the result of calling the [[Get]] internal - method of O with argument Pk.
-- Increase - k by 1.
-- If - kPresent is false, throw a TypeError - exception.
-- Repeat, - while k < len
-- Let - Pk be ToString(k).
-- Let - kPresent be the result of calling the [[HasProperty]] - internal method of O with argument Pk.
-- If - kPresent is true, then
-- Let - kValue be the result of calling the [[Get]] internal - method of O with argument Pk.
-- Let - accumulator be the result of calling the [[Call]] internal - method of callbackfn with undefined as the this - value and argument list containing accumulator, kValue, - k, and O.
-- Increase - k by 1.
-- Return - accumulator.
-
- The
- length property of
- the reduce method
- is 1.
NOTE The
- reduce function
- is intentionally generic; it does not require that its this
- value be an Array object. Therefore it can be transferred to other
- kinds of objects for use as a method. Whether the reduce
- function can be applied successfully to a host object is
- implementation-dependent.
- callbackfn should be a function that takes four arguments.
- reduceRight calls
- the callback, as a function, once for each element present in the array, in descending order.
- callbackfn is called with four arguments: the previousValue (or
- value from the previous call to callbackfn),
- the currentValue (value of the current element), the currentIndex,
- and the object being traversed. The first time the function is
- called, the previousValue and currentValue can be one of two values.
- If an initialValue was
- provided in the call to reduceRight,
- then previousValue will be equal to initialValue
- and currentValue will be equal to the last value in the array. If no
- initialValue was
- provided, then previousValue will be equal to the last value in the
- array and currentValue will be equal to the second-to-last value. It
- is a TypeError if the array contains no
- elements and
- initialValue is
- not provided.
- reduceRight
- does not directly mutate the object on which it is called
- but the object may be mutated by the calls to callbackfn.
- The
- range of elements processed by reduceRight is set before the first call to callbackfn.
- Elements that are appended to the array after the call to
- reduceRight begins
- will not be visited by callbackfn.
- If existing elements of the array are changed by callbackfn,
- their value as passed to callbackfn will be the value at the time reduceRight
- visits them; elements that are deleted after the call to
- reduceRight begins and
- before being visited are not visited.
- When
- the reduceRight method
- is called with one or two arguments, the following steps are taken:
-
- Let - O be the result of calling ToObject passing the this - value as the argument.
-
- Let
- lenValue be the result of calling the [[Get]] internal
- method of O with the argument "length".
- Let - len be ToUint32(lenValue ).
-- If - IsCallable(callbackfn) is false, throw a TypeError - exception.
-- If - len is 0 and initialValue is not present, throw a TypeError - exception.
-- Let - k be len-1.
-- If - initialValue is present, then
-- Set - accumulator to initialValue.
-- Else, - initialValue is not present
-- Let - kPresent be false.
-- Repeat, - while kPresent is false and k ≥ 0
-- Let - Pk be ToString(k).
-- Let - kPresent be the result of calling the [[HasProperty]] - internal method of O with argument Pk.
-- If - kPresent is true, then
-- Let - accumulator be the result of calling the [[Get]] internal - method of O with argument Pk.
-- Decrease - k by 1.
-- If - kPresent is false, throw a TypeError - exception.
-- Repeat, - while k ≥ 0
-- Let - Pk be ToString(k).
-- Let - kPresent be the result of calling the [[HasProperty]] - internal method of O with argument Pk.
-- If - kPresent is true, then
-- Let - kValue be the result of calling the [[Get]] internal - method of O with argument Pk.
-- Let - accumulator be the result of calling the [[Call]] internal - method of callbackfn with undefined as the this - value and argument list containing accumulator, kValue, - k, and O.
-- Decrease - k by 1.
-- Return - accumulator.
-
- The
- length property of
- the reduceRight
- method is 1.
NOTE The
- reduceRight function
- is intentionally generic; it does not require that its this value be
- an Array object. Therefore it can be transferred to other kinds of
- objects for use as a method. Whether the reduceRight
- function can be applied successfully to a host object is
- implementation-dependent.
- Array
- instances inherit properties from the Array prototype object and
- their [[Class]] internal property value is "Array".
- Array instances also have the following properties.
- Array - objects use a variation of the [[DefineOwnProperty]] internal method - used for other native ECMAScript objects (8.12.9).
-- Assume - A is an Array - object, Desc is a - Property Descriptor, and Throw is a Boolean flag.
-- In - the following algorithm, the term “Reject” - means “If Throw is true, - then throw a TypeError - exception, otherwise return false.”
-- When - the [[DefineOwnProperty]] internal method of A - is called with property P, - Property Descriptor Desc, - and Boolean flag Throw, - the following steps are taken:
-
- Let
- oldLenDesc be the result of calling the [[GetOwnProperty]]
- internal method of A passing "length"
- as the argument. The result will never be undefined or an
- accessor descriptor because Array objects are created with a length
- data property that cannot be deleted or reconfigured.
- Let - oldLen be oldLenDesc.[[Value]].
-
- If
- P is "length",
- then
- If - the [[Value]] field of Desc is absent, then
-
- Return
- the result of calling the default [[DefineOwnProperty]] internal
- method (8.12.9) on A passing "length",
- Desc, and Throw as arguments.
- Let - newLenDesc be a copy of Desc.
-- Let - newLen be ToUint32(Desc.[[Value]]).
-- If - newLen is not equal to ToNumber( Desc.[[Value]]), - throw a RangeError exception.
-- Set - newLenDesc.[[Value] to newLen.
-- If - newLen ≥oldLen, then
-
- Return
- the result of calling the default [[DefineOwnProperty]] internal
- method (8.12.9) on A passing "length",
- newLenDesc, and Throw as arguments.
- Reject - if oldLenDesc.[[Writable]] is false.
-- If - newLenDesc.[[Writable]] is absent or has the value true, - let newWritable be true.
-- Else,
-- Need - to defer setting the [[Writable]] attribute to false in - case any elements cannot be deleted.
-- Let - newWritable be false.
-- Set - newLenDesc.[[Writable] to true.
-
- Let
- succeeded be the result of calling the default
- [[DefineOwnProperty]] internal method (8.12.9) on A passing
- "length",
- newLenDesc, and Throw as arguments.
- If - succeeded is false, return false..
-- While - newLen < oldLen repeat,
-- Set - oldLen to oldLen – 1.
-- Let - deleteSucceeded - be the result of calling the [[Delete]] - internal method of A passing ToString(oldLen) and - false as arguments.
-- If - deleteSucceeded - is false, then
- -- If - newWritable is false, then
-
- Call
- the default [[DefineOwnProperty]] internal method (8.12.9) on A
- passing "length",
- Property Descriptor{[[Writable]]: false}, and false
- as arguments. This call will always return true.
- Return - true.
-- Else - if P is an array index (15.4), then
-- Let - index be ToUint32(P).
-- Reject - if index ≥ oldLen and oldLenDesc.[[Writable]] - is false.
-- Let - succeeded be the result of calling the default - [[DefineOwnProperty]] internal method (8.12.9) on A passing - P, Desc, and false as arguments.
-- Reject - if succeeded is false.
-- If - index ≥ oldLen
-- Set - oldLenDesc.[[Value]] to index + 1.
-
- Call
- the default [[DefineOwnProperty]] internal method (8.12.9) on A
- passing "length",
- oldLenDesc, and false as arguments. This call will
- always return true.
- Return - true.
-- Return - the result of calling the default [[DefineOwnProperty]] internal - method (8.12.9) on A passing P, Desc, and - Throw as arguments.
-
- The
- length property of
- this Array object is a data property whose value is always
- numerically greater than the name of every deletable property whose
- name is an array index.
- The
- length property
- initially has the attributes {
- [[Writable]]: true,
- [[Enumerable]]: false,
- [[Configurable]]: false
- }.
NOTE Attempting - to set the length property of an Array object to a value that is - numerically less than or equal to the largest numeric property name - of an existing array indexed non-deletable property of the array - will result in the length being set to a numeric value that is one - greater than that largest numeric property name. See 15.4.5.1.
-
- When
- String is called
- as a function rather than as a constructor, it performs a type
- conversion.
- Returns
- a String value (not a String object) computed by ToString(value).
- If value is not
- supplied, the empty String ""
- is returned.
- When
- String is called
- as part of a new
- expression, it is a constructor: it initialises the newly created
- object.
- The
- [[Prototype]] internal
- property of the newly constructed object is set to the standard
- built-in String prototype object that is the initial value of
- String.prototype
- (15.5.3.1).
- The
- [[Class]] internal
- property of the newly constructed object is set to "String".
- The - [[Extensible]] internal - property of the newly constructed object is set to true.
-- The - [[PrimitiveValue]] internal - property of the newly constructed object is set to ToString(value), - or to the empty String if value - is not supplied.
-- The - value of the [[Prototype]] internal property of the String - constructor is the standard built-in Function prototype object - (15.3.4).
-
- Besides
- the internal properties and the length
- property (whose value is 1), the String constructor has the
- following properties:
- The
- initial value of String.prototype
- is the standard built-in String prototype object (15.5.4).
- This - property has the attributes { [[Writable]]: false, - [[Enumerable]]: false, [[Configurable]]: false }.
-- Returns - a String value containing as many characters as the number of - arguments. Each argument specifies one character of the resulting - String, with the first argument specifying the first character, and - so on, from left to right. An argument is converted to a character - by applying the operation ToUint16 (9.7) and regarding the resulting - 16-bit integer as the code unit value of a character. If no - arguments are supplied, the result is the empty String.
-
- The
- length property of
- the fromCharCode
- function is 1.
- The
- String prototype object is itself a String object (its [[Class]] is
- "String")
- whose value is an empty String.
- The - value of the [[Prototype]] internal property of the String prototype - object is the standard built-in Object prototype object (15.2.4).
-
- The
- initial value of String.prototype.constructor
- is the built-in String
- constructor.
- Returns
- this String value. (Note that, for a String object, the toString
- method happens to return the same thing as the valueOf
- method.)
- The
- toString function
- is not generic; it throws a TypeError exception if its this
- value is not a String or a String object. Therefore, it cannot be
- transferred to other kinds of objects for use as a method.
- Returns - this String value.
-
- The
- valueOf function
- is not generic; it throws a TypeError exception if its this
- value is not a String or String object. Therefore, it cannot be
- transferred to other kinds of objects for use as a method.
- Returns - a String containing the character at position pos - in the String resulting from converting this object to a String. If - there is no character at that position, the result is the empty - String. The result is a String value, not a String object.
-
- If
- pos is a value of
- Number type that is an integer, then the result of x.charAt( pos)
- is equal to the result of x.substring( pos,
- pos+1).
- When
- the charAt method
- is called with one argument pos,
- the following steps are taken:
- Call - CheckObjectCoercible passing the this value as its argument.
-- Let - S be the result of calling ToString, giving it the this - value as its argument.
-- Let - position be ToInteger(pos).
-- Let - size be the number of characters in S.
-- If - position < 0 or position ≥ size, return - the empty String.
-- Return - a String of length 1, containing one character from S, - namely the character at position position, where the first - (leftmost) character in S is considered to be at position 0, - the next one at position 1, and so on.
-NOTE The
- charAt function is
- intentionally generic; it does not require that its this
- value be a String object. Therefore, it can be transferred to other
- kinds of objects for use as a method.
- Returns - a Number (a nonnegative integer less than 216) - representing the code unit value of the character at position pos - in the String resulting from converting this object to a String. If - there is no character at that position, the result is NaN.
-
- When
- the charCodeAt
- method is called with one argument pos,
- the following steps are taken:
- Call - CheckObjectCoercible passing the this value as its argument.
-- Let - S be the result of calling ToString, giving it the this - value as its argument.
-- Let - position be ToInteger(pos).
-- Let - size be the number of characters in S.
-- If - position < 0 or position ≥ size, return - NaN.
-- Return - a value of Number type, whose value is the code unit value of the - character at position position in the String S, where - the first (leftmost) character in S is considered to be at - position 0, the next one at position 1, and so on.
-NOTE The
- charCodeAt
- function is intentionally generic; it does not require that its this
- value be a String object. Therefore it can be transferred to other
- kinds of objects for use as a method.
- When
- the concat method
- is called with zero or more arguments string1,
- string2, etc., it
- returns a String consisting of the characters of this object
- (converted to a String) followed by the characters of each of
- string1, string2,
- etc. (where each argument is converted to a String). The result is a
- String value, not a String object. The following steps are taken:
- Call - CheckObjectCoercible passing the this value as its argument.
-- Let - S be the result of calling ToString, giving it the this - value as its argument.
-- Let - args be an internal list that is a copy of the argument list - passed to this function.
-- Let - R be S.
-- Repeat, - while args is not empty
-- Remove - the first element from args and let next be the - value of that element.
-- Let - R be the String value consisting of the characters in the - previous value of R followed by the characters of - ToString(next).
-- Return - R.
-
- The
- length property of
- the concat method
- is 1.
NOTE The
- concat function is
- intentionally generic; it does not require that its this
- value be a String object. Therefore it can be transferred to other
- kinds of objects for use as a method.
- If
- searchString
- appears as a substring of the result of converting this object to a
- String, at one or more positions that are greater than or equal to
- position, then the
- index of the smallest such position is returned; otherwise, -1
- is returned. If position
- is undefined, 0 is assumed, so as to search all of the
- String.
- The
- indexOf method
- takes two arguments, searchString and position,
- and performs the following steps:
- Call - CheckObjectCoercible passing the this value as its argument.
-- Let - S be the result of calling ToString, giving it the this - value as its argument.
-- Let - searchStr be ToString(searchString).
-
- Let
- pos be ToInteger(position). (If position is
- undefined, this step produces the value 0).
- Let - len be the number of characters in S.
-- Let - start be min(max(pos, 0), len).
-- Let - searchLen be the number of characters in searchStr.
-
- Return
- the smallest possible integer k not smaller than start
- such that k+ searchLen is not greater than len,
- and for all nonnegative integers j less than searchLen,
- the character at position k+j of S is the same
- as the character at position j of searchStr); but if
- there is no such integer k, then return the value -1.
- The
- length property of
- the indexOf method
- is 1.
NOTE The
- indexOf function
- is intentionally generic; it does not require that its this
- value be a String object. Therefore, it can be transferred to other
- kinds of objects for use as a method.
- If
- searchString
- appears as a substring of the result of converting this object to a
- String at one or more positions that are smaller than or equal to
- position, then the
- index of the greatest such position is returned; otherwise, -1
- is returned. If position
- is undefined, the length of the String value is assumed, so
- as to search all of the String.
- The
- lastIndexOf method
- takes two arguments, searchString and position,
- and performs the following steps:
- Call - CheckObjectCoercible passing the this value as its argument.
-- Let - S be the result of calling ToString, giving it the this - value as its argument.
-- Let - searchStr be ToString(searchString).
-- Let - numPos be ToNumber(position). (If position is - undefined, this step produces the value NaN).
-- If - numPos is NaN, let pos be +∞; - otherwise, let pos be ToInteger(numPos).
-- Let - len be the number of characters in S.
-- Let - start min(max(pos, 0), len).
-- Let - searchLen be the number of characters in searchStr.
-
- Return
- the largest possible nonnegative integer k not larger than
- start such that k+ searchLen is not greater
- than len, and for all nonnegative integers j less
- than searchLen, the character at position k+j
- of S is the same as the character at position j of
- searchStr; but if there is no such integer k, then
- return the value -1.
- The
- length property of
- the lastIndexOf
- method is 1.
NOTE The
- lastIndexOf
- function is intentionally generic; it does not require that its this
- value be a String object. Therefore, it can be transferred to other
- kinds of objects for use as a method.
- When
- the localeCompare
- method is called with one argument that,
- it returns a Number other than NaN that represents the result
- of a locale-sensitive String comparison of the this value (converted
- to a String) with that
- (converted to a String). The two Strings are S
- and That. The two
- Strings are compared in an implementation-defined fashion. The
- result is intended to order String values in the sort order
- specified by the system default locale, and will be negative, zero,
- or positive, depending on whether S
- comes before That
- in the sort order, the Strings are equal, or S
- comes after That
- in the sort order, respectively.
- Before - perform the comparisons the following steps are performed to prepare - the Strings:
-- Call - CheckObjectCoercible passing the this value as its argument.
-- Let - S be the result of calling ToString, giving it the this - value as its argument.
-- Let - That be ToString(that).
-
- The
- localeCompare
- method, if considered as a function of two arguments this and
- that, is a
- consistent comparison function (as defined in 15.4.4.11) on the set
- of all Strings.
- The
- actual return values are implementation-defined to permit
- implementers to encode additional information in the value, but the
- function is required to define a total ordering on all Strings and
- to return 0 when
- comparing Strings that are considered canonically equivalent by the
- Unicode standard.
- If no - language-sensitive comparison at all is available from the host - environment, this function may perform a bitwise comparison.
-NOTE 1 The localeCompare
- method itself is not directly suitable as an argument to
- Array.prototype.sort
- because the latter requires a function of two arguments.
NOTE 2 This function is intended to rely on whatever language-sensitive - comparison functionality is available to the ECMAScript environment - from the host environment, and to compare according to the rules of - the host environment’s current locale. It is strongly recommended - that this function treat Strings that are canonically equivalent - according to the Unicode standard as identical (in other words, - compare the Strings as if they had both been converted to Normalised - Form C or D first). It is also recommended that this function not - honour Unicode compatibility equivalences or decompositions.
-NOTE 3 The second parameter to this function is likely to be used in a - future version of this standard; it is recommended that - implementations do not use this parameter position for anything - else.
-NOTE 4 The localeCompare
- function is intentionally generic; it does not require that its this
- value be a String object. Therefore, it can be transferred to other
- kinds of objects for use as a method.
- When
- the match method
- is called with argument regexp,
- the following steps are taken:
- Call - CheckObjectCoercible passing the this value as its argument.
-- Let - S be the result of calling ToString, giving it the this - value as its argument.
-
- If
- Type(regexp) is Object and the value of the [[Class]]
- internal property of regexp is "RegExp",
- then let rx be regexp;
- Else,
- let rx be a new RegExp object created as if by the
- expression new
- RegExp( regexp)
- where RegExp is
- the standard built-in constructor with that name.
- Let
- global be the result of calling the [[Get]] internal method
- of rx with argument "global".
- Let
- exec be the standard built-in function RegExp.prototype.exec
- (see 15.10.6.2)
- If - global is not true, then
-- Return - the result of calling the [[Call]] internal method of exec - with rx as the this value and argument list - containing S.
-- Else, - global is true
-
- Call
- the [[Put]] internal method of rx with arguments
- "lastIndex"
- and 0.
- Let
- A be a new array created as if by the expression new
- Array() where Array
- is the standard built-in constructor with that name.
- Let - previousLastIndex be 0.
-- Let - n be 0.
-- Let - lastMatch be true.
-- Repeat, - while lastMatch is true
-- Let - result be the result of calling the [[Call]] internal - method of exec with rx as the this value and - argument list containing S.
-- If - result is null, then set lastMatch to false.
-- Else, - result is not null
-
- Let
- thisIndex be the result of calling the [[Get]] internal
- method of rx with argument "lastIndex".
- If - thisIndex = previousLastIndex then
-
- Call
- the [[Put]] internal method of rx with arguments
- "lastIndex"
- and thisIndex+1.
- Set - previousLastIndex to thisIndex+1.
-- Else, - set previousLastIndex to thisIndex.
-
- Let
- matchStr be the result of calling the [[Get]] internal
- method of result with argument "0".
- Call - the [[DefineOwnProperty]] internal method of A with - arguments ToString(n), the Property Descriptor - {[[Value]]: matchStr, [[Writable]]: true, - [[Enumerable]]: true, [[configurable]]: true}, and - false.
-- Increment - n.
-- If - n = 0, then return null.
-- Return - A.
-NOTE The
- match function is
- intentionally generic; it does not require that its this
- value be a String object. Therefore, it can be transferred to other
- kinds of objects for use as a method.
- First - set string according to the following steps:
-- Call - CheckObjectCoercible passing the this value as its argument.
-- Let - string be the result of calling ToString, giving it the this - value as its argument.
-
- If
- searchValue is a
- regular expression (an object whose [[Class]] internal property is
- "RegExp"),
- do the following: If searchValue.global
- is false, then search string
- for the first match of the regular expression searchValue.
- If searchValue.global
- is true, then search string
- for all matches of the regular expression searchValue.
- Do the search in the same manner as in String.prototype.match,
- including the update of searchValue.lastIndex.
- Let m be the
- number of left capturing parentheses in searchValue
- (using NcapturingParens
- as specified in 15.10.2.1).
- If - searchValue is not - a regular expression, let searchString - be ToString(searchValue) - and search string - for the first occurrence of searchString. - Let m be 0.
-- If - replaceValue is a - function, then for each matched substring, call the function with - the following m + - 3 arguments. Argument 1 is the substring that matched. If - searchValue is a - regular expression, the next m - arguments are all of the captures in the MatchResult (see - 15.10.2.1). Argument m - + 2 is the offset within string - where the match occurred, and argument m - + 3 is string. The - result is a String value derived from the original input by - replacing each matched substring with the corresponding return value - of the function call, converted to a String if need be.
-
- Otherwise,
- let newstring
- denote the result of converting replaceValue
- to a String. The result is a String value derived from the original
- input String by replacing each matched substring with a String
- derived from newstring
- by replacing characters in newstring
- by replacement text as specified in Table 22. These $
- replacements are done left-to-right, and, once such a replacement is
- performed, the new replacement text is not subject to further
- replacements. For example, "$1,$2".replace(/(\$(\d))/g,
- "$$1-$1$2") returns "$1-$11,$1-$22".
- A $ in newstring
- that does not match any of the forms below is left as is.
|
- - Characters - |
-
- - Replacement - text - |
-
|
-
- |
-
-
- |
-
|
-
- |
-
- - The - matched substring. - |
-
|
-
- |
-
- - The - portion of string - that precedes the matched substring. - |
-
|
-
- |
-
- - The - portion of string - that follows the matched substring. - |
-
|
-
- |
-
-
- The
- nth
- capture, where n
- is a single digit in the range 1
- to 9 and |
-
|
-
- |
-
- - The - nnth - capture, where nn - is a two-digit decimal number in the range 01 - to 99. If nn≤m - and the nnth - capture is undefined, use the empty String instead. If - nn>m, - the result is implementation-defined. - |
-
NOTE The
- replace function
- is intentionally generic; it does not require that its this
- value be a String object. Therefore, it can be transferred to other
- kinds of objects for use as a method.
- When - the search method is called with argument regexp, - the following steps are taken:
-- Call - CheckObjectCoercible passing the this value as its argument.
-- Let - string be the result of calling ToString, giving it the this - value as its argument.
-
- If
- Type(regexp) is Object and the value of the [[Class]]
- internal property of regexp is "RegExp",
- then let rx be regexp;
- Else,
- let rx be a new RegExp object created as if by the
- expression new
- RegExp( regexp)
- where RegExp is
- the standard built-in constructor with that name.
- Search
- the value string from its beginning for an occurrence of the
- regular expression pattern rx. Let result be a Number
- indicating the offset within string where the pattern
- matched, or –1 if there was no match. The lastIndex
- and global
- properties of regexp are ignored when performing the search. The
- lastIndex
- property of regexp is left unchanged.
- Return - result.
-NOTE The
- search function is
- intentionally generic; it does not require that its this
- value be a String object. Therefore, it can be transferred to other
- kinds of objects for use as a method.
- The
- slice method takes
- two arguments, start
- and end, and
- returns a substring of the result of converting this object to a
- String, starting from character position start
- and running to, but not including, character position end
- (or through the end of the String if end
- is undefined). If start
- is negative, it is treated as sourceLength+start where sourceLength
- is the length of the String. If end
- is negative, it is treated as sourceLength+end
- where sourceLength
- is the length of the String. The result is a String value, not a
- String object. The following steps are taken:
- Call - CheckObjectCoercible passing the this value as its argument.
-- Let - S be the result of calling ToString, giving it the this - value as its argument.
-- Let - len be the number of characters in S.
-- Let - intStart be ToInteger(start).
-- If - end is undefined, let intEnd be len; - else let intEnd be ToInteger(end).
-- If - intStart is negative, let from be max(len + intStart,0); else let from be min(intStart,len).
-- If - intEnd is negative, let to be max(len +intEnd,0); else let to be min(intEnd, len).
-- Let - span be max(to – from,0).
-- Return - a String containing span consecutive characters from S - beginning with the character at position from.
-
- The
- length property of
- the slice method
- is 2.
NOTE The
- slice function is
- intentionally generic; it does not require that its this
- value be a String object. Therefore it can be transferred to other
- kinds of objects for use as a method.
- Returns
- an Array object into which substrings of the result of converting
- this object to a String have been stored. The substrings are
- determined by searching from left to right for occurrences of
- separator; these
- occurrences are not part of any substring in the returned array, but
- serve to divide up the String value. The value of separator
- may be a String of any length or it may be a RegExp object (i.e., an
- object whose [[Class]] internal property is "RegExp";
- see 15.10).
- The
- value of separator
- may be an empty String, an empty regular expression, or a regular
- expression that can match an empty String. In this case, separator
- does not match the empty substring at the beginning or end of the
- input String, nor does it match the empty substring at the end of
- the previous separator match. (For example, if separator
- is the empty String, the String is split up into individual
- characters; the length of the result array equals the length of the
- String, and each substring contains one character.) If separator
- is a regular expression, only the first match at a given position of
- the this String is considered, even if backtracking could
- yield a non-empty-substring match at that position. (For example,
- "ab".split(/a*?/)
- evaluates to the array ["a","b"],
- while "ab".split(/a*/)
- evaluates to the array["","b"].)
- If - the this object is (or converts to) the empty String, the - result depends on whether separator - can match the empty String. If it can, the result array contains no - elements. Otherwise, the result array contains one element, which is - the empty String.
-If - separator is a - regular expression that contains capturing parentheses, then each - time separator is - matched the results (including any undefined results) of the - capturing parentheses are spliced into the output array. - For example,
-
- "A<B>bold</B>and<CODE>coded</CODE>".split(/<(\/)?([^<>]+)>/)
evaluates - to the array
-
- ["A",
- undefined, "B", "bold", "/", "B",
- "and", undefined,
"CODE", "coded",
- "/", "CODE", ""]
- If - separator is - undefined, then the result array contains just one String, - which is the this value (converted to a String). If limit - is not undefined, then the output array is truncated so that - it contains no more than limit - elements.
-
- When
- the split method
- is called, the following steps are taken:
- Call - CheckObjectCoercible passing the this value as its argument.
-- Let - S be the result of calling ToString, giving it the this - value as its argument.
-
- Let
- A be a new array created as if by the expression new
- Array()where Array
- is the standard built-in constructor with that name.
- Let - lengthA be 0.
-- If - limit is undefined, let lim = 232–1; - else let lim = ToUint32(limit).
-- Let - s be the number of characters in S.
-- Let - p = 0.
-
- If
- separator is a RegExp object (its [[Class]] is "RegExp"),
- let R = separator; otherwise let R =
- ToString(separator).
- If - lim = 0, return A.
-- If - separator is undefined, then
-
- Call
- the [[DefineOwnProperty]] internal method of A with
- arguments "0",
- Property Descriptor {[[Value]]: S, [[Writable]]: true,
- [[Enumerable]]: true, [[Configurable]]: true}, and
- false.
- Return - A.
-- If - s = 0, then
-- Call - SplitMatch(S, 0, R) and let z be its - MatchResult result.
-- If - z is not failure, return A.
-
- Call
- the [[DefineOwnProperty]] internal method of A with
- arguments "0",
- Property Descriptor {[[Value]]: S, [[Writable]]: true,
- [[Enumerable]]: true, [[Configurable]]: true}, and
- false.
- Return - A.
-- Let - q = p.
-- Repeat, - while q ≠ s
-- Call - SplitMatch(S, q, R) and let z - be its MatchResult result.
-- If - z is failure, then let q = q+1.
-- Else, - z is not failure
-- z - must be a State. Let e be z's endIndex and - let cap be z's captures array.
-- If - e = p, then let q = q+1.
-- Else, - e ≠ p
-- Let - T be a String value equal to the substring of S - consisting of the characters at positions p (inclusive) - through q (exclusive).
-- Call - the [[DefineOwnProperty]] internal method of A with - arguments ToString(lengthA), Property Descriptor - {[[Value]]: T, [[Writable]]: true, [[Enumerable]]: - true, [[Configurable]]: true}, and false.
-- Increment - lengthA by 1.
-- If - lengthA = lim, return A.
-- Let - p = e.
-- Let - i = 0.
-- Repeat, - while i is not equal to the number of elements in cap.
-- Let - i = i+1.
-- Call - the [[DefineOwnProperty]] internal method of A with - arguments ToString(lengthA), Property Descriptor - {[[Value]]: cap[i], [[Writable]]: true, - [[Enumerable]]: true, [[Configurable]]: true}, - and false.
-- Increment - lengthA by 1.
-- If - lengthA - = lim, return A.
-- Let - q = p.
-- Let - T be a String value equal to the substring of S - consisting of the characters at positions p (inclusive) - through s (exclusive).
-- Call - the [[DefineOwnProperty]] internal method of A with - arguments ToString(lengthA), Property Descriptor {[[Value]]: - T, [[Writable]]: true, [[Enumerable]]: true, - [[Configurable]]: true}, and false.
-- Return - A.
-- The - abstract operation SplitMatch - takes three parameters, a String S, - an integer q, and - a String or RegExp R, - and performs the following in order to return a MatchResult (see - 15.10.2.1):
-
- If
- R is a RegExp object (its [[Class]] is "RegExp"),
- then
- Call - the [[Match]] internal method of R giving it the arguments - S and q, and return the MatchResult result.
-- Type(R) - must be String. Let r be the number of characters in R.
-- Let - s be the number of characters in S.
-- If - q+r > s then return the MatchResult - failure.
-- If - there exists an integer i between 0 (inclusive) and r - (exclusive) such that the character at position q+i - of S is different from the character at position i of - R, then return failure.
-
- The
- length property of
- the split method
- is 2.
NOTE 1 The split method
- ignores the value of separator.global
- for separators that are RegExp objects.
NOTE 2 The split
- function is intentionally generic; it does not require that its this
- value be a String object. Therefore, it can be transferred to other
- kinds of objects for use as a method.
- The - substring method takes two arguments, start - and end, and - returns a substring of the result of converting this object to a - String, starting from character position start - and running to, but not including, character position end - of the String (or through the end of the String is end - is undefined). The result is a String value, not a String - object.
-- If - either argument is NaN or negative, it is replaced with zero; - if either argument is larger than the length of the String, it is - replaced with the length of the String.
-- If - start is larger - than end, they are - swapped.
-- The - following steps are taken:
-- Call - CheckObjectCoercible passing the this value as its argument.
-- Let - S be the result of calling ToString, giving it the this - value as its argument.
-- Let - len be the number of characters in S.
-- Let - intStart be ToInteger(start).
-- If - end is undefined, let intEnd be len; - else let intEnd be ToInteger(end).
-- Let - finalStart be min(max(intStart, 0), len).
-- Let - finalEnd be min(max(intEnd, 0), len).
-- Let - from be min(finalStart, finalEnd).
-- Let - to be max(finalStart, finalEnd).
-- Return - a String whose length is to - from, containing - characters from S, namely the characters with indices from - through to −1, in - ascending order.
-
- The
- length property of
- the substring
- method is 2.
NOTE The
- substring function
- is intentionally generic; it does not require that its this
- value be a String object. Therefore, it can be transferred to other
- kinds of objects for use as a method.
- The - following steps are taken:
-- Call - CheckObjectCoercible passing the this value as its argument.
-- Let - S be the result of calling ToString, giving it the this - value as its argument.
-- Let - L be a String where each character of L is either the - Unicode lowercase equivalent of the corresponding character of S - or the actual corresponding character of S if no Unicode - lowercase equivalent exists.
-- Return - L.
-- For - the purposes of this operation, the 16-bit code units of the Strings - are treated as code points in the Unicode Basic Multilingual Plane. - Surrogate code points are directly transferred from S - to L without any - mapping.
-The - result must be derived according to the case mappings in the Unicode - character database (this explicitly includes not only the - UnicodeData.txt file, but also the SpecialCasings.txt file that - accompanies it in Unicode 2.1.8 and later).
-NOTE 1 The case mapping of some characters may produce multiple
- characters. In this case the result String may not be the same
- length as the source String. Because both toUpperCase
- and toLowerCase
- have context-sensitive behaviour, the functions are not symmetrical.
- In other words, s.toUpperCase().toLowerCase()
- is not necessarily equal to s.toLowerCase().
NOTE 2 The toLowerCase
- function is intentionally generic; it does not require that its this
- value be a String object. Therefore, it can be transferred to other
- kinds of objects for use as a method.
- This
- function works exactly the same as toLowerCase
- except that its result is intended to yield the correct result for
- the host environment’s current locale, rather than a
- locale-independent result. There will only be a difference in the
- few cases (such as Turkish) where the rules for that language
- conflict with the regular Unicode case mappings.
NOTE 1 The first parameter to this function is likely to be used in a - future version of this standard; it is recommended that - implementations do not use this parameter position for anything - else.
-NOTE 2 The toLocaleLowerCase
- function is intentionally generic; it does not require that its this
- value be a String object. Therefore, it can be transferred to other
- kinds of objects for use as a method.
- This
- function behaves in exactly the same way as
- String.prototype.toLowerCase,
- except that characters are mapped to their uppercase
- equivalents as specified in the Unicode Character Database.
NOTE The
- toUpperCase
- function is intentionally generic; it does not require that its this
- value be a String object. Therefore, it can be transferred to other
- kinds of objects for use as a method.
- This
- function works exactly the same as toUpperCase
- except that its result is intended to yield the correct result for
- the host environment’s current locale, rather than a
- locale-independent result. There will only be a difference in the
- few cases (such as Turkish) where the rules for that language
- conflict with the regular Unicode case mappings.
NOTE 1 The first parameter to this function is likely to be used in a - future version of this standard; it is recommended that - implementations do not use this parameter position for anything - else.
-NOTE 2 The toLocaleUpperCase
- function is intentionally generic; it does not require that its this
- value be a String object. Therefore, it can be transferred to other
- kinds of objects for use as a method.
- The - following steps are taken:
-- Call - CheckObjectCoercible passing the this value as its argument.
-- Let - S be the result of calling ToString, giving it the this - value as its argument.
-- Let - T be a String value that is a copy of S with both - leading and trailing white space removed. The definition of white - space is the union of WhiteSpace and LineTerminator.
-- Return - T.
-NOTE The
- trim function is
- intentionally generic; it does not require that its this
- value be a String object. Therefore, it can be transferred to other
- kinds of objects for use as a method.
- String
- instances inherit properties from the String prototype object and
- their [[Class]] internal property value is "String".
- String instances also have a [[PrimitiveValue]] internal property, a
- length property,
- and a set of enumerable properties with array index names.
- The - [[PrimitiveValue]] internal property is the String value represented - by this String object. The array index named properties correspond - to the individual characters of the String value. A special - [[GetOwnProperty]] internal method is used to specify the number, - values, and attributes of the array index named properties. -
-- The - number of characters in the String value represented by this String - object.
-- Once - a String object is created, this property is unchanging. It has the - attributes { [[Writable]]: false, [[Enumerable]]: false, - [[Configurable]]: false }.
-- String - objects use a variation of the [[GetOwnProperty]] internal method - used for other native ECMAScript objects (8.12.1). - - This special internal method is used to add access for named properties - corresponding to individual characters of String objects.
-- Assume - S is a String - object and P is a - String.
-- When - the [[GetOwnProperty]] internal method of S is called with property name P, - the following steps are taken:
-- Let - desc be the result of calling the default [[GetOwnProperty]] - internal method (8.12.1) on S with argument P.
-- If - desc is not undefined return desc. -
-- If - ToString(abs(ToInteger(P))) - is not - the same value as P, - return undefined.
-- Let - str be the String value of the [[PrimitiveValue]] internal - property of S.
-- Let - index be - ToInteger(P).
- Let - len be the number of characters in str.
-- If - len ≤ index, return undefined.
-- Let - resultStr be a String of length 1, containing one character - from str, specifically the character at position index, - where the first (leftmost) character in str is considered to - be at position 0, the next one at position 1, and so on.
-- Return - a Property Descriptor { [[Value]]: resultStr, - [[Enumerable]]: true, [[Writable]]: false, - [[Configurable]]: false }
-
- When
- Boolean is called
- as a function rather than as a constructor, it performs a type
- conversion.
- Returns - a Boolean value (not a Boolean object) computed by ToBoolean(value).
-
- When
- Boolean is called
- as part of a new
- expression it is a constructor: it initialises the newly created
- object.
- The
- [[Prototype]] internal property of the newly constructed object is
- set to the original Boolean prototype object, the one that is the
- initial value of Boolean.prototype
- (15.6.3.1).
- The
- [[Class]] internal property of the newly constructed Boolean object
- is set to "Boolean".
- The - [[PrimitiveValue]] internal property of the newly constructed - Boolean object is set to ToBoolean(value).
-- The - [[Extensible]] internal property of the newly constructed object is - set to true.
-- The - value of the [[Prototype]] internal property of the Boolean - constructor is the Function prototype object (15.3.4).
-
- Besides
- the internal properties and the length
- property (whose value is 1), the Boolean constructor has the
- following property:
- The
- initial value of Boolean.prototype
- is the Boolean prototype object (15.6.4).
- This - property has the attributes { [[Writable]]: false, - [[Enumerable]]: false, [[Configurable]]: false }.
-
- The
- Boolean prototype object is itself a Boolean object (its [[Class]]
- is "Boolean")
- whose value is false.
- The - value of the [[Prototype]] internal property of the Boolean - prototype object is the standard built-in Object prototype object - (15.2.4).
-
- The
- initial value of Boolean.prototype.constructor
- is the built-in Boolean
- constructor.
- The - following steps are taken:
-- Let - B be the this value.
-- If - Type(B) is Boolean, then let b be B.
-
- Else
- if Type(B) is Object and the value of the [[Class]] internal
- property of B is "Boolean",
- then let b be the value of the [[PrimitiveValue]] internal
- property of B.
- Else - throw a TypeError exception.
-
- If
- b is true, then return "true";
- else return "false".
- The - following steps are taken:
-- Let - B be the this value.
-- If - Type(B) is Boolean, then let b be B.
-
- Else
- if Type(B) is Object and the value of the [[Class]] internal
- property of B is "Boolean",
- then let b be the value of the [[PrimitiveValue]] internal
- property of B.
- Else - throw a TypeError exception.
-- Return - b.
-
- Boolean
- instances inherit properties from the Boolean prototype object and
- their [[Class]] internal property value is "Boolean".
- Boolean instances also have a [[PrimitiveValue]] internal property.
- The - [[PrimitiveValue]] internal property is the Boolean value - represented by this Boolean object.
-
- When
- Number is called
- as a function rather than as a constructor, it performs a type
- conversion.
- Returns - a Number value (not a Number object) computed by ToNumber(value) - if value was - supplied, else returns +0.
-
- When
- Number is called
- as part of a new
- expression it is a constructor: it initialises the newly created
- object.
- The
- [[Prototype]] internal property of the newly constructed object is
- set to the original Number prototype object, the one that is the
- initial value of Number.prototype
- (15.7.3.1).
- The
- [[Class]] internal property of the newly constructed object is set
- to "Number".
- The - [[PrimitiveValue]] internal property of the newly constructed object - is set to ToNumber(value) - if value was - supplied, else to +0.
-- The - [[Extensible]] internal property of the newly constructed object is - set to true.
-- The - value of the [[Prototype]] internal property of the Number - constructor is the Function prototype object (15.3.4).
-
- Besides
- the internal properties and the length
- property (whose value is 1), the Number constructor has the
- following property:
- The
- initial value of Number.prototype
- is the Number prototype object (15.7.4).
- This - property has the attributes { [[Writable]]: false, - [[Enumerable]]: false, [[Configurable]]: false }.
-
- The
- value of Number.MAX_VALUE
- is the largest positive finite value of the Number type, which is
- approximately 1.7976931348623157 × 10308.
- This - property has the attributes { [[Writable]]: false, - [[Enumerable]]: false, [[Configurable]]: false }.
-
- The
- value of Number.MIN_VALUE
- is the smallest positive value of the Number type, which is
- approximately 5 × 10 324.
- This - property has the attributes { [[Writable]]: false, - [[Enumerable]]: false, [[Configurable]]: false }.
-
- The
- value of Number.NaN
- is NaN.
- This - property has the attributes { [[Writable]]: false, - [[Enumerable]]: false, [[Configurable]]: false }.
-- The - value of Number.NEGATIVE_INFINITY is −∞.
-- This - property has the attributes { [[Writable]]: false, - [[Enumerable]]: false, [[Configurable]]: false }.
-- The - value of Number.POSITIVE_INFINITY is +∞.
-- This - property has the attributes { [[Writable]]: false, - [[Enumerable]]: false, [[Configurable]]: false }.
-
- The
- Number prototype object is itself a Number object (its [[Class]] is
- "Number")
- whose value is +0.
- The - value of the [[Prototype]] internal property of the Number prototype - object is the standard built-in Object prototype object (15.2.4).
-
- Unless
- explicitly stated otherwise, the methods of the Number prototype
- object defined below are not generic and the this value passed to
- them must be either a Number value or an Object for which the value
- of the [[Class]] internal property is "Number".
- In
- the following descriptions of functions that are properties of the
- Number prototype object, the phrase “this Number object” refers
- to either the object that is the this value for the
- invocation of the function or, if Type(this value) is Number,
- an object that is created as if by the expression new
- Number(this value)
- where Number is
- the standard built-in constructor with that name. Also, the phrase
- “this Number value” refers to either the Number value
- represented by this Number object, that is, the value of the
- [[PrimitiveValue]] internal property of this Number object or the
- this value if its type is Number. A TypeError
- exception is thrown if the this value is neither an object
- for which the value of the [[Class]] internal property is "Number"
- or a value whose type is Number.
- The
- initial value of Number.prototype.constructor
- is the built-in Number
- constructor.
- The - optional radix - should be an integer value in the inclusive range 2 - to 36. If radix - not present or is undefined the Number 10 - is used as the value of radix. - If ToInteger(radix) - is the Number 10 then - this Number value is given as an argument to the ToString abstract - operation; the resulting String value is returned.
-
- If
- ToInteger(radix)
- is not an integer between 2 and 36 inclusive throw a RangeError
- exception. If ToInteger(radix)
- is an integer from 2 to 36, but not 10, the result is a String
- representation of this Number value using the specified radix.
- Letters a-z
- are used for digits with values 10 through 35. The precise algorithm
- is implementation-dependent if the radix is not 10, however the
- algorithm should be a generalization of that specified in 9.8.1.
- The
- toString function
- is not generic; it throws a TypeError exception if its this
- value is not a Number or a Number object. Therefore, it cannot be
- transferred to other kinds of objects for use as a method.
- Produces
- a String value that represents this Number value formatted according
- to the conventions of the host environment’s current locale. This
- function is implementation-dependent, and it is permissible, but not
- encouraged, for it to return the same thing as toString.
NOTE The - first parameter to this function is likely to be used in a future - version of this standard; it is recommended that implementations do - not use this parameter position for anything else.
-- Returns - this Number value.
-
- The
- valueOf function
- is not generic; it throws a TypeError exception if its this
- value is not a Number or a Number object. Therefore, it cannot be
- transferred to other kinds of objects for use as a method.
- Return - a String containing this Number value represented in decimal - fixed-point notation with fractionDigits - digits after the decimal point. If fractionDigits - is undefined, 0 is assumed. Specifically, perform the - following steps:
-
- Let
- f be ToInteger(fractionDigits). (If fractionDigits
- is undefined, this step produces the value 0).
- If - f < 0 or f > 20, throw a RangeError - exception.
-- Let - x be this Number value.
-
- If
- x is NaN, return the String "NaN".
- Let - s be the empty String.
-- If - x < 0, then
-
- Let
- s be "-".
- Let - x = –x.
-- If - x ≥ 1021, - then
-- Let - m = ToString(x).
-- Else, - x < 1021
-- Let - n be an integer for which the exact mathematical value of n - ÷ 10f – x - is as close to zero as possible. If there are two such n, - pick the larger n.
-
- If
- n = 0, let m be the String "0".
- Otherwise, let m be the String consisting of the digits of
- the decimal representation of n (in order, with no leading
- zeroes).
- If - f ≠ 0, then
-- Let - k be the number of characters in m.
-- If - k ≤ f, then
-
- Let
- z be the String consisting of f+1–k
- occurrences of the character ‘0’.
- Let - m be the concatenation of Strings z and m.
-- Let - k = f + 1.
-- Let - a be the first k–f characters of m, and - let b be the remaining f characters of m.
-
- Let
- m be the concatenation of the three Strings a, ".",
- and b.
- Return - the concatenation of the Strings s and m.
-
- The
- length property of
- the toFixed method
- is 1.
- If
- the toFixed method
- is called with more than one argument, then the behaviour is
- undefined (see clause 15).
- An
- implementation is permitted to extend the behaviour of toFixed
- for values of fractionDigits
- less than 0 or greater than 20. In this case toFixed
- would not necessarily throw RangeError for such values.
NOTE The
- output of toFixed
- may be more precise than toString
- for some values because toString only prints enough significant
- digits to distinguish the number from adjacent number values. For
- example,
-
(1000000000000000128).toString()
- returns "1000000000000000100",
while
- (1000000000000000128).toFixed(0)
- returns "1000000000000000128".
- Return - a String containing this Number value represented in decmal - exponential notation with one digit before the significand's decimal - point and fractionDigits - digits after the significand's decimal point. If fractionDigits - is undefined, include as many significand digits as necessary - to uniquely specify the Number (just like in ToString except that in - this case the Number is always output in exponential notation). - Specifically, perform the following steps:
-- Let - x be this Number value.
-- Let - f be ToInteger(fractionDigits).
-
- If
- x is NaN, return the String "NaN".
- Let - s be the empty String.
-- If - x < 0, then
-
- Let
- s be "-".
- Let - x = –x.
-- If - x = +∞, then
-
- Return
- the concatenation of the Strings s and "Infinity".
-
-
- If - fractionDigits is not undefined and (f < 0 - or f > 20), throw a RangeError exception.
-- If - x = 0, then
-- Let - f = 0.
-
- Let
- m be the String consisting of f+1 occurrences of the
- character ‘0’.
- Let - e = 0.
-- Else, - x ≠ 0
-- If - fractionDigits is not undefined, then
-- Let - e and n be integers such that 10f - ≤ n < 10f+1 - and for which the exact mathematical value of n × - 10e–f – x - is as close to zero as possible. If there are two such sets of e - and n, pick the e and n for which n × - 10e–f is larger.
-- Else, - fractionDigits is undefined -
-- Let - e, n, and f be integers such that f ≥ - 0, 10f ≤ n - < 10f+1, the number value for n × - 10e–f is x, - and f is as small as possible. Note that the decimal - representation of n has f+1 digits, n is not - divisible by 10, and the least significant digit of n is - not necessarily uniquely determined by these criteria.
-- Let - m be the String consisting of the digits of the decimal - representation of n (in order, with no leading zeroes).
-- If - f ≠ 0, then
-- Let - a be the first character of m, and let b be - the remaining f characters of m.
-
- Let
- m be the concatenation of the three Strings a, ".",
- and b.
- If - e = 0, then -
-
- Let
- c = "+".
- Let
- d = "0".
- Else
-
- If
- e > 0, then let c = "+".
- Else, - e ≤ 0
-
- Let
- c = "-".
- Let - e = –e.
-- Let - d be the String consisting of the digits of the decimal - representation of e (in order, with no leading zeroes).
-
- Let
- m be the concatenation of the four Strings m, "e",
- c, and d.
- Return - the concatenation of the Strings s and m.
-
- The
- length property of
- the toExponential
- method is 1.
- If
- the toExponential
- method is called with more than one argument, then the behaviour is
- undefined (see clause 15).
- An
- implementation is permitted to extend the behaviour of toExponential
- for values of fractionDigits
- less than 0 or greater than 20. In this case toExponential
- would not necessarily throw RangeError for such values.
NOTE For - implementations that provide more accurate conversions than required - by the rules above, it is recommended that the following alternative - version of step 9.b.i be used as a guideline:
-- Let - e, - n, - and f be - integers such that f - ≥ - 0, 10f - ≤ - n < 10f+1, - the number value for n × - 10e–f - is x, and f - is as small as possible. If there are multiple possibilities for - n, - choose the value of n - for which n - × - 10e–f - is closest in value to x. - If there are two such possible values of n, - choose the one that is even.
-- Return - a String containing this Number value represented either in decimal - exponential notation with one digit before the significand's decimal - point and precision–1 - digits after the significand's decimal point or in decimal fixed - notation with precision - significant digits. If precision - is undefined, call ToString (9.8.1) instead. Specifically, - perform the following steps:
-- Let - x be this Number value.
-- If - precision is undefined, return ToString(x).
-- Let - p be ToInteger(precision).
-
- If
- x is NaN, return the String "NaN".
- Let - s be the empty String.
-- If - x < 0, then
-
- Let
- s be "-".
- Let - x = –x.
-- If - x = +∞, then
-
- Return
- the concatenation of the Strings s and "Infinity".
- If - p < 1 or p > 21, throw a RangeError - exception.
-- If - x = 0, then
-
- Let
- m be the String consisting of p occurrences of the
- character ‘0’.
- Let - e = 0.
-- Else - x ≠ 0,
-- Let - e and n be integers such that 10p–1 - ≤ n < 10p - and for which the exact mathematical value of n × - 10e–p+1 - – x is as close to zero as possible. If there are two - such sets of e and n, pick the e and n - for which n × 10e–p+1 - is larger.
-- Let - m be the String consisting of the digits of the decimal - representation of n (in order, with no leading zeroes).
-- If - e < –6 or e ≥ - p, then
-- Let - a be the first character of m, and let b be - the remaining p–1 characters of m.
-
- Let
- m be the concatenation of the three Strings a, ".",
- and b.
- If - e = 0, then
-
- Let
- c = "+"
- and d = "0".
- Else - e ≠ 0,
-- If - e > 0, then -
-
- Let
- c = "+".
- Else - e < 0,
-
- Let
- c = "-".
- Let - e = –e.
-- Let - d be the String consisting of the digits of the decimal - representation of e (in order, with no leading zeroes).
-
- Let
- m be the concatenation of the five Strings s, m,
- "e",
- c, and d.
- If - e = p–1, then return the concatenation of the - Strings s and m.
-- If - e ≥ 0, then
-
- Let
- m be the concatenation of the first e+1 characters
- of m, the character ‘.’,
- and the remaining p– (e+1) characters of m.
- Else - e < 0,
-
- Let
- m be the concatenation of the String "0.",
- –(e+1) occurrences of the character ‘0’,
- and the String m.
- Return - the concatenation of the Strings s and m.
-
- The
- length property of
- the toPrecision
- method is 1.
- If
- the toPrecision
- method is called with more than one argument, then the behaviour is
- undefined (see clause 15).
- An
- implementation is permitted to extend the behaviour of toPrecision
- for values of precision
- less than 1 or greater than 21. In this case toPrecision
- would not necessarily throw RangeError for such values.
- Number
- instances inherit properties from the Number prototype object and
- their [[Class]] internal property value is "Number".
- Number instances also have a [[PrimitiveValue]] internal property.
- The - [[PrimitiveValue]] internal property is the Number value represented - by this Number object.
-- The - Math object is a single object that has some named properties, some - of which are functions.
-
- The
- value of the [[Prototype]] internal property of the Math object is
- the standard built-in Object prototype object (15.2.4). The value of
- the [[Class]] internal property of the Math object is "Math".
- The
- Math object does not have a [[Construct]] internal property; it is
- not possible to use the Math object as a constructor with the new
- operator.
- The - Math object does not have a [[Call]] internal property; it is not - possible to invoke the Math object as a function.
-NOTE In - this specification, the phrase “the Number value for x” - has a technical meaning defined in 8.5.
-- The - Number value for e, - the base of the natural logarithms, which is approximately - 2.7182818284590452354.
-- This - property has the attributes { [[Writable]]: false, - [[Enumerable]]: false, [[Configurable]]: false }.
-- The - Number value for the natural logarithm of 10, which is approximately - 2.302585092994046.
-- This - property has the attributes { [[Writable]]: false, - [[Enumerable]]: false, [[Configurable]]: false }.
-- The - Number value for the natural logarithm of 2, which is approximately - 0.6931471805599453.
-- This - property has the attributes { [[Writable]]: false, - [[Enumerable]]: false, [[Configurable]]: false }.
-- The - Number value for the base-2 - logarithm of e, - the base of the natural logarithms; this value is approximately - 1.4426950408889634.
-- This - property has the attributes { [[Writable]]: false, - [[Enumerable]]: false, [[Configurable]]: false }.
-NOTE The
- value of Math.LOG2E
- is approximately the reciprocal of the value of Math.LN2.
- The - Number value for the base-10 - logarithm of e, - the base of the natural logarithms; this value is approximately - 0.4342944819032518.
-- This - property has the attributes { [[Writable]]: false, - [[Enumerable]]: false, [[Configurable]]: false }.
-NOTE The
- value of Math.LOG10E
- is approximately the reciprocal of the value of Math.LN10.
- The - Number value for π, the ratio of - the circumference of a circle to its diameter, which is - approximately 3.1415926535897932.
-- This - property has the attributes { [[Writable]]: false, - [[Enumerable]]: false, [[Configurable]]: false }.
-- The - Number value for the square root of ½, - which is approximately 0.7071067811865476.
-- This - property has the attributes { [[Writable]]: false, - [[Enumerable]]: false, [[Configurable]]: false }.
-NOTE The
- value of Math.SQRT1_2
- is approximately the reciprocal of the value of Math.SQRT2.
- The - Number value for the square root of 2, - which is approximately 1.4142135623730951.
-- This - property has the attributes { [[Writable]]: false, - [[Enumerable]]: false, [[Configurable]]: false }.
-
- Each
- of the following Math object functions applies the ToNumber abstract operator to each of
- its arguments (in left-to-right order if there is more than one) and
- then performs a computation on the resulting Number value(s).
- In - the function descriptions below, the symbols NaN, −0, - +0, −∞ and +∞ - refer to the Number values described in 8.5.
-NOTE The
- behaviour of the functions acos,
- asin, atan,
- atan2, cos,
- exp, log,
- pow, sin,
- and sqrt is not
- precisely specified here except to require specific results for
- certain argument values that represent boundary cases of interest.
- For other argument values, these functions are intended to compute
- approximations to the results of familiar mathematical functions,
- but some latitude is allowed in the choice of approximation
- algorithms. The general intent is that an implementer should be able
- to use the same mathematical library for ECMAScript on a given
- hardware platform that is available to C programmers on that
- platform.
- Although
- the choice of algorithms is left to the implementation, it is
- recommended (but not specified by this standard) that
- implementations use the approximation algorithms for IEEE 754
- arithmetic contained in fdlibm,
- the freely distributable mathematical library from Sun Microsystems
- (http://www.netlib.org/fdlibm).
-
-
- Returns - the absolute value of x; - the result has the same magnitude as x - but has positive sign.
-- If - x - is NaN, the result is NaN.
-- If - x - is −0, - the result is +0.
-- If - x - is −∞, - the result is +∞.
-- Returns - an implementation-dependent approximation to the arc cosine of x. - The result is expressed in radians and ranges from +0 - to +π.
-- If - x - is NaN, the result is NaN.
-- If - x - is greater than 1, the result is NaN.
-- If - x - is less than −1, - the result is NaN.
-- If - x - is exactly 1, the result is +0.
-- Returns - an implementation-dependent approximation to the arc sine of x. - The result is expressed in radians and ranges from −π/2 - to +π/2.
-- If - x - is NaN, the result is NaN.
-- If - x - is greater than 1, the result is NaN.
-- If - x - is less than –1, the result is NaN.
-- If - x - is +0, the result is +0.
-- If - x - is −0, - the result is −0.
-- Returns - an implementation-dependent approximation to the arc tangent of x. - The result is expressed in radians and ranges from −π/2 - to +π/2.
-- If - x - is NaN, the result is NaN.
-- If - x - is +0, the result is +0.
-- If - x - is −0, - the result is −0.
-- If - x - is +∞, - the result is an implementation-dependent approximation to +π/2.
-- If - x - is −∞, - the result is an implementation-dependent approximation to −π/2.
-- Returns - an implementation-dependent approximation to the arc tangent of the - quotient y/x - of the arguments y - and x, where the - signs of y and x - are used to determine the quadrant of the result. Note that it is - intentional and traditional for the two-argument arc tangent - function that the argument named y - be first and the argument named x - be second. The result is expressed in radians and ranges from −π - to +π.
-- If - either x - or y - is NaN, the result is NaN.
-- If - y>0 - and x - is +0, the result is an implementation-dependent approximation to - +π/2.
-- If - y>0 - and x - is −0, - the result is an implementation-dependent approximation to +π/2.
-- If - y - is +0 and x>0, - the result is +0.
-- If - y - is +0 and x - is +0, the result is +0.
-- If - y - is +0 and x - is −0, - the result is an implementation-dependent approximation to +π.
-- If - y - is +0 and x<0, - the result is an implementation-dependent approximation to +π.
-- If - y - is −0 - and x>0, - the result is −0.
-- If - y - is −0 - and x - is +0, the result is −0.
-- If - y - is −0 - and x - is −0, - the result is an implementation-dependent approximation to −π.
-- If - y - is −0 - and x<0, - the result is an implementation-dependent approximation to −π.
-- If - y<0 - and x - is +0, the result is an implementation-dependent approximation to - −π/2.
-- If - y<0 - and x - is −0, - the result is an implementation-dependent approximation to −π/2.
-- If - y>0 - and y - is finite and x - is +∞, - the result is +0.
-- If - y>0 - and y - is finite and x - is −∞, - the result if an implementation-dependent approximation to +π.
-- If - y<0 - and y - is finite and x - is +∞, - the result is −0.
-- If - y<0 - and y - is finite and x - is −∞, - the result is an implementation-dependent approximation to −π.
-- If - y - is +∞ - and x - is finite, the result is an implementation-dependent approximation - to +π/2.
-- If - y - is −∞ - and x - is finite, the result is an implementation-dependent approximation - to −π/2.
-- If - y - is +∞ - and x - is +∞, - the result is an implementation-dependent approximation to +π/4.
-- If - y - is +∞ - and x - is −∞, - the result is an implementation-dependent approximation to +3π/4.
-- If - y - is −∞ - and x - is +∞, - the result is an implementation-dependent approximation to −π/4.
-- If - y - is −∞ - and x - is −∞, - the result is an implementation-dependent approximation to −3π/4.
-- Returns - the smallest (closest to −∞) - Number value that is not less than x - and is equal to a mathematical integer. If x - is already an integer, the result is x.
-- If - x - is NaN, the result is NaN.
-- If - x - is +0, the result is +0.
-- If - x - is −0, - the result is −0.
-- If - x - is +∞, - the result is +∞.
-- If - x - is −∞, - the result is −∞.
-- If - x - is less than 0 but greater than -1, the result is −0.
-
- The
- value of Math.ceil(x)
- is the same as the value of -Math.floor(-x).
- Returns - an implementation-dependent approximation to the cosine of x. - The argument is expressed in radians.
-- If - x - is NaN, the result is NaN.
-- If - x - is +0, the result is 1.
-- If - x - is −0, - the result is 1.
-- If - x - is +∞, - the result is NaN.
-- If - x - is −∞, - the result is NaN.
-- Returns - an implementation-dependent approximation to the exponential - function of x (e - raised to the power of x, - where e is the - base of the natural logarithms).
-- If - x - is NaN, the result is NaN.
-- If - x - is +0, the result is 1.
-- If - x - is −0, - the result is 1.
-- If - x - is +∞, - the result is +∞.
-- If - x - is −∞, - the result is +0.
-- Returns - the greatest (closest to +∞) - Number value that is not greater than x - and is equal to a mathematical integer. If x - is already an integer, the result is x.
-- If - x - is NaN, the result is NaN.
-- If - x - is +0, the result is +0.
-- If - x - is −0, - the result is −0.
-- If - x - is +∞, - the result is +∞.
-- If - x - is −∞, - the result is −∞.
-- If - x - is greater than 0 but less than 1, the result is +0.
-NOTE The
- value of Math.floor(x)
- is the same as the value of -Math.ceil(-x).
- Returns - an implementation-dependent approximation to the natural logarithm - of x.
-- If - x - is NaN, the result is NaN.
-- If - x - is less than 0, the result is NaN.
-- If - x - is +0 or −0, - the result is −∞.
-- If - x - is 1, the result is +0.
-- If - x - is +∞, - the result is +∞.
-- Given - zero or more arguments, calls ToNumber on each of the arguments and - returns the largest of the resulting values.
-- If - no arguments are given, the result is −∞.
-- If - any value is NaN, the result is NaN.
-- The - comparison of values to determine the largest value is done as in - 11.8.5 except that +0 is considered to be larger than −0.
-
- The
- length property of
- the max method is
- 2.
- Given - zero or more arguments, calls ToNumber on each of the arguments and - returns the smallest of the resulting values.
-- If - no arguments are given, the result is +∞.
-- If - any value is NaN, the result is NaN.
-- The - comparison of values to determine the smallest value is done as in - 11.8.5 except that +0 is considered to be larger than −0.
-
- The
- length property of
- the min method is
- 2.
- Returns - an implementation-dependent approximation to the result of raising x - to the power y.
-- If - y - is NaN, the result is NaN.
-- If - y - is +0, the result is 1, even if x - is NaN.
-- If - y - is −0, - the result is 1, even if x - is NaN.
-- If - x - is NaN and y - is nonzero, the result is NaN.
-- If - abs(x)>1 - and y - is +∞, - the result is +∞.
-- If - abs(x)>1 - and y - is −∞, - the result is +0.
-- If - abs(x)==1 - and y - is +∞, - the result is NaN.
-- If - abs(x)==1 - and y - is −∞, - the result is NaN.
-- If - abs(x)<1 - and y - is +∞, - the result is +0.
-- If - abs(x)<1 - and y - is −∞, - the result is +∞.
-- If - x - is +∞ - and y>0, - the result is +∞.
-- If - x - is +∞ - and y<0, - the result is +0.
-- If - x - is −∞ - and y>0 - and y - is an odd integer, the result is −∞.
-- If - x - is −∞ - and y>0 - and y - is not an odd integer, the result is +∞.
-- If - x - is −∞ - and y<0 - and y - is an odd integer, the result is −0.
-- If - x - is −∞ - and y<0 - and y - is not an odd integer, the result is +0.
-- If - x - is +0 and y>0, - the result is +0.
-- If - x - is +0 and y<0, - the result is +∞.
-- If - x - is −0 - and y>0 - and y - is an odd integer, the result is −0.
-- If - x - is −0 - and y>0 - and y - is not an odd integer, the result is +0.
-- If - x - is −0 - and y<0 - and y - is an odd integer, the result is −∞.
-- If - x - is −0 - and y<0 - and y - is not an odd integer, the result is +∞.
-- If - x<0 - and x - is finite and y - is finite and y - is not an integer, the result is NaN.
-- Returns - a Number value with positive sign, greater than or equal to 0 but - less than 1, chosen randomly or pseudo randomly with approximately - uniform distribution over that range, using an - implementation-dependent algorithm or strategy. This function takes - no arguments.
-- Returns - the Number value that is closest to x - and is equal to a mathematical integer. If two integer Number values - are equally close to x, - then the result is the Number value that is closer to +∞. - If x is already an - integer, the result is x.
-- If - x - is NaN, the result is NaN.
-- If - x - is +0, the result is +0.
-- If - x - is −0, - the result is −0.
-- If - x - is +∞, - the result is +∞.
-- If - x - is −∞, - the result is −∞.
-- If - x - is greater than 0 but less than 0.5, the result is +0.
-- If - x - is less than 0 but greater than or equal to -0.5, the result is −0.
-NOTE 1 Math.round(3.5)
- returns 4, but
- Math.round(–3.5)
- returns –3.
NOTE 2 The value of Math.round(x)
- is the same as the value of Math.floor(x+0.5),
- except when x is
- −0
- or is less than 0
- but greater than or equal to -0.5;
- for these cases Math.round(x)
- returns −0,
- but Math.floor(x+0.5)
- returns +0.
- Returns - an implementation-dependent approximation to the sine of x. - The argument is expressed in radians.
-- If - x - is NaN, the result is NaN.
-- If - x - is +0, the result is +0.
-- If - x - is −0, - the result is −0.
-- If - x - is +∞ - or −∞, - the result is NaN.
-- Returns - an implementation-dependent approximation to the square root of x.
-- If - x - is NaN, the result is NaN.
-- If - x - is less than 0, the result is NaN.
-- If - x - is +0, the result is +0.
-- If - x - is −0, - the result is −0.
-- If - x - is +∞, - the result is +∞.
-- Returns - an implementation-dependent approximation to the tangent of x. - The argument is expressed in radians.
-- If - x - is NaN, the result is NaN.
-- If - x - is +0, the result is +0.
-- If - x - is −0, - the result is −0.
-- If - x - is +∞ - or −∞, - the result is NaN.
-- The - following functions are abstract operations that operate on time - values (defined in 15.9.1.1). Note that, in every case, if any - argument to one of these functions is NaN, the result will be - NaN.
-- A - Date object contains a Number indicating a particular instant in - time to within a millisecond. Such a Number is called a time - value. A time value may also be NaN, indicating that the - Date object does not represent a specific instant of time.
-- Time - is measured in ECMAScript in milliseconds since 01 January, 1970 - UTC. In time values leap seconds are ignored. It is assumed that - there are exactly 86,400,000 milliseconds per day. ECMAScript Number - values can represent all integers from –9,007,199,254,740,991 to - 9,007,199,254,740,991; this range suffices to measure times to - millisecond precision for any instant that is within approximately - 285,616 years, either forward or backward, from 01 January, 1970 - UTC.
-- The - actual range of times supported by ECMAScript Date objects is - slightly smaller: exactly –100,000,000 days to 100,000,000 days - measured relative to midnight at the beginning of 01 January, 1970 - UTC. This gives a range of 8,640,000,000,000,000 milliseconds to - either side of 01 January, 1970 UTC.
-- The - exact moment of midnight at the beginning of 01 January, 1970 UTC is - represented by the value +0.
-- A - given time value t belongs to day number
-- Day(t) - = floor(t / msPerDay)
-- where - the number of milliseconds per day is
-- msPerDay - = 86400000
-- The - remainder is called the time within the day:
-- TimeWithinDay(t) - = t modulo msPerDay
-- ECMAScript - uses an extrapolated Gregorian system to map a day number to a year - number and to determine the month and date within that year. In this - system, leap years are precisely those which are (divisible by 4) - and ((not divisible by 100) - or (divisible by 400)). - The number of days in year number y - is therefore defined by
-
- DaysInYear(y)
- = 365 if (y modulo 4) ≠
- 0
= 366 if (y modulo 4) = 0 and (y modulo 100) ≠
- 0
= 365 if (y modulo 100) = 0 and (y modulo 400) ≠
- 0
= 366 if (y modulo 400) = 0
- All - non-leap years have 365 - days with the usual number of days per month and leap years have an - extra day in February. The day number of the first day of year y - is given by:
-- DayFromYear(y) = - 365 × (y−1970) - + floor((y−1969)/4) − - floor((y−1901)/100) + - floor((y−1601)/400)
-- The - time value of the start of a year is:
-- TimeFromYear(y) = - msPerDay × DayFromYear(y)
-- A - time value determines a year by:
-- YearFromTime(t) = - the largest integer y (closest to positive infinity) such - that TimeFromYear(y) ≤ t
-- The - leap-year function is 1 for a time within a leap year and otherwise - is zero:
-
- InLeapYear(t) =
- 0 if DaysInYear(YearFromTime(t)) = 365
= 1 if
- DaysInYear(YearFromTime(t)) = 366
- Months - are identified by an integer in the range 0 - to 11, inclusive. The - mapping MonthFromTime(t) from a time value t to a - month number is defined by:
-
- MonthFromTime(t) =
- 0 if 0 ≤ DayWithinYear(t)
- < 31
= 1 if 31 ≤
- DayWithinYear (t) < 59+InLeapYear(t)
=
- 2 if 59+InLeapYear(t) ≤
- DayWithinYear (t) < 90+InLeapYear(t)
=
- 3 if 90+InLeapYear(t) ≤
- DayWithinYear (t) < 120+InLeapYear(t)
=
- 4 if 120+InLeapYear(t) ≤
- DayWithinYear (t) < 151+InLeapYear(t)
=
- 5 if 151+InLeapYear(t) ≤
- DayWithinYear (t) < 181+InLeapYear(t)
=
- 6 if 181+InLeapYear(t) ≤
- DayWithinYear (t) < 212+InLeapYear(t)
=
- 7 if 212+InLeapYear(t) ≤
- DayWithinYear (t) < 243+InLeapYear(t)
=
- 8 if 243+InLeapYear(t) ≤
- DayWithinYear (t) < 273+InLeapYear(t)
=
- 9 if 273+InLeapYear(t) ≤
- DayWithinYear (t) < 304+InLeapYear(t)
=
- 10 if 304+InLeapYear(t) ≤
- DayWithinYear (t) < 334+InLeapYear(t)
=
- 11 if 334+InLeapYear(t) ≤
- DayWithinYear (t) < 365+InLeapYear(t)
where
-- DayWithinYear(t) = - Day(t)−DayFromYear(YearFromTime(t))
-- A - month value of 0 - specifies January; 1 - specifies February; 2 - specifies March; 3 - specifies April; 4 specifies - May; 5 specifies June; 6 - specifies July; 7 - specifies August; 8 - specifies September; 9 - specifies October; 10 - specifies November; and 11 - specifies December. Note that MonthFromTime(0) - = 0, corresponding to Thursday, 01 January, 1970.
-- A - date number is identified by an integer in the range 1 - through 31, inclusive. - The mapping DateFromTime(t) from a time value t to a - month number is defined by:
-
- DateFromTime(t) =
- DayWithinYear(t)+1 if MonthFromTime(t)=0
=
- DayWithinYear(t)−30 if
- MonthFromTime(t)=1
= DayWithinYear(t)−58−InLeapYear(t) if
- MonthFromTime(t)=2
= DayWithinYear(t)−89−InLeapYear(t) if
- MonthFromTime(t)=3
=
- DayWithinYear(t)−119−InLeapYear(t) if
- MonthFromTime(t)=4
=
- DayWithinYear(t)−150−InLeapYear(t) if
- MonthFromTime(t)=5
=
- DayWithinYear(t)−180−InLeapYear(t) if
- MonthFromTime(t)=6
=
- DayWithinYear(t)−211−InLeapYear(t) if
- MonthFromTime(t)=7
=
- DayWithinYear(t)−242−InLeapYear(t) if
- MonthFromTime(t)=8
=
- DayWithinYear(t)−272−InLeapYear(t) if
- MonthFromTime(t)=9
=
- DayWithinYear(t)−303−InLeapYear(t) if
- MonthFromTime(t)=10
=
- DayWithinYear(t)−333−InLeapYear(t) if
- MonthFromTime(t)=11
- The - weekday for a particular time value t - is defined as
-- WeekDay(t) - = (Day(t) + 4) modulo 7
-- A - weekday value of 0 - specifies Sunday; 1 - specifies Monday; 2 - specifies Tuesday; 3 - specifies Wednesday; 4 specifies - Thursday; 5 specifies - Friday; and 6 specifies - Saturday. Note that WeekDay(0) = - 4, corresponding to Thursday, 01 January, 1970.
-- An - implementation of ECMAScript is expected to determine the local time - zone adjustment. The local time zone adjustment is a value LocalTZA - measured in milliseconds which when added to UTC represents the - local standard time. Daylight saving time is not - reflected by LocalTZA. The value LocalTZA does not vary with time - but depends only on the geographic location.
-- An - implementation of ECMAScript is expected to determine the daylight - saving time algorithm. The algorithm to determine the daylight - saving time adjustment DaylightSavingTA(t), measured in - milliseconds, must depend only on four things:
-- (1) - the time since the beginning of the year
-- t - – TimeFromYear(YearFromTime(t))
-- (2) - whether t is in a - leap year
-- InLeapYear(t)
-- (3) - the week day of the beginning of the year
-- WeekDay(TimeFromYear(YearFromTime(t))
-- and - (4) the geographic location.
-- The - implementation of ECMAScript should not try to determine whether the - exact time was subject to daylight saving time, but just whether - daylight saving time would have been in effect if the current - daylight saving time algorithm had been used at the time. This - avoids complications such as taking into account the years that the - locale observed daylight saving time year round.
-- If - the host environment provides functionality for determining daylight - saving time, the implementation of ECMAScript is free to map the - year in question to an equivalent year (same leap-year-ness and same - starting week day for the year) for which the host environment - provides daylight saving time information. The only restriction is - that all equivalent years should produce the same result.
-- Conversion - from UTC to local time is defined by
-- LocalTime(t) - = t + LocalTZA + DaylightSavingTA(t)
-- Conversion - from local time to UTC is defined by
-- UTC(t) - = t – - LocalTZA – DaylightSavingTA(t - – LocalTZA)
-- Note - that UTC(LocalTime(t)) - is not necessarily always equal to t.
-- The - following functions are useful in decomposing time values:
-- HourFromTime(t) = - floor(t / msPerHour) modulo HoursPerDay
-- MinFromTime(t) = - floor(t / msPerMinute) modulo MinutesPerHour
-- SecFromTime(t) = - floor(t / msPerSecond) modulo SecondsPerMinute
-- msFromTime(t) = - t modulo msPerSecond
-- where
-- HoursPerDay = - 24
-- MinutesPerHour = - 60
-- SecondsPerMinute = - 60
-- msPerSecond = - 1000
-- msPerMinute = - 60000 = msPerSecond × - SecondsPerMinute
-- msPerHour = - 3600000 = msPerMinute × - MinutesPerHour
-- The - operator MakeTime calculates a number of milliseconds from its four - arguments, which must be ECMAScript Number values. This operator - functions as follows:
-- If - hour is not finite or min is not finite or sec - is not finite or ms is not finite, return NaN.
-- Let - h be ToInteger(hour).
-- Let - m be ToInteger(min).
-- Let - s be ToInteger(sec).
-- Let - milli be ToInteger(ms).
-
- Let
- t be h *
- msPerHour + m
- * msPerMinute +
- s *
- msPerSecond +
- milli, performing the arithmetic according to IEEE 754 rules
- (that is, as if using the ECMAScript operators *
- and +).
- Return - t.
-- The - operator MakeDay calculates a number of days from its three - arguments, which must be ECMAScript Number values. This operator - functions as follows:
-- If - year is not finite or month is not finite or date - is not finite, return NaN.
-- Let - y be ToInteger(year).
-- Let - m be ToInteger(month).
-- Let - dt be ToInteger(date).
-- Let - ym be y + floor(m /12).
-- Let - mn be m modulo 12.
-
- Find
- a value t such that YearFromTime(t) ==
- ym and MonthFromTime(t) ==
- mn) and DateFromTime(t) ==
- 1; but if this is not possible (because some argument is out of
- range), return NaN.
- Return - Day(t) + dt − 1.
-- The - operator MakeDate calculates a number of milliseconds from its two - arguments, which must be ECMAScript Number values. This operator - functions as follows:
-- If - day is not finite or time is not finite, return NaN.
-- Return - day × msPerDay + time.
-- The - operator TimeClip calculates a number of milliseconds from its - argument, which must be an ECMAScript Number value. This operator - functions as follows:
-- If - time is not finite, return NaN.
-- If - abs(time) > 8.64 x 1015, - return NaN.
-- Return - an implementation-dependent choice of either ToInteger(time) - or ToInteger(time) + (+0). (Adding a positive zero - converts −0 to - +0.)
--
NOTE The point of - step 3 is that an implementation is permitted a choice of internal - representations of time values, for example as a 64-bit signed - integer or as a 64-bit floating-point value. Depending on the - implementation, this internal representation may or may not - distinguish −0 and - +0.
-
- ECMAScript
- defines a string interchange format for date-times based upon a
- simplification of the ISO 8601 Extended Format. The format is as
- follows: YYYY-MM-DDTHH:mm:ss.sssZ
- Where - the fields are as follows:
-YYYY | is the decimal digits of the year in the Gregorian calendar. |
- | “:” (hyphen) appears literally twice in the string. |
MM | is the month of the year from 01 (January) to 12 (December). |
DD | is the day of the month from 01 to 31. |
T | “T” appears literally in the string, to indicate the beginning of the time element. |
HH | is the number of complete hours that have passed since midnight as two decimal digits. |
: | “:” (colon) appears literally twice in the string. |
mm | is the number of complete minutes since the start of the hour as two decimal digits. |
ss | is the number of complete seconds since the start of the minute as two decimal digits. |
. | “.” (dot) appears literally in the string. |
sss | is the number of complete milliseconds since the start of the second as three decimal digits. |
Z | is the time zone offset specified as “Z” (for UTC) or either
- “+” or “-” followed by a time expression hh:mm |
This - format includes date-only forms:
-YYYY
YYYY-MM
YYYY-MM-DD
It also includes “date-time” forms that consist of one of the above
-date-only forms immediately followed by “T”
-and one of the following time forms with an optional time zone offset
-appended:
- THH:mm
THH:mm:ss
THH:mm:ss.sss
All
- numbers must be base 10.
-If the MM or DD fields are absent
-“01” is used as the value. If the mm or
-ss fields are absent “00” is used as the value
-and the value of an absent sss file is “000”. The
-value of an absent time zone offset is “Z”.
- Illegal - values (out-of-bounds as well as syntax errors) in a format string - means that the format string is not a valid instance of this format.
-NOTE 1 As every day both starts and ends with
- midnight, the two notations 00:00
- and 24:00
- are available to distinguish the two midnights that can be
- associated with one date. This means that the following two
- notations refer to exactly the same point in time: 1995-02-04T24:00
- and 1995-02-05T00:00
NOTE 2 There exists no international standard that - specifies abbreviations for civil time zones like CET, EST, etc. and - sometimes the same abbreviation is even used for two very different - time zones. For this reason, ISO 8601 and this format specifies - numeric representations of date and time.
-- ECMAScript - requires the ability to specify 6 - digit years (extended years); approximately 285,616 - years, either forward or backward, from 01 January, 1970 UTC. To - represent years before 0 - or after 9999, ISO 8601 - permits the expansion of the year representation, but only by prior - agreement between the sender and the receiver. In the simplified - ECMAScript format such an expanded year representation shall have 2 - extra year digits and is always prefixed with a + or – sign. The - year 0 is considered - positive and hence prefixed with a + sign.
-
- When
- Date is called as
- a function rather than as a constructor, it returns a String
- representing the current time (UTC).
NOTE The
- function call Date(…)
- is not equivalent to the object creation expression new Date(…)
- with the same arguments.
- All
- of the arguments are optional; any arguments supplied are accepted
- but are completely ignored. A String is created and returned as if
- by the expression (new
- Date()).toString() where Date
- is the standard built-in constructor with that name and toString
- is the standard built-in method Date.prototype.toString.
- When
- Date is called as
- part of a new
- expression, it is a constructor: it initialises the newly created
- object.
- When - Date is called with two to seven arguments, it computes the - date from year, month, and (optionally) date, - hours, minutes, seconds and ms.
-
- The
- [[Prototype]] internal property of the newly constructed object is
- set to the original Date prototype object, the one that is the
- initial value of Date.prototype
- (15.9.4.1).
- The
- [[Class]] internal property of the newly constructed object is set
- to "Date".
- The - [[Extensible]] internal property of the newly constructed object is - set to true.
-- The - [[PrimitiveValue]] internal property of the newly constructed object - is set as follows:
-- Let - y be ToNumber(year).
-- Let - m be ToNumber(month).
-- If - date is supplied then let dt be ToNumber(date); - else let dt be 1.
-- If - hours is supplied then let h be ToNumber(hours); - else let h be 0.
-- If - minutes is supplied then let min be - ToNumber(minutes); else let min be 0.
-- If - seconds is supplied then let s be ToNumber(seconds); - else let s be 0.
-- If - ms is supplied then let milli be ToNumber(ms); - else let milli be 0.
-- If y is not NaN and 0 ≤ ToInteger(y) ≤ 99, then - let yr be 1900+ToInteger(y); otherwise, let yr - be y.
-- Let - finalDate be MakeDate(MakeDay(yr, m, dt), - MakeTime(h, min, s, milli)).
-- Set - the [[PrimitiveValue]] internal property of the newly constructed - object to TimeClip(UTC(finalDate)).
-
- The
- [[Prototype]] internal property of the newly constructed object is
- set to the original Date prototype object, the one that is the
- initial value of Date.prototype
- (15.9.4.1).
- The
- [[Class]] internal property of the newly constructed object is set
- to "Date".
- The - [[Extensible]] internal property of the newly constructed object is - set to true.
-- The - [[PrimitiveValue]] internal property of the newly constructed object - is set as follows:
-- Let - v be ToPrimitive(value).
-- If - Type(v) is String, then -
-
- Parse
- v as a date, in exactly the same manner as for the parse
- method (15.9.4.2); let V be the time value for this date.
- Else, - let V be ToNumber(v).
-- Set - the [[PrimitiveValue]] internal property of the newly constructed - object to TimeClip(V) and return.
-
- The
- [[Prototype]] internal property of the newly constructed object is
- set to the original Date prototype object, the one that is the
- initial value of Date.prototype
- (15.9.4.1).
- The
- [[Class]] internal property of the newly constructed object is set
- to "Date".
- The - [[Extensible]] internal property of the newly constructed object is - set to true.
-- The - [[PrimitiveValue]] internal property of the newly constructed object - is set to the time value (UTC) identifying the current time.
-- The - value of the [[Prototype]] internal property of the Date constructor - is the Function prototype object (15.3.4).
-
- Besides
- the internal properties and the length
- property (whose value is 7),
- the Date constructor has the following properties:
- The
- initial value of Date.prototype
- is the built-in Date prototype object (15.9.5).
- This - property has the attributes { [[Writable]]: false, - [[Enumerable]]: false, [[Configurable]]: false }.
-
- The
- parse function
- applies the ToString operator to its argument and interprets the
- resulting String as a date and time; it returns a Number, the UTC
- time value corresponding to the date and time. The String may be
- interpreted as a local time, a UTC time, or a time in some other
- time zone, depending on the contents of the String. The function
- first attempts to parse the format of the String according to the
- rules called out in Date Time String Format (15.9.1.15). If the
- String does not conform to that format the function may fall back to
- any implementation-specific heuristics or implementation-specific
- date formats. Unrecognizable Strings or dates containing illegal
- element values in the format String shall cause Date.parse
- to return NaN.
If - x is any Date - object whose milliseconds amount is zero within a particular - implementation of ECMAScript, then all of the following expressions - should produce the same numeric value in that implementation, if all - the properties referenced have their initial values:
-
- x.valueOf()
- Date.parse(x.toString())
- Date.parse(x.toUTCString())
- Date.parse(x.toISOString())
However, - the expression
-
- Date.parse( x.toLocaleString())
- is
- not required to produce the same Number value as the preceding three
- expressions and, in general, the value produced by Date.parse
- is implementation-dependent when given any String value that does
- not conform to the Date Time String Format (15.9.1.15) and that
- could not be produced in that implementation by the toString
- or toUTCString
- method.
- When
- the UTC function
- is called with fewer than two arguments, the behaviour is
- implementation-dependent. When the UTC
- function is called with two to seven arguments, it computes the date
- from year, month
- and (optionally) date,
- hours, minutes,
- seconds and ms.
- The following steps are taken:
- Let - y be ToNumber(year).
-- Let - m be ToNumber(month).
-- If - date is supplied then let dt be ToNumber(date); - else let dt be 1.
-- If - hours is supplied then let h be ToNumber(hours); - else let h be 0.
-- If - minutes is supplied then let min be - ToNumber(minutes); else let min be 0.
-- If - seconds is supplied then let s be ToNumber(seconds); - else let s be 0.
-- If - ms is supplied then let milli be ToNumber(ms); - else let milli be 0.
-- If y is not NaN and 0 ≤ ToInteger(y) ≤ 99, then - let yr be 1900+ToInteger(y); otherwise, let yr - be y.
-- Return - TimeClip(MakeDate(MakeDay(yr, m, dt), - MakeTime(h, min, s, milli))).
-
- The
- length property of
- the UTC function
- is 7.
NOTE The
- UTC function differs from
- the Date constructor in
- two ways: it returns a time value as a Number, rather than creating
- a Date object, and it interprets the arguments in UTC rather than as
- local time.
- The
- now function
- return a Number value that is the time value designating the UTC
- date and time of the occurrence of the call to now.
- The
- Date prototype object is itself a Date object (its [[Class]] is
- "Date")
- whose [[PrimitiveValue]] is NaN.
- The - value of the [[Prototype]] internal property of the Date prototype - object is the standard built-in Object prototype object (15.2.4).
-
- In
- following descriptions of functions that are properties of the Date
- prototype object, the phrase “this Date object” refers to the
- object that is the this value for the invocation of the
- function. Unless explicitly noted otherwise, none of these functions
- are generic; a TypeError exception is thrown if the this
- value is not an object for which the value of the [[Class]] internal
- property is "Date".
- Also, the phrase “this time value” refers to the Number value
- for the time represented by this Date object, that is, the value of
- the [[PrimitiveValue]] internal property of this Date object.
- The
- initial value of Date.prototype.constructor
- is the built-in Date
- constructor.
- This - function returns a String value. The contents of the String are - implementation-dependent, but are intended to represent the Date in - the current time zone in a convenient, human-readable form.
-NOTE For
- any Date value d
- whose milliseconds amount is zero, the result of
- Date.parse(d.toString())
- is equal to d.valueOf().
- See 15.9.4.2.
- This - function returns a String value. The contents of the String are - implementation-dependent, but are intended to represent the “date” - portion of the Date in the current time zone in a convenient, - human-readable form.
-- This - function returns a String value. The contents of the String are - implementation-dependent, but are intended to represent the “time” - portion of the Date in the current time zone in a convenient, - human-readable form.
-- This - function returns a String value. The contents of the String are - implementation-dependent, but are intended to represent the Date in - the current time zone in a convenient, human-readable form that - corresponds to the conventions of the host environment’s current - locale.
-NOTE The - first parameter to this function is likely to be used in a future - version of this standard; it is recommended that implementations do - not use this parameter position for anything else.
-- This - function returns a String value. The contents of the String are - implementation-dependent, but are intended to represent the “date” - portion of the Date in the current time zone in a convenient, - human-readable form that corresponds to the conventions of the host - environment’s current locale.
-NOTE The - first parameter to this function is likely to be used in a future - version of this standard; it is recommended that implementations do - not use this parameter position for anything else.
-- This - function returns a String value. The contents of the String are - implementation-dependent, but are intended to represent the “time” - portion of the Date in the current time zone in a convenient, - human-readable form that corresponds to the conventions of the host - environment’s current locale.
-NOTE The - first parameter to this function is likely to be used in a future - version of this standard; it is recommended that implementations do - not use this parameter position for anything else.
-
- The
- valueOf function
- returns a Number, which is this time value.
- Return - this time value.
-- Let - t be this time value.
-- If - t is NaN, return NaN.
-- Return - YearFromTime(LocalTime(t)).
-- Let - t be this time value.
-- If - t is NaN, return NaN.
-- Return - YearFromTime(t).
-- Let - t be this time value.
-- If - t is NaN, return NaN.
-- Return - MonthFromTime(LocalTime(t)).
-- Let - t be this time value.
-- If - t is NaN, return NaN.
-- Return - MonthFromTime(t).
-- Let - t be this time value.
-- If - t is NaN, return NaN.
-- Return - DateFromTime(LocalTime(t)).
-- Let - t be this time value.
-- If - t is NaN, return NaN.
-- Return - DateFromTime(t).
-- Let - t be this time value.
-- If - t is NaN, return NaN.
-- Let - t be this time value.
-- If - t is NaN, return NaN.
-- Return - WeekDay(t).
-- Let - t be this time value.
-- If - t is NaN, return NaN.
-- Return - HourFromTime(LocalTime(t)).
-- Let - t be this time value.
-- If - t is NaN, return NaN.
-- Return - HourFromTime(t).
-- Let - t be this time value.
-- If - t is NaN, return NaN.
-- Return - MinFromTime(LocalTime(t)).
-- Let - t be this time value.
-- If - t is NaN, return NaN.
-- Return - MinFromTime(t).
-- Let - t be this time value.
-- If - t is NaN, return NaN.
-- Return - SecFromTime(LocalTime(t)).
-- Let - t be this time value.
-- If - t is NaN, return NaN.
-- Return - SecFromTime(t).
-- Let - t be this time value.
-- If - t is NaN, return NaN.
-- Return - msFromTime(LocalTime(t)).
-- Let - t be this time value.
-- If - t is NaN, return NaN.
-- Return - msFromTime(t).
-- Returns - the difference between local time and UTC time in minutes.
-- Let - t be this time value.
-- If - t is NaN, return NaN.
-- Return - (t − LocalTime(t)) - / msPerMinute.
-- Set - the [[PrimitiveValue]] internal property of this Date object to v.
-- Return - v.
-- Let - t be the result of LocalTime(this time value).
-- Let - time be MakeTime(HourFromTime(t), MinFromTime(t), - SecFromTime(t), ToNumber(ms)).
-- Set - the [[PrimitiveValue]] internal property of this Date object to u.
-- Return - u.
-- Let - t be this time value.
-- Let - time be MakeTime(HourFromTime(t), MinFromTime(t), - SecFromTime(t), ToNumber(ms)).
-- Set - the [[PrimitiveValue]] internal property of this Date object to v.
-- Return - v.
-
- If ms
- is not specified, this behaves as if ms
- were specified with the value getMilliseconds().
- Let - t be the result of LocalTime(this time value).
-- Let - s be ToNumber(sec).
-- If - ms is not specified, then let milli be msFromTime(t); - otherwise, let milli be ToNumber(ms).
-- Let - date be MakeDate(Day(t), MakeTime(HourFromTime(t), - MinFromTime(t), s, milli)).
-- Set - the [[PrimitiveValue]] internal property of this Date object to u.
-- Return - u.
-
- The
- length property of
- the setSeconds
- method is 2.
- If ms
- is not specified, this behaves as if ms
- were specified with the value getUTCMilliseconds().
- Let - t be this time value.
-- Let - s be ToNumber(sec).
-- If - ms is not specified, then let milli be msFromTime(t); - otherwise, let milli be ToNumber(ms).
-- Let - date be MakeDate(Day(t), MakeTime(HourFromTime(t), - MinFromTime(t), s, milli)).
-- Let - v be TimeClip(date).
-- Set - the [[PrimitiveValue]] internal property of this Date object to v.
-- Return - v.
-
- The
- length property of
- the setUTCSeconds
- method is 2.
- If
- sec is not
- specified, this behaves as if sec
- were specified with the value getSeconds().
- If ms
- is not specified, this behaves as if ms
- were specified with the value getMilliseconds().
- Let - t be the result of LocalTime(this time value).
-- Let - m be ToNumber(min).
-- If - sec is not specified, then let s be SecFromTime(t); - otherwise, let s be ToNumber(sec).
-- If - ms is not specified, then let milli be msFromTime(t); - otherwise, let milli be ToNumber(ms).
-- Let - date be MakeDate(Day(t), MakeTime(HourFromTime(t), - m, s, milli)).
-- Set - the [[PrimitiveValue]] internal property of this Date object to u.
-- Return - u.
-
- The
- length property of
- the setMinutes
- method is 3.
- If
- sec is not
- specified, this behaves as if sec
- were specified with the value getUTCSeconds().
- If ms
- is not specified, this function behaves as if ms
- were specified with the value return by getUTCMilliseconds().
- Let - t be this time value.
-- Let - m be ToNumber(min).
-- If - sec is not specified, then let s be SecFromTime(t); - otherwise, let s be ToNumber(sec).
-- If - ms is not specified, then let milli be msFromTime(t); - otherwise, let milli be ToNumber(ms).
-- Let - date be MakeDate(Day(t), MakeTime(HourFromTime(t), - m, s, milli)).
-- Let - v be TimeClip(date).
-- Set - the [[PrimitiveValue]] internal property of this Date object to v.
-- Return - v.
-
- The
- length property of
- the setUTCMinutes
- method is 3.
- If
- min is not
- specified, this behaves as if min
- were specified with the value getMinutes().
- If
- sec is not
- specified, this behaves as if sec
- were specified with the value getSeconds().
- If ms
- is not specified, this behaves as if ms
- were specified with the value getMilliseconds().
- Let - t be the result of LocalTime(this time value).
-- Let - h be ToNumber(hour).
-- If - min is not specified, then let m be MinFromTime(t); - otherwise, let m be ToNumber(min).
-- If - If sec is not specified, then let s be - SecFromTime(t); otherwise, let s be ToNumber(sec).
-- If - ms is not specified, then let milli be msFromTime(t); - otherwise, let milli be ToNumber(ms).
-- Let - date be MakeDate(Day(t), MakeTime(h, m, - s, milli)).
-- Set - the [[PrimitiveValue]] internal property of this Date object to u.
-- Return - u.
-
- The
- length property of
- the setHours
- method is 4.
- If
- min is not
- specified, this behaves as if min
- were specified with the value getUTCMinutes().
- If
- sec is not
- specified, this behaves as if sec
- were specified with the value getUTCSeconds().
- If ms
- is not specified, this behaves as if ms
- were specified with the value getUTCMilliseconds().
- Let - t be this time value.
-- Let - h be ToNumber(hour).
-- If - min is not specified, then let m be MinFromTime(t); - otherwise, let m be ToNumber(min).
-- If - sec is not specified, then let s be SecFromTime(t); - otherwise, let s be ToNumber(sec).
-- If - ms is not specified, then let milli be msFromTime(t); - otherwise, let milli be ToNumber(ms).
-- Let - newDate be MakeDate(Day(t), MakeTime(h, m, - s, milli)).
-- Let - v be TimeClip(newDate).
-- Set - the [[PrimitiveValue]] internal property of this Date object to v.
-- Return - v.
-
- The
- length property of
- the setUTCHours
- method is 4.
- Let - t be the result of LocalTime(this time value).
-- Let - dt be ToNumber(date).
-- Let - newDate be MakeDate(MakeDay(YearFromTime(t), - MonthFromTime(t), dt), TimeWithinDay(t)).
-- Set - the [[PrimitiveValue]] internal property of this Date object to u.
-- Return - u.
-- Let - t be this time value.
-- Let - dt be ToNumber(date).
-- Let - newDate be MakeDate(MakeDay(YearFromTime(t), - MonthFromTime(t), dt), TimeWithinDay(t)).
-- Let - v be TimeClip(newDate).
-- Set - the [[PrimitiveValue]] internal property of this Date object to v.
-- Return - v.
-
- If
- date is not
- specified, this behaves as if date
- were specified with the value getDate().
- Let - t be the result of LocalTime(this time value).
-- Let - m be ToNumber(month).
-- If - date is not specified, then let dt be - DateFromTime(t); otherwise, let dt be ToNumber(date).
-- Let - newDate be MakeDate(MakeDay(YearFromTime(t), m, - dt), TimeWithinDay(t)).
-- Set - the [[PrimitiveValue]] internal property of this Date object to u.
-- Return - u.
-
- The
- length property of
- the setMonth
- method is 2.
- If
- date is not
- specified, this behaves as if date
- were specified with the value getUTCDate().
- Let - t be this time value.
-- Let - m be ToNumber(month).
-- If - date is not specified, then let dt be - DateFromTime(t); otherwise, let dt be ToNumber(date).
-- Let - newDate be MakeDate(MakeDay(YearFromTime(t), m, - dt), TimeWithinDay(t)).
-- Let - v be TimeClip(newDate).
-- Set - the [[PrimitiveValue]] internal property of this Date object to v.
-- Return - v.
-
- The
- length property of
- the setUTCMonth
- method is 2.
- If
- month is not
- specified, this behaves as if month
- were specified with the value getMonth().
- If
- date is not
- specified, this behaves as if date
- were specified with the value getDate().
- Let - t be the result of LocalTime(this time value); but if this time value is NaN, let t be +0.
-- Let - y be ToNumber(year).
-- If - month is not specified, then let m be - MonthFromTime(t); otherwise, let m be - ToNumber(month).
-- If - date is not specified, then let dt be - DateFromTime(t); otherwise, let dt be ToNumber(date).
-- Let - newDate be MakeDate(MakeDay(y, m, dt), - TimeWithinDay(t)).
-- Set - the [[PrimitiveValue]] internal property of this Date object to u.
-- Return - u.
-
- The
- length property of
- the setFullYear
- method is 3.
- If
- month is not
- specified, this behaves as if month
- were specified with the value getUTCMonth().
- If
- date is not
- specified, this behaves as if date
- were specified with the value getUTCDate().
- Let - t be this time value; but if this time value is NaN, - let t be +0.
-- Let - y be ToNumber(year).
-- If - month is not specified, then let m be - MonthFromTime(t); otherwise, let m be - ToNumber(month).
-- If - date is not specified, then let dt be - DateFromTime(t); otherwise, let dt be ToNumber(date).
-- Let - newDate be MakeDate(MakeDay(y, m, dt), - TimeWithinDay(t)).
-- Let - v be TimeClip(newDate).
-- Set - the [[PrimitiveValue]] internal property of this Date object to v.
-- Return - v.
-
- The
- length property of
- the setUTCFullYear
- method is 3.
- This - function returns a String value. The contents of the String are - implementation-dependent, but are intended to represent the Date in - a convenient, human-readable form in UTC.
-NOTE The
- intent is to produce a String representation of a date that is more
- readable than the format specified in 15.9.1.15. It is not essential
- that the chosen format be unambiguous or easily machine parsable. If
- an implementation does not have a preferred human-readable format it
- is recommended to use the format defined in 15.9.1.15 but with a
- space rather than a “T”
- used to separate the date and time elements.
- This - function returns a String value represent the instance in time - represented by this Date object. The format of the String is the - Date Time string format defined in 15.9.1.15. All fields are present - in the String. The time zone is always UTC, denoted by the suffix Z. - If the time value of this object is not a finite Number a RangeError - exception is thrown.
-
- This
- function provides a String representation of a Date object for use
- by JSON.stringify
- (15.12.3).
- When
- the toJSON method
- is called with argument key,
- the following steps are taken:
- Let - O be the result of calling ToObject, giving it the this - value as its argument.
-- Let - tv be ToPrimitive(O, hint Number).
-- If - tv is a Number and is not finite, return null.
-
- Let
- toISO be the result of calling the [[Get]] internal method
- of O with argument "toISOString".
- If - IsCallable(toISO) is false, throw a TypeError - exception.
-- Return - the result of calling the [[Call]] internal method of toISO - with O as the this value and an empty argument list.
-NOTE 1 The argument is ignored.
-NOTE 2 The toJSON
- function is intentionally generic; it does not require that its this
- value be a Date object. Therefore, it can be transferred to other
- kinds of objects for use as a method. However, it does require that
- any such object have a toISOString
- method. An object is free to use the argument key
- to filter its stringification.
-
- Date
- instances inherit properties from the Date prototype object and
- their [[Class]] internal property value is "Date".
- Date instances also have a [[PrimitiveValue]] internal property.
- The - [[PrimitiveValue]] internal property is time value represented by - this Date object.
-- A - RegExp object contains a regular expression and the associated - flags.
-NOTE The - form and functionality of regular expressions is modelled after the - regular expression facility in the Perl 5 programming language.
-
- The
- RegExp constructor
- applies the following grammar to the input pattern String. An error
- occurs if the grammar cannot interpret the String as an expansion of
- Pattern.
- Syntax
-- Pattern ::
-- Disjunction
-- Disjunction ::
-
- Alternative
- Alternative | Disjunction
- Alternative ::
-
- [empty]
Alternative
- Term
- Term ::
-
- Assertion
Atom
Atom
- Quantifier
- Assertion ::
-
- ^ $ \
- b \
- B
-
(?
- =
- Disjunction ) (
- ?
- !
- Disjunction )
- Quantifier ::
-
- QuantifierPrefix
QuantifierPrefix
- ?
- QuantifierPrefix ::
-
- *
+? { DecimalDigits } { DecimalDigits
- ,
- } { DecimalDigits
- , DecimalDigits }
- Atom ::
-
- PatternCharacter.\
- AtomEscape
CharacterClass
() (
- ?
- :
- Disjunction )
- PatternCharacter ::SourceCharacter but - not any - of:
-
- ^ $
- \ . * + ? ( ) [ ] { } |
- AtomEscape ::
-
- DecimalEscape
CharacterEscape
CharacterClassEscape
- CharacterEscape ::
-
- ControlEscapec
- ControlLetter
HexEscapeSequence
UnicodeEscapeSequence
IdentityEscape
- ControlEscape :: - one - of
-
- f
- n r t v
- ControlLetter :: - one - of
-
- a
- b c d e f g h i j k l m n o p q r s t u v w x
- y z
A B C D E F G H I J K L M N O P Q R S T
- U V W X Y Z
- IdentityEscape ::
-
- SourceCharacter but
- not
- IdentifierPart
<ZWJ>
<ZWNJ>
- DecimalEscape ::
-- DecimalIntegerLiteral [lookahead - ∉ - DecimalDigit]
-- CharacterClassEscape :: - one - of
-
- d
- D s S w W
- CharacterClass ::
-
- [
- [lookahead
- ∉
- {^}]
- ClassRanges
- ] [
- ^ ClassRanges
- ]
- ClassRanges ::
-
- [empty]
NonemptyClassRanges
- NonemptyClassRanges ::
-
- ClassAtom
ClassAtom
- NonemptyClassRangesNoDash
ClassAtom
- - ClassAtom ClassRanges
- NonemptyClassRangesNoDash ::
-
- ClassAtom
ClassAtomNoDash
- NonemptyClassRangesNoDash
ClassAtomNoDash
- - ClassAtom ClassRanges
- ClassAtom ::
-
- -
ClassAtomNoDash
- ClassAtomNoDash ::
-
- SourceCharacter but
- not one
- of \ or ] or - \
- ClassEscape
- ClassEscape ::
-
- DecimalEscapeb
CharacterEscape
- A - regular expression pattern is converted into an internal procedure - using the process described below. An implementation is encouraged - to use more efficient algorithms than the ones listed below, as long - as the results are the same. The internal procedure is used as the - value of a RegExp object’s [[Match]] internal property.
-- The - descriptions below use the following variables:
-- Input - is the String being matched by the regular expression pattern. The - notation input[n] - means the nth - character of input, - where n can range - between 0 (inclusive) and InputLength - (exclusive).
-- InputLength - is the number of characters in the Input - String.
-
- NcapturingParens
- is the total number of left capturing parentheses (i.e. the total
- number of times the Atom
- :: (
- Disjunction )
- production is expanded) in the pattern. A left capturing
- parenthesis is any (
- pattern character that is matched by the (
- terminal of the Atom
- :: (
- Disjunction )
- production.
- IgnoreCase
- is the setting of the RegExp object's ignoreCase
- property.
- Multiline
- is the setting of the RegExp object’s multiline
- property.
- Furthermore, - the descriptions below use the following internal data structures:
-- A - CharSet is a - mathematical set of characters.
-- A - State is an - ordered pair (endIndex, - captures) - where endIndex is - an integer and captures - is an internal array of NcapturingParens - values. States - are used to represent partial match states in the regular - expression matching algorithms. The endIndex - is one plus the index of the last input character matched so far by - the pattern, while captures - holds the results of capturing parentheses. The nth - element of captures - is either a String that represents the value obtained by the nth - set of capturing parentheses or undefined if the nth - set of capturing parentheses hasn’t been reached yet. Due to - backtracking, many States - may be in use at any time during the matching process.
-- A - MatchResult is - either a State or - the special token failure that indicates that the match - failed.
-- A - Continuation - procedure is an internal closure (i.e. an internal procedure with - some arguments already bound to values) that takes one State - argument and returns a MatchResult - result. If an internal closure references variables bound in the - function that creates the closure, the closure uses the values that - these variables had at the time the closure was created. The - Continuation - attempts to match the remaining portion (specified by the closure's - already-bound arguments) of the pattern against the input String, - starting at the intermediate state given by its State - argument. If the match succeeds, the Continuation - returns the final State - that it reached; if the match fails, the Continuation - returns failure.
-- A - Matcher procedure - is an internal closure that takes two arguments -- a State - and a Continuation - -- and returns a MatchResult - result. A Matcher - attempts to match a middle subpattern (specified by the closure's - already-bound arguments) of the pattern against the input String, - starting at the intermediate state given by its State - argument. The Continuation - argument should be a closure that matches the rest of the pattern. - After matching the subpattern of a pattern to obtain a new State, - the Matcher then - calls Continuation - on that new State - to test if the rest of the pattern can match as well. If it can, - the matcher returns the State - returned by Continuation; - if not, the Matcher - may try different choices at its choice points, repeatedly calling - Continuation - until it either succeeds or all possibilities have been exhausted.
-- An - AssertionTester - procedure is an internal closure that takes a State - argument and returns a Boolean result. The assertion tester tests a - specific condition (specified by the closure's already-bound - arguments) against the current place in the input String and - returns true if the condition matched or false if - not.
-- An - EscapeValue is - either a character or an integer. An EscapeValue - is used to denote the interpretation of a DecimalEscape - escape sequence: a character ch - means that the escape sequence is interpreted as the character ch, - while an integer n - means that the escape sequence is interpreted as a backreference to - the nth - set of capturing parentheses.
-- The - production Pattern - :: Disjunction - evaluates as follows:
-- Evaluate - Disjunction to obtain a Matcher m.
-- Return - an internal closure that takes two arguments, a String str - and an integer index, and performs the following:
-- Let - Input be the given String str. This variable will be - used throughout the algorithms in 15.10.2.
-- Let - InputLength be the length of Input. This variable - will be used throughout the algorithms in 15.10.2.
-- Let - c be a Continuation that always returns its State argument - as a successful MatchResult.
-- Let - cap be an internal array of NcapturingParens - undefined values, indexed 1 through NcapturingParens.
-- Let - x be the State (index, cap).
-- Call - m(x, c) and return its result.
-NOTE A
- Pattern evaluates ("compiles") to an internal procedure
- value. RegExp.prototype.exec
- can then apply this procedure to a String and an offset within the
- String to determine whether the pattern would match starting at
- exactly that offset within the String, and, if it does match, what
- the values of the capturing parentheses would be. The algorithms in
- 15.10.2 are designed so that compiling a pattern may throw a
- SyntaxError exception; on the other hand, once the pattern is
- successfully compiled, applying its result internal procedure to
- find a match in a String cannot throw an exception (except for any
- host-defined exceptions that can occur anywhere such as
- out-of-memory).
- The - production Disjunction - :: Alternative - evaluates by evaluating Alternative - to obtain a Matcher - and returning that Matcher.
-
- The
- production Disjunction
- :: Alternative
- | Disjunction
- evaluates as follows:
- Evaluate - Alternative to obtain a Matcher m1.
-- Evaluate - Disjunction to obtain a Matcher m2.
-- Return - an internal Matcher closure that takes two arguments, a State x - and a Continuation c, and performs the following:
-- Call - m1(x, c) and let r be its result.
-- If - r isn't failure, return r.
-- Call - m2(x, c) and return its result.
--
NOTE The
- | regular
- expression operator separates two alternatives. The pattern first
- tries to match the left Alternative
- (followed by the sequel of the regular expression); if it fails, it
- tries to match the right Disjunction
- (followed by the sequel of the regular expression). If the left
- Alternative, the
- right Disjunction,
- and the sequel all have choice points, all choices in the sequel are
- tried before moving on to the next choice in the left Alternative.
- If choices in the left Alternative
- are exhausted, the right Disjunction
- is tried instead of the left Alternative.
- Any capturing parentheses inside a portion of the pattern skipped by
- | produce
- undefined values instead of Strings. Thus, for example,
- /a|ab/.exec("abc")
returns
- the result "a"
- and not "ab".
- Moreover,
- /((a)|(ab))((c)|(bc))/.exec("abc")
returns - the array
-
- ["abc",
- "a", "a", undefined, "bc", undefined,
- "bc"]
and - not
-
- ["abc",
- "ab", undefined, "ab", "c", "c",
- undefined]
- The - production Alternative - :: [empty] - evaluates by returning a Matcher that takes two arguments, a State x - and a Continuation c, - and returns the result of calling c(x).
-- The - production Alternative - :: Alternative - Term evaluates as - follows:
-- Evaluate - Alternative to obtain a Matcher m1.
-- Evaluate - Term to obtain a Matcher m2.
-- Return - an internal Matcher closure that takes two arguments, a State x - and a Continuation c, and performs the following:
-- Create - a Continuation d that takes a State argument y and - returns the result of calling m2(y, c).
-- Call - m1(x, d) and return its result.
-NOTE Consecutive - Terms try to - simultaneously match consecutive portions of the input String. If - the left Alternative, - the right Term, - and the sequel of the regular expression all have choice points, all - choices in the sequel are tried before moving on to the next choice - in the right Term, - and all choices in the right Term - are tried before moving on to the next choice in the left - Alternative.
-- The - production Term :: - Assertion - evaluates by returning an internal Matcher closure that takes two - arguments, a State x - and a Continuation c, - and performs the following:
-- Evaluate - Assertion to obtain an AssertionTester t.
-- Call - t(x) and let r be the resulting Boolean value.
-- If - r is false, return failure.
-- Call - c(x) and return its result.
-- The - production Term :: - Atom evaluates - by evaluating Atom - to obtain a Matcher and returning that Matcher.
-- The - production Term :: - Atom - Quantifier - evaluates as follows:
-- Evaluate - Atom to obtain a Matcher m.
-- Evaluate - Quantifier to obtain the three results: an integer min, - an integer (or ∞) max, - and Boolean greedy.
-- If - max is finite and less than min, then throw a - SyntaxError exception.
-
- Let
- parenIndex be the number of left capturing parentheses in
- the entire regular expression that occur to the left of this
- production expansion's Term. This is the total number of
- times the Atom :: (
- Disjunction )
- production is expanded prior to this production's Term plus
- the total number of Atom :: (
- Disjunction )
- productions enclosing this Term.
- Let
- parenCount be the number of left capturing parentheses in
- the expansion of this production's Atom. This is the total
- number of Atom :: (
- Disjunction )
- productions enclosed by this production's Atom.
- Return - an internal Matcher closure that takes two arguments, a State x - and a Continuation c, and performs the following:
-- Call - RepeatMatcher(m, min, max, greedy, - x, c, parenIndex, parenCount) and - return its result.
-- The - abstract operation RepeatMatcher takes eight parameters, a - Matcher m, an - integer min, an - integer (or ∞) max, - a Boolean greedy, - a State x, a - Continuation c, an - integer parenIndex, - and an integer parenCount, - and performs the following:
-- If - max is zero, then call c(x) and return its - result.
-- Create - an internal Continuation closure d that takes one State argument y and performs the following:
-- If - min is zero and y's endIndex is equal to - x's endIndex, then return failure.
-- If - min is zero then let min2 be zero; otherwise let - min2 be min–1.
-- If - max is ∞, then let - max2 be ∞; otherwise - let max2 be max–1.
-- Call - RepeatMatcher(m, min2, max2, greedy, - y, c, parenIndex, parenCount) and - return its result.
-- Let - cap be a fresh copy of x's captures internal - array.
-- For - every integer k that satisfies parenIndex < k - and k ≤ - parenIndex+parenCount, set cap[k] to - undefined.
-- Let - e be x's endIndex.
-- Let - xr be the State (e, cap).
-- If - min is not zero, then call m(xr, d) and - return its result.
-- If - greedy is false, then
-- Call - c(x) and let z be its result.
-- If - z is not failure, return z.
-- Call - m(xr, d) and return its result.
-- Call - m(xr, d) and let z be its result.
-- If - z is not failure, return z.
-- Call - c(x) and return its result.
-NOTE An - Atom followed by a - Quantifier is - repeated the number of times specified by the Quantifier. - A Quantifier can - be non-greedy, in which case the Atom - pattern is repeated as few times as possible while still matching - the sequel, or it can be greedy, in which case the Atom - pattern is repeated as many times as possible while still matching - the sequel. The Atom - pattern is repeated rather than the input String that it matches, so - different repetitions of the Atom - can match different input substrings.
-NOTE 2 If the Atom and - the sequel of the regular expression all have choice points, the - Atom is first - matched as many (or as few, if non-greedy) times as possible. All - choices in the sequel are tried before moving on to the next choice - in the last repetition of Atom. - All choices in the last (nth) repetition of Atom - are tried before moving on to the next choice in the next-to-last - (n–1)st repetition of Atom; - at which point it may turn out that more or fewer repetitions of - Atom are now - possible; these are exhausted (again, starting with either as few or - as many as possible) before moving on to the next choice in the - (n-1)st repetition of Atom - and so on.
-Compare
-
- /a[a-z]{2,4}/.exec("abcdefghi")
which
- returns "abcde"
- with
- /a[a-z]{2,4}?/.exec("abcdefghi")
which
- returns "abc".
Consider - also
-
- /(aa|aabaac|ba|b|c)*/.exec("aabaac")
which, - by the choice point ordering above, returns the array
-
- ["aaba",
- "ba"]
and - not any of:
-
- ["aabaac",
- "aabaac"]
- ["aabaac",
- "c"]
The - above ordering of choice points can be used to write a regular - expression that calculates the greatest common divisor of two - numbers (represented in unary notation). The following example - calculates the gcd of 10 and 15:
-
- "aaaaaaaaaa,aaaaaaaaaaaaaaa".replace(/^(a+)\1*,\1+$/,"$1")
- which
- returns the gcd in unary notation "aaaaa".
NOTE 3 Step 4 of the RepeatMatcher clears Atom's - captures each time Atom - is repeated. We can see its behaviour in the regular expression
-
- /(z)((a+)?(b+)?(c))*/.exec("zaacbbbcac")
which - returns the array
-
- ["zaacbbbcac",
- "z", "ac", "a", undefined, "c"]
and - not
-
- ["zaacbbbcac",
- "z", "ac", "a", "bbb", "c"]
- because
- each iteration of the outermost *
- clears all captured Strings contained in the quantified Atom,
- which in this case includes capture Strings numbered 2, 3, and 4.
NOTE 4 Step 1 of the RepeatMatcher's d - closure states that, once the minimum number of repetitions has been - satisfied, any more expansions of Atom - that match the empty String are not considered for further - repetitions. This prevents the regular expression engine from - falling into an infinite loop on patterns such as:
-
- /(a*)*/.exec("b")
or - the slightly more complicated:
-
- /(a*)b\1+/.exec("baaaac")
which - returns the array
-
- ["b",
- ""]
- The
- production Assertion
- :: ^
- evaluates by returning an internal AssertionTester closure that
- takes a State argument x
- and performs the following:
- Let - e be x's endIndex.
-- If - e is zero, return true.
-- If - Multiline is false, return false.
-- If - the character Input[e–1] is one of LineTerminator, - return true.
-- Return - false.
-
- The
- production Assertion
- :: $
- evaluates by returning an internal AssertionTester closure that
- takes a State argument x
- and performs the following:
- Let - e be x's endIndex.
-- If - e is equal to InputLength, return true.
-- If - multiline is false, return false.
-- If - the character Input[e] is one of LineTerminator, - return true.
-- Return - false.
-
- The
- production Assertion
- :: \ b
- evaluates by returning an internal AssertionTester closure that
- takes a State argument x
- and performs the following:
- Let - e be x's endIndex.
-- Call - IsWordChar(e–1) and let a be the Boolean - result.
-- Call - IsWordChar(e) and let b be the Boolean result.
-- If - a is true and b is false, return true.
-- If - a is false and b is true, return true.
-- Return - false.
-
- The
- production Assertion
- :: \ B
- evaluates by returning an internal AssertionTester closure that
- takes a State argument x
- and performs the following:
- Let - e be x's endIndex.
-- Call - IsWordChar(e–1) and let a be the Boolean - result.
-- Call - IsWordChar(e) and let b be the Boolean result.
-- If - a is true and b is false, return false.
-- If - a is false and b is true, return false.
-- Return - true.
-
- The
- production Assertion
- :: ( ? = Disjunction
- ) evaluates as follows:
- Evaluate - Disjunction to obtain a Matcher m.
-- Return - an internal Matcher closure that takes two arguments, a State x - and a Continuation c, and performs the following steps:
-- Let - d be a Continuation that always returns its State argument as a successful MatchResult.
-- Call - m(x, d) and let r be its result.
-- If - r is failure, return failure.
-- Let - y be r's State.
-- Let - cap be y's captures internal array.
-- Let - xe be x's endIndex.
-- Let - z be the State (xe, cap).
-- Call - c(z) and return its result.
-
- The
- production Assertion ::
- ( ? ! Disjunction
- ) evaluates as follows:
- Evaluate - Disjunction to obtain a Matcher m.
-- Return - an internal Matcher closure that takes two arguments, a State x - and a Continuation c, and performs the following steps:
-- Let - d be a Continuation that always returns its State argument as a successful MatchResult.
-- Call - m(x, d) and let r be its result.
-- If - r isn't failure, return failure.
-- Call - c(x) and return its result.
-- The - abstract operation IsWordChar - takes an integer parameter e - and performs the following:
-- If - e == –1 or e == InputLength, return false.
-- Let - c be the character Input[e].
-- If - c is one of the sixty-three characters below, return true.
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- - | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -
- Return - false.
-- The - production Quantifier - :: QuantifierPrefix - evaluates as follows:
-- Evaluate - QuantifierPrefix to obtain the two results: an integer min - and an integer (or ∞) max.
-- Return - the three results min , max, and true.
-
- The
- production Quantifier
- :: QuantifierPrefix
- ? evaluates as follows:
- Evaluate - QuantifierPrefix to obtain the two results: an integer min - and an integer (or ∞) max.
-- Return - the three results min , max, and false.
-
- The
- production QuantifierPrefix
- :: *
- evaluates by returning the two results 0 and ∞.
- The
- production QuantifierPrefix
- :: +
- evaluates by returning the two results 1 and ∞.
- The
- production QuantifierPrefix
- :: ?
- evaluates by returning the two results 0 and 1.
- The
- production QuantifierPrefix
- :: { DecimalDigits
- } evaluates as follows:
- The
- production QuantifierPrefix
- :: { DecimalDigits
- , } evaluates as follows:
- Let - i be the MV of DecimalDigits.
-- Return - the two results i and ∞.
-
- The
- production QuantifierPrefix
- :: { DecimalDigits
- , DecimalDigits
- } evaluates as follows:
- Let - i be the MV of the first DecimalDigits.
-- Let - j be the MV of the second DecimalDigits.
-- Return - the two results i and j.
-- The - production Atom :: - PatternCharacter - evaluates as follows:
-- Let - ch be the character represented by PatternCharacter.
-- Let - A be a one-element CharSet containing the character ch.
-- Call - CharacterSetMatcher(A, false) and return its - Matcher result.
-
- The
- production Atom ::
- . evaluates as
- follows:
- Let - A be the set of all characters except LineTerminator.
-- Call - CharacterSetMatcher(A, false) and return its - Matcher result.
-
- The
- production Atom ::
- \ AtomEscape
- evaluates by evaluating AtomEscape
- to obtain a Matcher and returning that Matcher.
- The - production Atom :: - CharacterClass - evaluates as follows:
-- Evaluate - CharacterClass to obtain a CharSet A and a Boolean - invert.
-- Call - CharacterSetMatcher(A, invert) and return its - Matcher result.
-
- The
- production Atom ::
- ( Disjunction
- ) evaluates as follows:
- Evaluate - Disjunction to obtain a Matcher m.
-
- Let
- parenIndex be the number of left capturing parentheses in
- the entire regular expression that occur to the left of this
- production expansion's initial left parenthesis. This is the total
- number of times the Atom :: ( Disjunction )
- production is expanded prior to this production's Atom plus
- the total number of Atom :: ( Disjunction )
- productions enclosing this Atom.
- Return - an internal Matcher closure that takes two arguments, a State x - and a Continuation c, and performs the following steps:
-- Create - an internal Continuation closure d that takes one State argument y and performs the following steps:
-- Let - cap be a fresh copy of y's captures - internal array.
-- Let - xe be x's endIndex.
-- Let - ye be y's endIndex.
-- Let - s be a fresh String whose characters are the - characters of Input at positions xe (inclusive) - through ye (exclusive).
-- Set - cap[parenIndex+1] to s.
-- Let - z be the State (ye, cap).
-- Call - c(z) and return its result.
-- Call - m(x, d) and return its result.
-
- The
- production Atom ::
- ( ? : Disjunction
- ) evaluates by evaluating Disjunction
- to obtain a Matcher and returning that Matcher.
- The - abstract operation CharacterSetMatcher takes two arguments, a CharSet A - and a Boolean flag invert, - and performs the following:
-- Return - an internal Matcher closure that takes two arguments, a State x - and a Continuation c, and performs the following steps:
-- Let - e be x's endIndex.
-- If - e == InputLength, return failure.
-- Let - ch be the character Input[e].
-- Let - cc be the result of Canonicalize(ch).
-- If - invert is false, then
-- If - there does not exist a member a of set A such - that Canonicalize(a) == cc, return - failure.
-- Else - invert is true,
-- If - there exists a member a of set A such that - Canonicalize(a) == cc, return failure.
-- Let - cap be x's captures internal array.
-- Let - y be the State (e+1, cap).
-- Call - c(y) and return its result.
-- The - abstract operation Canonicalize takes a character parameter ch - and performs the following steps:
-- If - IgnoreCase is false, return ch.
-
- Let
- u be ch converted to upper case as if by calling the
- standard built-in method String.prototype.toUpperCase
- on the one-character String ch.
- If - u does not consist of a single character, return ch.
-- Let - cu be u's character.
-- If - ch's code unit value is greater than or equal to decimal 128 - and cu's code unit value is less than decimal 128, then - return ch.
-- Return - cu.
-NOTE 1 Parentheses of the form (
- Disjunction
- ) serve both to group the components of the Disjunction
- pattern together and to save the result of the match. The result can
- be used either in a backreference (\
- followed by a nonzero decimal number), referenced in a replace
- String, or returned as part of an array from the regular expression
- matching internal procedure. To inhibit the capturing behaviour of
- parentheses, use the form (?:
- Disjunction
- ) instead.
NOTE 2 The form (?= Disjunction
- ) specifies a zero-width positive lookahead. In order for
- it to succeed, the pattern inside Disjunction
- must match at the current position, but the current position is not
- advanced before matching the sequel. If Disjunction
- can match at the current position in several ways, only the first
- one is tried. Unlike other regular expression operators, there is no
- backtracking into a (?=
- form (this unusual behaviour is inherited from Perl). This only
- matters when the Disjunction
- contains capturing parentheses and the sequel of the pattern
- contains backreferences to those captures.
For - example,
-
- /(?=(a+))/.exec("baaabac")
matches
- the empty String immediately after the first b
- and therefore returns the array:
- ["",
- "aaa"]
To - illustrate the lack of backtracking into the lookahead, consider:
-
- /(?=(a+))a*b\1/.exec("baaabac")
This - expression returns
-
- ["aba",
- "a"]
and - not:
-
- ["aaaba",
- "a"]
NOTE 3 The form (?! Disjunction
- ) specifies a zero-width negative lookahead. In order for
- it to succeed, the pattern inside Disjunction
- must fail to match at the current position. The current position is
- not advanced before matching the sequel. Disjunction
- can contain capturing parentheses, but backreferences to them only
- make sense from within Disjunction
- itself. Backreferences to these capturing parentheses from elsewhere
- in the pattern always return undefined because the negative
- lookahead must fail for the pattern to succeed. For example,
- /(.*?)a(?!(a+)b\2c)\2(.*)/.exec("baaabaac")
looks
- for an a not
- immediately followed by some positive number n of a's,
- a b, another n a's
- (specified by the first \2)
- and a c. The
- second \2 is
- outside the negative lookahead, so it matches against undefined
- and therefore always succeeds. The whole expression returns the
- array:
- ["baaabaac",
- "ba", undefined, "abaac"]
- In
- case-insignificant matches all characters are implicitly converted
- to upper case immediately before they are compared. However, if
- converting a character to upper case would expand that character
- into more than one character (such as converting "ß"
- (\u00DF)
- into "SS"),
- then the character is left as-is instead. The character is also left
- as-is if it is not an ASCII character but converting it to upper
- case would make it into an ASCII character. This prevents Unicode
- characters such as \u0131
- and \u017F
- from matching regular expressions such as /[a z]/i,
- which are only intended to match ASCII letters. Furthermore, if
- these conversions were allowed, then /[^\W]/i
- would match each of a,
- b,
- …, h,
- but not i
- or s.
- The - production AtomEscape - :: DecimalEscape - evaluates as follows:
-- Evaluate - DecimalEscape to obtain an EscapeValue E.
-- If - E is a character, then
-- Let - ch be E's character.
-- Let - A be a one-element CharSet containing the character ch.
-- Call - CharacterSetMatcher(A, false) and return its - Matcher result.
-- E - must be an integer. Let n be that integer.
-- If - n=0 or n>NCapturingParens then throw a - SyntaxError exception.
-- Return - an internal Matcher closure that takes two arguments, a State x - and a Continuation c, and performs the following:
-- Let - cap be x's captures internal array.
-- Let - s be cap[n].
-- If - s is undefined, then call c(x) and - return its result.
-- Let - e be x's endIndex.
-- Let - len be s's length.
-- Let - f be e+len.
-- If - f>InputLength, return failure.
-- If - there exists an integer i between 0 (inclusive) and len - (exclusive) such that Canonicalize(s[i]) is - not the same character as Canonicalize(Input - [e+i]), then return failure.
-- Let - y be the State (f, cap).
-- Call - c(y) and return its result.
-- The - production AtomEscape - :: CharacterEscape - evaluates as follows:
-- Evaluate - CharacterEscape to obtain a character ch.
-- Let - A be a one-element CharSet containing the character ch.
-- Call - CharacterSetMatcher(A, false) and return its - Matcher result.
-- The - production AtomEscape - :: CharacterClassEscape - evaluates as follows:
-- Evaluate - CharacterClassEscape to obtain a CharSet A.
-- Call - CharacterSetMatcher(A, false) and return its - Matcher result.
-NOTE An
- escape sequence of the form \
- followed by a nonzero decimal number n
- matches the result of the nth
- set of capturing parentheses (see 15.10.2.11). It is an error if the
- regular expression has fewer than n
- capturing parentheses. If the regular expression has n
- or more capturing parentheses but the nth
- one is undefined because it has not captured anything, then
- the backreference always succeeds.
- The - production CharacterEscape - :: ControlEscape - evaluates by returning the character according to Table 23 -
-|
- - ControlEscape - - - |
-
- - Code - Unit - |
-
- - Name - |
-
- - Symbol - |
-
|
-
- |
-
-
- |
-
- - horizontal - tab - |
-
- - <HT> - |
-
|
-
- |
-
-
- |
-
- - line - feed (new line) - |
-
- - <LF> - |
-
|
-
- |
-
-
- |
-
- - vertical - tab - |
-
- - <VT> - |
-
|
-
- |
-
-
- |
-
- - form - feed - |
-
- - <FF> - |
-
|
-
- |
-
-
- |
-
- - carriage - return - |
-
- - <CR> - |
-
- The
- production CharacterEscape
- :: c ControlLetter
- evaluates as follows:
- Let - ch be the character represented by ControlLetter.
-- Let - i be ch's code unit value.
-- Let - j be the remainder of dividing i by 32.
-- Return - the code unit numbered j.
-- The - production CharacterEscape - :: HexEscapeSequence - evaluates by evaluating the CV of the HexEscapeSequence - (see 7.8.4) and returning its character result.
-- The - production CharacterEscape - :: UnicodeEscapeSequence - evaluates by evaluating the CV of the UnicodeEscapeSequence - (see 7.8.4) and returning its character result.
-- The - production CharacterEscape - :: IdentityEscape - evaluates by returning the character represented by IdentityEscape.
-- The - production DecimalEscape - :: DecimalIntegerLiteral - [lookahead ∉ - DecimalDigit] - evaluates as follows.
-- Let - i be the MV of DecimalIntegerLiteral.
-- If - i is zero, return the EscapeValue consisting of a <NUL> - character (Unicode value 0000).
-- Return - the EscapeValue consisting of the integer i.
-- The - definition of “the MV of DecimalIntegerLiteral” - is in 7.8.3.
-NOTE If
- \ is followed by a
- decimal number n
- whose first digit is not 0,
- then the escape sequence is considered to be a backreference. It is
- an error if n is
- greater than the total number of left capturing parentheses in the
- entire regular expression. \0
- represents the <NUL> character and cannot be followed by a
- decimal digit.
- The
- production CharacterClassEscape
- :: d
- evaluates by returning the ten-element set of characters containing
- the characters 0
- through 9
- inclusive.
- The
- production CharacterClassEscape
- :: D
- evaluates by returning the set of all characters not included in the
- set returned by CharacterClassEscape
- :: d.
- The
- production CharacterClassEscape
- :: s
- evaluates by returning the set of characters containing the
- characters that are on the right-hand side of the WhiteSpace
- (7.2) or LineTerminator
- (7.3) productions.
- The
- production CharacterClassEscape
- :: S
- evaluates by returning the set of all characters not included in the
- set returned by CharacterClassEscape
- :: s.
- The
- production CharacterClassEscape
- :: w
- evaluates by returning the set of characters containing the
- sixty-three characters:
|
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
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-
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- |
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-
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- - | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -
- The
- production CharacterClassEscape
- :: W
- evaluates by returning the set of all characters not included in the
- set returned by CharacterClassEscape
- :: w.
- The
- production CharacterClass
- :: [ [lookahead
- ∉
- {^}]
- ClassRanges
- ] evaluates by evaluating ClassRanges
- to obtain a CharSet and returning that CharSet and the Boolean
- false.
- The
- production CharacterClass
- :: [ ^ ClassRanges
- ] evaluates by evaluating ClassRanges
- to obtain a CharSet and returning that CharSet and the Boolean true.
- The
- production ClassRanges
- :: [empty]
- evaluates by returning the empty CharSet.
- The
- production ClassRanges
- :: NonemptyClassRanges
- evaluates by evaluating NonemptyClassRanges
- to obtain a CharSet and returning that CharSet.
- The - production NonemptyClassRanges - :: ClassAtom - evaluates by evaluating ClassAtom - to obtain a CharSet and returning that CharSet.
-- The - production NonemptyClassRanges :: ClassAtom - NonemptyClassRangesNoDash evaluates as follows:
-- Evaluate - ClassAtom to obtain a CharSet A.
-- Evaluate - NonemptyClassRangesNoDash to obtain a CharSet B.
-- Return - the union of CharSets A and B.
-
- The
- production NonemptyClassRanges :: ClassAtom
- - ClassAtom ClassRanges evaluates as follows:
- Evaluate - the first ClassAtom to obtain a CharSet A.
-- Evaluate - the second ClassAtom to obtain a CharSet B.
-- Evaluate - ClassRanges to obtain a CharSet C.
-- Call - CharacterRange(A, B) and let D be the - resulting CharSet.
-- Return - the union of CharSets D and C.
-- The - abstract operation CharacterRange - takes two CharSet parameters A - and B and performs - the following:
-- If - A does not contain exactly one character or B does - not contain exactly one character then throw a SyntaxError - exception.
-- Let - a be the one character in CharSet A.
-- Let - b be the one character in CharSet B.
-- Let - i be the code unit value of character a.
-- Let - j be the code unit value of character b.
-- If - i > j then throw a SyntaxError exception.
-- Return - the set containing all characters numbered i through j, - inclusive.
-- The - production NonemptyClassRangesNoDash - :: ClassAtom - evaluates by evaluating ClassAtom - to obtain a CharSet and returning that CharSet.
-- The - production NonemptyClassRangesNoDash - :: ClassAtomNoDash - NonemptyClassRangesNoDash - evaluates as follows:
-- Evaluate - ClassAtomNoDash to obtain a CharSet A.
-- Evaluate - NonemptyClassRangesNoDash to obtain a CharSet B.
-- Return - the union of CharSets A and B.
-
- The
- production NonemptyClassRangesNoDash
- :: ClassAtomNoDash
- - ClassAtom
- ClassRanges
- evaluates as follows:
- Evaluate - ClassAtomNoDash to obtain a CharSet A.
-- Evaluate - ClassAtom to obtain a CharSet B.
-- Evaluate - ClassRanges to obtain a CharSet C.
-- Call - CharacterRange(A, B) and let D be the - resulting CharSet.
-- Return - the union of CharSets D and C.
-NOTE 1 ClassRanges can
- expand into single ClassAtoms
- and/or ranges of two ClassAtoms
- separated by dashes. In the latter case the ClassRanges
- includes all characters between the first ClassAtom
- and the second ClassAtom,
- inclusive; an error occurs if either ClassAtom
- does not represent a single character (for example, if one is \w)
- or if the first ClassAtom's
- code unit value is greater than the second ClassAtom's
- code unit value.
NOTE 2 Even if the pattern ignores case, the case of the two ends of a
- range is significant in determining which characters belong to the
- range. Thus, for example, the pattern /[E-F]/i
- matches only the letters E,
- F, e,
- and f, while the
- pattern /[E-f]/i
- matches all upper and lower-case ASCII letters as well as the
- symbols [, \,
- ], ^,
- _, and `.
NOTE 3 A -
- character can be treated literally or it can denote a range. It is
- treated literally if it is the first or last character of
- ClassRanges,
- the beginning or end limit of a range specification, or immediately
- follows a range specification.
- The
- production ClassAtom
- :: -
- evaluates by returning the CharSet containing the one character -.
- The - production ClassAtom - :: ClassAtomNoDash - evaluates by evaluating ClassAtomNoDash - to obtain a CharSet and returning that CharSet.
-
- The
- production ClassAtomNoDash
- :: SourceCharacter
- but not one of \
- or ] or -
- evaluates by returning a one-element CharSet containing
- the character represented by SourceCharacter.
- The
- production ClassAtomNoDash
- :: \ ClassEscape
- evaluates by evaluating ClassEscape
- to obtain a CharSet and returning that CharSet.
- The - production ClassEscape - :: DecimalEscape - evaluates as follows:
-- Evaluate - DecimalEscape to obtain an EscapeValue E.
-- If - E is not a character then throw a SyntaxError - exception.
-- Let - ch be E's character.
-- Return - the one-element CharSet containing the character ch.
-
- The
- production ClassEscape
- :: b
- evaluates by returning the CharSet containing the one character <BS>
- (Unicode value 0008).
- The - production ClassEscape - :: CharacterEscape - evaluates by evaluating CharacterEscape - to obtain a character and returning a one-element CharSet containing - that character.
-- The - production ClassEscape - :: CharacterClassEscape - evaluates by evaluating CharacterClassEscape - to obtain a CharSet and returning that CharSet.
-NOTE A
- ClassAtom can use
- any of the escape sequences that are allowed in the rest of the
- regular expression except for \b,
- \B, and
- backreferences. Inside a CharacterClass,
- \b means the
- backspace character, while \B
- and backreferences raise errors. Using a backreference inside a
- ClassAtom causes
- an error.
- If
- pattern is an
- object R whose
- [[Class]] internal property is "RegExp"
- and flags is
- undefined, then return R
- unchanged. Otherwise call the standard built-in RegExp
- constructor (15.10.4.1) as if by the expression new
- RegExp( pattern,
- flags)
- and return the object constructed by that constructor.
- When
- RegExp is called
- as part of a new
- expression, it is a constructor: it initialises the newly created
- object.
- If
- pattern is an
- object R whose
- [[Class]] internal property is "RegExp"
- and flags is
- undefined, then let P
- be the pattern
- used to construct R
- and let F be the
- flags used to construct R.
- If pattern is an
- object R whose
- [[Class]] internal property is "RegExp"
- and flags is not
- undefined, then throw a TypeError exception.
- Otherwise, let P
- be the empty String if pattern
- is undefined and ToString(pattern)
- otherwise, and let F
- be the empty String if flags
- is undefined and ToString(flags)
- otherwise.
- If - the characters of P - do not have the syntactic form Pattern, - then throw a SyntaxError - exception. Otherwise let the newly constructed object have a - [[Match]] internal property obtained by - evaluating ("compiling") the characters of P - as a Pattern - as described in 15.10.2. -
-
- If
- F
- contains any character other than "g",
- "i",
- or "m",
- or if it contains the same character more than once, then throw a
- SyntaxError
- exception.
-
- If - a SyntaxError - exception is not thrown, then: -
-- Let - S - be a String in the form of a Pattern - equivalent to P, - in which certain characters are escaped as described below. S - may or may not be identical to P - or pattern; - however, the internal procedure that would result from evaluating S - as a Pattern - must behave identically to the internal procedure given by the - constructed object's [[Match]] internal property. - -
-
- The
- characters /
- or backslash
- \
- occurring in the pattern shall be escaped in S
- as necessary to ensure that the String value formed by concatenating
- the Strings "/",
- S,
- "/",
- and F
- can be parsed (in an appropriate lexical context) as a
- RegularExpressionLiteral
- that behaves identically to the constructed regular expression. For
- example, if P
- is "/",
- then S
- could be "\/"
- or "\u002F",
- among other possibilities, but not "/",
- because ///
- followed by F
- would be parsed as a SingleLineComment
- rather than a RegularExpressionLiteral.
- If P
- is the empty String, this specification can be met by letting S
- be "(?:)".
-
-
- The - following properties of the newly constructed object are data - properties with the attributes that are specified in 15.10.7. The - [[Value]] of each property is set as follows:
-
- The
- source property of
- the newly constructed object is set to S.
- The
- global property of
- the newly constructed object is set to a Boolean value that is true
- if F contains the
- character "g"
- and false otherwise.
- The
- ignoreCase
- property of the newly constructed object is set to a Boolean value
- that is true if F
- contains the character "i"
- and false otherwise.
- The
- multiline property
- of the newly constructed object is set to a Boolean value that is
- true if F
- contains the character "m"
- and false otherwise.
- The
- lastIndex property
- of the newly constructed object is set to 0.
- The - [[Prototype]] internal property of the newly constructed object is - set to the standard built-in RegExp prototype object as specified in - 15.10.6.
-
- The
- [[Class]] internal property of the newly constructed object is set
- to "RegExp".
NOTE If
- pattern is a StringLiteral,
- the usual escape sequence substitutions are performed before the
- String is processed by RegExp. If pattern must contain an escape
- sequence to be recognised by RegExp, any
- backslash \
- characters must be escaped within the StringLiteral
- to prevent them being removed when the contents of the StringLiteral
- are formed.
-
- The - value of the [[Prototype]] internal property of the RegExp - constructor is the standard built-in Function prototype object - (15.3.4).
-
- Besides
- the internal properties and the length
- property (whose value is 2), the RegExp constructor has the
- following properties:
- The
- initial value of RegExp.prototype
- is the RegExp prototype object (15.10.6).
- This - property shall have the attributes { [[Writable]]: false, - [[Enumerable]]: false, [[Configurable]]: false }.
-
- The
- value of the [[Prototype]] internal property of the RegExp prototype
- object is the standard built-in Object prototype object (15.2.4).
- The RegExp prototype object is itself a regular expression object;
- its [[Class]] is "RegExp".
- The initial values of the RegExp prototype object’s data
- properties (15.10.7) are set as if the object was created by the
- expression new RegExp()
- where RegExp is
- that standard built-in constructor with that name.
- The
- RegExp prototype object does not have a valueOf
- property of its own; however, it inherits the valueOf
- property from the Object prototype object.
- In
- the following descriptions of functions that are properties of the
- RegExp prototype object, the phrase “this RegExp object” refers
- to the object that is the this value for the invocation of
- the function; a TypeError exception is thrown if the this
- value is not an object or an object for which the value of the
- [[Class]] internal property is not "RegExp".
- The
- initial value of RegExp.prototype.constructor
- is the standard built-in RegExp
- constructor.
- Performs - a regular expression match of string - against the regular expression and returns an Array object - containing the results of the match, or null if string - did not match.
-- The - String ToString(string) - is searched for an occurrence of the regular expression pattern as - follows:
-- Let - R be this RegExp object.
-- Let - S be the value of ToString(string).
-- Let - length be the length of S.
-
- Let
- lastIndex be the result of calling the [[Get]] internal
- method of R with argument "lastIndex"..
- Let - i be the value of ToInteger(lastIndex).
-
- Let
- global be the result of calling the [[Get]] internal method
- of R with argument "global".
- If - global is false, then let i = 0.
-- Let - matchSucceeded be false.
-- Repeat, - while matchSucceeded is false
-- If - i < 0 or i > length, then
-
- Call
- the [[Put]] internal method of R with arguments
- "lastIndex",
- 0, and true.
- Return
- null.
- Call - the [[Match]] internal method of R with arguments S - and i.
-- If - [[Match]] returned failure, then -
-- Let - i = i+1.
-- else - -
-- Let - r be the State result of the call to [[Match]].
-- Set - matchSucceeded to true.
-- Let - e be r's endIndex value.
-- If - global is true,
-
- Call
- the [[Put]] internal method of R with arguments
- "lastIndex",
- e, and true.
- Let - n be the length of r's captures array. (This - is the same value as 15.10.2.1's NCapturingParens.)
-
- Let
- A be a new array created as if by the expression new
- Array() where Array
- is the standard built-in constructor with that name.
- Let - matchIndex be the position of the matched substring within - the complete String S.
-
- Call
- the [[DefineOwnProperty]] internal method of A with
- arguments "index",
- Property Descriptor {[[Value]]: matchIndex, [[Writable]:
- true, [[Enumerable]]: true, [[Configurable]]: true},
- and true.
- Call
- the [[DefineOwnProperty]] internal method of A with
- arguments "input",
- Property Descriptor {[[Value]]: S, [[Writable]: true,
- [[Enumerable]]: true, [[Configurable]]: true}, and
- true.
- Call
- the [[DefineOwnProperty]] internal method of A with
- arguments "length",
- Property Descriptor {[[Value]]: n + 1}, and true.
- Let - matchedSubstr be the matched substring (i.e. the portion of - S between offset i inclusive and offset e - exclusive).
-
- Call
- the [[DefineOwnProperty]] internal method of A with
- arguments "0",
- Property Descriptor {[[Value]]: matchedSubstr, [[Writable]:
- true, [[Enumerable]]: true, [[Configurable]]: true},
- and true.
- For - each integer i such that I > 0 and I ≤ - n
-- Let - captureI be ith element of r's - captures array.
-- Call - the [[DefineOwnProperty]] internal method of A with - arguments ToString(i), Property Descriptor {[[Value]]: - captureI, [[Writable]: true, [[Enumerable]]: true, - [[Configurable]]: true}, and true.
-- Return - A.
-- The - following steps are taken:
-
- Let
- match be the result of evaluating the RegExp.prototype.exec
- (15.10.6.2) algorithm upon this RegExp object using string
- as the argument.
- If - match is not null, then return true; else return - false.
-
- Return
- the String value formed by concatenating the Strings "/",
- the String value of the source property of this RegExp
- object, and "/";
- plus "g"
- if the global
- property is true, "i"
- if the ignoreCase
- property is true, and "m"
- if the multiline
- property is true.
NOTE The - returned String has the form of a - RegularExpressionLiteral - that evaluates to another RegExp object with the same - behaviour as this object. -
-
- RegExp
- instances inherit properties from the RegExp prototype object and
- their [[Class]] internal property value is "RegExp".
- RegExp instances also have a [[Match]] internal property and a
- length property.
- The - value of the [[Match]] internal property is an implementation - dependent representation of the Pattern - of the RegExp object.
-- RegExp - instances also have the following properties.
-
- The
- value of the source
- property is a String in the form of a Pattern
- representing the current regular expression. This property shall
- have the attributes { [[Writable]]: false,
- [[Enumerable]]: false, [[Configurable]]: false }.
- The
- value of the global
- property is a Boolean value indicating whether the flags contained
- the character “g”.
- This property shall have the attributes { [[Writable]]: false,
- [[Enumerable]]: false, [[Configurable]]: false }.
- The
- value of the ignoreCase
- property is a Boolean value indicating whether the flags contained
- the character “i”.
- This property shall have the attributes { [[Writable]]: false,
- [[Enumerable]]: false, [[Configurable]]: false }.
- The
- value of the multiline
- property is a Boolean value indicating whether the flags contained
- the character “m”.
- This property shall have the attributes { [[Writable]]: false,
- [[Enumerable]]: false, [[Configurable]]: false }.
- The
- value of the lastIndex
- property specifies the String position at which to start the next
- match. It is coerced to an integer when used (see
- 15.10.6.2). This property shall have the attributes
- { [[Writable]]: true, [[Enumerable]]: false,
- [[Configurable]]: false }.
NOTE Unlike
- the other standard built-in properties of RegExp instances,
- lastIndex is
- writable.
- Instances - of Error objects are thrown as exceptions when runtime errors occur. - The Error objects may also serve as base objects for user-defined - exception classes.
-
- When
- Error is
- called as a function rather than as a constructor, it creates and
- initialises a new Error object. Thus the function call Error(…)
- is equivalent to the object creation expression new
- Error(…)
- with the same arguments.
- The
- [[Prototype]] internal property of the newly constructed object is
- set to the original Error prototype object, the one that is the
- initial value of Error.prototype
- (15.11.3.1).
- The
- [[Class]] internal property of the newly constructed object is set
- to "Error".
- The - [[Extensible]] internal property of the newly constructed object is - set to true.
-
- If
- the argument message
- is not undefined, the message
- own property of the newly constructed object is set to
- ToString(message).
- When
- Error is called as
- part of a new
- expression, it is a constructor: it initialises the newly created
- object.
- The
- [[Prototype]] internal property of the newly constructed object is
- set to the original Error prototype object, the one that is the
- initial value of Error.prototype
- (15.11.3.1).
- The
- [[Class]] internal property of the newly constructed Error object is
- set to "Error".
- The - [[Extensible]] internal property of the newly constructed object is - set to true.
-
- If
- the argument message
- is not undefined, the message
- own property of the newly constructed object is set to
- ToString(message).
- The - value of the [[Prototype]] internal property of the Error - constructor is the Function prototype object (15.3.4).
-
- Besides
- the internal properties and the length
- property (whose value is 1), the Error constructor has the
- following property:
- The
- initial value of Error.prototype
- is the Error prototype object (15.11.4).
- This - property has the attributes { [[Writable]]: false, - [[Enumerable]]: false, [[Configurable]]: false }.
-
- The
- Error prototype object is itself an Error object (its [[Class]] is
- "Error").
- The - value of the [[Prototype]] internal property of the Error prototype - object is the standard built-in Object prototype object (15.2.4).
-
- The
- initial value of Error.prototype.constructor
- is the built-in Error
- constructor.
- The
- initial value of Error.prototype.name
- is "Error".
- The
- initial value of Error.prototype.message
- is the empty String.
- The - following steps are taken:
-- Let - O be the this value.
-
- Let
- name be the result of calling the [[Get]] internal method of
- O with argument "name".
- If
- name is undefined, then let name be "Error";
- else let name be ToString(name).
- Let
- msg be the result of calling the [[Get]] internal method of
- O with argument "message".
If - msg is undefined, then let - msg - be - the empty String; else let msg be ToString(msg).
If name and msg are both the empty String, return "Error".
If name is the empty String, return msg.
If msg is the empty String, return name.
Return the result of concatenating name, ":", a single space
- character, and msg.
- Error
- instances inherit properties from the Error prototype object and
- their [[Class]] internal property value is "Error".
- Error instances have no special properties.
- One - of the NativeError objects below is thrown when a runtime - error is detected. All of these objects share the same structure, as - described in 15.11.7.
-- This - exception is not currently used within this specification. This - object remains for compatibility with previous editions of this - specification.
-- Indicates - a numeric value has exceeded the allowable range. See 15.4.2.2, - 15.4.5.1, 15.7.4.2, 15.7.4.5, 15.7.4.6, and 15.7.4.7, 15.9.5.43.
-- Indicate - that an invalid reference value has been detected. See 8.7.1, 8.7.2, - 10.2.1, 10.2.1.1.4, 10.2.1.2.4, and 11.13.1.
-- Indicates - that a parsing error has occurred. See 11.1.5, 11.3.1, 11.3.2, - 11.4.1, 11.4.4, 11.4.5, 11.13.1, 11.13.2, 12.2.1, 12.10.1, 12.14.1, - 13.1, 15.1.2.1, 15.3.2.1, 15.10.2.2, 15.10.2.5, 15.10.2.9, - 15.10.2.15, 15.10.2.19, 15.10.4.1, and 15.12.2.
-- Indicates - the actual type of an operand is different than the expected type. - See 8.6.2, 8.7.2, 8.10.5, 8.12.5, 8.12.7, 8.12.8, 8.12.9, 9.9, 9.10, - 10.2.1, 10.2.1.1.3, 10.6, 11.2.2, 11.2.3, 11.4.1, 11.8.6, 11.8.7, - 11.3.1, 13.2, 13.2.3, 15, 15.2.3.2, 15.2.3.3, 15.2.3.4, 15.2.3.5, - 15.2.3.6, 15.2.3.7, 15.2.3.8, 15.2.3.9, 15.2.3.10, 15.2.3.11, - 15.2.3.12, 15.2.3.13, 15.2.3.14, 15.2.4.3, 15.3.4.2, 15.3.4.3, - 15.3.4.4, 15.3.4.5, 15.3.4.5.2, 15.3.4.5.3, 15.3.5, 15.3.5.3, - 15.3.5.4, 15.4.4.3, 15.4.4.11, 15.4.4.16, 15.4.4.17, 15.4.4.18, - 15.4.4.19, 15.4.4.20, 15.4.4.21, 15.4.4.22, 15.4.5.1, 15.5.4.2, - 15.5.4.3, 15.6.4.2, 15.6.4.3, 15.7.4, 15.7.4.2, 15.7.4.4, 15.7.4.8, - 15.9.5, 15.9.5.44, 15.10.4.1, 15.10.6, 15.11.4.4 and 15.12.3.
-- Indicates - that one of the global URI handling functions was used in a way that - is incompatible with its definition. See 15.1.3.
-
- When
- an ECMAScript implementation detects a runtime error, it throws an
- instance of one of the NativeError objects defined in
- 15.11.6. Each of these objects has the structure described below,
- differing only in the name used as the constructor name instead of
- NativeError, in the name property of the prototype
- object, and in the implementation-defined message
- property of the prototype object.
- For - each error object, references to NativeError in the - definition should be replaced with the appropriate error object name - from 15.11.6.
-- When - a NativeError constructor is called as a function rather than - as a constructor, it creates and initialises a new object. A call - of the object as a function is equivalent to calling it as a - constructor with the same arguments.
-
- The
- [[Prototype]] internal property of the newly constructed object is
- set to the prototype object for this error constructor. The
- [[Class]] internal property of the newly constructed object is set
- to "Error".
- The [[Extensible]] internal property of the newly constructed object
- is set to true.
- If
- the argument message
- is not undefined, the message
- own property of the newly constructed object is set to
- ToString(message).
- When
- a NativeError constructor is called as part of a new
- expression, it is a constructor: it initialises the newly created
- object.
- The
- [[Prototype]] internal property of the newly constructed object is
- set to the prototype object for this NativeError constructor.
- The [[Class]] internal property of the newly constructed object is
- set to "Error".
- The [[Extensible]] internal property of the newly constructed object
- is set to true.
- If
- the argument message
- is not undefined, the message
- property of the newly constructed object is set to
- ToString(message).
- The - value of the [[Prototype]] internal property of a NativeError - constructor is the Function prototype object (15.3.4).
-
- Besides
- the internal properties and the length
- property (whose value is 1), each NativeError
- constructor has the following property:
- The
- initial value of NativeError.prototype
- is a NativeError prototype object (15.11.7.7). Each
- NativeError constructor has a separate prototype object.
- This - property has the attributes { [[Writable]]: false, - [[Enumerable]]: false, [[Configurable]]: false }.
-
- Each
- NativeError prototype object is an Error object (its
- [[Class]] is "Error").
- The - value of the [[Prototype]] internal property of each NativeError - prototype object is the standard built-in Error prototype object - (15.11.4).
-
- The
- initial value of the constructor
- property of the prototype for a given NativeError constructor
- is the NativeError constructor function itself (15.11.7).
- The
- initial value of the name
- property of the prototype for a given NativeError constructor
- is the name of the constructor (the name used instead of
- NativeError).
- The
- initial value of the message
- property of the prototype for a given NativeError constructor
- is the empty String.
NOTE The
- prototypes for the NativeError constructors do not themselves
- provide a toString function,
- but instances of errors will inherit it from the Error prototype
- object.
- NativeError
- instances inherit properties from their NativeError prototype
- object and their [[Class]] internal property value is "Error".
- NativeError instances have no special properties.
- The - JSON object is a single object that contains two functions, - parse and stringify, that are used to parse and - construct JSON texts. The JSON Data Interchange Format is described - in RFC 4627 <http://www.ietf.org/rfc/rfc4627.txt>. The JSON - interchange format used in this specification is exactly that - described by RFC 4627 with two exceptions:
-- The - top level JSONText - production of the ECMAScript JSON grammar may consist of any - JSONValue rather - than being restricted to being a JSONObject - or a JSONArray as - specified by RFC 4627. -
-- Conforming - implementations of JSON.parse and JSON.stringify must - support the exact interchange format described in this - specification without any deletions or extensions to the format. - This differs from RFC 4627 which permits a JSON parser to accept - non-JSON forms and extensions.
-
- The
- value of the [[Prototype]] internal property of the JSON object is
- the standard built-in Object prototype object (15.2.4). The value of
- the [[Class]] internal property of the JSON object is "JSON".
- The value of the [[Extensible]] internal property of the JSON object
- is set to true.
- The
- JSON object does not have a [[Construct]] internal property; it is
- not possible to use the JSON object as a constructor with the new
- operator.
- The - JSON object does not have a [[Call]] internal property; it is not - possible to invoke the JSON object as a function.
-- JSON.stringify - produces a String that conforms to the following JSON grammar. - JSON.parse accepts a String that conforms to the JSON grammar.
-- JSON - is similar to ECMAScript source text in that it consists of a - sequence of characters conforming to the rules of SourceCharacter. - The JSON Lexical Grammar defines the tokens that make up a JSON text - similar to the manner that the ECMAScript lexical grammar defines - the tokens of an ECMAScript source test. The JSON Lexical grammar - only recognizes the white space character specified by the - production JSONWhiteSpace. - The JSON lexical grammar shares some productions with the - ECMAScript lexical grammar. All nonterminal symbols of the grammar - that do not begin with the characters “JSON” are defined by - productions of the ECMAScript lexical grammar.
-- Syntax
-- JSONWhiteSpace ::
-
- <TAB>
<CR>
<LF>
<SP>
- JSONString ::
-
- " JSONStringCharactersopt "
- JSONStringCharacters ::
-- JSONStringCharacter - JSONStringCharactersopt -
-- JSONStringCharacter ::
-
- SourceCharacter but
- not double-quote " orbackslash \
- orU+0000 thru U+001F
- \ JSONEscapeSequence
- JSONEscapeSequence ::
-- JSONEscapeCharacter
-- UnicodeEscapeSequence -
-- JSONEscapeCharacter :: one - of
-
- "
- / \ b f n r t
- JSONNumber ::
-
- -optDecimalIntegerLiteral JSONFractionoptExponentPartopt
- JSONFraction ::
-
- . DecimalDigits
- JSONNullLiteral ::
-- NullLiteral
-- JSONBooleanLiteral ::
-- BooleanLiteral
-- The - JSON Syntactic Grammar defines a valid JSON text in terms of tokens - defined by the JSON lexical grammar. The goal symbol of the grammar - is JSONText. -
-- Syntax
-- JSONText : -
-- JSONValue
-- JSONValue : -
-
- JSONNullLiteral
JSONBooleanLiteral
JSONObject
JSONArray
JSONString
JSONNumber
- JSONObject :
-
- {
- } { JSONMemberList }
- JSONMember :
-
- JSONString : JSONValue
- JSONMemberList :
-
- JSONMember
-
JSONMemberList ,
- JSONMember
-
- JSONArray :
-
- [
- ] [ JSONElementList
- ]
- JSONElementList :
-
- JSONValue
JSONElementList
- , JSONValue
- The
- parse function
- parses a JSON text (a JSON-formatted String) and produces an
- ECMAScript value. The JSON format is a restricted form of ECMAScript
- literal. JSON objects are realized as ECMAScript objects. JSON
- arrays are realized as ECMAScript arrays. JSON strings, numbers,
- booleans, and null are realized as ECMAScript Strings, Numbers,
- Booleans, and null. JSON uses a more limited set of white
- space characters than WhiteSpace
- and allows Unicode code points U+2028 and U+2029 to directly appear
- in JSONString
- literals without using an escape sequence. The process of parsing is
- similar to 11.1.4 and 11.1.5 as constrained by the JSON grammar.
- The - optional reviver parameter is a function that takes two - parameters, (key and value). It can filter and - transform the results. It is called with each of the key/value - pairs produced by the parse, and its return value is used instead of - the original value. If it returns what it received, the structure is - not modified. If it returns undefined then the property is - deleted from the result.
-- Let - JText be ToString(text).
-- Parse - JText using the grammars in 15.12.1. Throw a SyntaxError - exception if JText did not conform to the JSON grammar for - the goal symbol JSONText. -
-- Let - unfiltered be the result of parsing and evaluating JText - as if it was the source text of an ECMAScript Program but - using JSONString in place of StringLiteral. - Note that since JText conforms to the JSON grammar this - result will be either a primitive value or an object that is - defined by either an ArrayLiteral or an ObjectLiteral.
-- If - IsCallable(reviver) is true, then
-
- Let
- root be a new object created as if by the expression new
- Object(), where Object
- is the standard built-in constructor with that name.
- Call - the [[DefineOwnProperty]] internal method of root with the - empty String, the PropertyDescriptor {[[Value]]: unfiltered, - [[Writable]]: true, [[Enumerable]]: true, - [[Configurable]]: true}, and false as arguments.
-- Return - the result of calling the abstract operation Walk, passing root - and the empty String. The abstract operation Walk is described - below.
-- Else
-- Return - unfiltered.
-- The - abstract operation Walk is a recursive abstract operation that takes - two parameters: a holder - object and the String name - of a property in that object. Walk uses the value of reviver - that was originally passed to the above parse function.
-- Let - val be the result of calling the [[Get]] internal method of - holder with argument name.
-- If - val is an object, then
-
- If
- the [[Class]] internal property of val is "Array"
- Set - I to 0.
-
- Let
- len be the result of calling the [[Get]] internal method
- of val with argument "length".
- Repeat - while I < len, -
-- Let - newElement be the result of calling the abstract - operation Walk, passing val and ToString(I).
-- If - newElement is undefined, then
-- Call - the [[Delete]] internal method of val with ToString(I) - and false as arguments. -
-- Else
-- Call - the [[DefineOwnProperty]] internal method of val with - arguments ToString(I), the Property Descriptor - {[[Value]]: newElement, [[Writable]]: true, - [[Enumerable]]: true, [[Configurable]]: true}, and false.
-- Add - 1 to I.
-- Else
-- Let - keys be an internal List of String values consisting of - the names of all the own properties of val whose - [[Enumerable]] attribute is true. The ordering of the - Strings should be the same as that used by the - Object.keys - standard built-in function.
-- For - each String P in keys do, -
-- Let - newElement be the result of calling the abstract - operation Walk, passing val and P. -
-- If - newElement is undefined, then
-- Call - the [[Delete]] internal method of val with P and - false as arguments. -
-- Else
-- Call - the [[DefineOwnProperty]] internal method of val with - arguments P, the Property Descriptor {[[Value]]: - newElement, [[Writable]]: true, [[Enumerable]]: - true, [[Configurable]]: true}, and false.
-- Return - the result of calling the [[Call]] internal method of reviver - passing holder as the this value and with an argument - list consisting of name and val.
-
- It is
- not permitted for a conforming implementation of JSON.parse
- to extend the JSON grammars. If an implementation wishes to support
- a modified or extended JSON interchange format it must do so by
- defining a different parse function.
-
NOTE In - the case where there are duplicate name Strings within an object, - lexically preceding values for the same key shall be overwritten.
-
- The
- stringify function
- returns a String in JSON format representing an ECMAScript value. It
- can take three parameters. The first parameter is required. The
- value parameter is
- an ECMAScript value, which is usually an object or array, although
- it can also be a String, Boolean, Number or null. The
- optional replacer
- parameter is either a function that alters the way objects and
- arrays are stringified, or an array of Strings and Numbers that acts
- as a white list for selecting the object properties that will be
- stringified. The optional space
- parameter is a String or Number that allows the result to have white
- space injected into it to improve human readability.
- These - are the steps in stringifying an object:
-- Let - stack be an empty List.
-- Let - indent be the empty String.
-- Let - PropertyList and ReplacerFunction be undefined.
-- If - Type(replacer) is Object, then
-- If - IsCallable(replacer) is true, then
-- Let - ReplacerFunction be replacer.
-
- Else
- if the [[Class]] internal property of replacer is "Array",
- then
- Let - PropertyList be an empty internal List
-- For - each value v of a property of replacer that has an - array index property name. The properties are enumerated in the - ascending array index order of their names.
-- Let - item be undefined.
-- If - Type(v) is String then let item be v.
-- Else - if Type(v) is Object then,
-
- If
- the [[Class]] internal property of v is "String"
- or "Number"
- then let item be ToString(v).
- If - item is not undefined and item is not currently an - element of PropertyList then,
-- Append - item to the end of PropertyList.
-- If - Type(space) is Object then,
- -- If - Type(space) is Number
-- Let - space be min(10, ToInteger(space)).
-- Set - gap to a String containing space space characters. - This will be the empty String if space is less than 1.
-- Else - if Type(space) is String
-- If - the number of characters in space is 10 or less, set gap - to space otherwise set gap to a String consisting of - the first 10 characters of space.
-- Else
-- Set - gap to the empty String.
-
- Let
- wrapper be a new object created as if by the expression new
- Object(), where Object
- is the standard built-in constructor with that name.
- Call - the [[DefineOwnProperty]] internal method of wrapper with - arguments the empty String, the Property Descriptor {[[Value]]: - value, [[Writable]]: true, [[Enumerable]]: true, - [[Configurable]]: true}, and false.
-- Return - the result of calling the abstract operation Str with the - empty String and wrapper.
-
- The
- abstract operation Str(key,
- holder)
- has access to ReplacerFunction from the invocation of the stringify
- method. Its algorithm is as follows:
- Let - value be the result of calling the [[Get]] internal method - of holder with argument key.
-- If - Type(value) is Object, then
-
- Let
- toJSON be the result of calling the [[Get]] internal method
- of value with argument "toJSON".
- If - IsCallable(toJSON) is true
-- Let - value be the result of calling the [[Call]] internal - method of toJSON passing value as the this - value and with an argument list consisting of key.
-- If - ReplacerFunction is not undefined, then
-- Let - value be the result of calling the [[Call]] internal method - of ReplacerFunction passing holder as the this - value and with an argument list consisting of key and - value.
-- If - Type(value) is Object then,
-
- If
- the [[Class]] internal property of value is "Number"
- then,
- Let - value be ToNumber(value).
-
- Else
- if the [[Class]] internal property of value is "String"
- then,
- Let - value be ToString(value).
-
- Else
- if the [[Class]] internal property of value is "Boolean"
- then,
- Let - value be the value of the [[PrimitiveValue]] internal - property of value.
-
- If
- value is null then return "null".
- If
- value is true then return "true".
- If
- value is false then return "false".
- If - Type(value) is String, then return the result of calling the - abstract operation Quote with argument value.
-- If - Type(value) is Number
-- If - value is finite then return ToString(value).
-
- Else,
- return "null".
- If - Type(value) is Object, and IsCallable(value) is false
- -- Return - undefined.
-- The - abstract operation Quote(value) - wraps a String value in double quotes and escapes characters within - it. -
-- Let - product be the double quote character.
-- For - each character C in value
-- If - C is the double quote character or the backslash character
-- Let - product be the concatenation of product and the - backslash character.
-- Let - product be the concatenation of product and C.
-- Else - if C is backspace, formfeed, newline, carriage return, or - tab
-- Let - product be the concatenation of product and the - backslash character.
-- Let - abbrev be the character corresponding to the value of C - as follows:
-backspace "b"
formfeed "f"
newline "n"
carriage return "r"
tab "t"
- Let - product be the concatenation of product and abbrev.
-- Else - if C is a control character having a code unit value less - than the space character
-- Let - product be the concatenation of product and the - backslash character.
-
- Let
- product be the concatenation of product and "u".
- Let - hex be the result of converting the numeric code unit - value of C to a String of four hexadecimal digits.
-- Let - product be the concatenation of product and hex.
-- Else
-- Let - product be the concatenation of product and C.
-- Let - product be the concatenation of product and the - double quote character.
-- Return - product.
-- The - abstract operation JO(value) - serializes an object. It has access to the stack, - indent, gap, - PropertyList, - ReplacerFunction, - and space of the - invocation of the stringify method.
-- If - stack contains value then throw a TypeError - exception because the structure is cyclical.
-- Append - value to stack.
-- Let - stepback be indent.
-- Let - indent be the concatenation of indent and gap.
-- If - PropertyList is not undefined, then
-- Let - K be PropertyList.
-- Else
-- Let - K be an internal List of Strings consisting of the names of - all the own properties of value whose [[Enumerable]] - attribute is true. The ordering of the Strings should be - the same as that used by the Object.keys standard built-in - function.
-- Let - partial be an empty List.
-- For - each element P of K.
-- Let - strP be the result of calling the abstract operation Str - with arguments P and value.
-- If - strP is not undefined
-- Let - member be the result of calling the abstract operation - Quote with argument P.
-- Let - member be the concatenation of member and the colon - character.
-- If - gap is not the empty String
-- Let - member be the concatenation of member and the - space character.
-- Let - member be the concatenation of member and strP.
-- Append - member to partial.
-- If - partial is empty, then
-
- Let
- final be "{}".
- Else
-- If - gap is the empty String
-- Let - properties be a String formed by concatenating all the - element Strings of partial with each adjacent pair of - Strings separated with the comma character. A comma is not - inserted either before the first String or after the last String. - -
-
- Let
- final be the result of concatenating "{",
- properties, and "}".
- Else - gap is not the empty String
-- Let - separator be the result of concatenating the comma - character, the line feed character, and indent.
-- Let - properties be a String formed by concatenating all the - element Strings of partial with each adjacent pair of - Strings separated with separator. The separator - String is not inserted either before the first String or after - the last String.
-
- Let
- final be the result of concatenating "{",
- the line feed character, indent, properties, the
- line feed character, stepback, and "}".
- Remove - the last element of stack.
-- Let - indent be stepback.
-- Return - final.
-
- The
- abstract operation JA(value)
- serializes an array. It has access to the stack,
- indent, gap,
- and space of the
- invocation of the stringify method. The representation of arrays
- includes only the elements between zero and array.length
- – 1 inclusive. Named
- properties are excluded from the stringification. An array is
- stringified as an open left bracket, elements separated by comma,
- and a closing right bracket.
- If - stack contains value then throw a TypeError - exception because the structure is cyclical.
-- Append - value to stack.
-- Let - stepback be indent.
-- Let - indent be the concatenation of indent and gap.
-- Let - partial be an empty List.
-
- Let
- len be the result of calling the [[Get]] internal method of
- value with argument "length".
- Let - index be 0.
-- Repeat - while index < len
-- Let - strP be the result of calling the abstract operation Str - with arguments ToString(index) and value. -
-- If - strP is undefined
-
- Append
- "null"
- to partial.
- Else
-- Append - strP to partial.
-- Increment - index by 1.
-- If - partial is empty ,then
-
- Let
- final be "[]".
- Else
-- If - gap is the empty String
-- Let - properties be a String formed by concatenating all the - element Strings of partial with each adjacent pair of - Strings separated with the comma character. A comma is not - inserted either before the first String or after the last String. - -
-
- Let
- final be the result of concatenating "[",
- properties, and "]".
- Else
-- Let - separator be the result of concatenating the comma - character, the line feed character, and indent.
-- Let - properties be a String formed by concatenating all the - element Strings of partial with each adjacent pair of - Strings separated with separator. The separator - String is not inserted either before the first String or after - the last String.
-
- Let
- final be the result of concatenating "[",
- the line feed character, indent, properties, the
- line feed character, stepback, and "]".
- Remove - the last element of stack.
-- Let - indent be stepback.
-- Return - final.
-NOTE 1 JSON structures are allowed to be nested to any depth, but they - must be acyclic. If value - is or contains a cyclic structure, then the stringify function must - throw a TypeError exception. This is an example of a value - that cannot be stringified:
-a = [];
a[0] = a;
my_text = JSON.stringify(a); // This must throw an TypeError.
NOTE 2 Symbolic primitive values are rendered as follows:
-The
- null value is rendered in JSON text as the String null.
The - undefined value is not rendered.
-The
- true value is rendered in JSON text as the String true.
The
- false value is rendered in JSON text as the String false.
NOTE 3 String values are wrapped in double quotes. The characters "
- and \ are escaped
- with \ prefixes.
- Control characters are replaced with escape sequences \uHHHH,
- or with the shorter forms, \b
- (backspace), \f
- (formfeed), \n
- (newline), \r
- (carriage return), \t
- (tab).
NOTE 4 Finite numbers are stringified as if by calling ToString(number).
- NaN and Infinity regardless of sign are represented as the
- String null.
NOTE 5 Values that do not have a JSON representation (such as undefined
- and functions) do not produce a String. Instead they produce the
- undefined value. In arrays these values are represented as the
- String null.
- In objects an unrepresentable value causes the property to be
- excluded from stringification.
NOTE 6 An object is rendered as an opening left brace followed by zero or - more properties, separated with commas, closed with a right brace. A - property is a quoted String representing the key or property name, a - colon, and then the stringified property value. An array is rendered - as an opening left bracket followed by zero or more values, - separated with commas, closed with a right bracket.
-
- An
- implementation must report most errors at the time the relevant
- ECMAScript language construct is evaluated. An early error is
- an error that can be detected and reported prior to the evaluation
- of any construct in the Program
- containing the error. An implementation must report early errors in
- a Program prior to
- the first evaluation of that Program.
- Early errors in eval code are reported at the time eval
- is called but prior to evaluation of any construct within the eval
- code. All errors that are not early errors are runtime errors.
- An - implementation must treat any instance of the following kinds of - errors as an early error:
-- Any - syntax error.
-- Attempts - to define an ObjectLiteral that has multiple get property assignments with - the same name or multiple set property assignments with the - same name.
-- Attempts - to define an ObjectLiteral - that has both a data property assignment and a get or - set property assignment with the same name.
-- Errors - in regular expression literals that are not implementation-defined - syntax extensions.
-- Attempts - in strict mode code to define an ObjectLiteral - that has multiple data property assignments with the same name.
-- The - occurrence of a WithStatement - in strict mode code.
-- The - occurrence of an Identifier - value appearing more than once within a FormalParameterList - of an individual strict mode FunctionDeclaration - or FunctionExpression.
-
- Improper
- uses of return,
- break, and
- continue.
- Attempts
- to call PutValue on any value for which an early determination can
- be made that the value is not a Reference (for example, executing
- the assignment statement 3=4).
- An - implementation shall not treat other kinds of errors as early errors - even if the compiler can prove that a construct cannot execute - without error under any circumstances. An implementation may issue - an early warning in such a case, but it should not report the error - until the relevant construct is actually executed. -
-- An - implementation shall report all errors as specified, except for the - following:
-
- An
- implementation may extend program syntax and regular expression
- pattern or flag syntax. To permit this, all operations (such as
- calling eval,
- using a regular expression literal, or using the Function
- or RegExp
- constructor) that are allowed to throw SyntaxError
- are permitted to exhibit implementation-defined behaviour instead
- of throwing SyntaxError
- when they encounter an implementation-defined extension to the
- program syntax or regular expression pattern or flag syntax.
- An - implementation may provide additional types, values, objects, - properties, and functions beyond those described in this - specification. This may cause constructs (such as looking up a - variable in the global scope) to have implementation-defined - behaviour instead of throwing an error (such as ReferenceError).
-
- An
- implementation may define behaviour other than throwing RangeError
- for toFixed,
- toExponential,
- and toPrecision
- when the fractionDigits
- or precision
- argument is outside the specified range.
-
-- SourceCharacter ::See clause 6
-- any - Unicode code unit
-- InputElementDiv ::See clause 7
-
- WhiteSpace
LineTerminator
Comment
Token
DivPunctuator
- InputElementRegExp ::See clause 7
-
- WhiteSpace
LineTerminator
Comment
Token
RegularExpressionLiteral
- WhiteSpace ::See 7.2
-
- <TAB>
<VT>
<FF>
<SP>
<#x0a>
<BOM>
<USP>
- LineTerminator ::See 7.3
-
- <LF>
<CR>
<LS>
<PS>
- LineTerminatorSequence ::See 7.3
-
- <LF>
<CR>
- [lookahead
- ∉
- <LF>
- ]
<LS>
<PS>
<CR>
- <LF>
- Comment ::See 7.4
-
- MultiLineComment
SingleLineComment
- MultiLineComment ::See 7.4
-
- /* MultiLineCommentCharsopt */
- MultiLineCommentChars ::See 7.4
-
- MultiLineNotAsteriskChar
- MultiLineCommentCharsopt* PostAsteriskCommentCharsopt
- PostAsteriskCommentChars ::See 7.4
-
- MultiLineNotForwardSlashOrAsteriskChar
- MultiLineCommentCharsopt* PostAsteriskCommentCharsopt
- MultiLineNotAsteriskChar ::See 7.4
-
- SourceCharacter but
- not asterisk *
- MultiLineNotForwardSlashOrAsteriskChar ::See 7.4
-
- SourceCharacter but
- not forward-slash /
- orasterisk *
- SingleLineComment ::See 7.4
-
- // SingleLineCommentCharsopt
- SingleLineCommentChars ::See 7.4
-- SingleLineCommentChar - SingleLineCommentCharsopt
-- SingleLineCommentChar ::See 7.4
-- SourceCharacter - but - not - LineTerminator
-- Token ::See 7.5
-
- IdentifierName
Punctuator
NumericLiteral
StringLiteral
- Identifier ::See 7.6
-- IdentifierName but - not ReservedWord
-- IdentifierName ::See 7.6
-
- IdentifierStart
IdentifierName
- IdentifierPart
- IdentifierStart ::See 7.6
-
- UnicodeLetter$
_\ UnicodeEscapeSequence
- IdentifierPart ::See 7.6
-
- IdentifierStart
UnicodeCombiningMark
UnicodeDigit
UnicodeConnectorPunctuation
<ZWNJ>
<ZWJ>
- UnicodeLetter See 7.6
-- any - character in the Unicode categories “Uppercase letter (Lu)”, - “Lowercase letter (Ll)”, “Titlecase letter (Lt)”, “Modifier - letter (Lm)”, “Other letter (Lo)”, or “Letter number (Nl)”.
-- UnicodeCombiningMark See 7.6
-- any - character in the Unicode categories “Non-spacing mark (Mn)” or - “Combining spacing mark (Mc)”
-- UnicodeDigit See 7.6
-- any - character in the Unicode category “Decimal number (Nd)”
-- UnicodeConnectorPunctuation See 7.6
-- any - character in the Unicode category “Connector punctuation (Pc)”
-- ReservedWord ::See 7.6.1
-
- Keyword
FutureReservedWord
NullLiteral
BooleanLiteral
- Keyword :: one - ofSee 7.6.1.1
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-
- |
-
-
- |
-
-
- |
-
|
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
- - | -
- DivPunctuator :: - one - ofSee 7.7
-|
-
- |
-
-
- |
- - | -- | -- | -- | -
- Literal ::See 7.8
-
- NullLiteral
BooleanLiteral
NumericLiteral
StringLiteral
RegularExpressionLiteral
- NullLiteral ::See 7.8.1
-
- null
- BooleanLiteral ::See 7.8.2
-
- true
false
- NumericLiteral ::See 7.8.3
-
- DecimalLiteral
HexIntegerLiteral
- DecimalLiteral ::See 7.8.3
-
- DecimalIntegerLiteral . DecimalDigitsopt
- ExponentPartopt. DecimalDigits ExponentPartopt
DecimalIntegerLiteral
- ExponentPartopt
- DecimalIntegerLiteral ::See 7.8.3
-
- 0
NonZeroDigit
- DecimalDigitsopt
- DecimalDigits ::See 7.8.3
-
- DecimalDigit
DecimalDigits
- DecimalDigit
- DecimalDigit :: - one - ofSee 7.8.3
-
- 0
- 1 2 3 4 5 6 7 8 9
- NonZeroDigit:: - one - ofSee 7.8.3
-
- 1 2 3 4 5 6 7 8 9
- ExponentPart:: - See 7.8.3
-ExponentIndicator SignedInteger
-- ExponentIndicator :: - one - ofSee 7.8.3
-
- e
- E
- SignedInteger ::See 7.8.3
-
- DecimalDigits+ DecimalDigits- DecimalDigits
- HexIntegerLiteral ::See 7.8.3
-
- 0x HexDigit0X HexDigit
HexIntegerLiteral HexDigit
- HexDigit :: - one - ofSee 7.8.3
-
- 0
- 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F
- StringLiteral ::See 7.8.4
-
- "DoubleStringCharactersopt
- "'SingleStringCharactersopt
- '
- DoubleStringCharacters ::See 7.8.4
-- DoubleStringCharacter - DoubleStringCharactersopt
-- SingleStringCharacters ::See 7.8.4
-- SingleStringCharacter - SingleStringCharactersopt
-- DoubleStringCharacter ::See 7.8.4
-
- SourceCharacter but
- not double-quote "
- or
- backslash \ or
- LineTerminator\
- EscapeSequence
LineContinuation
- SingleStringCharacter ::See 7.8.4
-
- SourceCharacter but
- not single-quote '
- orbackslash \ or
- LineTerminator\
- EscapeSequence
LineContinuation
- LineContinuation ::See 7.8.4
-
- \
- LineTerminatorSequence
- EscapeSequence ::See 7.8.4
-
- CharacterEscapeSequence0 [lookahead
- ∉DecimalDigit]
HexEscapeSequence
UnicodeEscapeSequence
- CharacterEscapeSequence ::See 7.8.4
-
- SingleEscapeCharacter
NonEscapeCharacter
- SingleEscapeCharacter :: one - ofSee 7.8.4
-
- '
- " \ b f n r t v
- NonEscapeCharacter ::See 7.8.4
-- SourceCharacter - but - notEscapeCharacter or - LineTerminator
-- EscapeCharacter ::See 7.8.4
-
- SingleEscapeCharacter
DecimalDigitxu
- HexEscapeSequence ::See 7.8.4
-
- x
- HexDigit HexDigit
- UnicodeEscapeSequence ::See 7.8.4
-
- u HexDigit HexDigit HexDigit HexDigit
- RegularExpressionLiteral ::See 7.8.5
-
- / RegularExpressionBody /
- RegularExpressionFlags
- RegularExpressionBody ::See 7.8.5
-- RegularExpressionFirstChar - RegularExpressionChars
-- RegularExpressionChars ::See 7.8.5
-
- [empty]
RegularExpressionChars
- RegularExpressionChar
- RegularExpressionFirstChar ::See 7.8.5
-
- RegularExpressionNonTerminator but
- not *
- or
- \ or
- /
- or
- [
RegularExpressionBackslashSequence
RegularExpressionClass
- RegularExpressionChar ::See 7.8.5
-
- RegularExpressionNonTerminator but
- not \
- or
- /
- or
- [
RegularExpressionBackslashSequence
RegularExpressionClass
- RegularExpressionBackslashSequence ::See 7.8.5
-
- \ RegularExpressionNonTerminator
- RegularExpressionNonTerminator ::See 7.8.5
-- SourceCharacter but - not - LineTerminator
-- RegularExpressionClass ::See 7.8.5
-
- [
- RegularExpressionClassChars
- ]
- RegularExpressionClassChars
- ::See 7.8.5
- [empty]
RegularExpressionClassChars
- RegularExpressionClassChar
- RegularExpressionClassChar
- ::See 7.8.5
- RegularExpressionNonTerminator
- but
- not ]
- or
- \
RegularExpressionBackslashSequence
- RegularExpressionFlags ::See 7.8.5
-
- [empty]
RegularExpressionFlags
- IdentifierPart
- StringNumericLiteral :::See 9.3.1
-
- StrWhiteSpaceopt
StrWhiteSpaceoptStrNumericLiteral StrWhiteSpaceopt
- StrWhiteSpace :::See 9.3.1
-- StrWhiteSpaceChar - StrWhiteSpaceopt
-- StrWhiteSpaceChar :::See 9.3.1
-
- WhiteSpace
LineTerminator
- StrNumericLiteral :::See 9.3.1
-
- StrDecimalLiteral
HexIntegerLiteral
- StrDecimalLiteral :::See 9.3.1
-
- StrUnsignedDecimalLiteral+
- StrUnsignedDecimalLiteral-
- StrUnsignedDecimalLiteral
- StrUnsignedDecimalLiteral :::See 9.3.1
-
- Infinity
DecimalDigits . DecimalDigitsopt
- ExponentPartopt. DecimalDigits ExponentPartopt
DecimalDigits
- ExponentPartopt
- DecimalDigits :::See 9.3.1
-
- DecimalDigit
DecimalDigits
- DecimalDigit
- DecimalDigit ::: one - ofSee 9.3.1
-
- 0
- 1 2 3 4 5 6 7 8 9
- ExponentPart :::See 9.3.1
-- ExponentIndicator - SignedInteger
-- ExponentIndicator ::: - one - ofSee 9.3.1
-
- e
- E
- SignedInteger :::See 9.3.1
-
- DecimalDigits+
- DecimalDigits-
- DecimalDigits
- HexIntegerLiteral :::See 9.3.1
-
- 0x HexDigit0X HexDigit
HexIntegerLiteral HexDigit
- HexDigit ::: - one - ofSee 9.3.1
-
- 0
- 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F
- PrimaryExpression :See 11.1
-
- this
Identifier
Literal
ArrayLiteral
ObjectLiteral( Expression )
- ArrayLiteral :See 11.1.4
-
- [
- Elisionopt
- ] ElementList
[
-
- ] ElementList ,
- Elisionopt
[
-
- ]
- ElementList :See 11.1.4
-
- Elisionopt
- AssignmentExpression
ElementList
- ,
- Elisionopt
- AssignmentExpression
- Elision :See 11.1.4
-
- ,
Elision
- ,
- ObjectLiteral :See 11.1.5
-
- {
- } {
- PropertyNameAndValueList
- } PropertyNameAndValueList
{
-
- , }
- PropertyNameAndValueList :See 11.1.5
-
- PropertyAssignment
PropertyNameAndValueList
- , PropertyAssignment
- PropertyAssignment :See 11.1.5
-
- PropertyName
- :
- AssignmentExpressionget
- PropertyName()
- { FunctionBody } PropertyName
set
- (
- PropertySetParameterList
- ) { FunctionBody }
- PropertyName :See 11.1.5
-
- IdentifierName
StringLiteral
NumericLiteral
- PropertySetParameterList :See 11.1.5
-- Identifier
-- MemberExpression :See 11.2
-
- PrimaryExpression
FunctionExpression
MemberExpression [ Expression ] MemberExpression . IdentifierNamenew MemberExpression
- Arguments
- NewExpression :See 11.2
-
- MemberExpression
new
- CallExpression :See 11.2
-
- MemberExpression
- Arguments
- Arguments[ Expression ] CallExpression . IdentifierName
- Arguments :See 11.2
-
- ( ) ArgumentList
()
- ArgumentList :See 11.2
-
- AssignmentExpression
ArgumentList , AssignmentExpression
- LeftHandSideExpression :See 11.2
-
- NewExpression
CallExpression
- PostfixExpression :See 11.3
-
- LeftHandSideExpression
LeftHandSideExpression
- [noLineTerminator here]
- ++
LeftHandSideExpression
- [noLineTerminator here]
- --
- UnaryExpression :See 11.4
-
- PostfixExpression
delete
- void
- UnaryExpressiontypeof
- UnaryExpression
++-- UnaryExpression+ UnaryExpression- UnaryExpression~ UnaryExpression! UnaryExpression
- MultiplicativeExpression :See 11.5
-
- UnaryExpression
MultiplicativeExpression * UnaryExpression
MultiplicativeExpression / UnaryExpression
MultiplicativeExpression % UnaryExpression
- AdditiveExpression :See 11.6
-
- MultiplicativeExpression
AdditiveExpression + MultiplicativeExpression
AdditiveExpression - MultiplicativeExpression
- ShiftExpression :See 11.7
-
- AdditiveExpression
ShiftExpression << AdditiveExpression
ShiftExpression >> AdditiveExpression
ShiftExpression >>> AdditiveExpression
- RelationalExpression :See 11.8
-
- ShiftExpression
RelationalExpression < ShiftExpression
RelationalExpression > ShiftExpression
RelationalExpression <= ShiftExpression
RelationalExpression >= ShiftExpression
RelationalExpression instanceof ShiftExpression
RelationalExpression in ShiftExpression
- RelationalExpressionNoIn :See 11.8
-
- ShiftExpression
RelationalExpressionNoIn < ShiftExpression
RelationalExpressionNoIn > ShiftExpression
RelationalExpressionNoIn <= ShiftExpression
RelationalExpressionNoIn >= ShiftExpression
RelationalExpressionNoIn instanceof ShiftExpression
- EqualityExpression :See 11.9
-
- RelationalExpression
EqualityExpression == RelationalExpression
EqualityExpression != RelationalExpression
EqualityExpression === RelationalExpression
EqualityExpression !== RelationalExpression
- EqualityExpressionNoIn :See 11.9
-
- RelationalExpressionNoIn
EqualityExpressionNoIn == RelationalExpressionNoIn
EqualityExpressionNoIn != RelationalExpressionNoIn
EqualityExpressionNoIn === RelationalExpressionNoIn
EqualityExpressionNoIn !== RelationalExpressionNoIn
- BitwiseANDExpression :See 11.10
-
- EqualityExpression
BitwiseANDExpression & EqualityExpression
- BitwiseANDExpressionNoIn :See 11.10
-
- EqualityExpressionNoIn
BitwiseANDExpressionNoIn & EqualityExpressionNoIn
- BitwiseXORExpression :See 11.10
-
- BitwiseANDExpression
BitwiseXORExpression ^ BitwiseANDExpression
- BitwiseXORExpressionNoIn :See 11.10
-
- BitwiseANDExpressionNoIn
BitwiseXORExpressionNoIn ^ BitwiseANDExpressionNoIn
- BitwiseORExpression :See 11.10
-
- BitwiseXORExpression
BitwiseORExpression | BitwiseXORExpression
- BitwiseORExpressionNoIn :See 11.10
-
- BitwiseXORExpressionNoIn
BitwiseORExpressionNoIn | BitwiseXORExpressionNoIn
- LogicalANDExpression :See 11.11
-
- BitwiseORExpression
LogicalANDExpression && BitwiseORExpression
- LogicalANDExpressionNoIn :See 11.11
-
- BitwiseORExpressionNoIn
LogicalANDExpressionNoIn && BitwiseORExpressionNoIn
- LogicalORExpression :See 11.11
-
- LogicalANDExpression
LogicalORExpression || LogicalANDExpression
- LogicalORExpressionNoIn :See 11.11
-
- LogicalANDExpressionNoIn
LogicalORExpressionNoIn || LogicalANDExpressionNoIn
- ConditionalExpression :See 11.12
-
- LogicalORExpression
LogicalORExpression
- ? AssignmentExpression : AssignmentExpression
- ConditionalExpressionNoIn :See 11.12
-
- LogicalORExpressionNoIn
LogicalORExpressionNoIn
- ? AssignmentExpressionNoIn : AssignmentExpressionNoIn
- AssignmentExpression :See 11.13
-
- ConditionalExpression
LeftHandSideExpression
- AssignmentOperator AssignmentExpression
- AssignmentExpressionNoIn :See 11.13
-
- ConditionalExpressionNoIn
LeftHandSideExpression
- AssignmentOperator AssignmentExpressionNoIn
- AssignmentOperator : - one - ofSee 11.13
-|
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
-
- |
-
- Expression :See 11.14
-
- AssignmentExpression
Expression , AssignmentExpression
- ExpressionNoIn :See 11.14
-
- AssignmentExpressionNoIn
ExpressionNoIn , AssignmentExpressionNoIn
- Statement :See clause 12
-
- Block
VariableStatement
EmptyStatement
ExpressionStatement
IfStatement
IterationStatement
ContinueStatement
BreakStatement
ReturnStatement
WithStatement
LabelledStatement
SwitchStatement
ThrowStatement
TryStatement
DebuggerStatement
- Block :See 12.1
-
- { StatementListopt }
- StatementList :See 12.1
-
- Statement
StatementList
- Statement
- VariableStatement :See 12.2
-
- var VariableDeclarationList ;
- VariableDeclarationList :See 12.2
-
- VariableDeclaration
VariableDeclarationList , VariableDeclaration
- VariableDeclarationListNoIn :See 12.2
-
- VariableDeclarationNoIn
VariableDeclarationListNoIn , VariableDeclarationNoIn
- VariableDeclaration :See 12.2
-- Identifier - Initialiseropt
-- VariableDeclarationNoIn :See 12.2
-- Identifier - InitialiserNoInopt
-- Initialiser :See 12.2
-
- = AssignmentExpression
- InitialiserNoIn :See 12.2
-
- = AssignmentExpressionNoIn
- EmptyStatement :See 12.3
-
- ;
- ExpressionStatement :See 12.4
-
- [lookahead
- ∉
- {{,
- function}]Expression ;
- IfStatement :See 12.5
-
- if ( Expression ) Statement else Statementif ( Expression ) Statement
- IterationStatement :See 12.6
-
- do
- Statement
- while ( Expression ); while ( Expression ) Statementfor ( ExpressionNoInopt; Expressionopt ; Expressionopt ) Statementfor ( var VariableDeclarationListNoIn; Expressionopt ; Expressionopt ) Statementfor ( LeftHandSideExpression in Expression ) Statementfor ( var VariableDeclarationNoIn in Expression ) Statement
- ContinueStatement :See 12.7
-
- continue
- [noLineTerminator here]Identifieropt ;
- BreakStatement :See 12.8
-
- break
- [noLineTerminator here]Identifieropt ;
- ReturnStatement :See 12.9
-
- return
- [noLineTerminator here]Expressionopt ;
- WithStatement :See 12.10
-
- with ( Expression ) Statement
- SwitchStatement :See 12.11
-
- switch ( Expression ) CaseBlock
- CaseBlock :See 12.11
-
- { CaseClausesopt } { CaseClausesoptDefaultClause CaseClausesopt }
- CaseClauses :See 12.11
-
- CaseClause
CaseClauses
- CaseClause
- CaseClause :See 12.11
-
- case Expression : StatementListopt
- DefaultClause :See 12.11
-
- default : StatementListopt
- LabelledStatement :See 12.12
-
- Identifier : Statement
- ThrowStatement :See 12.13
-
- throw
- [noLineTerminator here]
- Expression ;
- TryStatement :See 12.14
-
- try Block Catchtry Block Finallytry Block Catch Finally
- Catch :See 12.14
-
- catch (
- Identifier ) Block
- Finally :See 12.14
-
- finally Block
- DebuggerStatement :See 12.15
-
- debugger ;
- FunctionDeclaration :See clause 13
-
- function Identifier ( FormalParameterListopt ) { FunctionBody }
- FunctionExpression :See clause 13
-
- function Identifieropt ( FormalParameterListopt ) { FunctionBody }
- FormalParameterList :See clause 13
-
- Identifier
FormalParameterList , Identifier
- FunctionBody :See clause 13
-- SourceElementsopt
-- Program :See clause 14
-- SourceElementsopt
-- SourceElements :See clause 14
-
- SourceElement
SourceElements
- SourceElement
- SourceElement :See clause 14
-
- Statement
FunctionDeclaration
- uri :::See 15.1.3
-- uriCharactersopt
-- uriCharacters :::See 15.1.3
-- uriCharacter - uriCharactersopt
-- uriCharacter :::See 15.1.3
-
- uriReserved
uriUnescaped
uriEscaped
- uriReserved ::: - one - ofSee 15.1.3
-
- ;
- / ? : @ & = + $ ,
- uriUnescaped :::See 15.1.3
-
- uriAlpha
DecimalDigit
uriMark
- uriEscaped :::See 15.1.3
-
- % HexDigit HexDigit
- uriAlpha ::: - one - ofSee 15.1.3
-
- a
- b c d e f g h i j k l m n o p q r s t u v w x
- y z
A B C D E F G H I J K L M N O P Q R S T
- U V W X Y Z
- uriMark ::: - one - ofSee 15.1.3
-
- -
- _ . ! ~ * ‘ ( )
- Pattern ::See 15.10.1
-- Disjunction
-- Disjunction ::See 15.10.1
-
- Alternative
- Alternative | Disjunction
- Alternative ::See 15.10.1
-
- [empty]
Alternative
- Term
- Term ::See 15.10.1
-
- Assertion
Atom
Atom
- Quantifier
- Assertion ::See 15.10.1
-
- ^ $ \
- b \
- B (
- ?
- =
- Disjunction ) (
- ?
- !
- Disjunction )
- Quantifier ::See 15.10.1
-
- QuantifierPrefix
QuantifierPrefix
- ?
- QuantifierPrefix ::See 15.10.1
-
- *
+? { DecimalDigits } { DecimalDigits
- ,
- } { DecimalDigits
- , DecimalDigits }
- Atom ::See 15.10.1
-
- PatternCharacter.\
- AtomEscape
CharacterClass
() (
- ?
- :
- Disjunction )
- PatternCharacter :: SourceCharacter but - not any - of:See 15.10.1
-
- ^
- $ \ . * + ? ( ) [ ] { } |
- AtomEscape ::See 15.10.1
-
- DecimalEscape
CharacterEscape
CharacterClassEscape
- CharacterEscape ::See 15.10.1
-
- ControlEscapec ControlLetter
HexEscapeSequence
UnicodeEscapeSequence
IdentityEscape
- ControlEscape :: one - ofSee 15.10.1
-
- f
- n r t v
- ControlLetter :: one - ofSee 15.10.1
-
- a
- b c d e f g h i j k l m n o p q r s t u v w x
- y z
A B C D E F G H I J K L M N O P Q R S T
- U V W X Y Z
- IdentityEscape ::See 15.10.1
-
- SourceCharacter but
- not
- IdentifierPart
<ZWJ>
<ZWNJ>
- DecimalEscape ::See 15.10.1
-- DecimalIntegerLiteral [lookahead - ∉ - DecimalDigit]
--
-- CharacterClassEscape :: - one - ofSee 15.10.1
-
- d
- D s S w W
- CharacterClass ::See 15.10.1
-
- [
- [lookahead
- ∉
- {^}]
- ClassRanges
- ] [
- ^ ClassRanges
- ]
- ClassRanges ::See 15.10.1
-
- [empty]
NonemptyClassRanges
- NonemptyClassRanges ::See 15.10.1
-
- ClassAtom
ClassAtom
- NonemptyClassRangesNoDash
ClassAtom
- – ClassAtom ClassRanges
- NonemptyClassRangesNoDash ::See 15.10.1
-
- ClassAtom
ClassAtomNoDash
- NonemptyClassRangesNoDash
ClassAtomNoDash
- – ClassAtom ClassRanges
- ClassAtom ::See 15.10.1
-
- -
ClassAtomNoDash
- ClassAtomNoDash ::See 15.10.1
-
- SourceCharacter but
- not one
- of \ or ]
- or - \
- ClassEscape
- ClassEscape ::See 15.10.1
-
- DecimalEscapeb
CharacterEscape
- JSONWhiteSpace ::See 15.12.1.1
-
- <TAB>
<CR>
<LF>
<SP>
- JSONString ::See 15.12.1.1
-
- "
- JSONStringCharactersopt "
- JSONStringCharacters ::See 15.12.1.1
-- JSONStringCharacter - JSONStringCharactersopt -
-- JSONStringCharacter ::See 15.12.1.1
-
- SourceCharacter but
- not double-quote " or backslash \
- or U+0000 thru
- U+001F
- \ JSONEscapeSequence
- JSONEscapeSequence ::See 15.12.1.1
-- JSONEscapeCharacter
-- UnicodeEscapeSequence -
-- JSONEscapeCharacter :: - one - ofSee 15.12.1.1
-
- "
- / \ b f n r t
- JSONNumber ::See 15.12.1.1
-
- -optDecimalIntegerLiteral JSONFractionoptExponentPartopt
- JSONFraction ::See 15.12.1.1
-
- . DecimalDigits
- JSONNullLiteral ::See 15.12.1.1
-- NullLiteral
-- JSONBooleanLiteral ::See 15.12.1.1
-- BooleanLiteral
-- JSONText :See 15.12.1.2
-- JSONValue
-- JSONValue :See 15.12.1.2 -
-
- JSONNullLiteral
JSONBooleanLiteral
JSONObject
JSONArray
JSONString
JSONNumber
- JSONObject :See 15.12.1.2
-
- {
- } { JSONMemberList }
- JSONMember :See 15.12.1.2
-
- JSONString : JSONValue
- JSONMemberList :See 15.12.1.2
-
- JSONMember
-
JSONMemberList ,
- JSONMember
-
- JSONArray :See 15.12.1.2
-
- [
- ] [ JSONElementList
- ]
- JSONElementList :See 15.12.1.2
-
- JSONValue
JSONElementList
- , JSONValue
- Past - editions of ECMAScript have included additional syntax and semantics - for specifying octal literals and octal escape sequences. These have - been removed from this edition of ECMAScript. This non-normative - annex presents uniform syntax and semantics for octal literals and - octal escape sequences for compatibility with some older ECMAScript - programs.
-- The - syntax and semantics of 7.8.3 can be extended as follows except that - this extension is not allowed for strict mode code:
-- Syntax
-- NumericLiteral ::
-
- DecimalLiteral
HexIntegerLiteral
OctalIntegerLiteral
- OctalIntegerLiteral ::
-
- 0 OctalDigit
OctalIntegerLiteral OctalDigit
- OctalDigit :: one - of
-
- 0
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- Semantics
-- The - MV of NumericLiteral - :: - OctalIntegerLiteral is - the MV of OctalIntegerLiteral.
-
- The
- MV of OctalDigit ::
- 0
- is 0.
- The
- MV of OctalDigit ::
- 1
- is 1.
- The
- MV of OctalDigit ::
- 2
- is 2.
- The
- MV of OctalDigit ::
- 3
- is 3.
- The
- MV of OctalDigit ::
- 4
- is 4.
- The
- MV of OctalDigit ::
- 5
- is 5.
- The
- MV of OctalDigit ::
- 6
- is 6.
- The
- MV of OctalDigit ::
- 7
- is 7.
- The
- MV of OctalIntegerLiteral ::
- 0
- OctalDigit is the MV
- of OctalDigit.
- The - MV of OctalIntegerLiteral :: - OctalIntegerLiteral - OctalDigit is (the MV - of OctalIntegerLiteral - times 8) plus the MV of OctalDigit.
-- The - syntax and semantics of 7.8.4 can be extended as follows except that - this extension is not allowed for strict mode code:
-- Syntax
-- EscapeSequence ::
-
- CharacterEscapeSequence
OctalEscapeSequence
HexEscapeSequence
UnicodeEscapeSequence
- OctalEscapeSequence ::
-
- OctalDigit [lookahead
- ∉
- DecimalDigit]
ZeroToThree
- OctalDigit [lookahead
- ∉DecimalDigit]
FourToSeven
- OctalDigit
ZeroToThree OctalDigit OctalDigit
- ZeroToThree :: one - of
-
- 0
- 1 2 3
- FourToSeven :: - one - of
-- 4 - 5 6 7
-- Semantics
-- The - CV of EscapeSequence :: - OctalEscapeSequence - is the CV of the OctalEscapeSequence.
-- The - CV of OctalEscapeSequence - :: - OctalDigit [lookahead - ∉ - DecimalDigit] - is the character whose code unit value is the MV of the - OctalDigit.
-- The - CV of OctalEscapeSequence - :: - ZeroToThree - OctalDigit [lookahead - ∉ - DecimalDigit] - is the character whose code unit value is (8 times the MV of the - ZeroToThree) plus the - MV of the OctalDigit.
-- The - CV of OctalEscapeSequence - :: - FourToSeven - OctalDigit is the - character whose code unit value is (8 times the MV of the - FourToSeven) plus the - MV of the OctalDigit.
-- The - CV of OctalEscapeSequence - :: - ZeroToThree - OctalDigit OctalDigit - is the character whose code unit value is (64 (that is, 82) - times the MV of the ZeroToThree) - plus (8 times the MV of the first OctalDigit) - plus the MV of the second OctalDigit.
-
- The
- MV of ZeroToThree ::
- 0
- is 0.
- The
- MV of ZeroToThree ::
- 1
- is 1.
- The
- MV of ZeroToThree ::
- 2
- is 2.
- The
- MV of ZeroToThree ::
- 3
- is 3.
- The
- MV of FourToSeven ::
- 4
- is 4.
- The
- MV of FourToSeven ::
- 5
- is 5.
- The
- MV of FourToSeven ::
- 6
- is 6.
- The
- MV of FourToSeven ::
- 7
- is 7.
- Some - implementations of ECMAScript have included additional properties - for some of the standard native objects. This non-normative annex - suggests uniform semantics for such properties without making the - properties or their semantics part of this standard.
-
- The
- escape function is
- a property of the global object. It computes a new version of a
- String value in which certain characters have been replaced by a
- hexadecimal escape sequence.
- For
- those characters being replaced whose code unit value is 0xFF
- or less, a two-digit escape sequence of the form % xx
- is used. For those characters being replaced whose code unit value
- is greater than 0xFF,
- a four-digit escape sequence of the form %u xxxx
- is used
- When
- the escape
- function is called with one argument string,
- the following steps are taken:
- Call - ToString(string).
-- Compute - the number of characters in Result(1).
-- Let - R be the empty string.
-- Let - k be 0.
-- If - k equals Result(2), return R.
-- Get - the character (represented as a 16-bit unsigned integer) at - position k within Result(1).
-
- If
- Result(6) is one of the 69 nonblank
- characters“ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789@*_+-./”then
- go to step 13.
- If - Result(6), is less than 256, go to step 11.
-
- Let
- S be a String containing six characters “%u wxyz”
- where wxyz are four hexadecimal digits encoding the value of
- Result(6).
- Go - to step 14.
-
- Let
- S be a String containing three characters “% xy”
- where xy are two hexadecimal digits encoding the value of
- Result(6).
- Go - to step 14.
-- Let - S be a String containing the single character Result(6).
-- Let - R be a new String value computed by concatenating the - previous value of R and S.
-- Increase - k by 1.
-- Go - to step 5.
-NOTE The - encoding is partly based on the encoding described in RFC 1738, but - the entire encoding specified in this standard is described above - without regard to the contents of RFC 1738. This encoding does not - reflect changes to RFC 1738 made by RFC 3986.
- -
- The
- unescape function
- is a property of the global object. It computes a new version of a
- String value in which each escape sequence of the sort that might be
- introduced by the escape
- function is replaced with the character that it represents.
- When
- the unescape
- function is called with one argument string,
- the following steps are taken:
- Call - ToString(string).
-- Compute - the number of characters in Result(1).
-- Let - R be the empty String.
-- Let - k be 0.
-- If - k equals Result(2), return R.
-- Let - c be the character at position k within Result(1).
-
- If
- c is not %,
- go to step 18.
- If - k is greater than Result(2)−6, - go to step 14.
-
- If
- the character at position k+1 within Result(1) is not u,
- go to step 14.
- If - the four characters at positions k+2, k+3, k+4, - and k+5 within Result(1) are not all hexadecimal digits, go - to step 14.
-- Let - c be the character whose code unit value is the integer - represented by the four hexadecimal digits at positions k+2,k+3, k+4, and k+5 within Result(1).
-- Increase - k by 5.
-- Go - to step 18.
-- If - k is greater than Result(2)−3, - go to step 18.
-- If - the two characters at positions k+1 and k+2 within - Result(1) are not both hexadecimal digits, go to step 18.
-- Let - c be the character whose code unit value is the integer - represented by two zeroes plus the two hexadecimal digits at - positions k+1 and k+2 within Result(1).
-- Increase - k by 2.
-- Let - R be a new String value computed by concatenating the - previous value of R and c.
-- Increase - k by 1.
-- Go - to step 5.
-
- The
- substr method
- takes two arguments, start
- and length, and
- returns a substring of the result of converting the this object to a
- String, starting from character position start
- and running for length
- characters (or through the end of the String if length
- is undefined). If start
- is negative, it is treated as (sourceLength+start)
- where sourceLength
- is the length of the String. The result is a String value, not a
- String object. The following steps are taken:
- Call - ToString, giving it the this value as its argument.
-- Call - ToInteger(start).
-- If - length is undefined, use +∞; - otherwise call ToInteger(length).
-- Compute - the number of characters in Result(1).
-- If - Result(2) is positive or zero, use Result(2); else use - max(Result(4)+Result(2),0).
-- Compute - min(max(Result(3),0), Result(4)–Result(5)).
-- If - Result(6) ≤ 0, return the empty - String “”.
-- Return - a String containing Result(6) consecutive characters from Result(1) - beginning with the character at position Result(5).
-
- The
- length property of
- the substr method
- is 2.
NOTE The
- substr function is
- intentionally generic; it does not require that its this
- value be a String object. Therefore it can be transferred to other
- kinds of objects for use as a method.
NOTE The
- getFullYear method
- is preferred for nearly all purposes, because it avoids the “year
- 2000 problem.”
- When - the getYear method is called with no arguments, the following - steps are taken:
-- Let - t be this time value.
-- If - t is NaN, return NaN.
-- Return - YearFromTime(LocalTime(t)) − - 1900.
-NOTE The
- setFullYear method
- is preferred for nearly all purposes, because it avoids the “year
- 2000 problem.”
- When - the setYear method is called with one argument year, - the following steps are taken:
-- Let - t be the result of LocalTime(this time value); but if this time value is NaN, let t be +0.
-- Call - ToNumber(year).
-- If - Result(2) is NaN, set the [[PrimitiveValue]] internal - property of the this value to NaN and return NaN.
-- If - Result(2) is not NaN and 0 ≤ - ToInteger(Result(2)) ≤ 99 then - Result(4) is ToInteger(Result(2)) + 1900. Otherwise, Result(4) - is Result(2).
-- Compute - MakeDay(Result(4), MonthFromTime(t), DateFromTime(t)).
-- Compute - UTC(MakeDate(Result(5), TimeWithinDay(t))).
-- Set - the [[PrimitiveValue]] internal property of the this value - to TimeClip(Result(6)).
-- Return - the value of the [[PrimitiveValue]] internal property of the this - value.
-NOTE The
- property toUTCString
- is preferred. The toGMTString
- property is provided principally for compatibility with old code. It
- is recommended that the toUTCString
- property be used in new ECMAScript code.
- The
- Function object that is the initial value of
- Date.prototype.toGMTString
- is the same Function object that is the initial value of
- Date.prototype.toUTCString.
- The - strict mode restriction and exceptions
-implements", "interface",
-"let", "package", "private",
-"protected", "public", "static", and
-"yield" are classified as FutureReservedWord tokens
-within strict mode code. (7.6.12).- A - conforming implementation, when processing strict mode code, may - not extend the syntax of NumericLiteral - (7.8.3) to include OctalIntegerLiteral - as described in B.1.1.
-- A - conforming implementation, when - processing strict mode code (see 10.1.1), may not extend the syntax - of EscapeSequence to - include OctalEscapeSequence - as described in B.1.2.
-
- Assignment
- to an undeclared identifier or otherwise unresolvable reference
- does not create a property in the global object. When a simple
- assignment occurs within strict mode code, its LeftHandSide must not evaluate to an
- unresolvable Reference. If it does a ReferenceError
- exception is thrown (8.7.2). The LeftHandSide also
- may not be a reference to a data property with the attribute value
- {[[Writable]]:false},
- to an accessor property with the attribute value
- {[[Set]]:undefined},
- nor to a non-existent
- property of an object whose [[Extensible]] internal property has
- the value false.
- In these cases a TypeError
- exception is thrown (11.13.1).
- The
- identifier eval
- or arguments
- may not appear as the LeftHandSideExpression
- of an Assignment operator (11.13) or of a PostfixExpression
- (11.3) or as the UnaryExpression
- operated upon by a Prefix Increment (11.4.4) or a Prefix Decrement
- (11.4.5) operator.
-
- Arguments
- objects for strict mode functions define non-configurable accessor
- properties named "caller"
- and "callee"
- which throw a TypeError exception on access
- (10.6).
- Arguments - objects for strict mode functions do not dynamically share their - array indexed property values with the corresponding formal - parameter bindings of their functions. (10.6).
-
- For
- strict mode functions, if an arguments object is created the
- binding of the local identifier arguments
- to the arguments object is immutable and hence may not be the
- target of an assignment expression. (10.5).
- It - is a SyntaxError - if strict mode code contains an - ObjectLiteral with - more than one definition of any data property (11.1.5).
-
- It
- is a SyntaxError
- if the Identifier
- "eval"
- or the Identifier "arguments"
- occurs as the Identifier
- in a PropertySetParameterList
- of a
- PropertyAssignment
- that is contained in strict code or
- if its FunctionBody is
- strict code (11.1.5).
- Strict - mode eval code cannot instantiate variables or functions in the - variable environment of the caller to eval. Instead, a new variable - environment is created and that environment is used for declaration - binding instantiation for the eval code (10.4.2).
-
- If
- this
- is evaluated within strict mode code, then the this
- value is not coerced to
- an object. A this
- value of null
- or undefined
- is not converted to the global object and primitive values are not
- converted to wrapper objects. The this
- value passed via a function call (including calls made using
- Function.prototype.apply
- and Function.prototype.call)
- do not coerce the passed this value to an object (10.4.3, 11.1.1,
- 15.3.4.3, 15.3.4.4).
- When
- a delete
- operator occurs within strict mode code,
- a SyntaxError is thrown if its
- UnaryExpression is a
- direct reference to a variable, function argument, or function
- name(11.4.1).
- When
- a delete
- operator occurs within strict mode code, a TypeError
-is thrown if the property to
- be deleted has the attribute { [[Configurable]]:false
- } (11.4.1).
- It
- is a SyntaxError
- if a VariableDeclaration
- or VariableDeclarationNoIn
- occurs within strict code and its Identifier
- is eval
- or
- arguments
- (12.2.1).
- Strict - mode code may not include a WithStatement. - The occurrence of a WithStatement - in such a context is an SyntaxError - (12.10).
-
- It
- is a SyntaxError if a TryStatement
- with a Catch
- occurs within strict code and the Identifier
- of the Catch
- production is eval
- or arguments
- (12.14.1)
- It
- is a SyntaxError if the identifier eval
- or arguments
- appears within a FormalParameterList
- of a strict mode FunctionDeclaration
- or FunctionExpression
- (13.1)
- A
- strict mode function may not have two or more formal parameters
- that have the same name. An attempt to create such a function using
- a FunctionDeclaration,
- FunctionExpression, or
- Function
- constructor is a SyntaxError
- (13.1, 15.3.2).
- An
- implementation may not extend, beyond that defined in this specification,
- meanings within strict mode functions of properties named caller
- or arguments
- of function instances. ECMAScript code may not create or modify
- properties with these names on function objects that correspond to
- strict mode functions
- (10.6, 13.2, 15.3.4.5.3).
- It
- is a SyntaxError
- to use within strict mode code the identifiers eval
- or arguments
- as the Identifier of a
- FunctionDeclaration or
- FunctionExpression or
- as a formal parameter name (13.1). Attempting to dynamically define
- such a strict mode function using the Function
- constructor (15.3.2) will throw a SyntaxError
- exception.
- Throughout:
- In the Edition 3 specification the meaning of phrases such as “as
- if by the expression new
- Array()” are subject to misinterpretation. In the
- Edition 5 specification text for all internal references and
- invocations of standard built-in objects and methods has been
- clarified by making it explicit that the intent is that the actual
- built-in object is to be used rather than the current dynamic value
- of the correspondingly named property.
-
- 11.8.2, - 11.8.3, 11.8.5: ECMAScript generally uses a left to right evaluation - order, however the Edition 3 specification language for the > and - <= operators resulted in a partial right to left order. The - specification has been corrected for these operators such that it - now specifies a full left to right evaluation order. However, this - change of order is potentially observable if side-effects occur - during the evaluation process.
-- 11.1.4: - Edition 5 clarifies the fact that a trailing comma at the end of an - ArrayInitialiser - does not add to the length of the array. This is not a semantic - change from Edition 3 but some implementations may have previously - misinterpreted this.
-- 11.2.3: - Edition 5 reverses the order of steps 2 and 3 of the algorithm. The - original order as specified in Editions 1 through 3 was incorrectly - specified such that side-effects of evaluating Arguments - could affect the result of evaluating MemberExpression.
-
- 12.4:
- In Edition 3, an object is created, as if by new
- Object()to serve as the scope for resolving the name of
- the exception parameter passed to a catch
- clause of a try
- statement. If the actual exception object is a function and it is
- called from within the catch
- clause, the scope object will be passed as the this value of
- the call. The body of the function can then define new properties on
- its this value and those property names become visible
- identifiers bindings within the scope of the catch clause
- after the function returns. In Edition 5, when an exception
- parameter is called as a function, undefined is passed as the
- this value.
- 13:.
- In Edition 3, the algorithm for the production FunctionExpression
- with an Identifier
- adds an object created as if by new
- Object() to the scope chain to serve as a scope for
- looking up the name of the function. The identifier resolution rules
- (10.1.4 in Edition 3) when applied to such an object will, if
- necessary, follow the object’s prototype chain when attempting to
- resolve an identifier. This means all the properties of
- Object.prototype are visible as identifiers within that scope. In
- practice most implementations of Edition 3 have not implemented this
- semantics. Edition 5 changes the specified semantics by using a
- Declarative Environment Record to bind the name of the function.
- 14:.
- In Edition 3, the algorithm for the production SourceElements : SourceElements
- SourceElement did not correctly propagate statement
- result values in the same manner as Block.
- This could result in the eval function producing an incorrect result when evaluating a Program
- text. In practice most implementations of Edition 3 have implemented
- the correct propagation rather than what was specified in Edition 3.
- 15.10.6: - RegExp.prototype is now a RegExp object rather than an instance of - Object. The value of its [[Class]] internal property which is - observable using Object.prototype.toString - is now “RegExp” rather than “Object”.
-- 7.1: - Unicode format control characters are no longer stripped from - ECMAScript source text before processing. In Edition 5, if such a - character appears in a StringLiteral - or RegularExpressionLiteral - the character will be incorporated into the literal where in Edition - 3 the character would not be incorporated into the literal.
-- 7.2: - Unicode character <BOM> is now treated as whitespace and its - presence in the middle of what appears to be an identifier could - result in a syntax error which would not have occurred in Edition 3
-- 7.3: - Line terminator characters that are preceded by an escape sequence - are now allowed within a string literal token. In Edition 3 a - syntax error would have been produced.
-- 7.8.5: - Regular expression literals now return a unique object each time the - literal is evaluated. This change is detectable by any programs that - test the object identity of such literal values or that are - sensitive to the shared side effects.
-- 7.8.5: - Edition 5 requires early reporting of any possible RegExp - constructor errors that would be produced when converting a - RegularExpressionLiteral - to a RegExp object. Prior to Edition 5 implementations were - permitted to defer the reporting of such errors until the actual - execution time creation of the object.
-- 7.8.5: - In Edition 5 unescaped “/” characters may appear as a - CharacterClass in - a regular expression literal. In Edition 3 such a character would - have been interpreted as the final character of the literal.
-
- 10.4.2:
- In Edition 5, indirect calls to the eval function use the global environment as both the variable environment
- and lexical environment for the eval code. In Edition 3, the
- variable and lexical environments of the caller of an indirect eval
- was used as the environments for the eval code.
- 15.4.4:
- In Edition 5 all methods of Array.prototype
- are intentionally generic. In Edition 3 toString
- and toLocaleString
- were not generic and would throw a TypeError
- exception if applied to objects that were not instances of Array.
- 10.6: - In Edition 5 the array indexed properties of argument objects that - correspond to actual formal parameters are enumerable. In Edition - 3, such properties were not enumerable.
-
- 10.6:
- In Edition 5 the value of the [[Class]] internal property of an
- arguments object is "Arguments".
- In Edition 3, it was "Object".
- This is observable if toString
- is called as a method of an arguments object.
-
- 12.6.4:
- for-in statements no longer throw a TypeError if the in
- expression evaluates to null or undefined. Instead,
- the statement behaves as if the value of the expression was an
- object with no enumerable properties.
- 15:
- In Edition 5, the following new properties are defined on built-in
- objects that exist in Edition 3:
-Object.getPrototypeOf,
-Object.getOwnPropertyDescriptor,
-Object.getOwnPropertyNames,
-Object.create,
-Object.defineProperty,
- Object.defineProperties,
- Object.seal,
- Object.freeze,
- Object.preventExtensions,
- Object.isSealed,
- Object.isFrozen,
- Object.isExtensible,
- Object.keys,
- Function.prototype.bind,
- Array.prototype.indexOf,
- Array.prototype.lastIndexOf,
- Array.prototype.every,
- Array.prototype.some,
- Array.prototype.forEach,
- Array.prototype.map,
- Array.prototype.filter,
- Array.prototype.reduce,
- Array.prototype.reduceRight,
- String.prototype.trim,
- Date.now,
- Date.prototype.toISOString,
- Date.prototype.toJSON.
-
- 15: - Implementations are now required to ignore extra arguments to - standard built-in methods unless otherwise explicitly specified. In - Edition 3 the handling of extra arguments was unspecified and - implementations were explicitly allowed to throw a TypeError - exception.
-- 15.1.1: - The value properties NaN, Infinity, and undefined - of the Global Object have been changed to be read-only properties.
-- 15.1.2.1. - Implementations are no longer permitted to restrict the use of eval - in ways that are not a direct call. In addition, any invocation of - eval that is not a direct call uses the global environment as its - variable environment rather than the caller’s variable - environment.
-
- 15.1.2.2:
- The specification of the function parseInt
- no longer allows implementations to treat Strings beginning with a 0
- character as octal values.
- 15.3.4.3:
- In Edition 3, a TypeError is thrown if the second argument
- passed to Function.prototype.apply
- is neither an array object nor an arguments object. In Edition 5,
- the second argument may be any kind of generic array-like object
- that has a valid length
- property.
- 15.3.4.3, 15.3.4.4:
- In Edition 3 passing undefined or null as the first
- argument to either Function.prototype.apply
- or Function.prototype.call
- causes the global object to be passed to the indirectly invoked
- target function as the this value. If the first argument is a
- primitive value the result of calling ToObject on the primitive value is passed as the this value. In Edition 5, these
- transformations are not performed and the actual first argument
- value is passed as the this value. This difference will
- normally be unobservable to existing ECMAScript Edition 3 code
- because a corresponding transformation takes place upon activation
- of the target function. However, depending upon the implementation,
- this difference may be observable by host object functions called
- using apply or
- call. In addition,
- invoking a standard built-in function in this manner with null
- or undefined passed as the this value will in many cases
- cause behaviour in Edition 5 implementations that differ from
- Edition 3 behaviour. In particular, in Edition 5 built-in functions
- that are specified to actually use the passed this value as
- an object typically throw a TypeError exception if passed
- null or undefined as the this value.
- 15.3.5.2:
- In Edition 5, the prototype
- property of Function instances is not enumerable. In Edition 3, this
- property was enumerable.
- 15.5.5.2: - In Edition 5, the individual characters of a String object’s - [[PrimitiveValue] may be accessed as array indexed properties of the - String object. These properties are non-writable and - non-configurable and shadow any inherited properties with the same - names. In Edition 3, these properties did not exist and ECMAScript - code could dynamically add and remove writable properties with such - names and could access inherited properties with such names. -
-
- 15.9.4.2:
- Date.parse is now
- required to first attempt to parse its argument as an ISO format
- string. Programs that use this format but depended upon
- implementation specific behaviour (including failure) may behave
- differently.
- 15.10.2.12:
- In Edition 5, \s
- now additionally matches <BOM>.
- 15.10.4.1:
- In Edition 3, the exact form of the String value of the source
- property of an object created by the RegExp
- constructor is implementation defined. In Edition 5, the String must
- conform to certain specified requirements and hence may be different
- from that produced by an Edition 3 implementation.
- 15.10.6.4:
- In Edition 3, the result of RegExp.prototype.toString
- need not be derived from the value of the RegExp object’s source
- property. In Edition 5 the result must be derived from the source
- property in a specified manner and hence may be different from the
- result produced by an Edition 3 implementation.
- 15.11.2.1,
- 15.11.4.3: In Edition 5, if an initial value for the message
- property of an Error object is not specified via the Error
- constructor the initial value of the property is the empty String.
- In Edition 3, such an initial value is implementation defined.
- 15.11.4.4:
- In Edition 3, the result of Error.prototype.toString
- is implementation defined. In Edition 5, the result is fully
- specified and hence may differ from some Edition 3 implementations.
- 15.12:
- In Edition 5, the name JSON
- is defined in the global environment. In Edition 3, testing for the
- presence of that name will show it to be undefined unless it is
- defined by the program or implementation.
- ANSI/IEEE - Std 754-1985: IEEE Standard for Binary Floating-Point Arithmetic. - Institute of Electrical and Electronic Engineers, New York (1985)
-- The - Unicode Consortium. The Unicode Standard, Version 3.0, defined by: - The Unicode Standard, Version 3.0 (Boston, MA, Addison-Wesley, - 2000. ISBN 0-201-61635-5)
-- Unicode - Inc. (1998), Unicode Technical Report #15: Unicode Normalization - Forms
-ISO 8601:2004(E) Data elements and interchange -formats – Information interchange -- Representation of dates and times
RFC 1738 “Uniform Resource Locators (URL)”, available at -<http://tools.ietf.org/html/rfc1738>
RFC 2396 “Uniform Resource Identifiers (URI): Generic Syntax”, -available at -<http://tools.ietf.org/html/rfc2396>
RFC 3629 “UTF-8, a transformation format of ISO 10646”, available at -<http://tools.ietf.org/html/rfc3629>
RFC 4627 “The application/json Media Type for JavaScript Object -Notation (JSON)“ , available at -<http://tools.ietf.org/html/rfc4627>
-
-‟Ex igne vita”
- - - - + \ No newline at end of file diff --git a/introduction.html b/introduction.html new file mode 100644 index 0000000..91ecb50 --- /dev/null +++ b/introduction.html @@ -0,0 +1,79 @@ + +‟Ex igne vita”
+ +This Ecma Standard is based on several originating technologies, the most + well known being JavaScript (Netscape) and JScript (Microsoft). The + language was invented by Brendan Eich at Netscape and first appeared + in that company’s Navigator 2.0 browser. It has appeared in all + subsequent browsers from Netscape and in all browsers from Microsoft + starting with Internet Explorer 3.0.
++ The + development of this Standard started in November 1996. The first + edition of this Ecma Standard was adopted by the Ecma General + Assembly of June 1997.
++ That + Ecma Standard was submitted to ISO/IEC JTC 1 for adoption under the + fast-track procedure, and approved as international standard ISO/IEC + 16262, in April 1998. The Ecma General Assembly of June 1998 + approved the second edition of ECMA-262 to keep it fully aligned + with ISO/IEC 16262. Changes between the first and the second edition + are editorial in nature.
++ The + third edition of the Standard introduced powerful regular + expressions, better string handling, new control statements, + try/catch exception handling, tighter definition of errors, + formatting for numeric output and minor changes in anticipation of + forthcoming internationalisation + facilities and future language growth. The third edition of the + ECMAScript standard was adopted by the Ecma General Assembly of + December 1999 and published as ISO/IEC 16262:2002 in June 2002.
++ Since + publication of the third edition, ECMAScript has achieved massive + adoption in conjunction with the World Wide Web where it has become + the programming language that is supported by essentially all web + browsers. Significant work was done to + develop a fourth edition of ECMAScript. Although that work was not + completed and not published + [1] + + as the fourth edition of ECMAScript, it informs continuing evolution + of the language. The present fifth edition of ECMAScript (published + as ECMA-262 5th + edition) codifies de facto interpretations of the language + specification that have become common among browser implementations + and adds support for new features that have emerged since the + publication of the third edition. Such features include accessor + properties, reflective creation and inspection of objects, program + control of property attributes, additional array manipulation + functions, support for the JSON object encoding format, and a strict + mode that provides enhanced error checking and program security.
++ ECMAScript + is a vibrant language and the evolution of the language is not + complete. Significant technical enhancement will continue with + future editions of this specification.
+1 + Note: Please note that for ECMAScript Edition 4 the Ecma standard + number “ECMA-262 Edition 4” was reserved but not used in the + Ecma publication process. Therefore “ECMA-262 Edition 4” as an + Ecma International publication does not exist.
+toc · single-page version · source
') +alt_version_notice.getparent().replace(alt_version_notice, replacement) + +pages.append( (index_page, page, 'Front cover') ) + +# Section/subsection pages: + +def should_split(e): + if e.tag == 'h2': return True + if e.get('id') in split_exceptions: return True + if e.tag == 'div': + c = e.getchildren() + if len(c): + if c[0].tag == 'h2': return True + if c[0].get('id') in split_exceptions: return True + return False + +def get_heading_text_and_id(e): + if e.tag == 'div': + node = e.getchildren()[0] + else: + node = e + title = re.sub('\s+', ' ', etree.tostring(node, encoding=unicode, method='text').strip()) + return title, node.get('id') + +for heading in child_iter: + # Handle the heading for this section + title, name = get_heading_text_and_id(heading) + if name == index_page: name = 'section-%s' % name + print ' <%s> %s - %s' % (heading.tag, name, title) + + page = deepcopy(doc) + add_class(page.getroot(), 'split chapter') + + anno_script = etree.XML('') + # append a script element for the anno script + page.getroot().append(anno_script); + + page_body = page.find('body') + + page.find('//title').text = title + u' \u2014 ' + doctitle + + # Add the header + page_body.append(deepcopy(short_header)) + + # Add the page heading + page_body.append(deepcopy(heading)) + extract_ids(name, heading) + + # Keep copying stuff from the source, until we reach the end of the + # document or find a header to split on + e = heading + while e.getnext() is not None and not should_split(e.getnext()): + e = child_iter.next() + extract_ids(name, e) + page_body.append(deepcopy(e)) + + pages.append( (name, page, title) ) + +# Fix the links, and add some navigation: + +for i in range(len(pages)): + name, doc, title = pages[i] + + fix_refs(name, doc) + + if name == index_page: continue # don't add nav links to the TOC page + + head = doc.find('head') + + if w3c: + nav = etree.Element('div') # HTML 4 compatibility + else: + nav = etree.Element('nav') + nav.text = '\n ' + nav.tail = '\n\n ' + + if i > 1: + href = get_page_filename(pages[i-1][0]) + title = pages[i-1][2] + title = title[:title.find("#")] + a = etree.XML(u'\u2190 %s' % (href, title)) + a.tail = u' \u2013\n ' + nav.append(a) + link = etree.XML('' % (href, title)) + link.tail = '\n ' + head.append(link) + + a = etree.XML('TOC' % index_page) + a.tail = '\n ' + nav.append(a) + link = etree.XML('' % index_page) + link.tail = '\n ' + head.append(link) + + if i != len(pages)-1: + href = get_page_filename(pages[i+1][0]) + title = pages[i+1][2] + title = title[:title.find("#")] + a = etree.XML(u'%s \u2192' % (href, title)) + a.tail = '\n ' + nav.append(a) + a.getprevious().tail = u' \u2013\n ' + link = etree.XML('' % (href, title)) + link.tail = '\n ' + head.append(link) + + # Add a subset of the TOC to each page: + + # Find the items that are on this page + new_toc_items = [ (d, id, e) for (d, id, e) in toc_items if id_pages[id] == name ] + if len(new_toc_items) > 1: # don't bother if there's only one item, since it looks silly + # Construct the new toc
+
+‟Ex igne vita”
+ + +toc · multi-page version · source
+NOTE This is not the normative ECMAScript Language specification.
+The normative ECMAScript specification (ECMA 262) is a PDF file maintained by +ECMA TC39 and is available at the following location:
+ +http://www.ecma-international.org/publications/standards/Ecma-262.htm
+This document is an annotated, +hyperlinked, HTML version + of Edition 5.1 of the ECMAScript Specification. + It’s provided as a means for making annotations to the spec available + online, in HTML and at “point of use”, for the purposes of + explaining the spec and assisting in its implementation that are + allowed for in the spec license.
+ +This version is maintained by Michael[tm] Smith + <sideshowbarker@gmail.com>
+ +No copyright is asserted on the front matter of this version (everything + up to and including the Table of Contents). However, any reuse of the body + text from this document (everything following the Table of Contents) must + adhere to the terms of the license on the normative spec. See the spec’s + copyright + notice and + license + statement.
+ +The complete source for this version is available at + https://github.com/es5/es5.github.com
+ +To view annotations for a particular section of the present + document, follow the hyperlinks + marked Ⓐ, Ⓓ, Ⓡ, Ⓖ, Ⓔ, and ① in + the section headings. The different types of annotations provided by each + of those are as follows:
+ +Jason Orendorff was the first to make a usefully hyperlinked +version of the ECMAScript spec. The hyperlinking here just follows +his example. His version remains available at +http://people.mozilla.org/~jorendorff/es5.html
+ +© Ecma International 2010
+"DISCLAIMER
+ This + document may be copied and furnished to others, and derivative + works that comment on or otherwise explain it or assist in its + implementation may be prepared, copied, published, and distributed, + in whole or in part, without restriction of any kind, provided that + the above copyright notice and this section are included on all such + copies and derivative works. However, this document itself may not + be modified in any way, including by removing the copyright notice + or references to Ecma International, except as needed for the + purpose of developing any document or deliverable produced by Ecma + International. +The + limited permissions are granted through the standardization phase + and will not be revoked by Ecma International or its successors or + assigns during this time.
+This + document and the information contained herein is provided on an "AS + IS" basis and ECMA INTERNATIONAL DISCLAIMS ALL WARRANTIES, + EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT + THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY OWNERSHIP + RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS + FOR A PARTICULAR PURPOSE."
+This Ecma Standard is based on several originating technologies, the most + well known being JavaScript (Netscape) and JScript (Microsoft). The + language was invented by Brendan Eich at Netscape and first appeared + in that company’s Navigator 2.0 browser. It has appeared in all + subsequent browsers from Netscape and in all browsers from Microsoft + starting with Internet Explorer 3.0.
++ The + development of this Standard started in November 1996. The first + edition of this Ecma Standard was adopted by the Ecma General + Assembly of June 1997.
++ That + Ecma Standard was submitted to ISO/IEC JTC 1 for adoption under the + fast-track procedure, and approved as international standard ISO/IEC + 16262, in April 1998. The Ecma General Assembly of June 1998 + approved the second edition of ECMA-262 to keep it fully aligned + with ISO/IEC 16262. Changes between the first and the second edition + are editorial in nature.
++ The + third edition of the Standard introduced powerful regular + expressions, better string handling, new control statements, + try/catch exception handling, tighter definition of errors, + formatting for numeric output and minor changes in anticipation of + forthcoming internationalisation + facilities and future language growth. The third edition of the + ECMAScript standard was adopted by the Ecma General Assembly of + December 1999 and published as ISO/IEC 16262:2002 in June 2002.
++ Since + publication of the third edition, ECMAScript has achieved massive + adoption in conjunction with the World Wide Web where it has become + the programming language that is supported by essentially all web + browsers. Significant work was done to + develop a fourth edition of ECMAScript. Although that work was not + completed and not published + [1] + + as the fourth edition of ECMAScript, it informs continuing evolution + of the language. The present fifth edition of ECMAScript (published + as ECMA-262 5th + edition) codifies de facto interpretations of the language + specification that have become common among browser implementations + and adds support for new features that have emerged since the + publication of the third edition. Such features include accessor + properties, reflective creation and inspection of objects, program + control of property attributes, additional array manipulation + functions, support for the JSON object encoding format, and a strict + mode that provides enhanced error checking and program security.
++ ECMAScript + is a vibrant language and the evolution of the language is not + complete. Significant technical enhancement will continue with + future editions of this specification.
+1 + Note: Please note that for ECMAScript Edition 4 the Ecma standard + number “ECMA-262 Edition 4” was reserved but not used in the + Ecma publication process. Therefore “ECMA-262 Edition 4” as an + Ecma International publication does not exist.
++ This + Standard defines the ECMAScript scripting language.
++ A + conforming implementation of ECMAScript must provide and support all + the types, values, objects, properties, functions, and program + syntax and semantics described in this specification.
++ A + conforming implementation of this International standard shall + interpret characters in conformance with the Unicode Standard, + Version 3.0 or later and ISO/IEC 10646-1 with either UCS-2 or UTF-16 + as the adopted encoding form, implementation level 3. If the adopted + ISO/IEC 10646-1 subset is not otherwise specified, it is presumed to + be the BMP subset, collection 300. If the adopted encoding form is + not otherwise specified, it presumed to be the UTF-16 encoding form.
++ A + conforming implementation of ECMAScript is permitted to provide + additional types, values, objects, properties, and functions beyond + those described in this specification. In particular, a conforming + implementation of ECMAScript is permitted to provide properties not + described in this specification, and values for those properties, + for objects that are described in this specification.
++ A + conforming implementation of ECMAScript is permitted to support + program and regular expression syntax not described in this + specification. In particular, a conforming implementation of + ECMAScript is permitted to support program syntax that makes use of + the “future reserved words” listed in 7.6.1.2 of this + specification.
++ The + following referenced documents are indispensable for the application + of this document. For dated references, only the edition cited + applies. For undated references, the latest edition of the + referenced document (including any amendments) applies.
++ ISO/IEC 9899:1996, + Programming Languages – C, including amendment 1 and technical + corrigenda 1 and 2
++ ISO/IEC 10646-1:1993, + Information Technology – Universal Multiple-Octet Coded Character + Set (UCS) plus its amendments and corrigenda
++ This + section contains a non-normative overview of the ECMAScript + language.
++ ECMAScript + is an object-oriented programming language for performing + computations and manipulating computational objects within a host + environment. ECMAScript as defined here is not intended to be + computationally self-sufficient; indeed, there are no provisions in + this specification for input of external data or output of computed + results. Instead, it is expected that the computational environment + of an ECMAScript program will provide not only the objects and other + facilities described in this specification but also certain + environment-specific host objects, whose description and + behaviour are beyond the scope of this specification except to + indicate that they may provide certain properties that can be + accessed and certain functions that can be called from an ECMAScript + program.
++ A + scripting language is a programming language that is + used to manipulate, customise, and automate the facilities of an + existing system. In such systems, useful functionality is already + available through a user interface, and the scripting language is a + mechanism for exposing that functionality to program control. In + this way, the existing system is said to provide a host environment + of objects and facilities, which completes the capabilities of the + scripting language. A scripting language is intended for use by both + professional and non-professional programmers.
++ ECMAScript + was originally designed to be a Web scripting language, + providing a mechanism to enliven Web pages in browsers and to + perform server computation as part of a Web-based client-server + architecture. ECMAScript can provide core scripting capabilities for + a variety of host environments, and therefore the core scripting + language is specified in this document apart from any particular + host environment.
++ Some + of the facilities of ECMAScript are similar to those used in other + programming languages; in particular Java™, + Self, and Scheme as described in:
++ Gosling, + James, Bill Joy and Guy Steele. The Java™ + Language Specification. Addison Wesley Publishing Co., 1996.
++ Ungar, + David, and Smith, Randall B. Self: The Power of Simplicity. OOPSLA + '87 Conference Proceedings, pp. 227–241, Orlando, FL, October + 1987.
++ IEEE + Standard for the Scheme Programming Language. IEEE Std 1178-1990.
++ A web + browser provides an ECMAScript host environment for client-side + computation including, for instance, objects that represent windows, + menus, pop-ups, dialog boxes, text areas, anchors, frames, history, + cookies, and input/output. Further, the host environment provides a + means to attach scripting code to events such as change of focus, + page and image loading, unloading, error and abort, selection, form + submission, and mouse actions. Scripting code appears within the + HTML and the displayed page is a combination of user interface + elements and fixed and computed text and images. The scripting code + is reactive to user interaction and there is no need for a main + program.
++ A web + server provides a different host environment for server-side + computation including objects representing requests, clients, and + files; and mechanisms to lock and share data. By using browser-side + and server-side scripting together, it is possible to distribute + computation between the client and server while providing a + customised user interface for a Web-based application.
++ Each + Web browser and server that supports ECMAScript supplies its own + host environment, completing the ECMAScript execution environment.
++ The + following is an informal overview of ECMAScript—not all parts of + the language are described. This overview is not part of the + standard proper.
++ ECMAScript + is object-based: basic language and host facilities are provided by + objects, and an ECMAScript program is a cluster of communicating + objects. An ECMAScript object is a collection of + properties each with zero or more attributes + that determine how each property can be used—for example, when the + Writable attribute for a property is set to false, any + attempt by executed ECMAScript code to change the value of the + property fails. Properties are containers that hold other objects, + primitive values, or functions. A + primitive value is a member of one of the following built-in types: +Undefined, +Null, +Boolean, +Number, +and +String; +an object is a member of the remaining built-in type +Object; and a function is a + callable object. A function that + is associated with an object via a property is a method.
++ ECMAScript + defines a collection of built-in objects that round + out the definition of ECMAScript entities. These built-in objects + include the global object, the Object object, the Function object, the Array object, the String object, the + Boolean object, the Number object, the Math object, the Date object, the RegExp object, the JSON object, and the Error objects Error, EvalError, RangeError, + ReferenceError, SyntaxError, TypeError and URIError.
++ ECMAScript + also defines a set of built-in operators. ECMAScript + operators include various +unary operations, +multiplicative operators, +additive operators, +bitwise shift operators, +relational operators, +equality operators, +binary bitwise operators, +binary logical operators, +assignment operators, and +the comma operator.
++ ECMAScript + syntax intentionally resembles Java syntax. ECMAScript syntax + is relaxed to enable it to serve as an easy-to-use scripting + language. For example, a variable is not required to have its type + declared nor are types associated with properties, and defined + functions are not required to have their declarations appear + textually before calls to them.
+
+ ECMAScript
+ does not use classes such as those in C++, Smalltalk, or Java.
+ Instead objects may be created in various ways including via a
+ literal notation or via constructors which create
+ objects and then execute code that initialises all or part of them
+ by assigning initial values to their properties. Each constructor is
+ a function that has a property named “prototype”
+ that is used to implement prototype-based inheritance
+ and shared properties. Objects are created by using
+ constructors in new expressions; for example, new
+ Date(2009,11) creates a new Date object. Invoking
+ a constructor without using new has consequences that depend
+ on the constructor. For example, Date()
+ produces a string representation of the current date and time rather
+ than an object.
+ Every
+ object created by a constructor has an implicit reference (called
+ the object’s prototype) to the value of its constructor’s
+ “prototype”
+ property. Furthermore, a prototype may have a non-null implicit
+ reference to its prototype, and so on; this is called the prototype
+ chain. When a reference is made to a property in an object, that
+ reference is to the property of that name in the first object in the
+ prototype chain that contains a property of that name. In other
+ words, first the object mentioned directly is examined for such a
+ property; if that object contains the named property, that is the
+ property to which the reference refers; if that object does not
+ contain the named property, the prototype for that object is
+ examined next; and so on.
Figure 1 — Object/Prototype Relationships
++ In a + class-based object-oriented language, in general, state is carried + by instances, methods are carried by classes, and inheritance is + only of structure and behaviour. In ECMAScript, the state and + methods are carried by objects, and structure, behaviour, and state + are all inherited.
++ All + objects that do not directly contain a particular property that + their prototype contains share that property and its value. Figure 1 + illustrates this:
+
+ CF
+ is a constructor (and also an object). Five objects have been
+ created by using new
+ expressions: cf1, cf2,
+ cf3, cf4, and cf5.
+ Each of these objects contains properties named q1
+ and q2. The dashed lines
+ represent the implicit prototype relationship; so, for example,
+ cf3’s prototype is CFp.
+ The constructor, CF, has two properties itself, named P1
+ and P2, which are not
+ visible to CFp, cf1,
+ cf2, cf3, cf4,
+ or cf5. The property named CFP1
+ in CFp is shared by cf1,
+ cf2, cf3, cf4,
+ and cf5 (but not by CF), as are any
+ properties found in CFp’s implicit
+ prototype chain that are not named q1,
+ q2, or CFP1.
+ Notice that there is no implicit prototype link between CF
+ and CFp.
+ Unlike + class-based object languages, properties can be added to objects + dynamically by assigning values to them. That is, constructors are + not required to name or assign values to all or any of the + constructed object’s properties. In the above diagram, one could + add a new shared property for cf1, cf2, + cf3, cf4, and cf5 + by assigning a new value to the property in CFp.
++ The + ECMAScript Language recognizes the possibility that some users of + the language may wish to restrict their usage of some features + available in the language. They might do so in the interests of + security, to avoid what they consider to be error-prone features, to + get enhanced error checking, or for other reasons of their choosing. + In support of this possibility, ECMAScript defines a strict variant + of the language. The strict variant of the language excludes some + specific syntactic and semantic features of the regular ECMAScript + language and modifies the detailed semantics of some features. The + strict variant also specifies additional error conditions that must + be reported by throwing error exceptions in situations that are not + specified as errors by the non-strict form of the language.
++ The + strict variant of ECMAScript is commonly referred to as the strict + mode of the language. Strict mode selection and use of the + strict mode syntax and semantics of ECMAScript is explicitly made at + the level of individual ECMAScript code units. Because strict mode + is selected at the level of a syntactic code unit, strict mode only + imposes restrictions that have local effect within such a code unit. + Strict mode does not restrict or modify any aspect of the ECMAScript + semantics that must operate consistently across multiple code units. + A complete ECMAScript program may be composed for both strict mode + and non-strict mode ECMAScript code units. In this case, strict mode + only applies when actually executing code that is defined within a + strict mode code unit. +
++ In + order to conform to this specification, an ECMAScript implementation + must implement both the full unrestricted ECMAScript language and + the strict mode variant of the ECMAScript language as defined by + this specification. In addition, an implementation must support the + combination of unrestricted and strict mode code units into a single + composite program.
++ For + the purposes of this document, the following terms and definitions + apply.
++ set + of data values as defined in Clause 8 of this specification.
++ member + of one of the types Undefined, Null, Boolean, Number, or String as + defined in Clause 8.
+NOTE A + primitive value is a datum that is represented directly at the + lowest level of the language implementation.
++ member + of the type Object.
+NOTE An + object is a collection of properties and has a single prototype + object. The prototype may be the null value.
++ Function + object that creates and initialises objects.
+NOTE The
+ value of a constructor’s “prototype”
+ property is a prototype object that is used to implement inheritance
+ and shared properties.
+ object + that provides shared properties for other objects.
+NOTE When
+ a constructor creates an object, that object implicitly references
+ the constructor’s “prototype”
+ property for the purpose of resolving property references. The
+ constructor’s “prototype”
+ property can be referenced by the program expression
+ constructor.prototype,
+ and properties added to an object’s prototype are shared, through
+ inheritance, by all objects sharing the prototype. Alternatively, a
+ new object may be created with an explicitly specified prototype by
+ using the Object.create
+ built-in function.
+ object + in an ECMAScript implementation whose semantics are fully defined by + this specification rather than by the host environment.
+NOTE Standard + native objects are defined in this specification. Some native + objects are built-in; others may be constructed during the course of + execution of an ECMAScript program.
++ object + supplied by an ECMAScript implementation, independent of the host + environment, that is present at the start of the execution of an + ECMAScript program.
+NOTE Standard + built-in objects are defined in this specification, and an + ECMAScript implementation may specify and define others. Every + built-in object is a native object. A built-in constructor + is a built-in object that is also a constructor.
++ object + supplied by the host environment to complete the execution + environment of ECMAScript.
+NOTE Any + object that is not native is a host object.
++ primitive value used when a variable has not been assigned a value.
++ type + whose sole value is the undefined value. +
++ primitive value that represents the intentional absence of any object value.
++ type + whose sole value is the null value.
++ member + of the Boolean type.
+NOTE There + are only two Boolean values, true and false.
++ type + consisting of the primitive values true and false.
+
+ member
+ of the Object type that is an instance of the standard built-in
+ Boolean
+ constructor.
NOTE A
+ Boolean object is created by using the Boolean
+ constructor in a new
+ expression, supplying a Boolean value as an argument. The resulting
+ object has an internal property whose value is the Boolean value. A
+ Boolean object can be coerced to a Boolean value.
+ primitive value that is a finite ordered sequence of zero or more 16-bit + unsigned integer. +
+NOTE A + String value is a member of the String type. Each integer value in + the sequence usually represents a single 16-bit unit of UTF-16 text. + However, ECMAScript does not place any restrictions or requirements + on the values except that they must be 16-bit unsigned integers.
++ set + of all possible String values.
+
+ member
+ of the Object type that is an instance of the standard built-in
+ String
+ constructor.
NOTE A
+ String object is created by using the String
+ constructor in a new
+ expression, supplying a String value as an argument. The resulting
+ object has an internal property whose value is the String value. A
+ String object can be coerced to a String value by calling the String
+ constructor as a function (15.5.1).
+ primitive value corresponding to a double-precision 64-bit binary format IEEE + 754 value.
+NOTE A + Number value is a member of the Number type and is a direct + representation of a number.
++ set + of all possible Number values including the special “Not-a-Number” + (NaN) values, positive infinity, and negative infinity.
+
+ member
+ of the Object type that is an instance of the standard built-in
+ Number
+ constructor.
NOTE A
+ Number object is created by using the Number
+ constructor in a new
+ expression, supplying a Number value as an argument. The resulting
+ object has an internal property whose value is the Number value. A
+ Number object can be coerced to a Number value by calling the Number
+ constructor as a function (15.7.1).
+ Number + value that is the + positive infinite Number value.
++ Number + value that is a IEEE 754 “Not-a-Number” value.
+
+ member
+ of the Object type that is an instance of the standard built-in
+ Function
+ constructor and that may be invoked as a subroutine.
NOTE In + addition to its named properties, a function contains executable + code and state that determine how it behaves when invoked. A + function’s code may or may not be written in ECMAScript.
++ built-in + object that is a function.
+NOTE Examples
+ of built-in functions include parseInt
+ and Math.exp. An
+ implementation may provide implementation-dependent built-in
+ functions that are not described in this specification.
+
+
+ association + between a name and a value that is a part of an object.
+NOTE Depending + upon the form of the property the value may be represented either + directly as a data value (a primitive value, an object, or a + function object) or indirectly by a pair of accessor functions.
++ function + that is the value of a property.
+NOTE When + a function is called as a method of an object, the object is passed + to the function as its this value.
++ method + that is a built-in function.
+NOTE Standard + built-in methods are defined in this specification, and an + ECMAScript implementation may specify and provide other additional + built-in methods. +
++ internal + value that defines some characteristic of a property.
++ property + that is directly contained by its object.
++ property + of an object that is not an own property but is a property (either + own or inherited) of the object’s prototype.
++ A + context-free grammar consists of a number of productions. + Each production has an abstract symbol called a nonterminal + as its left-hand side, and a sequence of zero or more + nonterminal and terminal symbols as its right-hand side. + For each grammar, the terminal symbols are drawn from a specified + alphabet.
++ Starting + from a sentence consisting of a single distinguished nonterminal, + called the goal symbol, a given context-free grammar + specifies a language, namely, the (perhaps infinite) set of + possible sequences of terminal symbols that can result from + repeatedly replacing any nonterminal in the sequence with a + right-hand side of a production for which the nonterminal is the + left-hand side.
++ A + lexical grammar for ECMAScript is given in clause 7. This + grammar has as its terminal symbols characters (Unicode code units) + that conform to the rules for SourceCharacter + defined in Clause 6. It defines a set of productions, starting from + the goal symbol InputElementDiv + or InputElementRegExp, + that describe how sequences of such characters are translated into a + sequence of input elements.
+
+ Input
+ elements other than white space and comments form the terminal
+ symbols for the syntactic grammar for ECMAScript and are called
+ ECMAScript tokens. These tokens are the reserved words,
+ identifiers, literals, and punctuators of the ECMAScript language.
+ Moreover, line terminators, although not considered to be tokens,
+ also become part of the stream of input elements and guide the
+ process of automatic semicolon insertion (7.9). Simple white space
+ and single-line comments are discarded and do not appear in the
+ stream of input elements for the syntactic grammar. A
+ MultiLineComment
+ (that is, a comment of the form “/*…*/”
+ regardless of whether it spans more than one line) is likewise
+ simply discarded if it contains no line terminator; but if a
+ MultiLineComment
+ contains one or more line terminators, then it is replaced by a
+ single line terminator, which becomes part of the stream of input
+ elements for the syntactic grammar.
+ A + RegExp grammar for ECMAScript is given in 15.10. This grammar + also has as its terminal symbols the characters as defined by + SourceCharacter. + It defines a set of productions, starting from the goal symbol + Pattern, that + describe how sequences of characters are translated into regular + expression patterns.
++ Productions + of the lexical and RegExp grammars are distinguished by having two + colons “::” as separating punctuation. The lexical and + RegExp grammars share some productions.
++ Another + grammar is used for translating Strings into numeric values. This + grammar is similar to the part of the lexical grammar having to do + with numeric literals and has as its terminal symbols + SourceCharacter. + This grammar appears in 9.3.1.
++ Productions + of the numeric string grammar are distinguished by having three + colons “:::” as punctuation.
++ The + syntactic grammar for ECMAScript is given in clauses 11, 12, + 13 and 14. This grammar has ECMAScript tokens defined by the lexical + grammar as its terminal symbols (5.1.2). It defines a set of + productions, starting from the goal symbol Program, + that describe how sequences of tokens can form syntactically correct + ECMAScript programs.
++ When + a stream of characters is to be parsed as an ECMAScript program, it + is first converted to a stream of input elements by repeated + application of the lexical grammar; this stream of input elements is + then parsed by a single application of the syntactic grammar. The + program is syntactically in error if the tokens in the stream of + input elements cannot be parsed as a single instance of the goal + nonterminal Program, + with no tokens left over.
++ Productions + of the syntactic grammar are distinguished by having just one colon + “:” as punctuation.
++ The + syntactic grammar as presented in clauses 11, 12, 13 and 14 is + actually not a complete account of which token sequences are + accepted as correct ECMAScript programs. Certain additional token + sequences are also accepted, namely, those that would be described + by the grammar if only semicolons were added to the sequence in + certain places (such as before line terminator characters). + Furthermore, certain token sequences that are described by the + grammar are not considered acceptable if a terminator character + appears in certain “awkward” places.
++ The + JSON grammar is used to translate a String describing a set of + ECMAScript objects into actual objects. The JSON grammar is given in + 15.12.1.
++ The + JSON grammar consists of the JSON lexical grammar and the JSON + syntactic grammar. The JSON lexical grammar is used to translate + character sequences into tokens and is similar to parts of the + ECMAScript lexical grammar. The JSON syntactic grammar describes how + sequences of tokens from the JSON lexical grammar can form + syntactically correct JSON object descriptions.
++ Productions + of the JSON lexical grammar are distinguished by having two colons + “::” as separating punctuation. The JSON lexical grammar + uses some productions from the ECMAScript lexical grammar. The JSON + syntactic grammar is similar to parts of the ECMAScript syntactic + grammar. Productions of the JSON syntactic grammar are distinguished + by using one colon “:” as separating punctuation.
+
+ Terminal
+ symbols of the lexical and string grammars, and some of the terminal
+ symbols of the syntactic grammar, are shown in fixed
+ width font, both in the productions of the grammars and
+ throughout this specification whenever the text directly refers to
+ such a terminal symbol. These are to appear in a program exactly as
+ written. All terminal symbol characters specified in this way are to
+ be understood as the appropriate Unicode character from the ASCII
+ range, as opposed to any similar-looking characters from other
+ Unicode ranges.
+ Nonterminal + symbols are shown in italic + type. The definition of a nonterminal is introduced by the name of + the nonterminal being defined followed by one or more colons. (The + number of colons indicates to which grammar the production belongs.) + One or more alternative right-hand sides for the nonterminal then + follow on succeeding lines. For example, the syntactic definition:
++ WhileStatement :
+
+ while
+ (
+ Expression )
+ Statement
+ states
+ that the nonterminal WhileStatement
+ represents the token while,
+ followed by a left parenthesis token, followed by an Expression,
+ followed by a right parenthesis token, followed by a Statement.
+ The occurrences of Expression
+ and Statement are
+ themselves nonterminals. As another example, the syntactic
+ definition:
+ ArgumentList + :
+
+ AssignmentExpression
ArgumentList
+ , AssignmentExpression
+ states + that an ArgumentList + may represent either a single AssignmentExpression + or an ArgumentList, + followed by a comma, followed by an AssignmentExpression. + This definition of ArgumentList + is recursive, that is, it is defined in terms of itself. The result + is that an ArgumentList + may contain any positive number of arguments, separated by commas, + where each argument expression is an AssignmentExpression. + Such recursive definitions of nonterminals are common.
++ The + subscripted suffix “opt”, which may appear after a + terminal or nonterminal, indicates an optional symbol. The + alternative containing the optional symbol actually specifies two + right-hand sides, one that omits the optional element and one that + includes it. This means that:
++ VariableDeclaration + :
++ Identifier + Initialiseropt
++ is a + convenient abbreviation for:
++ VariableDeclaration + :
+
+ Identifier
Identifier
+ Initialiser
+ and + that:
++ IterationStatement + :
+
+ for
+ ( ExpressionNoInopt
+ ; Expressionopt
+ ; Expressionopt
+ ) Statement
+ is a + convenient abbreviation for:
++ IterationStatement + :
+
+ for
+ ( ; Expressionopt
+ ; Expressionopt
+ ) Statement
for
+ (
+ ; Expressionopt
+ ; Expressionopt
+ ) Statement
+ which + in turn is an abbreviation for:
++ IterationStatement + :
+
+ for
+ ( ; ; Expressionopt
+ ) Statement
for
+ ( ;
+ ; Expressionopt
+ )
+ Statement
for
+ (
+ ; ; Expressionopt
+ )
+ Statement
for
+ (
+ ; Expression
+ ; Expressionopt
+ )
+ Statement
+ which + in turn is an abbreviation for:
++ IterationStatement + :
+
+ for
+ ( ; ; ) Statementfor
+ ( ; ; Expression
+ ) Statement
for
+ ( ;
+ ; ) Statement
for
+ ( ;
+ ; Expression
+ ) Statement
for
+ (;
+ ; ) Statement
for
+ (;
+ ; Expression
+ ) Statement
for
+ (;
+ Expression
+ ; ) Statement
for
+ (;
+ Expression
+ ; Expression
+ ) Statement
+ so + the nonterminal IterationStatement + actually has eight alternative right-hand sides.
++ If + the phrase “[empty]” + appears as the right-hand side of a production, it indicates that + the production's right-hand side contains no terminals or + nonterminals.
++ If + the phrase + “[lookahead ∉ set]” + appears in the right-hand side of a production, it indicates that + the production may not be used if the immediately following input + token is a member of the given set. + The set can be + written as a list of terminals enclosed in curly braces. For + convenience, the set can also be written as a nonterminal, in which + case it represents the set of all terminals to which that + nonterminal could expand. For example, given the definitions
++ DecimalDigit :: + one + of
+
+ 0
+ 1 2 3 4 5 6 7 8 9
+ DecimalDigits + ::
+
+ DecimalDigit
DecimalDigits
+ DecimalDigit
+ the + definition
++ LookaheadExample + ::
+
+ n
+ [lookahead
+ ∉
+ {1 , 3 , 5 , 7 , 9}]DecimalDigits
DecimalDigit [lookahead
+ ∉
+ DecimalDigit ]
+ matches
+ either the letter n
+ followed by one or more decimal digits the first of which is even,
+ or a decimal digit not followed by another decimal digit.
+ If the phrase “[no LineTerminator here]” appears in the right-hand side of a production of + the syntactic grammar, it indicates that the production is a restricted production: it may not be used if a LineTerminator + occurs in the input stream at the indicated position. For example, + the production:
++ ReturnStatement + :
+
+ return
+ [no LineTerminator here]
+ Expressionopt ;
+ indicates
+ that the production may not be used if a LineTerminator
+ occurs in the program between the return
+ token and the Expression.
+ Unless + the presence of a LineTerminator + is forbidden by a restricted production, any number of occurrences + of LineTerminator + may appear between any two consecutive tokens in the stream of input + elements without affecting the syntactic acceptability of the + program.
++ When + the words “one of” follow the colon(s) in a grammar + definition, they signify that each of the terminal symbols on the + following line or lines is an alternative definition. For example, + the lexical grammar for ECMAScript contains the production:
++ NonZeroDigit :: + one + of
+
+ 1
+ 2 3 4 5 6 7 8 9
+ which + is merely a convenient abbreviation for:
++ NonZeroDigit ::
+
+ 1
2
3
4
5
6
7
8
9
+ When + an alternative in a production of the lexical grammar or the numeric + string grammar appears to be a multi-character token, it represents + the sequence of characters that would make up such a token.
++ The + right-hand side of a production may specify that certain expansions + are not permitted by using the phrase “but not” and then + indicating the expansions to be excluded. For example, the + production:
++ Identifier + ::
++ IdentifierName but + not ReservedWord
++ means + that the nonterminal Identifier + may be replaced by any sequence of characters that could replace + IdentifierName + provided that the same sequence of characters could not replace + ReservedWord.
++ Finally, + a few nonterminal symbols are described by a descriptive phrase in + sans-serif type in cases where it would be impractical to list all + the alternatives:
++ SourceCharacter + ::
++ any + Unicode code unit
++ The + specification often uses a numbered list to specify steps in an + algorithm. These algorithms are used to precisely specify the + required semantics of ECMAScript language constructs. The algorithms + are not intended to imply the use of any specific implementation + technique. In practice, there may be more efficient algorithms + available to implement a given feature.
++ In + order to facilitate their use in multiple parts of this + specification, some algorithms, called abstract operations, + are named and written in parameterized functional form so that they + may be referenced by name from within other algorithms.
++ When + an algorithm is to produce a value as a result, the directive + “return x” + is used to indicate that the result of the algorithm is the value of + x and that the + algorithm should terminate. The notation Result(n) + is used as shorthand for “the result + of step n”. + +
++ For + clarity of expression, algorithm steps may be subdivided into + sequential substeps. Substeps are indented and may themselves be + further divided into indented substeps. Outline numbering + conventions are used to identify substeps with the first level of + substeps labelled with lower case alphabetic characters and the + second level of substeps labelled with lower case roman numerals. + If more than three levels are required these rules repeat with the + fourth level using numeric labels. For example:
++ Top-level + step
++ Substep.
++ Substep + +
++ Subsubstep.
++ Subsubstep.
++ Subsubsubstep
++ Subsubsubsubstep
++ A + step or substep may be written as an “if” predicate that + conditions its substeps. In this case, the substeps are only + applied if the predicate is true. If a step or substep begins with + the word “else”, it is a predicate that is the negation of the + preceding “if” predicate step at the same level.
++ A + step may specify the iterative application of its substeps.
++ Mathematical + operations such as addition, subtraction, negation, multiplication, + division, and the mathematical functions defined later in this + clause should always be understood as computing exact mathematical + results on mathematical real numbers, which do not include + infinities and do not include a negative zero that is distinguished + from positive zero. Algorithms in this standard that model + floating-point arithmetic include explicit steps, where necessary, + to handle infinities and signed zero and to perform rounding. If a + mathematical operation or function is applied to a floating-point + number, it should be understood as being applied to the exact + mathematical value represented by that floating-point number; such a + floating-point number must be finite, and if it is +0 + or −0 + then the corresponding mathematical value is simply 0.
++ The + mathematical function abs(x) + yields the absolute value of x, + which is −x + if x is negative + (less than zero) and otherwise is x + itself.
++ The + mathematical function sign(x) + yields 1 if x + is positive and −1 + if x is negative. + The sign function is not used in this standard for cases when x + is zero.
++ The + notation “x modulo y” (y + must be finite and nonzero) computes a value k + of the same sign as y + (or zero) such that abs(k) + < abs(y) + and x−k = q + × + y for some + integer q.
++ The + mathematical function floor(x) + yields the largest integer (closest to positive infinity) that is + not larger than x.
+NOTE floor(x) + = x−(x + modulo 1).
++ If an + algorithm is defined to “throw an exception”, execution of the + algorithm is terminated and no result is returned. The calling + algorithms are also terminated, until an algorithm step is reached + that explicitly deals with the exception, using terminology such as + “If an exception was thrown…”. Once such an algorithm step has + been encountered the exception is no longer considered to have + occurred.
++ ECMAScript + source text is represented as a sequence of characters in the + Unicode character encoding, version 3.0 or later. The text is + expected to have been normalised to Unicode Normalised Form C + (canonical composition), as described in Unicode Technical Report + #15. Conforming ECMAScript implementations are not required to + perform any normalisation of text, or behave as though they were + performing normalisation of text, themselves. ECMAScript source + text is assumed to be a sequence of 16-bit code units for the + purposes of this specification. Such a source text may include + sequences of 16-bit code units that are not valid UTF-16 character + encodings. If an actual source text is encoded in a form other than + 16-bit code units it must be processed as if it was first convert to + UTF-16.
++ SourceCharacter ::
++ any + Unicode code unit
++ Throughout + the rest of this document, the phrase “code unit” and the word + “character” will be used to refer to a 16-bit unsigned value + used to represent a single 16-bit unit of text. The phrase “Unicode + character” will be used to refer to the abstract linguistic or + typographical unit represented by a single Unicode scalar value + (which may be longer than 16 bits and thus may be represented by + more than one code unit). The phrase “code point” refers to such + a Unicode scalar value. “Unicode character” only refers to + entities represented by single Unicode scalar values: the components + of a combining character sequence are still individual “Unicode + characters,” even though a user might think of the whole sequence + as a single character.
+
+ In
+ string literals, regular expression literals, and identifiers, any
+ character (code unit) may also be expressed as a Unicode escape
+ sequence consisting of six characters, namely \u
+ plus four hexadecimal digits. Within a comment, such an escape
+ sequence is effectively ignored as part of the comment. Within a
+ string literal or regular expression literal, the Unicode escape
+ sequence contributes one character to the value of the literal.
+ Within an identifier, the escape sequence contributes one character
+ to the identifier.
NOTE Although + this document sometimes refers to a “transformation” between a + “character” within a “string” and the 16-bit unsigned + integer that is the code unit of that character, there is actually + no transformation because a “character” within a “string” is + actually represented using that 16-bit unsigned value.
+
+ ECMAScript
+ differs from the Java programming language in the behaviour of
+ Unicode escape sequences. In a Java program, if the Unicode escape
+ sequence \u000A,
+ for example, occurs within a single-line comment, it is interpreted
+ as a line terminator (Unicode character 000A
+ is line feed) and therefore the next character is not part of the
+ comment. Similarly, if the Unicode escape sequence \u000A
+ occurs within a string literal in a Java program, it is likewise
+ interpreted as a line terminator, which is not allowed within a
+ string literal—one must write \n
+ instead of \u000A
+ to cause a line feed to be part of the string value of a string
+ literal. In an ECMAScript program, a Unicode escape sequence
+ occurring within a comment is never interpreted and therefore cannot
+ contribute to termination of the comment. Similarly, a Unicode
+ escape sequence occurring within a string literal in an ECMAScript
+ program always contributes a character to the String value of the
+ literal and is never interpreted as a line terminator or as a quote
+ mark that might terminate the string literal.
+ The + source text of an ECMAScript program is first converted into a + sequence of input elements, which are tokens, line terminators, + comments, or white space. The source text is scanned from left to + right, repeatedly taking the longest possible sequence of characters + as the next input element.
+
+ There
+ are two goal symbols for the lexical grammar. The InputElementDiv
+ symbol is used in those syntactic grammar contexts where a leading
+ division (/) or
+ division-assignment (/=)
+ operator is permitted. The InputElementRegExp
+ symbol is used in other syntactic grammar contexts.
NOTE There + are no syntactic grammar contexts where both a leading division or + division-assignment, and a leading RegularExpressionLiteral + are permitted. This is not affected by semicolon insertion (see + 7.9); in examples such as the following:
+
+ a
+ = b
/hi/g.exec(c).map(d);
+ where
+ the first non-whitespace, non-comment
+ character after a LineTerminator
+ is slash
+ (/)
+ and the syntactic context allows division
+ or division-assignment, no semicolon is inserted at the
+ LineTerminator.
+ That is, the above example is interpreted in the same way as:
+ a
+ = b / hi / g.exec(c).map(d);
+ Syntax
++ InputElementDiv ::
+
+ WhiteSpace
LineTerminator
Comment
Token
DivPunctuator
+
+ InputElementRegExp ::
+
+ WhiteSpace
LineTerminator
Comment
Token
RegularExpressionLiteral
+ The + Unicode format-control characters (i.e., the characters in category + “Cf” in the Unicode Character Database such as left-to-right + mark or right-to-left + mark) are control codes used to control the formatting of a + range of text in the absence of higher-level protocols for this + (such as mark-up languages).
++ It is + useful to allow format-control characters in source text to + facilitate editing and display. All format control characters may be + used within comments, and within string literals and regular + expression literals.
++ <ZWNJ> + and <ZWJ> are + format-control characters that are used to make necessary + distinctions when forming words or phrases in certain languages. In + ECMAScript source text, <ZWNJ> + and <ZWJ> + may also be used in an identifier after the first character. +
++ <BOM> + is a format-control character used primarily at the start of a text + to mark it as Unicode and to allow detection of the text's encoding + and byte order. <BOM> + characters intended for this purpose can sometimes also appear after + the start of a text, for example as a result of concatenating files. + <BOM> characters are treated as white space characters (see + 7.2). +
++ The + special treatment of certain format-control characters outside of + comments, string literals, and regular expression literals is + summarized in Table 1.
+|
+ + Code + Unit Value + |
+
+ + Name + |
+
+ + Formal + Name + |
+
+ + Usage + |
+
|
+
+ |
+
+ + Zero + width non-joiner + |
+
+ + <ZWNJ> + |
+
+ + IdentifierPart + |
+
|
+
+ |
+
+ + Zero + width joiner + |
+
+ + <ZWJ> + |
+
+ + IdentifierPart + |
+
|
+
+ |
+
+ + Byte + Order Mark + |
+
+ + <BOM> + |
+
+ + Whitespace + |
+
+ White + space characters are used to improve source text readability and to + separate tokens (indivisible lexical units) from each other, but are + otherwise insignificant. White space characters may occur between + any two tokens and at the start or end of input. White space + characters may also occur within a StringLiteral + or a RegularExpressionLiteral + (where they are considered significant characters forming part of + the literal value) or within a Comment, + but cannot appear within any other kind of token.
++ The + ECMAScript white space characters are listed in Table 2.
+|
+ + Code + Unit Value + |
+
+ + Name + |
+
+ + Formal + Name + |
+
|
+
+ |
+
+ + Tab + |
+
+ + <TAB> + |
+
|
+
+ |
+
+ + Vertical + Tab + |
+
+ + <VT> + |
+
|
+
+ |
+
+ + Form + Feed + |
+
+ + <FF> + |
+
|
+
+ |
+
+ + Space + |
+
+ + <SP> + |
+
|
+
+ |
+
+ + No-break + space + |
+
+ + <#x0a> + |
+
|
+
+ + Other + category “Zs” + |
+
+ + Byte + Order Mark ++ Any + other Unicode “space separator” + |
+
+ + <BOM> ++ <USP> + |
+
+ ECMAScript + implementations must recognize all of the white space characters + defined in Unicode 3.0. Later editions of the Unicode Standard may + define other white space characters. ECMAScript implementations may + recognize white space characters from later editions of the Unicode + Standard.
++ Syntax
++ WhiteSpace + ::
+
+ <TAB>
<VT>
<FF>
<SP>
<#x0a>
<BOM>
<USP>
+ Like + white space characters, line terminator characters are used to + improve source text readability and to separate tokens (indivisible + lexical units) from each other. However, unlike white space + characters, line terminators have some influence over the behaviour + of the syntactic grammar. In general, line terminators may occur + between any two tokens, but there are a few places where they are + forbidden by the syntactic grammar. Line terminators also affect the + process of automatic semicolon insertion (7.9). A line terminator + cannot occur within any token except a StringLiteral. + Line terminators may only occur within a StringLiteral + token as part of a LineContinuation. + +
++ A + line terminator can occur within a MultiLineComment + (7.4) but cannot occur within a SingleLineComment. + +
+
+ Line
+ terminators are included in the set of white space characters that
+ are matched by the \s
+ class in regular expressions.
+ The + ECMAScript line terminator characters are listed in Table 3.
+|
+ + Code + Unit Value + |
+
+ + Name + |
+
+ + Formal + Name + |
+
|
+
+ |
+
+ + Line + Feed + |
+
+ + <LF> + |
+
|
+
+ |
+
+ + Carriage + Return + + |
+
+ + <CR> + |
+
|
+
+ |
+
+ + Line + separator + |
+
+ + <LS> + |
+
|
+
+ |
+
+ + Paragraph + separator + |
+
+ + <PS> + |
+
+ Only + the characters in Table 3 are treated as line terminators. Other new + line or line breaking characters are treated as white space but not + as line terminators. The character sequence <CR><LF> is + commonly used as a line terminator. It should be considered a single + character for the purpose of reporting line numbers.
++ Syntax
++ LineTerminator ::
+
+ <LF>
<CR>
<LS>
<PS>
+ LineTerminatorSequence ::
+
+ <LF>
<CR>
+ [lookahead
+ ∉
+ <LF>
+ ]
<LS>
<PS>
<CR>
+ <LF>
+ Comments + can be either single or multi-line. Multi-line comments cannot nest.
+
+ Because
+ a single-line comment can contain any character except a
+ LineTerminator
+ character, and because of the general rule that a token is always as
+ long as possible, a single-line comment always consists of all
+ characters from the //
+ marker to the end of the line. However, the LineTerminator
+ at the end of the line is not considered to be part of the
+ single-line comment; it is recognised separately by the lexical
+ grammar and becomes part of the stream of input elements for the
+ syntactic grammar. This point is very important, because it implies
+ that the presence or absence of single-line comments does not affect
+ the process of automatic semicolon insertion (see 7.9).
+ Comments + behave like white space and are discarded except that, if a + MultiLineComment + contains a line terminator character, then the entire comment is + considered to be a LineTerminator + for purposes of parsing by the syntactic grammar.
++ Syntax
++ Comment ::
+
+ MultiLineComment
SingleLineComment
+ MultiLineComment ::
+
+ /* MultiLineCommentCharsopt */
+ MultiLineCommentChars ::
+
+ MultiLineNotAsteriskChar
+ MultiLineCommentCharsopt* PostAsteriskCommentCharsopt
+ PostAsteriskCommentChars ::
+
+ MultiLineNotForwardSlashOrAsteriskChar
+ MultiLineCommentCharsopt* PostAsteriskCommentCharsopt
+ MultiLineNotAsteriskChar + ::
+
+ SourceCharacter but
+ not asterisk *
+ MultiLineNotForwardSlashOrAsteriskChar ::
+
+ SourceCharacter
+ but
+ not forward-slash /
+ orasterisk *
+ SingleLineComment ::
+
+ // SingleLineCommentCharsopt
+ SingleLineCommentChars ::
++ SingleLineCommentChar + SingleLineCommentCharsopt
++ SingleLineCommentChar ::
++ SourceCharacter + but + not LineTerminator
++ Syntax
++ Token ::
+
+ IdentifierName
Punctuator
NumericLiteral
StringLiteral
+
NOTE The + DivPunctuator and + RegularExpressionLiteral + productions define tokens, but are not included in the Token + production.
++ Identifier + Names are tokens that are interpreted according to the grammar given + in the “Identifiers” section of chapter 5 of the Unicode + standard, with some small modifications. An Identifier + is an IdentifierName + that is not a ReservedWord + (see 7.6.1). The Unicode identifier grammar is based on both + normative and informative character categories specified by the + Unicode Standard. The characters in the specified categories in + version 3.0 of the Unicode standard must be treated as in those + categories by all conforming ECMAScript implementations.
+
+ This
+ standard specifies specific character additions: The dollar sign ($)
+ and the underscore (_)
+ are permitted anywhere in an IdentifierName.
+ Unicode
+ escape sequences are also permitted in an IdentifierName,
+ where they contribute a single character to the IdentifierName,
+ as computed by the CV of the UnicodeEscapeSequence
+ (see 7.8.4). The \
+ preceding the UnicodeEscapeSequence
+ does not contribute a character to the IdentifierName.
+ A UnicodeEscapeSequence
+ cannot be used to put a character into an IdentifierName that would otherwise be illegal. In other words, if a \
+ UnicodeEscapeSequence
+ sequence were replaced by its UnicodeEscapeSequence's
+ CV, the result must still be a valid IdentifierName that has the exact same sequence of characters as the
+ original IdentifierName.
+ All interpretations of identifiers within this specification are
+ based upon their actual characters regardless of whether or not an
+ escape sequence was used to contribute any particular characters.
+ Two + IdentifierName that + are canonically equivalent according to the Unicode standard are not + equal unless they are represented by the exact same sequence of code + units (in other words, conforming ECMAScript implementations are + only required to do bitwise comparison on IdentifierName values). + The intent is that the incoming source text has been converted to + normalised form C before it reaches the compiler.
++ ECMAScript + implementations may recognize identifier characters defined in later + editions of the Unicode Standard. If portability is a concern, + programmers should only employ identifier characters defined in + Unicode 3.0.
++ Syntax
++ Identifier ::
++ IdentifierName but + not ReservedWord
++ IdentifierName + ::
+
+ IdentifierStart
IdentifierName
+ IdentifierPart
+ IdentifierStart ::
+
+ UnicodeLetter$
_\
+ UnicodeEscapeSequence
+ IdentifierPart ::
+
+ IdentifierStart
UnicodeCombiningMark
UnicodeDigit
UnicodeConnectorPunctuation
<ZWNJ>
<ZWJ>
+ UnicodeLetter
++ any + character in the Unicode categories “Uppercase letter (Lu)”, + “Lowercase letter (Ll)”, “Titlecase letter (Lt)”, “Modifier + letter (Lm)”, “Other letter (Lo)”, or “Letter number (Nl)”.
++ UnicodeCombiningMark
++ any + character in the Unicode categories “Non-spacing mark (Mn)” or + “Combining spacing mark (Mc)”
++ UnicodeDigit
++ any + character in the Unicode category “Decimal number (Nd)”
++ UnicodeConnectorPunctuation
++ any + character in the Unicode category “Connector punctuation (Pc)”
++ UnicodeEscapeSequence
++ see + 7.8.4.
++ A + reserved word is an IdentifierName + that cannot be used as an Identifier.
++ Syntax
++ ReservedWord + ::
+
+ Keyword
FutureReservedWord
NullLiteral
BooleanLiteral
+ The + following tokens are ECMAScript keywords and may not be used as + Identifiers in + ECMAScript programs.
++ Syntax
++ Keyword :: one + of
+|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+ + | +
|
+
+ |
+
+
+ |
+
+
+ |
+ + | +
+ The + following words are used as keywords in proposed extensions and are + therefore reserved to allow for the possibility of future adoption + of those extensions.
++ Syntax
++ FutureReservedWord + :: + one + of
+|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+ + | +
+ The + following tokens are also considered to be FutureReservedWords + when they occur within strict mode code (see 10.1.1). The + occurrence of any of these tokens within strict mode code in any + context where the occurrence of a FutureReservedWord + would produce an error must also produce an equivalent error:
+|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+ + | +
+ Syntax
++ Punctuator :: one + of
+|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+ + | +
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+ + | +
+ DivPunctuator :: one + of
+|
+
+ |
+
+
+ |
+ + | ++ | ++ | ++ | +
+ Syntax
++ Literal ::
+
+ NullLiteral
BooleanLiteral
NumericLiteral
StringLiteral
+
RegularExpressionLiteral
+ Syntax
++ NullLiteral ::
+
+ null
+ Semantics
+
+ The
+ value of the null literal null
+ is the sole value of the Null type, namely null.
+ Syntax
++ BooleanLiteral ::
+
+ true
false
+ Semantics
+
+ The
+ value of the Boolean literal true
+ is a value of the Boolean type, namely true.
+ The
+ value of the Boolean literal false
+ is a value of the Boolean type, namely false.
+ Syntax
++ NumericLiteral + ::
+
+ DecimalLiteral
HexIntegerLiteral
+ DecimalLiteral ::
+
+ DecimalIntegerLiteral . DecimalDigitsopt
+ ExponentPartopt. DecimalDigits ExponentPartopt
DecimalIntegerLiteral
+ ExponentPartopt
+ DecimalIntegerLiteral + ::
+
+ 0
NonZeroDigit
+ DecimalDigitsopt
+ DecimalDigits ::
+
+ DecimalDigit
DecimalDigits
+ DecimalDigit
+ DecimalDigit :: + one + of
+
+ 0
+ 1 2 3 4 5 6 7 8 9
+ NonZeroDigit :: + one + of
+
+ 1
+ 2 3 4 5 6 7 8 9
+ ExponentPart ::
++ ExponentIndicator + SignedInteger
++ ExponentIndicator :: + one + of
+
+ e
+ E
+ SignedInteger + ::
+
+ DecimalDigits+ DecimalDigits- DecimalDigits
+ HexIntegerLiteral ::
+
+ 0x HexDigit0X HexDigit
HexIntegerLiteral HexDigit
+ HexDigit :: one + of
+
+ 0
+ 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F
+ The + source character immediately following a NumericLiteral + must not be an IdentifierStart + or DecimalDigit.
++
NOTE For example:
+3in
is
+ an error and not the two input elements 3
+ and in.
+ Semantics
++ A + numeric literal stands for a value of the Number type. This value is + determined in two steps: first, a mathematical value (MV) is derived + from the literal; second, this mathematical value is rounded as + described below.
++ The + MV of NumericLiteral :: + DecimalLiteral is the MV of + DecimalLiteral.
++ The + MV of NumericLiteral :: + HexIntegerLiteral is the MV + of HexIntegerLiteral.
+
+ The
+ MV of DecimalLiteral ::
+ DecimalIntegerLiteral .
+ is the MV of
+ DecimalIntegerLiteral.
+ The
+ MV of DecimalLiteral ::
+ DecimalIntegerLiteral . DecimalDigits is
+ the MV of DecimalIntegerLiteral plus
+ (the MV of DecimalDigits times
+ 10–n),
+ where n is the
+ number of characters in DecimalDigits.
+ The
+ MV of DecimalLiteral ::
+ DecimalIntegerLiteral . ExponentPart is the MV of
+ DecimalIntegerLiteral times
+ 10e,
+ where e is
+ the MV of ExponentPart.
+ The
+ MV of DecimalLiteral ::
+ DecimalIntegerLiteral . DecimalDigits ExponentPart is
+ (the MV of DecimalIntegerLiteral plus
+ (the MV of DecimalDigits times
+ 10–n))
+ times 10e,
+ where n is the
+ number of characters in DecimalDigits and
+ e is the MV of
+ ExponentPart.
+ The
+ MV of DecimalLiteral ::. DecimalDigits is the MV of
+ DecimalDigits times
+ 10–n,
+ where n is the
+ number of characters in DecimalDigits.
+ The
+ MV
+ of DecimalLiteral ::. DecimalDigits ExponentPart is
+ the MV of DecimalDigits times
+ 10e–n,
+ where n is the
+ number of characters in DecimalDigits and
+ e is the MV of
+ ExponentPart.
+ The + MV of DecimalLiteral :: + DecimalIntegerLiteral is + the MV of DecimalIntegerLiteral.
++ The + MV of DecimalLiteral :: + DecimalIntegerLiteral ExponentPart is + the MV of DecimalIntegerLiteral times + 10e, + where e is the MV of + ExponentPart.
+
+ The
+ MV of DecimalIntegerLiteral ::
+ 0 is 0.
+ The + MV of DecimalIntegerLiteral :: + NonZeroDigit DecimalDigits is + (the MV of NonZeroDigit times + 10n) plus + the MV of DecimalDigits, + where n + is the number of characters in DecimalDigits.
++ The + MV of DecimalDigits :: + DecimalDigit is the MV of + DecimalDigit.
++ The + MV of DecimalDigits :: + DecimalDigits DecimalDigit is + (the MV of DecimalDigits times + 10) plus the MV of DecimalDigit.
++ The + MV of ExponentPart :: + ExponentIndicator SignedInteger is + the MV of SignedInteger.
++ The + MV of SignedInteger :: + DecimalDigits is + the MV of DecimalDigits.
+
+ The
+ MV of SignedInteger ::
+ + DecimalDigits is
+ the MV of DecimalDigits.
+ The
+ MV of SignedInteger ::
+ - DecimalDigits is
+ the negative of the MV of DecimalDigits.
+ The
+ MV of DecimalDigit ::
+ 0 or
+ of HexDigit ::
+ 0 is
+ 0.
+ The
+ MV of DecimalDigit ::
+ 1 or
+ of NonZeroDigit ::
+ 1 or
+ of HexDigit ::
+ 1 is
+ 1.
+ The
+ MV of DecimalDigit ::
+ 2 or
+ of NonZeroDigit ::
+ 2 or
+ of HexDigit ::
+ 2 is
+ 2.
+ The
+ MV of DecimalDigit ::
+ 3 or
+ of NonZeroDigit ::
+ 3 or
+ of HexDigit ::
+ 3 is
+ 3.
+ The
+ MV of DecimalDigit ::
+ 4 or
+ of NonZeroDigit ::
+ 4 or
+ of HexDigit ::
+ 4 is
+ 4.
+ The
+ MV of DecimalDigit ::
+ 5 or
+ of NonZeroDigit ::
+ 5 or
+ of HexDigit ::
+ 5 is
+ 5.
+ The
+ MV of DecimalDigit ::
+ 6 or
+ of NonZeroDigit ::
+ 6 or
+ of HexDigit ::
+ 6 is
+ 6.
+ The
+ MV of DecimalDigit ::
+ 7 or
+ of NonZeroDigit ::
+ 7 or
+ of HexDigit ::
+ 7 is
+ 7.
+ The
+ MV of DecimalDigit ::
+ 8 or
+ of NonZeroDigit ::
+ 8 or
+ of HexDigit ::
+ 8 is
+ 8.
+ The
+ MV of DecimalDigit ::
+ 9 or
+ of NonZeroDigit ::
+ 9 or
+ of HexDigit ::
+ 9 is
+ 9.
+ The
+ MV of HexDigit ::
+ a or
+ of HexDigit ::
+ A is
+ 10.
+ The
+ MV of HexDigit ::
+ b or
+ of HexDigit ::
+ B is
+ 11.
+ The
+ MV of HexDigit ::
+ c or
+ of HexDigit ::
+ C is
+ 12.
+ The
+ MV of HexDigit ::
+ d or
+ of HexDigit ::
+ D is
+ 13.
+ The
+ MV of HexDigit ::
+ e or
+ of HexDigit ::
+ E is
+ 14.
+ The
+ MV of HexDigit ::
+ f or
+ of HexDigit ::
+ F is
+ 15.
+ The
+ MV of HexIntegerLiteral ::
+ 0x HexDigit
+ is the MV of HexDigit.
+ The
+ MV of HexIntegerLiteral ::
+ 0X HexDigit
+ is the MV of HexDigit.
+ The + MV of HexIntegerLiteral :: + HexIntegerLiteral HexDigit is + (the MV of HexIntegerLiteral times + 16) plus the MV of + HexDigit.
+
+ Once
+ the exact MV for a numeric literal has been determined, it is then
+ rounded to a value of the Number type. If the MV is 0, then the
+ rounded value is +0;
+ otherwise, the rounded value must be the Number value for the
+ MV (as specified in 8.5), unless the literal is a DecimalLiteral
+ and the literal has more than 20 significant digits, in which case
+ the Number value may be either the Number value for the MV of a
+ literal produced by replacing each significant digit after the 20th
+ with a 0 digit or
+ the Number value for the MV of a literal produced by replacing each
+ significant digit after the 20th with a 0
+ digit and then incrementing the literal at the 20th significant
+ digit position. A digit is significant if it is not part of
+ an ExponentPart
+ and
+ it
+ is not 0;
+ or
+ there + is a nonzero digit to its left and there is a nonzero digit, not + in the ExponentPart, + to its right.
++ A + conforming implementation, when processing strict mode code (see + 10.1.1), must not extend the syntax of NumericLiteral + to include OctalIntegerLiteral + as described in B.1.1.
++ A + string literal is zero or more characters enclosed in single or + double quotes. Each character may be represented by an escape + sequence. All characters may appear literally in a string literal + except for the closing quote character, backslash, carriage return, + line separator, paragraph separator, and line feed. Any character + may appear in the form of an escape sequence.
++ Syntax
++ StringLiteral ::
+
+ " DoubleStringCharactersopt
+ " SingleStringCharactersopt
+
''
+ DoubleStringCharacters ::
++ DoubleStringCharacter + DoubleStringCharactersopt
++ SingleStringCharacters ::
++ SingleStringCharacter + SingleStringCharactersopt
++ DoubleStringCharacter ::
+
+ SourceCharacter but
+ not double-quote "
+ or
+ backslash \ or
+ LineTerminator\
+ EscapeSequence
LineContinuation
+ SingleStringCharacter ::
+
+ SourceCharacter but
+ not single-quote '
+ orbackslash \ or
+ LineTerminator\
+ EscapeSequence
LineContinuation
+ LineContinuation ::
+
+ \
+ LineTerminatorSequence
+ EscapeSequence ::
+
+ CharacterEscapeSequence0 [lookahead
+ ∉
+ DecimalDigit]
HexEscapeSequence
UnicodeEscapeSequence
+ CharacterEscapeSequence ::
+
+ SingleEscapeCharacter
NonEscapeCharacter
+ SingleEscapeCharacter :: + one + of
+
+ '
+ " \ b f n r t v
+ NonEscapeCharacter + ::
++ SourceCharacter + but + not EscapeCharacter or + LineTerminator
++ EscapeCharacter ::
+
+ SingleEscapeCharacter
DecimalDigitx u
+ HexEscapeSequence ::
+
+ x
+ HexDigit HexDigit
+ UnicodeEscapeSequence ::
+
+ u HexDigit HexDigit HexDigit HexDigit
+ The + definitions of the nonterminal HexDigit + is given in 7.6. SourceCharacter + is defined in clause 6.
++ Semantics
++ A + string literal stands for a value of the String type. The String + value (SV) of the literal is described in terms of character values + (CV) contributed by the various parts of the string literal. As part + of this process, some characters within the string literal are + interpreted as having a mathematical value (MV), as described below + or in 7.8.3.
+
+ The
+ SV of StringLiteral ::
+ "" is
+ the empty character sequence.
+ The
+ SV of StringLiteral ::
+ '' is
+ the empty character sequence.
+ The
+ SV of StringLiteral ::
+ "
+ DoubleStringCharacters "
+ is the SV of
+ DoubleStringCharacters.
+ The
+ SV of StringLiteral ::
+ '
+ SingleStringCharacters '
+ is the SV of
+ SingleStringCharacters.
+ The + SV of DoubleStringCharacters :: + DoubleStringCharacter is a + sequence of one character, the CV of DoubleStringCharacter.
++ The + SV of DoubleStringCharacters :: + DoubleStringCharacter DoubleStringCharacters is + a sequence of the CV of DoubleStringCharacter + followed by all the characters in + the SV of DoubleStringCharacters + in order.
++ The + SV of SingleStringCharacters :: + SingleStringCharacter is a + sequence of one character, the CV of + SingleStringCharacter.
++ The + SV of SingleStringCharacters :: + SingleStringCharacter SingleStringCharacters + is a sequence of the CV of SingleStringCharacter + followed by all the characters in + the SV of SingleStringCharacters in + order.
+
+ The
+ SV of LineContinuation ::
+ \
+ LineTerminatorSequence is
+ the empty character sequence.
+ The
+ CV of DoubleStringCharacter ::
+ SourceCharacter but not
+ double-quote "
+ or backslash
+ \ or
+ LineTerminator is theSourceCharacter character
+ itself.
+ The
+ CV of DoubleStringCharacter ::
+ \
+ EscapeSequence is
+ the CV of the EscapeSequence.
The +CV of DoubleStringCharacter :: +LineContinuation is the +empty character sequence.
+ The
+ CV of SingleStringCharacter ::
+ SourceCharacter but not
+ single-quote '
+ or backslash
+ \ or
+ LineTerminator is theSourceCharacter character
+ itself.
+ The
+ CV of SingleStringCharacter ::
+ \
+ EscapeSequence is
+ the CV of the EscapeSequence.
The +CV of SingleStringCharacter :: +LineContinuation is +the empty character sequence.
+ The + CV of EscapeSequence :: + CharacterEscapeSequence is + the CV of the CharacterEscapeSequence.
+
+ The
+ CV of EscapeSequence ::
+ 0 [lookahead
+ ∉
+ DecimalDigit]
+ is a <NUL>
+ character (Unicode value 0000).
+ The + CV of EscapeSequence :: + HexEscapeSequence is the CV + of the HexEscapeSequence.
++ The + CV of EscapeSequence :: + UnicodeEscapeSequence is + the CV of the UnicodeEscapeSequence.
++ The CV of CharacterEscapeSequence ::SingleEscapeCharacter is the + character whose code unit value is determined by theSingleEscapeCharacter according + to Table 4:
+|
+ + Escape + Sequence + |
+
+ + Code + Unit Value + |
+
+ + Name + |
+
+ + Symbol + |
+
|
+
+ |
+
+
+ |
+
+ + backspace + |
+
+ + <BS> + |
+
|
+
+ |
+
+
+ |
+
+ + horizontal + tab + |
+
+ + <HT> + |
+
|
+
+ |
+
+
+ |
+
+ + line + feed (new line) + |
+
+ + <LF> + |
+
|
+
+ |
+
+
+ |
+
+ + vertical + tab + |
+
+ + <VT> + |
+
|
+
+ |
+
+
+ |
+
+ + form + feed + |
+
+ + <FF> + |
+
|
+
+ |
+
+
+ |
+
+ + carriage + return + |
+
+ + <CR> + |
+
|
+
+ |
+
+
+ |
+
+ + double + quote + |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+ + single + quote + |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+ + backslash + |
+
+
+ |
+
+ The + CV of CharacterEscapeSequence :: + NonEscapeCharacter is the + CV of the NonEscapeCharacter.
++ The + CV of NonEscapeCharacter :: + SourceCharacter but + not EscapeCharacter or + LineTerminator is the + SourceCharacter character + itself.
+
+ The
+ CV of HexEscapeSequence ::
+ x HexDigit
+ HexDigit is the character
+ whose code unit value is (16
+ times the MV of the first HexDigit)
+ plus the MV of the second HexDigit.
+ The
+ CV of UnicodeEscapeSequence ::
+ u HexDigit
+ HexDigit HexDigit HexDigit is the
+ character whose code unit value is (4096
+ times the MV of the first HexDigit)
+ plus (256 times the MV of
+ the second HexDigit)
+ plus (16 times the MV of
+ the third HexDigit)
+ plus the MV of the fourth HexDigit.
+ A + conforming implementation, when processing strict mode code (see + 10.1.1), may not extend the syntax of EscapeSequence + to include OctalEscapeSequence + as described in B.1.2.
++
NOTE A line
+ terminator character cannot appear in a string literal, except as
+ part of a LineContinuation
+ to produce the empty character sequence. The correct way to cause a
+ line terminator character to be part of the String value of a string
+ literal is to use an escape sequence such as \n
+ or \u000A.
+ A
+ regular expression literal is an input element that is converted to
+ a RegExp object (see 15.10) each time the literal is evaluated. Two
+ regular expression literals in a program evaluate to regular
+ expression objects that never compare as ===
+ to each other even if the two literals' contents are identical. A
+ RegExp object may also be created at runtime by new
+ RegExp (see 15.10.4) or calling the RegExp
+ constructor as a function (15.10.3).
+ The + productions below describe the syntax for a regular expression + literal and are used by the input element scanner to find the end of + the regular expression literal. The Strings of characters comprising + the RegularExpressionBody + and the RegularExpressionFlags + are passed uninterpreted to the regular expression constructor, + which interprets them according to its own, more stringent grammar. + An implementation may extend the regular expression constructor's + grammar, but it must not extend the RegularExpressionBody + and RegularExpressionFlags + productions or the productions used by these productions.
++ Syntax
++ RegularExpressionLiteral ::
+
+ / RegularExpressionBody /
+ RegularExpressionFlags
+ RegularExpressionBody + ::
++ RegularExpressionFirstChar + RegularExpressionChars
++ RegularExpressionChars ::
+
+ [empty]
RegularExpressionChars
+ RegularExpressionChar
+ RegularExpressionFirstChar ::
+
+ RegularExpressionNonTerminator but
+ not *
+ or
+ \ or
+ /
+ or
+ [
RegularExpressionBackslashSequence
RegularExpressionClass
+ RegularExpressionChar ::
+
+ RegularExpressionNonTerminator
+ but
+ not \
+ or
+ /
+ or
+ [
RegularExpressionBackslashSequence
RegularExpressionClass
+ RegularExpressionBackslashSequence ::
+
+ \ RegularExpressionNonTerminator
+ RegularExpressionNonTerminator ::
++ SourceCharacter + but + not LineTerminator
++ RegularExpressionClass ::
+
+ [
+ RegularExpressionClassChars
+ ]
+ RegularExpressionClassChars
+ ::
+ [empty]
RegularExpressionClassChars
+ RegularExpressionClassChar
+ RegularExpressionClassChar
+ ::
+ RegularExpressionNonTerminator
+ but
+ not ]
+ or
+ \
RegularExpressionBackslashSequence
+ RegularExpressionFlags + ::
+
+ [empty]
RegularExpressionFlags
+ IdentifierPart
NOTE Regular
+ expression literals may not be empty; instead of representing an
+ empty regular expression literal, the characters //
+ start a single-line comment. To specify an empty regular expression,
+ use: /(?:)/.
+ Semantics
+
+ A
+ regular expression literal evaluates to a value of the Object type
+ that is an instance of the standard built-in constructor RegExp.
+ This value is determined in two steps: first, the characters
+ comprising the regular expression's RegularExpressionBody
+ and RegularExpressionFlags
+ production expansions are collected uninterpreted into two Strings
+ Pattern and Flags, respectively. Then each time the literal is
+ evaluated, a new object is created as if by the expression new
+ RegExp(Pattern,
+ Flags)
+ where RegExp is the standard built-in constructor with that name.
+ The newly constructed object becomes the value of the
+ RegularExpressionLiteral.
+ If the call to new RegExp
+ would generate an error as specified in 15.10.4.1, the error must be
+ treated as an early error (Clause 16).
+ Certain
+ ECMAScript statements (empty statement, variable statement,
+ expression statement, do-while
+ statement, continue
+ statement, break
+ statement, return
+ statement, and throw
+ statement) must be terminated with semicolons. Such semicolons may
+ always appear explicitly in the source text. For convenience,
+ however, such semicolons may be omitted from the source text in
+ certain situations. These situations are described by saying that
+ semicolons are automatically inserted into the source code token
+ stream in those situations.
+ There + are three basic rules of semicolon insertion:
++ When, + as the program is parsed from left to right, a token (called the + offending token) + is encountered that is not allowed by any production of the + grammar, then a semicolon is automatically inserted before the + offending token if one or more of the following conditions is + true:
++ The + offending token is separated from the previous token by at least + one LineTerminator.
+
+ The
+ offending token is }.
+ When, + as the program is parsed from left to right, the end of the input + stream of tokens is encountered and the parser is unable to parse + the input token stream as a single complete ECMAScript Program, + then a semicolon is automatically inserted at the end of the + input stream.
++ When, + as the program is parsed from left to right, a token is + encountered that is allowed by some production of the grammar, + but the production is a restricted + production and the + token would be the first token for a terminal or nonterminal + immediately following the annotation “[no LineTerminator here]” + within the restricted production + (and therefore such a token is called a restricted token), and + the restricted token is separated from the previous token by at + least one LineTerminator, + then a semicolon is automatically inserted before the restricted + token.
+
+ However,
+ there is an additional overriding condition on the preceding rules:
+ a semicolon is never inserted automatically if the semicolon would
+ then be parsed as an empty statement or if that semicolon would
+ become one of the two semicolons in the header of a for
+ statement (see 12.6.3).
+ +
NOTE The following + are the only restricted productions in the grammar:
++ PostfixExpression :
+
+ LeftHandSideExpression
+ [no LineTerminator here]
+ ++
LeftHandSideExpression
+ [no LineTerminator here]
+ --
+ ContinueStatement :
+
+ continue [no LineTerminator here] Identifier;
+ BreakStatement :
+
+ break [no LineTerminator here] Identifier;
+ ReturnStatement :
+
+ return [no LineTerminator here] Expression;
+ ThrowStatement + :
+
+ throw [no LineTerminator here] Expression;
+ The + practical effect of these restricted productions is as follows:
+
+ When
+ a ++
+ or --
+ token is encountered where the parser would treat it as a postfix
+ operator, and at least one LineTerminator
+ occurred between the preceding token and the ++
+ or --
+ token, then a semicolon is automatically inserted before the ++
+ or --
+ token.
+ When
+ a continue,
+ break,
+ return,
+ or throw
+ token is encountered and a LineTerminator
+ is encountered before the next token, a semicolon is automatically
+ inserted after the continue,
+ break,
+ return,
+ or throw
+ token.
+ The + resulting practical advice to ECMAScript programmers is:
+
+ A
+ postfix ++
+ or --
+ operator should appear on the same line as its operand.
+ An
+ Expression
+ in a return
+ or throw
+ statement should start on the same line as the return
+ or throw
+ token.
+ A
+ Identifier
+ in a break
+ or continue
+ statement should be on the same line as the break
+ or continue
+ token.
+ The + source
+
+ {
+ 1 2 } 3
is + not a valid sentence in the ECMAScript grammar, even with the + automatic semicolon insertion rules. In contrast, the source
+
+ {
+ 1
2 } 3
is + also not a valid ECMAScript sentence, but is transformed by + automatic semicolon insertion into the following:
+
+ {
+ 1
;2 ;} 3;
+ which + is a valid ECMAScript sentence.
+The + source
+
+ for
+ (a; b
)
+ is
+ not a valid ECMAScript sentence and is not altered by automatic
+ semicolon insertion because the semicolon is needed for the header
+ of a for
+ statement. Automatic semicolon insertion never inserts one of the
+ two semicolons in the header of a for
+ statement.
The + source
+return
a
+ + b
is + transformed by automatic semicolon insertion into the following:
+
+ return;
a
+ + b;
NOTE The
+ expression a + b
+ is not treated as a value to be returned by the return
+ statement, because a LineTerminator
+ separates it from the token return.
The + source
+
+ a
+ = b
++c
is + transformed by automatic semicolon insertion into the following:
+
+ a
+ = b;
++c;
NOTE The
+ token ++ is not
+ treated as a postfix operator applying to the variable b,
+ because a LineTerminator
+ occurs between b
+ and ++.
The + source
+
+ if
+ (a > b)
else c = d
+ is
+ not a valid ECMAScript sentence and is not altered by automatic
+ semicolon insertion before the else
+ token, even though no production of the grammar applies at that
+ point, because an automatically inserted semicolon would then be
+ parsed as an empty statement.
The + source
+
+ a
+ = b + c
(d + e).print()
is + not transformed by automatic semicolon insertion, because the + parenthesised expression that begins the second line can be + interpreted as an argument list for a function call:
+
+ a
+ = b + c(d + e).print()
+ In + the circumstance that an assignment statement must begin with a left + parenthesis, it is a good idea for the programmer to provide an + explicit semicolon at the end of the preceding statement rather than + to rely on automatic semicolon insertion.
++ Algorithms + within this specification manipulate values each of which has an + associated type. The possible value types are exactly those defined + in this clause. Types are further subclassified into ECMAScript + language types and specification types.
++ An + ECMAScript language type corresponds to values that are directly + manipulated by an ECMAScript programmer using the ECMAScript + language. The ECMAScript language types are +Undefined, +Null, +Boolean, +String, +Number, +and +Object.
++ A + specification type corresponds to meta-values that are used within + algorithms to describe the semantics of ECMAScript language + constructs and ECMAScript language types. The specification types + are +Reference, +List, +Completion, +Property Descriptor, +Property Identifier, +Lexical Environment, +and +Environment Record. + Specification type values are specification artefacts that do not + necessarily correspond to any specific entity within an ECMAScript + implementation. Specification type values may be used to describe + intermediate results of ECMAScript expression evaluation but such + values cannot be stored as properties of objects or values of + ECMAScript language variables.
++ Within + this specification, the notation “Type(x)” + is used as shorthand for “the + type of x” + where “type” refers + to the ECMAScript language and specification types defined in this + clause.
++ The + Undefined type has exactly one value, called undefined. Any + variable that has not been assigned a value has the value undefined.
++ The + Null type has exactly one value, called null.
++ The + Boolean type represents a logical entity having two values, called + true and false.
++ The + String type is the set of all finite ordered sequences of zero or + more 16-bit unsigned integer values (“elements”). The String + type is generally used to represent textual data in a running + ECMAScript program, in which case each element in the String is + treated as a code unit value (see Clause 6). Each element is + regarded as occupying a position within the sequence. These + positions are indexed with nonnegative integers. The first element + (if any) is at position 0, the next element (if any) at position 1, + and so on. The length of a String is the number of elements (i.e., + 16-bit values) within it. The empty String has length zero and + therefore contains no elements.
++ When + a String contains actual textual data, each element is considered to + be a single UTF-16 code unit. Whether or not this is the actual + storage format of a String, the characters within a String are + numbered by their initial code unit element position as though they + were represented using UTF-16. All operations on Strings (except as + otherwise stated) treat them as sequences of undifferentiated 16-bit + unsigned integers; they do not ensure the resulting String is in + normalised form, nor do they ensure language-sensitive results.
+NOTE The + rationale behind this design was to keep the implementation of + Strings as simple and high-performing as possible. The intent is + that textual data coming into the execution environment from outside + (e.g., user input, text read from a file or received over the + network, etc.) be converted to Unicode Normalised Form C before the + running program sees it. Usually this would occur at the same time + incoming text is converted from its original character encoding to + Unicode (and would impose no additional overhead). Since it is + recommended that ECMAScript source code be in Normalised Form C, + string literals are guaranteed to be normalised (if source text is + guaranteed to be normalised), as long as they do not contain any + Unicode escape sequences.
+
+ The
+ Number type has exactly 18437736874454810627
+ (that is, 264−253+3)
+ values, representing the double-precision 64-bit format IEEE 754
+ values as specified in the IEEE Standard for Binary Floating-Point
+ Arithmetic, except that the 9007199254740990
+ (that is, 253−2)
+ distinct “Not-a-Number” values of the IEEE Standard are
+ represented in ECMAScript as a single special NaN value.
+ (Note that the NaN value is produced by the program
+ expression NaN.)
+ In some implementations, external code might be able to detect a
+ difference between various Not-a-Number values, but such behaviour
+ is implementation-dependent; to ECMAScript code, all NaN values are
+ indistinguishable from each other.
+ There
+ are two other special values, called positive Infinity and
+ negative Infinity. For brevity, these values are also
+ referred to for expository purposes by the symbols +∞
+ and −∞, respectively.
+ (Note that these two infinite Number values are produced by the
+ program expressions +Infinity
+ (or simply Infinity)
+ and -Infinity.)
+ The + other 18437736874454810624 + (that is, 264−253) + values are called the finite numbers. Half of these are positive + numbers and half are negative numbers; for every finite positive + Number value there is a corresponding negative value having the same + magnitude.
+
+ Note
+ that there is both a positive zero and a negative zero.
+ For brevity, these values are also referred to for expository
+ purposes by the symbols +0
+ and −0,
+ respectively. (Note that these two different zero Number values are
+ produced by the program expressions +0
+ (or simply 0) and
+ -0.)
+ The + 18437736874454810622 + (that is, 264−253−2) + finite nonzero values are of two kinds:
++ 18428729675200069632 + (that is, 264−254) + of them are normalised, having the form
++ s + × m × + 2e
++ where + s is +1 + or −1, + m is a positive + integer less than 253 + but not less than 252, + and e is an + integer ranging from −1074 + to 971, inclusive.
++ The + remaining 9007199254740990 + (that is, 253−2) + values are denormalised, having the form
++ s + × m × + 2e
++ where + s + is +1 or −1, + m is a positive + integer less than 252, + and e is −1074.
+
+ Note
+ that all the positive and negative integers whose magnitude is no
+ greater than 253
+ are representable in the Number type (indeed, the integer 0
+ has two representations, +0
+ and -0).
+ A + finite number has an odd significand if it is nonzero and the + integer m used to + express it (in one of the two forms shown above) is odd. Otherwise, + it has an even significand.
++ In + this specification, the phrase “the + Number value for x” + where x represents + an exact nonzero real mathematical quantity (which might even be an + irrational number such as π) + means a Number value chosen in the following manner. Consider the + set of all finite values of the Number type, with −0 + removed and with two additional values added to it that are not + representable in the Number type, namely 21024 + (which is +1 × + 253 + × + 2971) + and −21024 + (which is −1 + × + 253 + × + 2971). + Choose the member of this set that is closest in value to x. + If two values of the set are equally close, then the one with an + even significand is chosen; for this purpose, the two extra values + 21024 + and −21024 + are considered to have even significands. Finally, if 21024 + was chosen, replace it with +∞; + if −21024 + was chosen, replace it with −∞; + if +0 was chosen, + replace it with −0 + if and only if x + is less than zero; any other chosen value is used unchanged. The + result is the Number value for x. + (This procedure corresponds exactly to the behaviour of the IEEE 754 + “round to nearest” mode.)
++ Some + ECMAScript operators deal only with integers in the range −231 + through 231−1, + inclusive, or in the range 0 + through 232−1, + inclusive. These operators accept any value of the Number type but + first convert each such value to one of 232 + integer values. See the descriptions of the ToInt32 and ToUint32 + operators in 9.5 and 9.6, respectively.
++ An + Object is a collection of properties. Each property is either + a named data property, a named accessor property, or an internal + property:
++ A + named data property associates a name with an ECMAScript + language value and a set of Boolean attributes.
++ A + named accessor property associates a name with one or two + accessor functions, and a set of Boolean attributes. The accessor + functions are used to store or retrieve an ECMAScript language + value that is associated with the property. +
++ An + internal property has no name and is not directly accessible + via ECMAScript language operators. Internal properties exist purely + for specification purposes. +
++ There + are two kinds of access for named (non-internal) properties: get and put, corresponding to retrieval and assignment, + respectively.
++ Attributes + are used in this specification to define and explain the state of + named properties. A named data property associates a name with the + attributes listed in Table 5
+|
+ + Attribute + Name + |
+
+ + Value + Domain + |
+
+ + Description + |
+
|
+ + [[Value]] + + + |
+
+ + Any + ECMAScript language type + |
+
+ + The + value retrieved by reading the property. + |
+
|
+ + [[Writable]] + + + |
+
+ + Boolean + |
+
+ + If + false, attempts by ECMAScript code to change the + property’s [[Value]] attribute using [[Put]] will not succeed. + |
+
|
+ + [[Enumerable]] + |
+
+ + Boolean + |
+
+ + If + true, the property will be enumerated by a for-in + enumeration (see 12.6.4). Otherwise, the property is said to be + non-enumerable. + |
+
|
+ + [[Configurable]] + |
+
+ + Boolean + |
+
+ + If + false, attempts to delete the property, change the + property to be an accessor property, or change its attributes + (other than [[Value]]) will fail. + |
+
+ A + named accessor property associates a name with the attributes listed + in Table 6.
+|
+ + Attribute + Name + |
+
+ + Value + Domain + |
+
+ + Description + |
+
|
+ + [[Get]] + |
+
+ + Object + or Undefined + |
+
+ + If + the value is an Object it must be a function Object. The + function’s [[Call]] internal method (8.6.2) is called with an + empty arguments list to return the property value each time a + get access of the property is performed. + |
+
|
+ + [[Set]] + |
+
+ + Object + or Undefined + |
+
+ + If + the value is an Object it must be a function Object. The + function’s [[Call]] internal method (8.6.2) is called with an + arguments list containing the assigned value as its sole + argument each time a set access of the property is performed. + The effect of a property's [[Set]] internal method may, but is + not required to, have an effect on the value returned by + subsequent calls to the property's [[Get]] internal method. + |
+
|
+ + [[Enumerable]] + |
+
+ + Boolean + |
+
+ + If + true, the property is to be enumerated by a for-in + enumeration (see 12.6.4). Otherwise, the property is said to be + non-enumerable. + |
+
|
+ + [[Configurable]] + |
+
+ + Boolean + |
+
+ + If + false, attempts to delete the property, change the + property to be a data property, or change its attributes will + fail. + |
+
+ If + the value of an attribute is not explicitly specified by this + specification for a named property, the default value defined in + Table 7 is used.
+|
+ + Attribute + Name + |
+
+ + Default + Value + |
+
|
+ + [[Value]] + |
+
+ + undefined + |
+
|
+ + [[Get]] + |
+
+ + undefined + |
+
|
+ + [[Set]] + |
+
+ + undefined + |
+
|
+ + [[Writable]] + |
+
+ + false + |
+
|
+ + [[Enumerable]] + |
+
+ + false + |
+
|
+ + [[Configurable]] + |
+
+ + false + |
+
+ This + specification uses various internal properties to define the + semantics of object values. These internal properties are not part + of the ECMAScript language. They are defined by this specification + purely for expository purposes. An implementation of ECMAScript must + behave as if it produced and operated upon internal properties in + the manner described here. The names of internal properties are + enclosed in double square brackets [[ ]]. When an algorithm uses an + internal property of an object and the object does not implement the + indicated internal property, a TypeError exception is thrown.
++ The + Table 8 summarises the internal properties used by this + specification that are applicable to all ECMAScript objects. The + Table 9 summarises the internal properties used by this + specification that are only applicable to some ECMAScript objects. + The descriptions in these tables indicates their behaviour for + native ECMAScript objects, unless stated otherwise in this document + for particular kinds of native ECMAScript objects. Host objects may + support these internal properties with any implementation-dependent + behaviour as long as it is consistent with the specific host object + restrictions stated in this document.
++ The + “Value Type Domain” columns of the following tables define the + types of values associated with internal properties. The type names + refer to the types defined in Clause 8 augmented by the following + additional names. “any” means the value may be any + ECMAScript language type. “primitive” means Undefined, + Null, Boolean, String, or Number. “SpecOp” means the + internal property is an internal method, an implementation provided + procedure defined by an abstract operation specification. “SpecOp” + is followed by a list of descriptive parameter names. If a parameter + name is the same as a type name then the name describes the type of + the parameter. If a “SpecOp” returns a value, its parameter list + is followed by the symbol “→” and the type of the returned + value.
+|
+ + Internal + Property + |
+
+ + Value + Type Domain + |
+
+ + Description + |
+
|
+ + [[Prototype]] + |
+
+ + Object + or Null + |
+
+ + The + prototype of this object. + |
+
|
+ + [[Class]] + |
+
+ + String + |
+
+ + A + String value indicating a specification defined classification + of objects. + |
+
|
+ + [[Extensible]] + |
+
+ + Boolean + |
+
+ + If + true, own properties may be added to the object. + |
+
|
+ + [[Get]] + |
+
+ + SpecOp(propertyName) + → any + |
+
+ + Returns + the value of the named property. + |
+
|
+ + [[GetOwnProperty]] + |
+
+ + SpecOp + (propertyName) → ++ Undefinedor + Property Descriptor + |
+
+ + Returns + the Property Descriptor of the named own property of this + object, or undefined if absent. + |
+
|
+ + [[GetProperty]] + |
+
+ + SpecOp + (propertyName) → ++ Undefinedor + Property Descriptor + |
+
+ + Returns + the fully populated Property Descriptor of the named property of + this object, or undefined if absent. + |
+
|
+ + [[Put]] + |
+
+ + SpecOp + (propertyName, any, Boolean) + |
+
+ + Sets + the specified named property to the value of the second + parameter. The flag controls failure handling. + |
+
|
+ + [[CanPut]] + |
+
+ + SpecOp + (propertyName) → + Boolean + |
+
+ + Returns + a Boolean value indicating whether a [[Put]] operation with + PropertyName can be performed. + |
+
|
+ + [[HasProperty]] + |
+
+ + SpecOp + (propertyName) → + Boolean + |
+
+ + Returns + a Boolean value indicating whether the object already has a + property with the given name. + |
+
|
+ + [[Delete]] + |
+
+ + SpecOp + (propertyName, Boolean) → + Boolean + |
+
+ + Removes + the specified named own property from the object. The flag + controls failure handling. + |
+
|
+ + [[DefaultValue]] + |
+
+ + SpecOp + (Hint) → + primitive + |
+
+ + Hint + is a String. Returns a default value for the object. + |
+
|
+ + [[DefineOwnProperty]] + |
+
+ + SpecOp + (propertyName, PropertyDescriptor, Boolean) + → Boolean + |
+
+ + Creates + or alters the named own property to have the state described by + a Property Descriptor. The flag controls failure handling. + |
+
+ Every + object (including host objects) must implement all of the internal + properties listed in Table 8. However, the [[DefaultValue]] internal + method may, for some objects, simply throw a TypeError + exception.
++ All + objects have an internal property called [[Prototype]]. The value of + this property is either null or an object and is used for + implementing inheritance. Whether or not a native object can have a + host object as its [[Prototype]] depends on the implementation. + Every [[Prototype]] chain must have finite length (that is, starting + from any object, recursively accessing the [[Prototype]] internal + property must eventually lead to a null value). Named data + properties of the [[Prototype]] object are inherited (are visible as + properties of the child object) for the purposes of get access, but + not for put access. Named accessor properties are inherited for both + get access and put access.
++ Every + ECMAScript object has a Boolean-valued [[Extensible]] internal + property that controls whether or not named properties may be added + to the object. If the value of the [[Extensible]] internal property + is false then additional named properties may not be added to + the object. In addition, if [[Extensible]] is false the + value of the [[Class]] and [[Prototype]] internal properties of the + object may not be modified. Once the value of an [[Extensible]] + internal property has been set to false it may not be + subsequently changed to true.
+NOTE This + specification defines no ECMAScript language operators or built-in + functions that permit a program to modify an object’s [[Class]] or + [[Prototype]] internal properties or to change the value of + [[Extensible]] from false to true. Implementation + specific extensions that modify [[Class]], [[Prototype]] or + [[Extensible]] must not violate the invariants defined in the + preceding paragraph.
+
+ The
+ value of the [[Class]] internal property is defined by this
+ specification for every kind of built-in object. The value of the
+ [[Class]] internal property of a host object may be any String value
+ except one of "Arguments",
+ "Array",
+ "Boolean",
+ "Date",
+ "Error",
+ "Function",
+ "JSON",
+ "Math",
+ "Number",
+ "Object",
+ "RegExp",
+ and "String".
+ The value of a [[Class]] internal property is used internally to
+ distinguish different kinds of objects. Note that this specification
+ does not provide any means for a program to access that value except
+ through Object.prototype.toString
+ (see 15.2.4.2).
+ Unless + otherwise specified, the common internal methods of native + ECMAScript objects behave as described in 8.12. Array objects have a + slightly different implementation of the [[DefineOwnProperty]] + internal method (see 15.4.5.1) and String objects have a slightly + different implementation of the [[GetOwnProperty]] internal method + (see 15.5.5.2). Arguments objects (10.6) have different + implementations of [[Get]], [[GetOwnProperty]], + [[DefineOwnProperty]], and [[Delete]]. Function objects (15.3) have + a different implementation of [[Get]].
++ Host + objects may implement these internal methods in any manner unless + specified otherwise; for example, one possibility is that [[Get]] + and [[Put]] for a particular host object indeed fetch and store + property values but [[HasProperty]] always generates false. + However, if any specified manipulation of a host object's internal + properties is not supported by an implementation, that manipulation + must throw a TypeError exception when attempted.
++ The + [[GetOwnProperty]] internal method of a host object must conform to + the following invariants for each property of the host object:
++ If a + property is described as a data property and it may return + different values over time, then either or both of the [[Writable]] + and [[Configurable] attributes must be true even if no + mechanism to change the value is exposed via the other internal + methods.
++ If a + property is described as a data property and its [[Writable]] and + [[Configurable]] are both false, then the SameValue + (according to 9.12) must be returned for the [[Value]] attribute of + the property on all calls to [[GetOwnProperty]].
++ If + the attributes other than [[Writable]] may change over time or if + the property might disappear, then the [[Configurable]] attribute + must be true.
++ If + the [[Writable]] attribute may change from false to true, + then the [[Configurable]] attribute must be true.
++ If + the value of the host object’s [[Extensible]] internal property + is has been observed by ECMAScript code to be false, then if + a call to [[GetOwnProperty]] describes a property as non-existent + all subsequent calls must also describe that property as + non-existent.
++ The + [[DefineOwnProperty]] internal method of a host object must not + permit the addition of a new property to a host object if the + [[Extensible]] internal property of that host object has been + observed by ECMAScript code to be false. +
++ If + the [[Extensible]] internal property of that host object has been + observed by ECMAScript code to be false then it must not + subsequently become true.
+|
+ + Internal + Property + |
+
+ + Value + Type Domain + |
+
+ + Description + |
+
|
+ + [[PrimitiveValue]] + |
+
+ + primitive + |
+
+ + Internal + state information associated with this object. Of the standard + built-in ECMAScript objects, only Boolean, Date, Number, and + String objects implement [[PrimitiveValue]]. + |
+
|
+ + [[Construct]] + |
+ + + | +
+
+ Creates
+ an object. Invoked via the |
+
|
+ + [[Call]] + |
+ + + | +
+ + Executes + code associated with the object. Invoked via a function call + expression. The arguments to the SpecOp are a this object and a + list containing the arguments passed to the function call + expression. Objects that implement this internal method are + callable. Only callable objects that are host objects may + return Reference values. + |
+
|
+ + [[HasInstance]] + |
+
+ + SpecOp(any) + → + Boolean + |
+
+ + Returns + a Boolean value indicating whether the argument is likely an + Object that was constructed by this object. Of the standard + built-in ECMAScript objects, only Function objects implement + [[HasInstance]]. + |
+
|
+ + [[Scope]] + |
+ + + | +
+ + A + lexical environment that defines the environment in which a + Function object is executed. Of the standard built-in ECMAScript + objects, only Function objects implement [[Scope]]. + |
+
|
+ + [[FormalParameters]] + |
+
+ + List + of Strings + |
+
+ + A + possibly empty List containing the identifier Strings of a + Function’s FormalParameterList. + Of the standard built-in ECMAScript objects, only Function + objects implement [[FormalParameterList]]. + |
+
|
+ + [[Code]] + |
+
+ + ECMAScript + code + |
+
+ + The + ECMAScript code of a function. Of the standard built-in + ECMAScript objects, only Function objects implement [[Code]]. + |
+
|
+ + [[TargetFunction]] + |
+
+ + Object + |
+
+ + The + target function of a function object created using the standard + built-in Function.prototype.bind method. Only ECMAScript objects + created using Function.prototype.bind have a [[TargetFunction]] + internal property. + |
+
|
+ + [[BoundThis]] + |
+
+ + any + |
+
+ + The + pre-bound this value of a function Object created using the + standard built-in Function.prototype.bind method. Only + ECMAScript objects created using Function.prototype.bind have a + [[BoundThis]] internal property. + |
+
|
+ + [[BoundArguments]] + |
+
+ + List + of any + |
+
+ + The + pre-bound argument values of a function Object created using the + standard built-in Function.prototype.bind method. Only + ECMAScript objects created using Function.prototype.bind have a + [[BoundArguments]] internal property. + |
+
|
+ + [[Match]] + |
+
+ + SpecOp(String, + index) → + MatchResult + |
+
+ + Tests + for a regular expression match and returns a MatchResult value + (see 15.10.2.1). Of the standard built-in ECMAScript objects, + only RegExp objects implement [[Match]]. + |
+
|
+ + [[ParameterMap]] + |
+
+ + Object + |
+
+ + Provides + a mapping between the properties of an arguments object (see + 10.6) and the formal parameters of the associated function. Only + ECMAScript objects that are arguments objects have a + [[ParameterMap]] internal property. + |
+
+ The
+ Reference type is used to explain the behaviour of such operators as
+ delete, typeof,
+ and the assignment operators. For example, the left-hand operand of
+ an assignment is expected to produce a reference. The behaviour of
+ assignment could, instead, be explained entirely in terms of a case
+ analysis on the syntactic form of the left-hand operand of an
+ assignment operator, but for one difficulty: function calls are
+ permitted to return references. This possibility is admitted purely
+ for the sake of host objects. No built-in ECMAScript function
+ defined by this specification returns a reference and there is no
+ provision for a user-defined function to return a reference.
+ (Another reason not to use a syntactic case analysis is that it
+ would be lengthy and awkward, affecting many parts of the
+ specification.)
+ A + Reference is a resolved name binding. A Reference consists of + three components, the base value, the referenced + name and the Boolean valued strict + reference flag. The base value is either undefined, + an Object, a Boolean, a String, a Number, or an environment record + (10.2.1). A base value of undefined indicates that the + reference could not be resolved to a binding. The referenced name is + a String.
++ The + following abstract operations are used in this specification to + access the components of references:
+GetBase(V). + Returns the base value component of the reference V.
+GetReferencedName(V). + Returns the referenced name component of the reference V.
+IsStrictReference(V). + Returns the strict reference component of the reference V.
+HasPrimitiveBase(V). + Returns true if the base value is a Boolean, String, or + Number.
+IsPropertyReference(V). + Returns true if either the base value is an object or + HasPrimitiveBase(V) is true; otherwise returns false.
+IsUnresolvableReference(V). + Returns true if the base value is undefined and false + otherwise.
++ The + following abstract operations are used in this specification to + operate on references:
++ Let + base be the result of calling GetBase(V).
++ If + IsUnresolvableReference(V), throw a ReferenceError + exception.
++ If + IsPropertyReference(V), then
++ If + HasPrimitiveBase(V) is false, then let get be + the [[Get]] internal method of base, otherwise let get + be the special [[Get]] internal method defined below.
++ Return + the result of calling the get internal method using base as its this value, and passing GetReferencedName(V) + for the argument.
++ Else, + base must be an environment record.
++ Return + the result of calling the GetBindingValue (see 10.2.1) concrete + method of base passing GetReferencedName(V) and + IsStrictReference(V) as arguments.
++ The + following [[Get]] internal method is used by GetValue when V + is a property reference with a primitive base value. It is called + using base as its + this value and with property P + as its argument. The following steps are taken:
++ Let + O be ToObject(base).
++ Let + desc be the result of calling the [[GetProperty]] internal + method of O with property name P.
++ If + desc is undefined, return undefined.
++ If + IsDataDescriptor(desc) is true, return + desc.[[Value]].
++ Otherwise, + IsAccessorDescriptor(desc) must be true so, let + getter be desc.[[Get]].
++ If + getter is undefined, return undefined.
++ Return + the result calling the [[Call]] internal method of getter providing base as the this value and providing no + arguments.
+NOTE The + object that may be created in step 1 is not accessible outside of + the above method. An implementation might choose to avoid the actual + creation of the object. The only situation where such an actual + property access that uses this internal method can have visible + effect is when it invokes an accessor function.
++ If + Type(V) is not Reference, + throw a ReferenceError + exception.
++ Let + base be the result of calling GetBase(V).
++ If + IsUnresolvableReference(V), then
++ If + IsStrictReference(V) is true, then
++ Throw + ReferenceError exception.
++ Call + the [[Put]] internal method of the global object, passing + GetReferencedName(V) for the property name, W for + the value, and false for the Throw flag.
++ Else + if IsPropertyReference(V), then
++ If + HasPrimitiveBase(V) is false, then let put be + the [[Put]] internal method of base, otherwise let put + be the special [[Put]] internal method defined below.
++ Call + the put internal method using base as its this + value, and passing GetReferencedName(V) for the + property name, W for the value, and IsStrictReference(V) + for the Throw flag.
++ Else + base must be a reference whose base is an environment record. So,
++ Call + the SetMutableBinding (10.2.1) concrete method of base, + passing GetReferencedName(V), W, and + IsStrictReference(V) as arguments.
++ Return.
++ The + following [[Put]] internal method is used by PutValue when V + is a property reference with a primitive base value. It is called + using base as its + this value and with property P, + value W, and + Boolean flag Throw + as arguments. The following steps are taken:
++ Let + O be ToObject(base).
++ If + the result of calling the [[CanPut]] internal method of O + with argument P is false, then
++ If + Throw is true, then throw a TypeError + exception.
++ Else + return.
++ Let + ownDesc be the result of calling the [[GetOwnProperty]] + internal method of O with argument P.
++ If + IsDataDescriptor(ownDesc) is true, then
++ If + Throw is true, then throw a TypeError + exception.
++ Else + Return.
++ Let + desc be the result of calling the [[GetProperty]] internal + method of O with argument P. This may be either an + own or inherited accessor property descriptor + or an inherited data property descriptor.
++ If + IsAccessorDescriptor(desc) is true, then
++ Let + setter be desc.[[Set]] which cannot be undefined.
++ Call + the [[Call]] internal method of setter providing base + as the this value and an argument list containing only W.
++ Else, + this is a request to create an own property on the transient object + O
++ If + Throw is true, then throw a TypeError + exception.
++ Return.
+NOTE The + object that may be created in step 1 is not accessible outside of + the above method. An implementation might choose to avoid the + actual creation of that transient object. The only situations where + such an actual property assignment that uses this internal method + can have visible effect are when it either invokes an accessor + function or is in violation of a Throw + predicated error check. When Throw + is true any property assignment that would create a new + property on the transient object throws an error.
+
+ The
+ List type is used to explain the evaluation of argument lists (see
+ 11.2.4) in new
+ expressions, in function calls, and in other algorithms where a
+ simple list of values is needed. Values of the List type are simply
+ ordered sequences of values. These sequences may be of any length.
+ The
+ Completion type is used to explain the behaviour of statements
+ (break, continue,
+ return and throw)
+ that perform nonlocal transfers of control. Values of the Completion
+ type are triples of the form (type, value, target),
+ where type is one of normal, break, continue,
+ return, or throw, value is any ECMAScript
+ language value or empty, and target is any ECMAScript
+ identifier or empty.
+ The + term “abrupt completion” refers to any completion with a type + other than normal.
++ The + Property Descriptor type is used to explain the manipulation and + reification of named property attributes. Values of the Property + Descriptor type are records composed of named fields where each + field’s name is an attribute name and its value is a corresponding + attribute value as specified in 8.6.1. In addition, any field may be + present or absent.
++ Property + Descriptor values may be further classified as data property + descriptors and accessor property descriptors based upon the + existence or use of certain fields. A data property descriptor is + one that includes any fields named either [[Value]] or [[Writable]]. + An accessor property descriptor is one that includes any fields + named either [[Get]] or [[Set]]. Any property descriptor may have + fields named [[Enumerable]] and [[Configurable]]. A Property + Descriptor value may not be both a data property descriptor and an + accessor property descriptor; however, it may be neither. A generic + property descriptor is a Property Descriptor value that is neither a + data property descriptor nor an accessor property descriptor. + A fully populated property descriptor is one that is either an + accessor property descriptor or a data property descriptor and that + has all of the fields that correspond to the property attributes + defined in either 8.6.1 Table 5 or Table 6.
++ For + notational convenience within this specification, an object + literal-like syntax can be used to define a property descriptor + value. For example, Property Descriptor {[[Value]]: 42, + [[Writable]]: false, [[Configurable]]: true} defines a + data property descriptor. Field name order is not significant. Any + fields that are not explicitly listed are considered to be absent.
++ In + specification text and algorithms, dot notation may be used to refer + to a specific field of a Property Descriptor. For example, if D is a + property descriptor then D.[[Value]] is shorthand for “the field + of D named [[Value]]”.
++ The + Property Identifier type is used to associate a property name with a + Property Descriptor. Values of the Property Identifier type are + pairs of the form (name, descriptor), where name is a String and + descriptor is a Property Descriptor value. +
++ The + following abstract operations are used in this specification to + operate upon Property Descriptor values:
++ When + the abstract operation IsAccessorDescriptor is called with property descriptor Desc, + the following steps are taken:
++ If + Desc + is undefined, + then return false.
++ If + both Desc.[[Get]] + and Desc.[[Set]] + are absent, then return false.
++ Return + true.
++ When + the abstract operation IsDataDescriptor is called with property descriptor Desc, + the following steps are taken:
++ If + Desc + is undefined, + then return false.
++ If + both Desc.[[Value]] + and Desc.[[Writable]] + are absent, then return false.
++ Return + true.
++ When + the abstract operation IsGenericDescriptor is called with property descriptor Desc, + the following steps are taken:
++ If + Desc + is undefined, + then return false.
++ If + IsAccessorDescriptor(Desc) + and IsDataDescriptor(Desc) + are both false, + then return true.
++ Return + false.
++ When + the abstract operation FromPropertyDescriptor is called with + property descriptor Desc, + the following steps are taken:
++ The + following algorithm assumes that Desc is a fully populated Property Descriptor, such as that + returned from [[GetOwnProperty]] (see 8.12.1).
++ If + Desc + is undefined, + then return undefined.
++ Let + obj be + the result of creating a new object as if by the expression new + Object() where + Object is the + standard built-in constructor with that name.
++ If + IsDataDescriptor(Desc) + is true, + then +
+
+ Call
+ the [[DefineOwnProperty]] internal method of obj
+ with arguments "value",
+ Property Descriptor {[[Value]]: Desc.[[Value]],
+ [[Writable]]: true,
+ [[Enumerable]]: true,
+ [[Configurable]]: true},
+ and false.
+
+
+ Call
+ the [[DefineOwnProperty]] internal method of obj
+ with arguments "writable",
+ Property Descriptor {[[Value]]: Desc.[[Writable]],
+ [[Writable]]: true,
+ [[Enumerable]]: true,
+ [[Configurable]]: true},
+ and false.
+
+
+ Else, + IsAccessorDescriptor(Desc) + must be true, + so
+
+ Call
+ the [[DefineOwnProperty]] internal method of obj
+ with arguments "get",
+ Property Descriptor {[[Value]]: Desc.[[Get]],
+ [[Writable]]: true,
+ [[Enumerable]]: true,
+ [[Configurable]]: true},
+ and false.
+ Call
+ the [[DefineOwnProperty]] internal method of obj
+ with arguments "set",
+ Property Descriptor {[[Value]]: Desc.[[Set]],
+ [[Writable]]: true,
+ [[Enumerable]]: true,
+ [[Configurable]]: true},
+ and false.
+
+
+ Call
+ the [[DefineOwnProperty]] internal method of obj
+ with arguments "enumerable",
+ Property Descriptor {[[Value]]: Desc.[[Enumerable]],
+ [[Writable]]: true,
+ [[Enumerable]]: true,
+ [[Configurable]]: true},
+ and false.
+
+
+ Call
+ the [[DefineOwnProperty]] internal method of obj
+ with arguments "configurable",
+ Property Descriptor {[[Value]]: Desc.[[Configurable]],
+ [[Writable]]: true,
+ [[Enumerable]]: true,
+ [[Configurable]]: true},
+ and false.
+
+
+ Return + obj.
++ When + the abstract operation ToPropertyDescriptor is called with object + Desc, the + following steps are taken:
++ If + Type(Obj) is not Object throw a TypeError exception.
++ Let + desc be the result of creating a new Property Descriptor + that initially has no fields.
+
+ If
+ the result of calling the [[HasProperty]] internal method of Obj
+ with argument "enumerable"
+ is true, then
+ Let
+ enum be the result of calling the [[Get]] internal method
+ of Obj with "enumerable".
+ Set + the [[Enumerable]] field of desc to ToBoolean(enum).
+
+ If
+ the result of calling the [[HasProperty]] internal method of Obj
+ with argument "configurable"
+ is true, then
+ Let
+ conf be the result of calling the [[Get]] internal method
+ of Obj with argument "configurable".
+ Set + the [[Configurable]] field of desc to ToBoolean(conf).
+
+ If
+ the result of calling the [[HasProperty]] internal method of Obj
+ with argument "value"
+ is true, then
+ Let
+ value be the result of calling the [[Get]] internal method
+ of Obj with argument “value”.
+ Set + the [[Value]] field of desc to value.
+
+ If
+ the result of calling the [[HasProperty]] internal method of Obj
+ with argument "writable"
+ is true, then
+ Let
+ writable be the result of calling the [[Get]] internal
+ method of Obj with argument "writable".
+ Set + the [[Writable]] field of desc to ToBoolean(writable).
+
+ If
+ the result of calling the [[HasProperty]] internal method of Obj
+ with argument "get"
+ is true, then
+ Let
+ getter be the result of calling the [[Get]] internal method
+ of Obj with argument "get".
+ If + IsCallable(getter) is false and getter is not + undefined, then throw a TypeError exception.
++ Set + the [[Get]] field of desc to getter.
+
+ If
+ the result of calling the [[HasProperty]] internal method of Obj
+ with argument "set"
+ is true, then
+ Let
+ setter be the result of calling the [[Get]] internal method
+ of Obj with argument "set".
+ If + IsCallable(setter) is false and setter is not + undefined, then throw a TypeError exception.
++ Set + the [[Set]] field of desc to setter.
++ If + either desc.[[Get]] or desc.[[Set]] are present, then
++ If + either desc.[[Value]] or desc.[[Writable]] are + present, then throw a TypeError exception.
++ Return + desc.
++ The + Lexical Environment and Environment Record types are used to explain + the behaviour of name resolution in nested functions and blocks. + These types and the operations upon them are defined in Clause 10.
++ In + the following algorithm descriptions, assume O + is a native ECMAScript object, P + is a String, Desc + is a Property Description record, and Throw + is a Boolean flag.
++ When + the [[GetOwnProperty]] internal method of O + is called with property name P, + the following steps are taken:
++ If + O doesn’t have an own property with name P, return + undefined.
++ Let + D be a newly created Property Descriptor with no fields.
++ Let + X be O’s own property named P.
++ If + X is a data property, then
++ Set + D.[[Value]] to the value of X’s [[Value]] + attribute.
++ Set + D.[[Writable]] to the value of X’s [[Writable]] + attribute
++ Else + X is an accessor property, so
++ Set + D.[[Get]] to the value of X’s [[Get]] attribute.
++ Set + D.[[Set]] to the value of X’s [[Set]] attribute.
++ Set + D.[[Enumerable]] to the value of X’s [[Enumerable]] + attribute.
++ Set + D.[[Configurable]] to the value of X’s + [[Configurable]] attribute.
++ Return + D.
++ However, + if O is a String + object it has a more elaborate [[GetOwnProperty]] internal method + defined in 15.5.5.2.
++ When + the [[GetProperty]] internal method of O + is called with property name P, + the following steps are taken:
++ Let + prop be the result of calling the [[GetOwnProperty]] + internal method of O with property name P.
++ If + prop is not undefined, return prop.
++ Let + proto be the value of the [[Prototype]] internal property of + O.
++ If + proto is null, return undefined.
++ Return + the result of calling the [[GetProperty]] internal method of proto + with argument P.
++ When + the [[Get]] internal method of O + is called with property name P, + the following steps are taken:
++ Let + desc be the result of calling the [[GetProperty]] internal + method of O with property name P.
++ If + desc is undefined, return undefined.
++ If + IsDataDescriptor(desc) is true, return + desc.[[Value]].
++ Otherwise, + IsAccessorDescriptor(desc) must be true so, let getter + be desc.[[Get]].
++ If + getter is undefined, return undefined.
++ Return + the result calling the [[Call]] internal method of getter providing O as the this value and providing no + arguments.
++ When + the [[CanPut]] internal method of O is called with property name P, + the following steps are taken:
++ Let + desc be the result of calling the [[GetOwnProperty]] + internal method of O with argument P.
++ If + desc is not undefined, then
++ If + IsAccessorDescriptor(desc) is true, then
++ If + desc.[[Set]] is undefined, then return false.
++ Else + return true.
++ Else, + desc must be a DataDescriptor so return the value of + desc.[[Writable]].
++ Let + proto be the [[Prototype]] internal property of O.
++ If + proto is null, then return the value of the + [[Extensible]] internal property of O.
++ Let + inherited be the result of calling the [[GetProperty]] + internal method of proto with property name P.
++ If + inherited is undefined, return the value of the + [[Extensible]] internal property of O.
++ If + IsAccessorDescriptor(inherited) is true, then
++ If + inherited.[[Set]] is undefined, then return false.
++ Else + return true.
++ Else, + inherited must be a DataDescriptor
++ If + the [[Extensible]] internal property of O is false, + return false.
++ Else + return the value of inherited.[[Writable]].
+Host + objects may define additional constraints upon [[Put]] operations. + If possible, host objects should not allow [[Put]] operations in + situations where this definition of [[CanPut]] returns false.
++ When + the [[Put]] internal method of O + is called with property P, + value V, and + Boolean flag Throw, + the following steps are taken:
++ If + the result of calling the [[CanPut]] internal method of O with + argument P is false, then
++ If + Throw is true, then throw a TypeError exception.
++ Else + return.
++ Let + ownDesc be the result of calling the [[GetOwnProperty]] + internal method of O with argument P.
++ If + IsDataDescriptor(ownDesc) is true, then
++ Let + valueDesc be the Property Descriptor {[[Value]]: V}.
++ Call + the [[DefineOwnProperty]] internal method of O passing P, + valueDesc, and Throw as arguments.
++ Return.
++ Let + desc be the result of calling the [[GetProperty]] internal + method of O with argument P. This may be either an + own or inherited accessor property descriptor + or an inherited data property descriptor.
++ If + IsAccessorDescriptor(desc) is true, then
++ Let + setter be desc.[[Set]] which cannot be undefined.
++ Call + the [[Call]] internal method of setter providing O as + the this value and providing V as the sole argument.
++ Else, + create a named data property named P on object O as + follows
+
+ Let
+ newDesc be the Property Descriptor
{[[Value]]: V,
+ [[Writable]]: true, [[Enumerable]]: true,
+ [[Configurable]]: true}.
+ Call + the [[DefineOwnProperty]] internal method of O passing P, + newDesc, and Throw as arguments.
++ Return.
++ When + the [[HasProperty]] internal method of O + is called with property name P, + the following steps are taken:
++ Let + desc be the result of calling the [[GetProperty]] internal + method of O with property name P.
++ If + desc is undefined, then return false.
++ Else + return true.
++ When + the [[Delete]] internal method of O + is called with property name P and the Boolean flag Throw, + the following steps are taken:
++ Let + desc be the result of calling the [[GetOwnProperty]] + internal method of O with property name P.
++ If + desc is undefined, then return true.
++ If + desc.[[Configurable]] is true, then
++ Remove + the own property with name P from O.
++ Return + true.
++ Else + if Throw, then throw a TypeError exception.
++ Return + false.
++ When + the [[DefaultValue]] internal method of O + is called with hint String, the following steps are taken:
+
+ Let
+ toString be the result of calling the [[Get]] internal
+ method of object O with argument "toString".
+ If + IsCallable(toString) is true then,
++ Let + str be the result of calling the [[Call]] internal method + of toString, with O as the this value and an + empty argument list.
++ If + str is a primitive value, return str.
+
+ Let
+ valueOf be the result of calling the [[Get]] internal method
+ of object O with argument "valueOf".
+ If + IsCallable(valueOf) is true then, +
++ Let + val be the result of calling the [[Call]] internal method + of valueOf, with O as the this value and an empty + argument list.
++ If + val is a primitive value, return val.
++ Throw + a TypeError exception.
++ When + the [[DefaultValue]] internal method of O + is called with hint Number, the following steps are taken:
+
+ Let
+ valueOf be the result of calling the [[Get]] internal method
+ of object O with argument "valueOf".
+ If + IsCallable(valueOf) is true then,
++ Let + val be the result of calling the [[Call]] internal method + of valueOf, with O as the this value and an + empty argument list.
++ If + val is a primitive value, return val.
+
+ Let
+ toString be the result of calling the [[Get]] internal
+ method of object O with argument "toString".
+ If + IsCallable(toString) is true then,
++ Let + str be the result of calling the [[Call]] internal method + of toString, with O as the this value and an empty + argument list.
++ If + str is a primitive value, return str.
++ Throw + a TypeError exception.
++ When + the [[DefaultValue]] internal method of O + is called with no hint, then it behaves as if the hint were Number, + unless O is a Date + object (see 15.9.6), in which case it behaves as if the hint were + String.
++ The + above specification of [[DefaultValue]] for native objects can + return only primitive values. If a host object implements its own + [[DefaultValue]] internal method, it must ensure that its + [[DefaultValue]] internal method can return only primitive values.
++ In + the following algorithm, the term “Reject” means “If Throw + is true, then throw a TypeError exception, otherwise + return false”. The algorithm contains steps that test + various fields of the Property Descriptor Desc + for specific values. The fields that are tested in this manner need + not actually exist in Desc. + If a field is absent then its value is considered to be false.
++ When + the [[DefineOwnProperty]] internal method of O + is called with property name P, + property descriptor Desc, + and Boolean flag Throw, + the following steps are taken:
++ Let + current be the result of calling the [[GetOwnProperty]] + internal method of O with property name P.
++ Let + extensible be the value of the [[Extensible]] internal + property of O.
++ If + current is undefined and extensible is false, + then Reject.
++ If + current is undefined and extensible is true, + then
++ If + IsGenericDescriptor(Desc) or IsDataDescriptor(Desc) + is true, then
++ Create + an own data property named P of object O whose + [[Value]], [[Writable]], [[Enumerable]] and [[Configurable]] + attribute values are described by Desc. If the value of an + attribute field of Desc is absent, the attribute of the + newly created property is set to its default value.
++ Else, + Desc must be an + accessor Property Descriptor so,
++ Create + an own accessor property named P of object O whose + [[Get]], [[Set]], [[Enumerable]] and [[Configurable]] attribute + values are described by Desc. If the value of an attribute + field of Desc is absent, the attribute of the newly + created property is set to its default value.
++ Return + true.
++ Return + true, if every field in Desc is absent.
++ Return + true, if every field in Desc also occurs in current + and the value of every field in Desc is the same value as + the corresponding field in current when compared using the + SameValue algorithm (9.12).
++ If + the [[Configurable]] field of current is false then
+ ++ If + IsGenericDescriptor(Desc) is true, then no further + validation is required.
++ Else, + if IsDataDescriptor(current) and IsDataDescriptor(Desc) + have different results, then
++ Reject, + if the [[Configurable]] field of current is false. +
++ If + IsDataDescriptor(current) is true, then
++ Convert + the property named P of object O from a data + property to an accessor property. Preserve the existing values of + the converted property’s [[Configurable]] and [[Enumerable]] + attributes and set the rest of the property’s attributes to + their default values.
++ Else,
++ Convert + the property named P of object O from an accessor + property to a data property. Preserve the existing values of the + converted property’s [[Configurable]] and [[Enumerable]] + attributes and set the rest of the property’s attributes to + their default values.
++ Else, + if IsDataDescriptor(current) and IsDataDescriptor(Desc) + are both true, then
++ If + the [[Configurable]] field of current is false, then
+ ++ else, + the [[Configurable]] field of current is true, so + any change is acceptable.
++ Else, + IsAccessorDescriptor(current) and IsAccessorDescriptor(Desc) + are both true so,
+ ++ For + each attribute field of Desc that is present, set the + correspondingly named attribute of the property named P of + object O to the value of the field.
++ Return + true.
++ However, + if O is an Array + object, it has a more elaborate [[DefineOwnProperty]] internal + method defined in 15.4.5.1.
+NOTE Step + 10.b allows any field of Desc to be different from the corresponding + field of current if current’s [[Configurable]] field is true. + This even permits changing the [[Value]] of a property whose + [[Writable]] attribute is false. This is allowed because a + true [[Configurable]] attribute would permit an equivalent + sequence of calls where [[Writable]] is first set to true, a + new [[Value]] is set, and then [[Writable]] is set to false.
++ The + ECMAScript runtime system performs automatic type conversion as + needed. To clarify the semantics of certain constructs it is useful + to define a set of conversion abstract operations. These abstract + operations are not a part of the language; they are defined here to + aid the specification of the semantics of the language. The + conversion abstract operations are polymorphic; that is, they can + accept a value of any ECMAScript language type, but not of + specification types.
++ The + abstract operation ToPrimitive takes an input + argument and an optional argument PreferredType. + The abstract operation ToPrimitive converts its input + argument to a non-Object type. If an object is capable of converting + to more than one primitive type, it may use the optional hint + PreferredType to + favour that type. Conversion occurs according to Table 10:
+|
+ + Input + Type + |
+
+ + Result + |
+
|
+ + Undefined + |
+
+ + The + result equals the input + argument (no conversion). + |
+
|
+ + Null + |
+
+ + The + result equals the input + argument (no conversion). + |
+
|
+ + Boolean + |
+
+ + The + result equals the input + argument (no conversion). + |
+
|
+ + Number + |
+
+ + The + result equals the input + argument (no conversion). + |
+
|
+ + String + |
+
+ + The + result equals the input + argument (no conversion). + |
+
|
+ + Object + |
+
+ + Return + a default value for the Object. The default value of an object + is retrieved by calling the [[DefaultValue]] internal method of + the object, passing the optional hint PreferredType. + The behaviour of the [[DefaultValue]] internal method is defined + by this specification for all native ECMAScript objects in + 8.12.8. + |
+
+ The + abstract operation ToBoolean converts its argument to a value of + type Boolean according to Table 11:
+|
+ + Argument + Type + |
+
+ + Result + |
+
|
+ + Undefined + |
+
+ + false + |
+
|
+ + Null + |
+
+ + false + |
+
|
+ + Boolean + |
+
+ + The + result equals the input argument (no conversion). + |
+
|
+ + Number + |
+
+ + The + result is false if the argument is +0, −0, + or NaN; otherwise the result is true. + + |
+
|
+ + String + |
+
+ + The + result is false if the argument is the empty String (its + length is zero); otherwise the result is true. + |
+
|
+ Object + |
+
+ true + |
+
+ The + abstract operation ToNumber converts its argument to a value of type + Number according to Table 12:
+|
+ + Argument + Type + |
+
+ + Result + |
+
|
+ + Undefined + |
+
+ + NaN + |
+
|
+ + Null + |
+
+ + +0 + |
+
|
+ + Boolean + |
+
+ + The + result is 1 if the argument is true. The result is + +0 if the argument is false. + |
+
|
+ + Number + |
+
+ + The + result equals the input argument (no conversion). + |
+
|
+ + String + |
+
+ + See + grammar and note below. + |
+
|
+ + Object + |
+
+ + Apply + the following steps: +
|
+
+ ToNumber + applied to Strings applies the following grammar to the input + String. If the grammar cannot interpret the String as an expansion + of StringNumericLiteral, + then the result of ToNumber is NaN.
++ StringNumericLiteral :::
+
+ StrWhiteSpaceopt
StrWhiteSpaceoptStrNumericLiteral StrWhiteSpaceopt
+ StrWhiteSpace :::
++ StrWhiteSpaceChar + StrWhiteSpaceopt
++ StrWhiteSpaceChar :::
+
+ WhiteSpace
LineTerminator
+ StrNumericLiteral :::
+
+ StrDecimalLiteral
HexIntegerLiteral
+ StrDecimalLiteral :::
+
+ StrUnsignedDecimalLiteral+
+ StrUnsignedDecimalLiteral-
+ StrUnsignedDecimalLiteral
+ StrUnsignedDecimalLiteral :::
+
+ Infinity
+ DecimalDigits . DecimalDigitsopt
+ ExponentPartopt. DecimalDigits ExponentPartopt
DecimalDigits
+ ExponentPartopt
+ DecimalDigits :::
+
+ DecimalDigit
DecimalDigits
+ DecimalDigit
+ DecimalDigit ::: + one + of
+
+ 0
+ 1 2 3 4 5 6 7 8 9
+ ExponentPart :::
++ ExponentIndicator + SignedInteger
++ ExponentIndicator ::: + one + of
+
+ e
+ E
+ SignedInteger :::
+
+ DecimalDigits+
+ DecimalDigits-
+ DecimalDigits
+ HexIntegerLiteral :::
+
+ 0x HexDigit0X HexDigit
HexIntegerLiteral HexDigit
+ HexDigit ::: one + of
+
+ 0
+ 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F
+ Some + differences should be noted between the syntax of a + StringNumericLiteral + and a NumericLiteral + (see 7.8.3):
++ A + StringNumericLiteral + may be preceded and/or followed by white space and/or line + terminators.
+
+ A
+ StringNumericLiteral
+ that is decimal may have any number of leading 0
+ digits.
+ A
+ StringNumericLiteral
+ that is decimal may be preceded by +
+ or - to indicate
+ its sign.
+ A + StringNumericLiteral + that is empty or contains only white space is converted to +0.
++ The + conversion of a String to a Number value is similar overall to the + determination of the Number value for a numeric literal (see 7.8.3), + but some of the details are different, so the process for converting + a String numeric literal to a value of Number type is given here in + full. This value is determined in two steps: first, a mathematical + value (MV) is derived from the String numeric literal; second, this + mathematical value is rounded as described below.
++ The + MV of StringNumericLiteral + ::: [empty] + is 0.
++ The + MV of StringNumericLiteral + ::: StrWhiteSpace + is 0.
++ The + MV of StringNumericLiteral + ::: StrWhiteSpaceopt + StrNumericLiteral + StrWhiteSpaceopt + is the MV of StrNumericLiteral, + no matter whether white space is present or not.
++ The + MV of StrNumericLiteral + ::: StrDecimalLiteral + is the MV of StrDecimalLiteral.
++ The + MV of StrNumericLiteral + ::: HexIntegerLiteral + is the MV of HexIntegerLiteral.
++ The + MV of StrDecimalLiteral + ::: StrUnsignedDecimalLiteral + is the MV of StrUnsignedDecimalLiteral.
+
+ The
+ MV of StrDecimalLiteral
+ ::: +
+ StrUnsignedDecimalLiteral
+ is the MV of StrUnsignedDecimalLiteral.
+ The
+ MV of StrDecimalLiteral
+ ::: -
+ StrUnsignedDecimalLiteral
+ is the negative of the MV of StrUnsignedDecimalLiteral.
+ (Note that if the MV of StrUnsignedDecimalLiteral
+ is 0, the negative of this MV is also 0. The rounding rule
+ described below handles the conversion of this signless
+ mathematical zero to a floating-point +0 or −0
+ as appropriate.)
+ The
+ MV of StrUnsignedDecimalLiteral:::
+ Infinity
+ is 1010000
+ (a value so large that it will round to +∞).
+ The
+ MV of StrUnsignedDecimalLiteral:::
+ DecimalDigits.
+ is the MV of DecimalDigits.
+ The
+ MV of StrUnsignedDecimalLiteral:::
+ DecimalDigits . DecimalDigits
+ is the MV of the first DecimalDigits
+ plus (the MV of the second DecimalDigits
+ times 10−n),
+ where n is the
+ number of characters in the second DecimalDigits.
+ The
+ MV of StrUnsignedDecimalLiteral::: DecimalDigits. ExponentPart is the MV of
+ DecimalDigits times 10e, where e
+ is the MV of ExponentPart.
+ The
+ MV of StrUnsignedDecimalLiteral::: DecimalDigits. DecimalDigits ExponentPart is (the MV of the first
+ DecimalDigits plus (the MV of the second DecimalDigits
+ times 10−n))
+ times 10e, where n is the number of
+ characters in the second DecimalDigits and e is
+ the MV of ExponentPart.
+ The
+ MV of StrUnsignedDecimalLiteral:::. DecimalDigits is the MV of
+ DecimalDigits times 10−n,
+ where n is the number of characters in DecimalDigits.
+ The
+ MV of StrUnsignedDecimalLiteral:::. DecimalDigits ExponentPart is
+ the MV of DecimalDigits times 10e−n,
+ where n is the number of characters in DecimalDigits
+ and e is the MV of
+ ExponentPart.
+ The + MV of StrUnsignedDecimalLiteral::: DecimalDigits + is the MV of DecimalDigits.
++ The + MV of StrUnsignedDecimalLiteral::: DecimalDigits + ExponentPart is the MV of + DecimalDigits times 10e, where e + is the MV of ExponentPart.
++ The + MV of DecimalDigits ::: DecimalDigit is + the MV of DecimalDigit.
++ The + MV of DecimalDigits ::: DecimalDigits + DecimalDigit is (the MV of DecimalDigits times 10) + plus the MV of DecimalDigit.
++ The + MV of ExponentPart ::: ExponentIndicator + SignedInteger is + the MV of SignedInteger.
++ The + MV of SignedInteger ::: DecimalDigits + is the MV of DecimalDigits.
+
+ The
+ MV of SignedInteger ::: + DecimalDigits is
+ the MV of DecimalDigits.
+ The
+ MV of SignedInteger ::: - DecimalDigits is the negative of the MV of
+ DecimalDigits.
+ The
+ MV of DecimalDigit ::: 0
+ or of HexDigit :::
+ 0 is 0.
+ The
+ MV of DecimalDigit ::: 1
+ or of HexDigit :::
+ 1 is 1.
+ The
+ MV of DecimalDigit ::: 2
+ or of HexDigit :::
+ 2 is 2.
+ The
+ MV of DecimalDigit ::: 3
+ or of HexDigit :::
+ 3 is 3.
+ The
+ MV of DecimalDigit ::: 4
+ or of HexDigit :::
+ 4 is 4.
+ The
+ MV of DecimalDigit ::: 5
+ or of HexDigit :::
+ 5 is 5.
+ The
+ MV of DecimalDigit ::: 6
+ or of HexDigit :::
+ 6 is 6.
+ The
+ MV of DecimalDigit ::: 7
+ or of HexDigit :::
+ 7 is 7.
+ The
+ MV of DecimalDigit ::: 8
+ or of HexDigit :::
+ 8 is 8.
+ The
+ MV of DecimalDigit ::: 9
+ or of HexDigit :::
+ 9 is 9.
+ The
+ MV of HexDigit ::: a
+ or of HexDigit :::
+ A is 10.
+ The
+ MV of HexDigit ::: b
+ or of HexDigit :::
+ B is 11.
+ The
+ MV of HexDigit ::: c
+ or of HexDigit :::
+ C is 12.
+ The
+ MV of HexDigit ::: d
+ or of HexDigit :::
+ D is 13.
+ The
+ MV of HexDigit ::: e
+ or of HexDigit :::
+ E is 14.
+ The
+ MV of HexDigit ::: f
+ or of HexDigit :::
+ F is 15.
+ The
+ MV of HexIntegerLiteral ::: 0x
+ HexDigit is the MV of
+ HexDigit.
+ The
+ MV of HexIntegerLiteral ::: 0X
+ HexDigit is the MV of
+ HexDigit.
+ The + MV of HexIntegerLiteral ::: HexIntegerLiteral + HexDigit is (the MV of HexIntegerLiteral times 16) + plus the MV of HexDigit.
+
+ Once
+ the exact MV for a String numeric literal has been determined, it is
+ then rounded to a value of the Number type. If the MV is 0, then the
+ rounded value is +0 unless the first non white space character in
+ the String numeric literal is ‘-’,
+ in which case the rounded value is −0.
+ Otherwise, the rounded value must be the Number value for the MV (in
+ the sense defined in 8.5), unless the literal includes a
+ StrUnsignedDecimalLiteral
+ and the literal has more than 20 significant digits, in which case
+ the Number value may be either the Number value for the MV of a
+ literal produced by replacing each significant digit after the 20th
+ with a 0 digit or the Number value for the MV of a literal produced
+ by replacing each significant digit after the 20th with a 0 digit
+ and then incrementing the literal at the 20th digit position. A
+ digit is significant if it is not part of an ExponentPart
+ and
+ it + is not 0; + or
++ there + is a nonzero digit to its left and there is a nonzero digit, not in + the ExponentPart, + to its right.
++ The + abstract operation ToInteger converts its argument to an integral + numeric value. This abstract operation functions as follows:
++ Let + number be the result of calling ToNumber on the input + argument.
++ If + number is NaN, return +0.
++ If + number is +0, −0, + +∞, or −∞, + return number.
++ Return + the result of computing sign(number) * floor(abs(number)).
++ The + abstract operation ToInt32 converts its argument to one of 232 + integer values in the range −231 + through 231−1, + inclusive. This abstract operation functions as follows:
++ Let + number be the result of calling ToNumber on the input + argument.
++ If + number is NaN, +0, −0, + +∞, or −∞, + return +0.
++ Let + int32bit be posInt modulo 232; that is, a + finite integer value k of Number type with positive sign and less + than 232 in magnitude such that the mathematical + difference of posInt and k is mathematically an integer + multiple of 232.
++ If + int32bit is greater than or equal to 231, return + int32bit − 232, + otherwise return int32bit.
++
NOTE Given the above definition of ToInt32:
++ The ToInt32 + abstract operation is idempotent: if applied to a result that it + produced, the second application leaves that value unchanged.
++ ToInt32(ToUint32(x)) + is equal to ToInt32(x) + for all values of x. + (It is to preserve this latter property that +∞ + and −∞ + are mapped to +0.)
++ ToInt32 maps −0 + to +0.
++ The + abstract operation ToUint32 converts its argument to one of 232 + integer values in the range 0 + through 232−1, + inclusive. This abstraction operation functions as follows:
++ Let + number be the result of calling ToNumber on the input + argument.
++ If + number is NaN, +0, −0, + +∞, or −∞, + return +0.
++ Let + int32bit be posInt modulo 232; that is, a + finite integer value k of Number type with positive sign and less + than 232 in magnitude such that the mathematical + difference of posInt and k is mathematically an integer + multiple of 232.
++ Return + int32bit.
++
NOTE Given the above definition of ToUInt32:
++ Step 5 is the + only difference between ToUint32 and ToInt32.
++ The ToUint32 + abstract operation is idempotent: if applied to a result that it + produced, the second application leaves that value unchanged.
++ ToUint32(ToInt32(x)) + is equal to ToUint32(x) + for all values of x. + (It is to preserve this latter property that +∞ + and −∞ are mapped to + +0.)
++ ToUint32 maps −0 + to +0.
++ The + abstract operation ToUint16 converts its argument to one of 216 + integer values in the range 0 + through 216−1, + inclusive. This abstract operation functions as follows:
++ Let + number be the result of calling ToNumber on the input + argument.
++ If + number is NaN, +0, −0, + +∞, or −∞, + return +0.
++ Let + int16bit be posInt modulo 216; that is, a + finite integer value k of Number type with positive sign and + less than 216 in magnitude such that the mathematical + difference of posInt and k is mathematically an + integer multiple of 216.
++ Return + int16bit.
++
NOTE Given the above definition of ToUint16:
++ The substitution + of 216 + for 232 + in step 4 is the only difference between ToUint32 and ToUint16.
++ ToUint16 maps −0 + to +0.
++ The + abstract operation ToString converts its argument to a value of type + String according to Table 13:
+|
+ + Argument + Type + |
+
+ + Result + |
+
|
+ + Undefined + |
+
+
|
+
|
+ + Null + |
+
+
|
+
|
+ + Boolean + |
+
+ If
+ the argument is true, then the result is If
+ the argument is false, then the result is |
+
|
+ + Number + |
+
+ See + 9.8.1. + |
+
|
+ + String + |
+
+ Return + the input argument (no conversion) + |
+
|
+ + Object + |
+
+ Apply + the following steps: ++ 1. + Let primValue + be ToPrimitive(input argument, hint String). ++ 2. + Return ToString(primValue). + |
+
+ The + abstract operation ToString converts a Number m + to String format as follows:
+
+ If
+ m is NaN, return the String "NaN".
+ If
+ m is +0 or −0,
+ return the String "0".
+ If
+ m is less than zero, return the String concatenation of the
+ String "-"
+ and ToString(−m).
+ If
+ m is infinity, return the String "Infinity".
+ Otherwise, + let n, k, and s be integers such that k + ≥ 1, 10k−1 + ≤ s < 10k, + the Number value for s × + 10n−k + is m, and k is as small as possible. Note that k + is the number of digits in the decimal representation of s, + that s is not divisible by 10, and that the least + significant digit of s is not necessarily uniquely + determined by these criteria.
+
+ If
+ k ≤ n ≤
+ 21, return the String consisting of the k digits of the
+ decimal representation of s (in order, with no leading zeroes),
+ followed by n−k
+ occurrences of the character ‘0’.
+ If
+ 0 < n ≤ 21, return the
+ String consisting of the most significant n digits of the
+ decimal representation of s, followed by a decimal point
+ ‘.’, followed
+ by the remaining k−n
+ digits of the decimal representation of s.
+ If
+ −6 < n ≤
+ 0, return the String consisting of the character ‘0’,
+ followed by a decimal point ‘.’,
+ followed by −n
+ occurrences of the character ‘0’,
+ followed by the k digits of the decimal representation of s.
+ Otherwise,
+ if k = 1, return the String consisting of the single digit
+ of s, followed by lowercase character ‘e’,
+ followed by a plus sign ‘+’
+ or minus sign ‘−’
+ according to whether n−1
+ is positive or negative, followed by the decimal representation of
+ the integer abs(n−1)
+ (with no leading zeros).
+ Return + the String consisting of the most significant digit of the decimal + representation of s, followed by a decimal point ‘.’, followed + by the remaining k−1 digits of + the decimal representation of s, followed by the lowercase + character ‘e’, followed by a plus sign ‘+’ or minus sign + ‘−’ according to whether + n−1 is positive or negative, + followed by the decimal representation of the integer abs(n−1) + (with no leading zeros).
+NOTE 1 The following observations may be useful as guidelines for + implementations, but are not part of the normative requirements of + this Standard:
++ If x is any + Number value other than −0, + then ToNumber(ToString(x)) is exactly the same Number value as x.
++ The least + significant digit of s is not always uniquely determined by the + requirements listed in step 5.
+NOTE 2 For implementations that provide more accurate conversions than + required by the rules above, it is recommended that the following + alternative version of step 5 be used as a guideline:
++ Otherwise, + let n, + k, + and s + be integers such that k + ≥ + 1, 10k−1 + ≤ + s + < 10k, + the Number value for s + × + 10n−k + is m, + and k + is as small as possible. If there are multiple possibilities for s, + choose the value of s + for which s + × + 10n−k + is closest in value to m. + If there are two such possible values of s, + choose the one that is even. Note that k + is the number of digits in the decimal representation of s + and that s + is not divisible by 10.
+NOTE 3 Implementers of ECMAScript may find useful the paper and code + written by David M. Gay for binary-to-decimal conversion of + floating-point numbers:
+
+ Gay, David M.
+ Correctly Rounded Binary-Decimal and Decimal-Binary Conversions.
+ Numerical Analysis, Manuscript 90-10. AT&T Bell Laboratories
+ (Murray Hill, New Jersey). November 30, 1990. Available
+ as
+
http://cm.bell-labs.com/cm/cs/doc/90/4-10.ps.gz.
+ Associated code available
+ as
+
http://cm.bell-labs.com/netlib/fp/dtoa.c.gz
+ and as
+
http://cm.bell-labs.com/netlib/fp/g_fmt.c.gz
+ and may also be found at the various netlib
+ mirror sites.
+ The + abstract operation ToObject converts its argument to a value of type + Object according to Table 14:
+|
+ + Argument + Type + |
+
+ + Result + |
+
|
+ + Undefined + |
+
+ + Throw + a TypeError exception. + |
+
|
+ + Null + |
+
+ + Throw + a TypeError exception. + |
+
|
+ + Boolean + |
+
+ + Create + a new Boolean object whose [[PrimitiveValue]] internal property + is set to the value of the argument. See 15.6 for a description + of Boolean objects. + |
+
|
+ + Number + |
+
+ + Create + a new Number object whose [[PrimitiveValue]] internal property + is set to the value of the argument. See 15.7 for a description + of Number objects. + |
+
|
+ + String + |
+
+ + Create + a new String object whose [[PrimitiveValue]] internal property + is set to the value of the argument. See 15.5 for a description + of String objects. + |
+
|
+ Object + |
+
+ The + result is the input argument (no conversion). + |
+
+ The + abstract operation CheckObjectCoercible throws an error if its + argument is a value that cannot be converted to an Object using + ToObject. It is defined by Table 15:
+|
+ + Argument + Type + |
+
+ + Result + |
+
|
+ + Undefined + |
+
+ + Throw + a TypeError exception. + |
+
|
+ + Null + |
+
+ + Throw + a TypeError exception. + |
+
|
+ + Boolean + |
+
+ + Return + |
+
|
+ + Number + |
+
+ + Return + |
+
|
+ + String + |
+
+ + Return + |
+
|
+ Object + |
+
+ Return + |
+
+ The + abstract operation IsCallable determines if its argument, which must + be an ECMAScript language value, is a callable function Object + according to Table 16:
+|
+ + Argument + Type + |
+
+ + Result + |
+
|
+ + Undefined + |
+
+ + Return + false. + |
+
|
+ + Null + |
+
+ + Return + false. + |
+
|
+ + Boolean + |
+
+ + Return + false. + |
+
|
+ + Number + |
+
+ + Return + false. + |
+
|
+ + String + |
+
+ + Return + false. + |
+
|
+ Object + |
+
+ If + the argument object has an [[Call]] internal method, then return + true, otherwise return false. + |
+
+ The + internal comparison abstract operation SameValue(x, + y), where x + and y are + ECMAScript language values, produces true or false. + Such a comparison is performed as follows:
++ If + Type(x) is Undefined, return true.
++ If + Type(x) is Null, return true.
++ If + Type(x) is Number, then.
++ If + x is NaN and y is NaN, return true.
++ If + x is +0 and y is -0, return false.
++ If + x is -0 and y is +0, return false.
++ If + x is the same Number value as y, return true.
++ Return + false.
++ If + Type(x) is String, then return true if x and y + are exactly the same sequence of characters (same length and same + characters in corresponding positions); otherwise, return false.
++ If + Type(x) is Boolean, return true if x and y + are both true or both false; otherwise, return false.
++ Return + true if x and y refer to the same object. Otherwise, + return false.
++ There + are three types of ECMAScript executable code:
+Global code is source text that + is treated as an ECMAScript Program. + The global code of a particular Program + does not include any source text that is parsed as part of a + FunctionBody.
+Eval code is the source text
+ supplied to the built-in eval function. More precisely, if the parameter to the built-in eval function is a String, it is treated as an ECMAScript Program.
+ The eval code for a particular invocation of eval
+ is the global code portion of that Program.
Function code is source text that
+ is parsed as part of a FunctionBody.
+ The function code
+ of a particular FunctionBody
+ does not include any source text that is parsed as part of a nested
+ FunctionBody. Function
+ code also denotes the
+ source text supplied when using the built-in Function object as a constructor. More precisely, the last parameter
+ provided to the Function
+ constructor is converted to a String and treated as the
+ FunctionBody. If more
+ than one parameter is provided to the Function
+ constructor, all parameters except the last one are converted to
+ Strings and concatenated together, separated by commas. The
+ resulting String is interpreted as the FormalParameterList
+ for the FunctionBody
+ defined by the last parameter. The function code for a particular
+ instantiation of a Function
+ does not include any source text that is parsed as part of a nested
+ FunctionBody.
+ An + ECMAScript Program + syntactic unit may be processed using either unrestricted or strict + mode syntax and semantics. When processed using strict mode the + three types of ECMAScript code are referred to as strict global + code, strict eval code, and strict function code. Code is + interpreted as strict mode code in the following situations:
++ Global code is strict global code if it begins with a Directive Prologue + that contains a Use Strict Directive (see 14.1).
++ Eval code is strict eval code if it begins with a Directive Prologue + that contains a Use Strict Directive or if the call to eval is a + direct call (see 15.1.2.1.1) to the eval function that is contained + in strict mode code. +
++ Function code that is part of a FunctionDeclaration, + FunctionExpression, + or accessor PropertyAssignment + is strict function code if its FunctionDeclaration, + FunctionExpression, + or PropertyAssignment + is contained in strict mode code or if the function code begins + with a Directive Prologue that contains a Use Strict Directive.
++ Function code that is supplied as the last argument to the built-in Function + constructor is strict function code if the last argument is a + String that when processed as a FunctionBody + begins with a Directive Prologue that contains a Use Strict + Directive.
++ A + Lexical Environment is a specification type used to define + the association of Identifiers + to specific variables and functions based upon the lexical nesting + structure of ECMAScript code. A Lexical Environment consists of an + Environment Record and a possibly null reference to an outer + Lexical Environment. Usually a Lexical Environment is associated + with some specific syntactic structure of ECMAScript code such as a + FunctionDeclaration, + a WithStatement, + or a Catch clause + of a TryStatement + and a new Lexical Environment is created each time such code is + evaluated.
++ An + Environment Record records the identifier bindings that are + created within the scope of its associated Lexical Environment.
++ The + outer environment reference is used to model the logical nesting of + Lexical Environment values. The outer reference of a (inner) Lexical + Environment is a reference to the Lexical Environment that logically + surrounds the inner Lexical Environment. An outer Lexical + Environment may, of course, have its own outer Lexical Environment. + A Lexical Environment may serve as the outer environment for + multiple inner Lexical Environments. For example, if a + FunctionDeclaration + contains two nested FunctionDeclarations + then the Lexical Environments of each of the nested functions will + have as their outer Lexical Environment the Lexical Environment of + the current execution of the surrounding function.
++ Lexical + Environments and Environment Record values are purely specification + mechanisms and need not correspond to any specific artefact of an + ECMAScript implementation. It is impossible for an ECMAScript + program to directly access or manipulate such values.
++ There + are two kinds of Environment Record values used in this + specification: declarative environment records and object + environment records. Declarative environment records are used + to define the effect of ECMAScript language syntactic elements such + as FunctionDeclarations, + VariableDeclarations, + and Catch clauses + that directly associate identifier bindings with ECMAScript + language values. Object environment records are used to define the + effect of ECMAScript elements such as Program + and WithStatement + that associate identifier bindings with the properties of + some object.
++ For + specification purposes Environment Record values can be thought of + as existing in a simple object-oriented hierarchy where Environment + Record is an abstract class with two concrete subclasses, + declarative environment record + and object environment record. The + abstract class includes the abstract specification methods defined + in Table 17. These abstract methods have distinct concrete + algorithms for each of the concrete subclasses. +
+|
+ + Method + |
+
+ + Purpose + |
+
|
+ + HasBinding(N) + |
+
+ + Determine + if an environment record has a binding for an identifier. Return + true if it + does and false + if it does not. The String value N + is the text of the identifier. + |
+
|
+ + CreateMutableBinding(N, + D) + |
+
+ + Create + a new mutable binding in an environment record. The String value + N is the text + of the bound name. If the optional Boolean argument D + is true the binding is may be subsequently deleted. + + |
+
|
+ + SetMutableBinding(N,V, + S) + |
+
+ + Set + the value of an already existing mutable binding in an + environment record. The String value N + is the text of the bound name. V + is the value for the binding and may be a value of any + ECMAScript language type. S + is a Boolean flag. If S + is true and + the binding cannot be set throw a TypeError exception. S + is used to identify strict mode references. + |
+
|
+ + GetBindingValue(N,S) + |
+
+ + Returns + the value of an already existing binding from an environment + record. The String value N + is the text of the bound name. S + is used to identify strict mode references. If S + is true and + the binding does not exist or is uninitialized throw a + ReferenceError exception. + + |
+
|
+ + DeleteBinding(N) + |
+
+ + Delete + a binding from an environment record. The String value N + is the text of the bound name If a binding for N + exists, remove the binding and return true. If the + binding exists but cannot be removed return false. If the + binding does not exist return true. + |
+
|
+ ImplicitThisValue() + |
+
+ Returns + the value to use as the this value on calls to function + objects that are obtained as binding values from this + environment record. + + |
+
+ Each + declarative environment record is associated with an ECMAScript + program scope containing variable and/or function declarations. A + declarative environment record binds the set of identifiers defined + by the declarations contained within its scope.
++ In + addition to the mutable bindings supported by all Environment + Records, declarative environment records also provide for immutable + bindings. An immutable binding is one where the association between + an identifier and a value may not be modified once it has been + established. Creation and initialization of immutable binding are + distinct steps so it is possible for such bindings to exist in + either an initialized or uninitialized state. Declarative + environment records support the methods listed in Table 18 in + addition to the Environment Record abstract specification methods:
+|
+ + Method + |
+
+ + Purpose + |
+
| + + | +
+ + Create + a new but uninitialized immutable binding in an environment + record. The String value N + is the text of the bound name. + |
+
| + + | +
+ Set + the value of an already existing but uninitialized immutable binding in an environment record. The String value N + is the text of the bound name. V + is the value for the binding and is a value of any ECMAScript + language type. + + |
+
+ The + behaviour of the concrete specification methods for Declarative + Environment Records are defined by the following algorithms.
++ The + concrete environment record method HasBinding for declarative + environment records simply determines if the argument identifier is + one of the identifiers bound by the record:
++ Let + envRec be the declarative environment record for which the + method was invoked.
++ If + envRec has a binding for the name that is the value of N, + return true.
++ If + it does not have such a binding, return false
++ The + concrete Environment Record method CreateMutableBinding for + declarative environment records creates a new mutable binding for + the name N that is + initialized to the value undefined. A binding must not + already exist in this Environment Record for N. + If Boolean argument D + is provided and has the value true the new binding is marked + as being subject to deletion.
++ Let + envRec be the declarative environment record for which the + method was invoked.
++ Assert: + envRec does not already have a binding for N.
++ Create + a mutable binding in envRec for N and set its bound + value to undefined. If D is true record that the + newly created binding may be deleted by a subsequent DeleteBinding + call.
++ The + concrete Environment Record method SetMutableBinding for declarative + environment records attempts to change the bound value of the + current binding of the identifier whose name is the value of the + argument N to the + value of argument V. + A binding for N + must already exist. If the binding is an immutable binding, a + TypeError is + thrown + if S is true. +
+ ++ Let + envRec be the declarative environment record for which the + method was invoked.
++ Assert: + envRec must have a binding for N.
++ If + the binding for N in envRec is a mutable binding, + change its bound value to V.
++ Else + this must be an attempt to change the value of an immutable binding + so + if S is true + throw a + TypeError + exception.
++ The + concrete Environment Record method GetBindingValue for declarative + environment records simply returns the value of its bound identifier + whose name is the value of the argument N. + The binding must already exist. If S + is true and the binding is an uninitialized immutable binding + throw a ReferenceError exception.
++ Let + envRec be the declarative environment record for which the + method was invoked.
++ Assert: + envRec has a binding for N.
++ If + the binding for N in envRec is an uninitialized + immutable binding, then
++ If + S is false, return the value undefined, + otherwise throw a ReferenceError exception.
++ Else, + return the value currently bound to N in envRec.
++ The + concrete Environment Record method DeleteBinding for declarative + environment records can only delete bindings that have been + explicitly designated as being subject to deletion.
++ Let + envRec be the declarative environment record for which the + method was invoked.
++ If + envRec does not have a binding for the name that is the + value of N, return true.
++ If + the binding for N in envRec is cannot be deleted, + return false.
++ Remove + the binding for N from envRec.
++ Return + true.
++ Declarative + Environment Records always return undefined as their + ImplicitThisValue.
++ Return + undefined.
++ The + concrete Environment Record method CreateImmutableBinding for + declarative environment records creates a new immutable binding for + the name N that is + initialized to the value undefined. A binding must not + already exist in this environment record for N.
++ Let + envRec be the declarative environment record for which the + method was invoked.
++ Assert: + envRec does not already have a binding for N.
++ Create + an immutable binding in envRec for N and record that + it is uninitialized.
++ The + concrete Environment Record method InitializeImmutableBinding for + declarative environment records is used to set the bound value of + the current binding of the identifier whose name is the value of the + argument N to the + value of argument V. + An uninitialized immutable binding for N + must already exist. +
++ Let + envRec be the declarative environment record for which the + method was invoked.
++ Assert: + envRec must have an uninitialized immutable binding for N.
++ Set + the bound value for N in envRec to V.
++ Record + that the immutable binding for N in envRec has been + initialized.
++ Each + object environment record is associated with an object called its + binding object. An object environment record binds the set of + identifier names that directly correspond to the property names of + its binding object. Property names that are not an IdentifierName are not included in the set of bound identifiers. Both + own and inherited properties are included in the set regardless of + the setting of their [[Enumerable]] attribute. Because properties + can be dynamically added and deleted from objects, the set of + identifiers bound by an object environment record may potentially + change as a side-effect of any operation that adds or deletes + properties. Any bindings that are created as a result of such a + side-effect are considered to be a mutable binding even if the + Writable attribute of the corresponding property has the value + false. Immutable bindings do not exist for object environment + records.
++ Object + environment records can be configured to provide their binding + object as an implicit this value for use in function calls. This + capability is used to specify the behaviour of With Statement + (12.10) induced bindings. The capability is controlled by a + provideThis + Boolean value that is associated with each object environment + record. By default, the value of provideThis + is false for any object environment record.
++ The + behaviour of the concrete specification methods for Object + Environment Records is defined by the following algorithms.
++ The + concrete Environment Record method HasBinding for object environment + records determines if its associated binding object has a property + whose name is the value of the argument N:
++ Let + envRec be the object environment record for which the method + was invoked.
++ Let + bindings be the binding object for envRec.
++ Return + the result of calling the [[HasProperty]] internal method of + bindings, passing N as the property name.
++ The + concrete Environment Record method CreateMutableBinding for object + environment records creates in an environment record’s associated + binding object a property whose name is the String value and + initializes it to the value undefined. A property named N + must not already exist in the binding object. If Boolean argument D + is provided and has the value true the new property’s + [[Configurable]] attribute is set to true, otherwise it is + set to false.
++ Let + envRec be the object environment record for which the method + was invoked.
++ Let + bindings be the binding object for envRec.
++ Assert: + The result of calling the [[HasProperty]] internal method of + bindings, passing N as the property name, is false.
++ If + D is true then let configValue be true + otherwise let configValue be false.
++ Call + the [[DefineOwnProperty]] internal method of bindings, + passing N, Property Descriptor {[[Value]]:undefined, + [[Writable]]: true, [[Enumerable]]: true , + [[Configurable]]: configValue}, and + true + as + arguments.
++ The + concrete Environment Record method SetMutableBinding for object + environment records attempts to set the value of the environment + record’s associated binding object’s property whose name is the + value of the argument N + to the value of argument V. + A property named N + should already exist but if it does not or is not currently + writable, error handling is determined by the value of the Boolean + argument S.
++ Let + envRec be the object environment record for which the method + was invoked.
++ Let + bindings be the binding object for envRec.
++ Call + the [[Put]] internal method of bindings with arguments N, + V, and S.
++ The + concrete Environment Record method GetBindingValue for object + environment records returns the value of its associated binding object’s property whose name is the String value of the argument + identifier N. The + property should already exist but if it does not the result depends + upon the value of the S + argument:
++ Let + envRec be the object environment record for which the method + was invoked.
++ Let + bindings be the binding object for envRec.
++ Let + value be the result of calling the [[HasProperty]] internal + method of bindings, passing N as the property name.
++ If + value is false, then
++ If + S is false, return the value undefined, + otherwise throw a ReferenceError exception.
++ Return + the result of calling the [[Get]] internal method of bindings, + passing N for the argument.
++ The + concrete Environment Record method DeleteBinding for object + environment records can only delete bindings that correspond to + properties of the environment object whose [[Configurable]] + attribute have the value true.
++ Let + envRec be the object environment record for which the method + was invoked.
++ Let + bindings be the binding object for envRec.
++ Return + the result of calling the [[Delete]] internal method of bindings, + passing N and false as arguments.
++ Object + Environment Records return undefined as their + ImplicitThisValue unless their provideThis + flag is true.
++ Let + envRec be the object environment record for which the method + was invoked.
++ If + the provideThis flag of envRec is true, return + the binding object for envRec.
++ Otherwise, + return undefined.
++ The + following abstract operations are used in this specification to + operate upon lexical environments:
++ The + abstract operation GetIdentifierReference is called with a Lexical Environment lex, + an identifier String name, + and a Boolean flag strict. The value of lex may be null. When called, the following steps are + performed:
++ If + lex is the value null, then
++ Return + a value of type Reference whose base value is undefined, + whose referenced name is name, and whose strict mode flag + is strict.
++ Let + envRec be lex’s environment record.
++ Let + exists be the result of calling the HasBinding(N) + concrete method of envRec passing name as the + argument N.
+
+ If
+ exists is true,
+ then
+ Return + a value of type Reference whose base value is envRec, whose + referenced name is name, and whose strict mode flag is + strict.
++ Else
++ Let + outer be the value of lex’s outer environment reference.
++ Return + the result of calling GetIdentifierReference passing outer, + name, and strict as arguments.
++ When + the abstract operation NewDeclarativeEnvironment is called with + either a Lexical Environment or null as argument E the following steps are performed:
++ Let + env be a new Lexical Environment.
++ Let + envRec be a new declarative environment record containing no + bindings.
++ Set + env’s environment record to be envRec.
++ Set + the outer lexical environment reference of env to E.
++ Return + env.
++ When + the abstract operation NewObjectEnvironmentis called with an Object + O and a Lexical Environment E (or + null) as arguments, the following steps are performed:
++ Let + env be a new Lexical Environment.
++ Let + envRec be a new object environment record containing O + as the binding object.
++ Set + env’s environment record to be envRec.
++ Set + the outer lexical environment reference of env to E.
++ Return + env.
++ The + global environment is a unique Lexical Environment which is + created before any ECMAScript code is executed. The global + environment’s Environment Record is an object environment record + whose binding object is the global object (15.1). The global + environment’s outer environment reference is null.
++ As + ECMAScript code is executed, additional properties may be added to + the global object and the initial properties may be modified. + +
++ When + control is transferred to ECMAScript executable code, control is + entering an execution context. Active execution contexts + logically form a stack. The top execution context on this logical + stack is the running execution context. A new execution context is + created whenever control is transferred from the executable code + associated with the currently running execution context to + executable code that is not associated with that execution context. + The newly created execution context is pushed onto the stack and + becomes the running execution context.
++ An + execution context contains whatever state is necessary to track the + execution progress of its associated code. In addition, each + execution context has the state components listed in Table 19.
+|
+ + Component + |
+
+ + Purpose + |
+
|
+ + LexicalEnvironment + |
+
+ + Identifies + the Lexical Environment used to resolve identifier references + made by code within this execution context. + |
+
|
+ + VariableEnvironment + |
+
+ + Identifies + the Lexical Environment whose environment record holds bindings + created by VariableStatements + and FunctionDeclarations + within this execution context. + |
+
|
+ ThisBinding + |
+
+ The
+ value associated with the |
+
+ The + LexicalEnvironment and VariableEnvironment components of an + execution context are always Lexical Environments. When an execution + context is created its LexicalEnvironment and VariableEnvironment + components initially have the same value. The value of the + VariableEnvironment component never changes while the value of the + LexicalEnvironment component may change during execution of code + within an execution context.
++ In + most situations only the running execution context (the top of the + execution context stack) is directly manipulated by algorithms + within this specification. Hence when the terms + “LexicalEnvironment”, “VariableEnvironment” and + “ThisBinding” are used without qualification they are in + reference to those components of the running execution context.
++ An + execution context is purely a specification mechanism and need not + correspond to any particular artefact of an ECMAScript + implementation. It is impossible for an ECMAScript program to + access an execution context. +
++ Identifier + resolution is the process of determining the binding of an + Identifier using + the LexicalEnvironment of the running execution context. During + execution of ECMAScript code, the syntactic production + PrimaryExpression + : + Identifier is + evaluated using the following algorithm:
++ Let + env be the running execution context’s LexicalEnvironment.
++ If + the syntactic production that is being evaluated is contained in a + strict mode code, then let strict be true, else let + strict be false.
++ Return + the result of calling GetIdentifierReference function passing env, + Identifier, and strict as arguments.
++ The + result of evaluating an identifier is always a value of type + Reference with its referenced name component equal to the Identifier + String.
++ Evaluation + of global code or code using the eval function (15.1.2.1) + establishes and enters a new execution context. Every invocation of + an ECMAScript code function (13.2.1) also establishes and enters a + new execution context, even if a function is calling itself + recursively. Every return exits an execution context. A thrown + exception may also exit one or more execution contexts.
++ When + control enters an execution context, the execution context’s + ThisBinding is set, its VariableEnvironment and initial + LexicalEnvironment are defined, and declaration binding + instantiation (10.5) is performed. The exact manner in which these + actions occur depend on the type of code being entered.
++ The + following steps are performed when control enters the execution + context for global code:
++ Initialize + the execution context using the global code as described in + 10.4.1.1.
++ Perform + Declaration Binding Instantiation as described in 10.5 using the + global code.
++ The + following steps are performed to initialize a global execution + context for ECMAScript code C:
++ Set + the VariableEnvironment to the Global Environment.
++ Set + the LexicalEnvironment to the Global Environment.
++ Set + the ThisBinding to the global object.
++ The + following steps are performed when control enters the execution + context for eval code:
++ If + there is no calling context or if the eval code is not being + evaluated by a direct call (15.1.2.1.1) to the eval function then,
+ ++ Else,
++ Set + the ThisBinding to the same value as the ThisBinding of the + calling execution context.
++ Set + the LexicalEnvironment to the same value as the LexicalEnvironment + of the calling execution context.
++ Set + the VariableEnvironment to the same value as the + VariableEnvironment of the calling execution context.
++ If + the eval code is strict code, then
++ Let + strictVarEnv be the result of calling + NewDeclarativeEnvironment passing the LexicalEnvironment as the + argument.
++ Set + the LexicalEnvironment to strictVarEnv.
++ Set + the VariableEnvironment to strictVarEnv.
++ Perform + Declaration Binding Instantiation as described in 10.5 using the + eval code.
++ The + eval code cannot instantiate variable or function bindings in the + variable environment of the calling context that invoked the eval if + either the code of the calling context or the eval code is strict code. Instead such bindings are instantiated in a new + VariableEnvironment that is only accessible to the eval code.
++ The + following steps are performed when control enters the execution + context for function code contained in function object F, + a caller provided thisArg, + and a caller provided argumentsList:
++ If + the function code is strict code, set the ThisBinding to thisArg.
++ Else + if thisArg is null or undefined, set the + ThisBinding to the global object.
++ Else + if Type(thisArg) is not Object, set the ThisBinding to + ToObject(thisArg).
++ Else + set the ThisBinding to thisArg.
++ Let + localEnv be the result of calling NewDeclarativeEnvironment + passing the value of the [[Scope]] internal property of F as + the argument.
++ Set + the LexicalEnvironment to localEnv.
++ Set + the VariableEnvironment to localEnv.
++ Let + code be the value of F’s [[Code]] internal + property.
++ Perform + Declaration Binding Instantiation using the function code code + and argumentList as described in 10.5.
++ Every + execution context has an associated VariableEnvironment. Variables + and functions declared in ECMAScript code evaluated in an execution + context are added as bindings in that VariableEnvironment’s + Environment Record. For function code, parameters are also added as + bindings to that Environment Record.
++ Which + Environment Record is used to bind a declaration and its kind + depends upon the type of ECMAScript code executed by the execution + context, but the remainder of the behaviour is generic. On entering + an execution context, bindings are created in the + VariableEnvironment as follows using the caller provided code and, if it is function code, argument List args:
++ Let + env be the environment record component of the running + execution context’s VariableEnvironment.
++ If + code is eval code, then let configurableBindings be + true else let configurableBindings be false.
++ If + code is strict mode code, then let strict be true + else let strict be false.
++ If + code is function code, then
++ Let + func be the function whose [[Call]] internal method + initiated execution of code. Let names be the value + of func’s [[FormalParameters]] internal property. +
++ Let + argCount be the number of elements in args.
++ Let + n be the number 0.
++ For + each String argName in names, in list order do
++ Let + n be the current value of n plus 1.
++ If + n is greater than argCount, let v be + undefined otherwise let v be the value of the n’th + element of args.
++ Let + argAlreadyDeclared be the result of calling env’s + HasBinding concrete method passing argName as the + argument.
++ If + argAlreadyDeclared is false, call env’s + CreateMutableBinding concrete method passing argName as + the argument.
++ Call + env’s SetMutableBinding concrete method passing argName, + v, and strict as the arguments.
++ For each + FunctionDeclaration f in code, in source text + order do
+Let + fn be the Identifier in FunctionDeclaration + f.
+Let + fo be the result of instantiating FunctionDeclaration f + as described in Clause 13.
+Let + funcAlreadyDeclared be the result of calling env’s + HasBinding concrete method passing fn as the argument.
+If + funcAlreadyDeclared is false, call env’s + CreateMutableBinding concrete method passing fn and + configurableBindings as the arguments.
+Else + if env + is the environment record component of the global environment then
+Let + go + be the global object.
+Let + existingProp + be the resulting of calling the [[GetProperty]] internal method + of go + with argument fn.
+If + existingProp + .[[Configurable]] is true, + then
+Call + the [[DefineOwnProperty]] internal method of go, + passing fn, + Property Descriptor {[[Value]]: + undefined, + [[Writable]]: true, + [[Enumerable]]: true + , [[Configurable]]: configurableBindings + }, and true + as arguments.
+Else + if IsAccessorDescrptor(existingProp) + or existingProp + does not have attribute values {[[Writable]]: true, + [[Enumerable]]: true}, + then
+Throw + a TypeError exception.
+Call + env’s SetMutableBinding concrete method passing fn, + fo, and strict as the arguments.
+
+ Let
+ argumentsAlreadyDeclared be the result of calling env’s
+ HasBinding concrete method passing "arguments"
+ as the argument
+ If + code is function code and argumentsAlreadyDeclared is + false, then
++ Let + argsObj be the result of calling the abstract operation + CreateArgumentsObject (10.6) passing func, names, args, + env and strict as arguments.
++ If + strict is true, then +
+
+ Call
+ env’s CreateImmutableBinding concrete method passing the
+ String "arguments"
+ as the argument.
+ Call
+ env’s InitializeImmutableBinding concrete method passing
+ "arguments"
+ and argsObj as arguments.
+ Else,
+
+ Call
+ env’s CreateMutableBinding concrete method passing the
+ String "arguments"
+ as the argument.
+ Call
+ env’s SetMutableBinding concrete method passing
+ "arguments",
+ argsObj, and false as arguments.
+ For + each VariableDeclaration and VariableDeclarationNoIn + d in code, in source text order do
++ Let + dn be the Identifier in d.
++ Let + varAlreadyDeclared be the result of calling env’s + HasBinding concrete method passing dn as the argument.
++ If + varAlreadyDeclared is false, then
++ Call + env’s CreateMutableBinding concrete method passing dn and configurableBindings as the arguments.
++ Call + env’s SetMutableBinding concrete method passing dn, + undefined, and strict as the arguments.
+
+ When
+ control enters an execution context for function code, an arguments
+ object is created unless (as specified in 10.5) the identifier
+ arguments occurs
+ as an Identifier
+ in the function’s FormalParameterList
+ or occurs as the Identifier
+ of a VariableDeclaration
+ or FunctionDeclaration
+ contained in the function code.
+ The + arguments object is created by calling the abstract operation + CreateArgumentsObject with arguments func + the function object whose code is to be evaluated, + names a List containing the function’s formal parameter + names, args the + actual arguments passed to the [[Call]] internal method, env the variable environment for the function code, and + strict a Boolean + that indicates whether or not the function code is strict code. When + CreateArgumentsObject is called the following steps are performed:
++ Let + len be the number of elements in args.
++ Let + obj be the result of creating a new ECMAScript object.
++ Set + all the internal methods of obj as specified in 8.12.
+
+ Set
+ the [[Class]] internal property of obj to "Arguments".
+ Let + Object be the standard built-in Object constructor (15.2.2).
++ Set + the [[Prototype]] internal property of obj to the standard + built-in Object prototype object (15.2.4).
+
+ Call
+ the [[DefineOwnProperty]] internal method on obj passing
+ "length",
+ the Property Descriptor {[[Value]]: len, [[Writable]]: true,
+ [[Enumerable]]: false, [[Configurable]]: true}, and
+ false as arguments.
+ Let
+ map be the result of creating a new object as if by the
+ expression new Object()
+ where Object is
+ the standard built-in constructor with that name
+ Let + mappedNames be an empty List.
++ Let + indx = len - 1.
++ Repeat + while indx >= 0, +
++ Let + val be the element of args at 0-origined list + position indx.
++ Call + the [[DefineOwnProperty]] internal method on obj passing + ToString(indx), the property descriptor {[[Value]]: val, + [[Writable]]: true, [[Enumerable]]: true, + [[Configurable]]: true}, and false as arguments.
++ If + indx is less than the number of elements in names, + then
++ Let + name be the element of names at 0-origined list + position indx.
++ If + strict is false and name is not an element + of mappedNames, then
++ Add + name as an element of the list mappedNames.
++ Let + g be the result of calling the MakeArgGetter + abstract operation with arguments name and env.
++ Let + p be the result of calling the MakeArgSetter + abstract operation with arguments name and env.
++ Call + the [[DefineOwnProperty]] internal method of map passing + ToString(indx), the Property Descriptor {[[Set]]: p, + [[Get]]: g, [[Configurable]]: true}, and false + as arguments.
++ Let + indx = indx - 1
++ If + mappedNames is not empty, then
++ Set + the [[ParameterMap]] internal property of obj to map.
++ Set + the [[Get]], [[GetOwnProperty]], [[DefineOwnProperty]], and + [[Delete]] internal methods of obj to the definitions + provided below.
++ If + strict is false, then
+
+ Call
+ the [[DefineOwnProperty]] internal method on obj passing
+ "callee",
+ the property descriptor {[[Value]]: func, [[Writable]]:
+ true, [[Enumerable]]: false, [[Configurable]]:
+ true}, and false as arguments.
+ Else, + strict is true so
++ Let + thrower be the [[ThrowTypeError]] function Object (13.2.3).
+
+ Call
+ the [[DefineOwnProperty]] internal method of obj with
+ arguments "caller",
+ PropertyDescriptor {[[Get]]: thrower, [[Set]]: thrower,
+ [[Enumerable]]: false, [[Configurable]]: false}, and
+ false.
+ Call
+ the [[DefineOwnProperty]] internal method of obj with
+ arguments "callee",
+ PropertyDescriptor {[[Get]]: thrower, [[Set]]: thrower,
+ [[Enumerable]]: false, [[Configurable]]: false}, and
+ false.
+ Return + obj
++ The + abstract operation MakeArgGetter called with String name + and environment record env + creates a function object that when executed returns the value bound + for name in env. + It performs the following steps:
+
+ Let
+ body be the result of concatenating the Strings "return
+ ", name, and ";"
+ Return + the result of creating a function object as described in 13.2 using + no FormalParameterList, body for FunctionBody, + env as Scope, and true for Strict.
++ The + abstract operation MakeArgSetter called with String name + and environment record env + creates a function object that when executed sets the value bound + for name in env. + It performs the following steps:
+
+ Let
+ param be the String name concatenated with the String
+ "_arg"
+ Let
+ body be the String "<name> =
+ <param>;"
+ with <name> replaced by the value of name and
+ <param> replaced by the value of param.
+ Return + the result of creating a function object as described in 13.2 using + a List containing the single String param as + FormalParameterList, body for FunctionBody, + env as Scope, and true for Strict.
++ The + [[Get]] internal method of an arguments object for a non-strict mode + function with formal parameters when called with a property name P + performs the following steps:
++ Let + map be the value of the [[ParameterMap]] internal property + of the arguments object.
++ Let + isMapped be the result of calling the [[GetOwnProperty]] + internal method of map passing P as the argument.
++ If + the value of isMapped is undefined, then
+ ++ Else, + map contains a formal parameter mapping for P so, +
++ Return + the result of calling the [[Get]] internal method of map + passing P as the argument.
++ The + [[GetOwnProperty]] internal method of an arguments object for a + non-strict mode function with formal parameters when called with a + property name P + performs the following steps:
++ Let + desc be the result of calling the default [[GetOwnProperty]] + internal method (8.12.1) on the arguments object passing P + as the argument.
++ If + desc is undefined then return desc.
++ Let + map be the value of the [[ParameterMap]] internal property + of the arguments object.
++ Let + isMapped be the result of calling the [[GetOwnProperty]] + internal method of map passing P as the argument.
++ If + the value of isMapped is not undefined, then
++ Set + desc.[[Value]] to the result of calling the [[Get]] + internal method of map passing P as the argument.
++ Return + desc. +
++ The + [[DefineOwnProperty]] internal method of an arguments object for a + non-strict mode function with formal parameters when called with a + property name P, + Property Descriptor Desc, + and Boolean flag Throw + performs the following steps:
++ Let + map be the value of the [[ParameterMap]] internal property + of the arguments object.
++ Let + isMapped be the result of calling the [[GetOwnProperty]] + internal method of map passing P as the argument.
++ Let + allowed be the result of calling the default + [[DefineOwnProperty]] internal method (8.12.9) on the arguments + object passing P, Desc, and false as the + arguments.
++ If + allowed is false, then
++ If + Throw is true then throw a TypeError exception, + otherwise return false.
++ If + the value of isMapped is not undefined, then
++ If + IsAccessorDescriptor(Desc) is true, then
++ Call + the [[Delete]] internal method of map passing P, + and false as the arguments.
++ Else
++ If + Desc.[[Value]] is present, then
++ Call + the [[Put]] internal method of map passing P, + Desc.[[Value]], and Throw as the arguments.
++ If + Desc.[[Writable]] is present and its value is false, + then
++ Call + the [[Delete]] internal method of map passing P and + false as arguments.
++ Return + true.
++ The + [[Delete]] internal method of an arguments object for a non-strict + mode function with formal parameters when called with a property + name P and Boolean + flag Throw + performs the following steps:
++ Let + map be the value of the [[ParameterMap]] internal property + of the arguments object.
++ Let + isMapped be the result of calling the [[GetOwnProperty]] + internal method of map passing P as the argument.
++ Let + result be the result of calling the default [[Delete]] + internal method (8.12.7) on the arguments object passing P and + Throw as the arguments.
++ If + result is true and the value of isMapped is + not undefined, then
++ Call + the [[Delete]] internal method of map passing P, and + false as the arguments.
++ Return + result.
+NOTE 1 For non-strict mode functions the array index (defined in 15.4) + named data properties of an arguments object whose numeric name + values are less than the number of formal parameters of the + corresponding function object initially share their values with the + corresponding argument bindings in the function’s execution + context. This means that changing the property changes the + corresponding value of the argument binding and vice-versa. This + correspondence is broken if such a property is deleted and then + redefined or if the property is changed into an accessor property. + For strict mode functions, the values of the arguments object‘s + properties are simply a copy of the arguments passed to the function + and there is no dynamic linkage between the property values and the + formal parameter values.
+NOTE 2 The ParameterMap object and its property values are used as a + device for specifying the arguments object correspondence to + argument bindings. The ParameterMap object and the objects that are + the values of its properties are not directly accessible from + ECMAScript code. An ECMAScript implementation does not need to + actually create or use such objects to implement the specified + semantics.
+NOTE 3 Arguments objects for strict mode functions define
+ non-configurable accessor properties named "caller"
+ and "callee"
+ which throw a TypeError exception on access. The "callee"
+ property has a more specific meaning for non-strict mode functions
+ and a "caller"
+ property has historically been provided as an implementation-defined
+ extension by some ECMAScript implementations. The strict mode
+ definition of these properties exists to ensure that neither of them
+ is defined in any other manner by conforming ECMAScript
+ implementations.
+ Syntax + +
++ PrimaryExpression :
+
+ this
Identifier
Literal
ArrayLiteral
ObjectLiteral( Expression )
+ The
+ this keyword
+ evaluates to the value of the ThisBinding of the current execution
+ context.
+ An + Identifier is + evaluated by performing Identifier Resolution as specified in + 10.3.1. The result of evaluating an Identifier + is always a value of type Reference.
++ A + Literal is + evaluated as described in 7.8.
++ An + array initialiser is an expression describing the initialisation of + an Array object, written in a form of a literal. It is a list of + zero or more expressions, each of which represents an array element, + enclosed in square brackets. The elements need not be literals; they + are evaluated each time the array initialiser is evaluated.
++ Array elements may be elided at the beginning, middle or end of the + element list. Whenever a comma in the element list is not preceded + by an AssignmentExpression + (i.e., a comma at the beginning or after another comma), the missing + array element contributes to the length of the Array and increases + the index of subsequent elements. Elided array elements are not + defined. If an element is elided at the end of an array, that + element does not contribute to the length of the Array.
++ Syntax
++ ArrayLiteral :
+
+ [
+ Elisionopt
+ ] ElementList
[
+
+ ] ElementList , Elisionopt
[
+
+ ]
+ ElementList :
+
+ Elisionopt
+ AssignmentExpression
ElementList , Elisionopt
+ AssignmentExpression
+ Elision :
+
+ ,
Elision ,
+ Semantics
+
+ The
+ production ArrayLiteral
+ : [ Elisionopt
+ ] is
+ evaluated as follows:
+ Let
+ array be the result of creating a new object as if by the
+ expression new Array() where
+ Array is the standard built-in constructor with that
+ name.
+ Let + pad be the result of evaluating Elision; if not + present, use the numeric value zero.
+
+ Call
+ the [[Put]] internal method of array with arguments
+ "length",
+ pad, and false.
+ Return + array.
+
+ The
+ production ArrayLiteral
+ : [ ElementList
+ ] is
+ evaluated as follows:
+ Return + the result of evaluating ElementList.
+
+ The
+ production ArrayLiteral
+ : [ ElementList
+ , Elisionopt
+ ] is
+ evaluated as follows:
+ Let + array be the result of evaluating ElementList.
++ Let + pad be the result of evaluating Elision; if not + present, use the numeric value zero.
+
+ Let
+ len be the result of calling the [[Get]] internal method of
+ array with argument "length".
+ Call
+ the [[Put]] internal method of array with arguments
+ "length",
+ ToUint32(pad+len), and false.
+ Return + array.
+
+ The
+ production ElementList
+ : Elisionopt
+ AssignmentExpression
+ is evaluated as follows:
+ Let
+ array be the result of creating a new object as if by the
+ expression new Array() where
+ Array is the standard built-in constructor with that
+ name.
+ Let + firstIndex be the result of evaluating Elision; if + not present, use the numeric value zero.
++ Let + initResult be the result of evaluating AssignmentExpression.
++ Let + initValue be GetValue(initResult).
++ Call + the [[DefineOwnProperty]] internal method of array with + arguments ToString(firstIndex), the Property Descriptor { + [[Value]]: initValue, [[Writable]]: true, + [[Enumerable]]: true, [[Configurable]]: true}, and + false.
++ Return + array.
+
+ The
+ production ElementList
+ : ElementList
+ , Elisionopt
+ AssignmentExpression
+ is evaluated as follows:
+ Let + array be the result of evaluating ElementList.
++ Let + pad be the result of evaluating Elision; if not + present, use the numeric value zero.
++ Let + initResult be the result of evaluating AssignmentExpression.
++ Let + initValue be GetValue(initResult).
+
+ Let
+ len be the result of calling the [[Get]] internal method of
+ array with argument "length".
+ Call + the [[DefineOwnProperty]] internal method of array with + arguments ToString(ToUint32((pad+len)) and the + Property Descriptor { [[Value]]: initValue, [[Writable]]: + true, [[Enumerable]]: true, [[Configurable]]: true}, + and false.
++ Return + array.
++ The + production Elision + : , is evaluated as follows:
++ Return + the numeric value 1.
++ The + production Elision + : Elision + , is evaluated as follows:
++ Let + preceding be the result of evaluating Elision.
++ Return + preceding+1.
++
NOTE + [[DefineOwnProperty]] is used to ensure that own properties are + defined for the array even if the standard built-in Array prototype + object has been modified in a manner that would preclude the + creation of new own properties using [[Put]].
++ An + object initialiser is an expression describing the initialisation of + an Object, written in a form resembling a literal. It is a list of + zero or more pairs of property names and associated values, enclosed + in curly braces. The values need not be literals; they are evaluated + each time the object initialiser is evaluated.
++ Syntax
++ ObjectLiteral :
+
+ {
+ } {
+ PropertyNameAndValueList
+ } PropertyNameAndValueList
{
+
+ , }
+ PropertyNameAndValueList :
+
+ PropertyAssignment
PropertyNameAndValueList
+ ,
+ PropertyAssignment
+ PropertyAssignment + :
+
+ PropertyName : AssignmentExpressionget
+ PropertyName (
+ ) { FunctionBody } set
+ PropertyName (
+ PropertySetParameterList )
+ { FunctionBody }
+ PropertyName :
+
+ IdentifierName
StringLiteral
NumericLiteral
+ PropertySetParameterList + :
++ Identifier
++ Semantics
+
+ The
+ production ObjectLiteral
+ : {
+ } is
+ evaluated as follows:
+ Return
+ a new object created as if by the expression new
+ Object() where Object
+ is the standard built-in constructor with that name.
+ The
+ productions ObjectLiteral
+ : {
+ PropertyNameAndValueList
+ }
+ and
ObjectLiteral
+ : {
+ PropertyNameAndValueList
+ ,}
+ are evaluated as follows:
+ Return + the result of evaluating PropertyNameAndValueList.
++ The + production PropertyNameAndValueList + : PropertyAssignment + is evaluated as follows:
+
+ Let
+ obj be the result of creating a new object as if by the
+ expression new Object()
+ where Object
+ is the standard built-in constructor with that name.
+ Let + propId be the result of evaluating PropertyAssignment.
++ Call + the [[DefineOwnProperty]] internal method of obj with + arguments propId.name, propId.descriptor, and false.
++ Return + obj.
+
+ The
+ production
PropertyNameAndValueList
+ : PropertyNameAndValueList
+ , PropertyAssignment
is
+ evaluated as follows:
+ Let + obj be the result of evaluating PropertyNameAndValueList.
++ Let + propId be the result of evaluating PropertyAssignment.
++ Let + previous be the result of calling the [[GetOwnProperty]] + internal method of obj with argument propId.name.
++ If + previous is not undefined then throw a SyntaxError + exception if any of the following conditions are true
++ This + production is contained in strict code and + IsDataDescriptor(previous) is true and + IsDataDescriptor(propId.descriptor) is true.
++ IsDataDescriptor(previous) + is true and IsAccessorDescriptor(propId.descriptor) + is true.
++ IsAccessorDescriptor(previous) + is true and IsDataDescriptor(propId.descriptor) is + true.
++ IsAccessorDescriptor(previous) + is true and IsAccessorDescriptor(propId.descriptor) + is true and either both previous and + propId.descriptor have [[Get]] fields or both previous + and propId.descriptor have [[Set]] fields
++ Call + the [[DefineOwnProperty]] internal method of obj with + arguments propId.name, propId.descriptor, and false.
++ Return + obj.
++ If + the above steps would throw a SyntaxError then an + implementation must treat the error as an early error (Clause 16).
+
+ The
+ production PropertyAssignment
+ : PropertyName
+ :
+ AssignmentExpression
+ is evaluated as follows:
+ Let + propName be the result of evaluating PropertyName.
++ Let + exprValue be the result of evaluating AssignmentExpression.
++ Let + propValue be GetValue(exprValue).
++ Let + desc be the Property Descriptor{[[Value]]: propValue, + [[Writable]]: true, [[Enumerable]]: true, + [[Configurable]]: true}
++ Return + Property Identifier (propName, desc).
+
+ The
+ production PropertyAssignment
+ : get
+ PropertyName (
+ ) { FunctionBody
+ } is
+ evaluated as follows:
+ Let + propName be the result of evaluating PropertyName.
++ Let + closure be the result of creating a new Function object as + specified in 13.2 with an empty parameter list and body specified + by FunctionBody. Pass in the LexicalEnvironment of the + running execution context as the Scope. Pass in true + as the Strict flag if the PropertyAssignment + is contained in strict code or if its FunctionBody is strict code.
++ Let + desc be the Property Descriptor{[[Get]]: closure, + [[Enumerable]]: true, [[Configurable]]: true}
++ Return + Property Identifier (propName, desc).
+
+ The
+ production PropertyAssignment
+ : set
+ PropertyName (
+ PropertySetParameterList
+ ) {
+ FunctionBody
+ } is evaluated as
+ follows:
+ Let + propName be the result of evaluating PropertyName.
++ Let + closure be the result of creating a new Function object as + specified in 13.2 with parameters specified by + PropertySetParameterList and body specified by FunctionBody. + Pass in the LexicalEnvironment of the running execution context as + the Scope. Pass in true as the Strict flag if + the PropertyAssignment + is contained in strict code or if its FunctionBody is strict code.
++ Let + desc be the Property Descriptor{[[Set]]: closure, + [[Enumerable]]: true, [[Configurable]]: true}
++ Return + Property Identifier (propName, desc).
+
+ It is
+ a SyntaxError if the Identifier
+ "eval"
+ or the Identifier "arguments"
+ occurs as the Identifier
+ in a PropertySetParameterList
+ of a
+ PropertyAssignment
+ that is contained in strict code
+ or if its FunctionBody
+ is strict code.
+ The + production PropertyName + : IdentifierName + is evaluated as follows:
++ Return + the String value containing the same sequence of characters as the + IdentifierName.
++ The + production PropertyName + : StringLiteral + is evaluated as follows:
++ Return + the SV of the StringLiteral.
++ The + production PropertyName + : NumericLiteral + is evaluated as follows:
++ Let + nbr be the result of forming the value of the + NumericLiteral.
++ Return + ToString(nbr).
+
+ The
+ production PrimaryExpression
+ : (
+ Expression )
+ is evaluated as follows:
+ Return + the result of evaluating Expression. This may be of type + Reference.
++
NOTE This
+ algorithm does not apply GetValue to the result of evaluating
+ Expression. The principal motivation for this is so that operators
+ such as delete and
+ typeof may be
+ applied to parenthesised expressions.
+ Syntax
++ MemberExpression :
+
+ PrimaryExpression
FunctionExpression
MemberExpression [ Expression ] MemberExpression . IdentifierNamenew MemberExpression
+ Arguments
+ NewExpression :
+
+ MemberExpression
new
+ CallExpression :
+
+ MemberExpression
+ Arguments
+ Arguments[ Expression ] CallExpression . IdentifierName
+ Arguments :
+
+ ( ) ArgumentList
()
+ ArgumentList :
+
+ AssignmentExpression
ArgumentList , AssignmentExpression
+ LeftHandSideExpression :
+
+ NewExpression
CallExpression
+ Properties + are accessed by name, using either the dot notation:
+
+ MemberExpression . IdentifierName
CallExpression . IdentifierName
+ or + the bracket notation:
+
+ MemberExpression [ Expression ]
CallExpression [ Expression ]
+ The + dot notation is explained by the following syntactic conversion:
+
+ MemberExpression . IdentifierName
+ is + identical in its behaviour to
+
+ MemberExpression [ <identifier-name-string> ]
+ and + similarly
+
+ CallExpression . IdentifierName
+ is + identical in its behaviour to
+
+ CallExpression [ <identifier-name-string> ]
+ where + <identifier-name-string> + is a string literal containing the same sequence of characters after + processing of Unicode escape sequences as the IdentifierName.
+
+ The
+ production MemberExpression
+ : MemberExpression
+ [ Expression
+ ] is evaluated as
+ follows:
+ Let + baseReference be the result of evaluating MemberExpression.
++ Let + baseValue be GetValue(baseReference).
++ Let + propertyNameReference be the result of evaluating + Expression.
++ Let + propertyNameValue be GetValue(propertyNameReference).
++ Call + CheckObjectCoercible(baseValue).
++ Let + propertyNameString be ToString(propertyNameValue).
++ If + the syntactic production that is being evaluated is contained in + strict mode code, let strict be true, else let strict + be false.
++ Return + a value of type Reference whose base value is baseValue and + whose referenced name is propertyNameString, and whose + strict mode flag is strict.
+
+ The
+ production CallExpression
+ : CallExpression [ Expression ] is evaluated
+ in exactly the same manner, except that the contained CallExpression
+ is evaluated in step 1.
+ The
+ production NewExpression : new NewExpression is evaluated as follows:
+ Let + ref be the result of evaluating NewExpression.
++ Let + constructor be GetValue(ref).
++ If + Type(constructor) is not Object, throw a TypeError + exception.
++ If + constructor does not implement the [[Construct]] internal + method, throw a TypeError exception.
++ Return + the result of calling the [[Construct]] internal method on + constructor, providing no arguments (that is, an empty list + of arguments).
+
+ The
+ production MemberExpression
+ : new
+ MemberExpression
+ Arguments is
+ evaluated as follows:
+ Let + ref be the result of evaluating MemberExpression.
++ Let + constructor be GetValue(ref).
++ Let + argList be the result of evaluating Arguments, + producing an internal list of argument values (11.2.4).
++ If + Type(constructor) is not Object, throw a TypeError + exception.
++ If + constructor does not implement the [[Construct]] internal + method, throw a TypeError exception.
++ Return + the result of calling the [[Construct]] internal method on + constructor, providing the list argList as the + argument values.
++ The + production CallExpression + : MemberExpression + Arguments is + evaluated as follows:
++ Let + ref be the result of evaluating MemberExpression.
++ Let + func be GetValue(ref).
++ Let + argList be the result of evaluating Arguments, + producing an internal list of argument values (see 11.2.4).
++ If + Type(func) is not Object, throw a TypeError + exception.
++ If + IsCallable(func) is false, throw a TypeError + exception.
++ If + Type(ref) is Reference, then
++ If + IsPropertyReference(ref) is true, then
++ Let + thisValue be GetBase(ref).
++ Else, + the base of ref is an Environment Record
++ Let + thisValue be the result of calling the ImplicitThisValue + concrete method of GetBase(ref).
++ Else, + Type(ref) is not Reference.
++ Let + thisValue be undefined.
++ Return + the result of calling the [[Call]] internal method on func, + providing thisValue as the this value and providing + the list argList as the argument values.
++ The + production CallExpression + : CallExpression + Arguments is + evaluated in exactly the same manner, except that the contained + CallExpression is + evaluated in step 1.
++
NOTE The returned + result will never be of type Reference if func + is a native ECMAScript object. Whether calling a host object can + return a value of type Reference is implementation-dependent. If a + value of type Reference is returned, it must be a non-strict + Property Reference.
++ The + evaluation of an argument list produces a List of values (see 8.8).
+
+ The
+ production Arguments :
+ ( ) is evaluated
+ as follows:
+ Return + an empty List.
+
+ The
+ production Arguments : (
+ ArgumentList
+ ) is evaluated as follows:
+ Return + the result of evaluating ArgumentList.
+
+ The
+ production ArgumentList :
+ AssignmentExpression
+ is evaluated as follows:
+ Let + ref be the result of evaluating AssignmentExpression.
++ Let + arg be GetValue(ref).
++ Return + a List whose sole item is arg.
+
+ The
+ production ArgumentList : ArgumentList
+ , AssignmentExpression
+ is evaluated as follows:
+ Let + precedingArgs be the result of evaluating ArgumentList.
++ Let + ref be the result of evaluating AssignmentExpression.
++ Let + arg be GetValue(ref).
++ Return + a List whose length is one greater than the length of precedingArgs + and whose items are the items of precedingArgs, in order, + followed at the end by arg which is the last item of the new + list.
++ The + production MemberExpression + : FunctionExpression + is evaluated as follows:
++ Return + the result of evaluating FunctionExpression.
++ Syntax
++ PostfixExpression :
+
+ LeftHandSideExpression
LeftHandSideExpression
+ [no LineTerminator here]
+ ++
LeftHandSideExpression
+ [no LineTerminator here]
+ --
+ The
+ production PostfixExpression
+ : LeftHandSideExpression
+ [no LineTerminator here] ++
+ is evaluated as follows:
+ Let + lhs be the result of evaluating LeftHandSideExpression.
++ Throw + a SyntaxError exception if the following conditions are all + true:
++ IsStrictReference(lhs) + is true
++ Type(GetBase(lhs)) + is Environment Record
+
+ GetReferencedName(lhs)
+ is either "eval"
+ or "arguments"
+ Let
+ newValue be the result of adding the value 1
+ to oldValue, using the same rules as for the +
+ operator (see 11.6.3).
+ Call + PutValue(lhs, newValue).
++ Return + oldValue.
+
+ The
+ production PostfixExpression
+ : LeftHandSideExpression
+ [no LineTerminator here]
+ -- is
+ evaluated as follows:
+ Let + lhs be the result of evaluating LeftHandSideExpression.
++ Throw + a SyntaxError exception if the following conditions are all + true:
++ IsStrictReference(lhs) + is true
++ Type(GetBase(lhs)) + is Environment Record
+
+ GetReferencedName(lhs)
+ is either "eval"
+ or "arguments"
+ Let
+ newValue be the result of subtracting the value 1
+ from oldValue, using the same rules as for the -
+ operator (11.6.3).
+ Call + PutValue(lhs, newValue).
++ Return + oldValue.
++ Syntax
++ UnaryExpression :
+
+ PostfixExpression
delete
+ void
+ UnaryExpressiontypeof
+ UnaryExpression
++-- UnaryExpression+ UnaryExpression- UnaryExpression~ UnaryExpression! UnaryExpression
+ The
+ production UnaryExpression
+ : delete UnaryExpression is evaluated as follows:
+ Let + ref be the result of evaluating UnaryExpression.
++ If + IsUnresolvableReference(ref) then,
++ If + IsStrictReference(ref) is true, throw a SyntaxError + exception.
++ Else, + return true.
++ If + IsPropertyReference(ref) is true, then
++ Return + the result of calling the [[Delete]] internal method on + ToObject(GetBase(ref)) providing GetReferencedName(ref) + and IsStrictReference(ref) as the arguments.
++ Else, + ref is a Reference to an Environment Record binding, so
++ If + IsStrictReference(ref) is true, throw a SyntaxError + exception.
++ Let + bindings be GetBase(ref).
++ Return + the result of calling the DeleteBinding concrete method of + bindings, providing GetReferencedName(ref) as the + argument.
+NOTE When
+ a delete operator
+ occurs within strict mode code, a SyntaxError exception is
+ thrown if its UnaryExpression
+ is a direct reference to a variable, function argument, or function
+ name. In addition, if a delete
+ operator occurs within strict mode code and the property to be
+ deleted has the attribute { [[Configurable]]: false }, a
+ TypeError exception is thrown.
+ The
+ production UnaryExpression
+ : void
+ UnaryExpression is
+ evaluated as follows:
+ Let + expr be the result of evaluating UnaryExpression.
++ Call + GetValue(expr).
++ Return + undefined.
+NOTE GetValue + must be called even though its value is not used because it may have + observable side-effects.
+
+ The
+ production UnaryExpression
+ : typeof UnaryExpression
+ is evaluated as follows:
+ Let + val be the result of evaluating UnaryExpression.
++ If + Type(val) is Reference, then
+
+ If
+ IsUnresolvableReference(val) is true, return
+ "undefined".
+ Let + val be GetValue(val).
++ Return + a String determined by Type(val) according to Table 20.
+|
+ + Type + of val + |
+
+ + Result + |
+
|
+ + Undefined + |
+
+
+ |
+
|
+ + Null + |
+
+
+ |
+
|
+ + Boolean + |
+
+
+ |
+
|
+ + Number + |
+
+
+ |
+
|
+ + String + |
+
+
+ |
+
|
+ + Object + (native and does not implement [[Call]]) + |
+
+
+ |
+
|
+ Object + (native or host and does implement [[Call]]) + |
+
+
|
+
|
+ Object + (host and does not implement [[Call]]) + |
+
+
+ Implementation-defined
+ except may not be |
+
+ The
+ production UnaryExpression : ++
+ UnaryExpression
+ is evaluated as follows:
+ Let + expr be the result of evaluating UnaryExpression.
++ Throw + a SyntaxError exception if the following conditions are all + true:
++ IsStrictReference(expr) + is true
++ Type(GetBase(expr)) + is Environment Record
+
+ GetReferencedName(expr)
+ is either "eval"
+ or "arguments"
+ Let
+ newValue be the result of adding the value 1
+ to oldValue, using the same rules as for the +
+ operator (see 11.6.3).
+ Call + PutValue(expr, newValue).
++ Return + newValue.
+
+ The
+ production UnaryExpression : --
+ UnaryExpression
+ is evaluated as follows:
+ Let + expr be the result of evaluating UnaryExpression.
++ Throw + a SyntaxError exception if the following conditions are all + true:
++ IsStrictReference(expr) + is true
++ Type(GetBase(expr)) + is Environment Record
+
+ GetReferencedName(expr)
+ is either "eval"
+ or "arguments"
+ Let
+ newValue be the result of subtracting the value 1
+ from oldValue, using the same rules as for the -
+ operator (see 11.6.3).
+ Call + PutValue(expr, newValue).
++ Return + newValue.
++ The + unary + operator converts its operand to Number type.
+
+ The
+ production UnaryExpression : +
+ UnaryExpression is
+ evaluated as follows:
+ Let + expr be the result of evaluating UnaryExpression.
+
+ The
+ unary - operator
+ converts its operand to Number type and then negates it. Note that
+ negating +0 produces −0,
+ and negating −0
+ produces +0.
+ The
+ production UnaryExpression : -
+ UnaryExpression is
+ evaluated as follows:
+ Let + expr be the result of evaluating UnaryExpression.
++ If + oldValue is NaN, return NaN.
++ Return + the result of negating oldValue; that is, compute a Number + with the same magnitude but opposite sign.
+
+ The
+ production UnaryExpression : ~
+ UnaryExpression is
+ evaluated as follows:
+ Let + expr be the result of evaluating UnaryExpression.
++ Return + the result of applying bitwise complement to oldValue. The + result is a signed 32-bit integer.
+
+ The
+ production UnaryExpression : !
+ UnaryExpression is
+ evaluated as follows:
+ Let + expr be the result of evaluating UnaryExpression.
++ If + oldValue is true, return false.
++ Return + true.
++ Syntax
++ MultiplicativeExpression :
+
+ UnaryExpression
MultiplicativeExpression * UnaryExpression
MultiplicativeExpression / UnaryExpression
MultiplicativeExpression % UnaryExpression
+ Semantics
++ The + production MultiplicativeExpression : MultiplicativeExpression@ UnaryExpression, + where @ stands for one of the operators in the above definitions, is + evaluated as follows:
++ Let + left be the result of evaluating MultiplicativeExpression.
++ Let + leftValue be GetValue(left).
++ Let + right be the result of evaluating UnaryExpression.
++ Let + rightValue be GetValue(right).
++ Let + leftNum be ToNumber(leftValue).
++ Let + rightNum be ToNumber(rightValue).
++ Return + the result of applying the specified operation (*, /, or %) to + leftNum and rightNum. See the Notes below 11.5.1, + 11.5.2, 11.5.3.
+
+ The *
+ operator performs multiplication, producing the product of its
+ operands. Multiplication is commutative. Multiplication is not
+ always associative in ECMAScript, because of finite precision.
The + result of a floating-point multiplication is governed by the rules + of IEEE 754 binary double-precision arithmetic:
++ If + either operand is NaN, + the result is NaN.
++ The + sign of the result is positive if both operands have the same + sign, negative if the operands have different signs.
++ Multiplication + of an infinity by a zero results in NaN.
++ Multiplication + of an infinity by an infinity results in an infinity. The sign is + determined by the rule already stated above.
++ Multiplication + of an infinity by a finite non-zero value results in a signed + infinity. The sign is determined by the rule already stated above.
++ In + the remaining cases, where neither an infinity or NaN is involved, + the product is computed and rounded to the nearest representable + value using IEEE 754 round-to-nearest mode. If the magnitude is + too large to represent, the result is then an infinity of + appropriate sign. If the magnitude is too small to represent, the + result is then a zero of appropriate sign. The ECMAScript language + requires support of gradual underflow as defined by IEEE 754.
+The
+ / operator
+ performs division, producing the quotient of its operands. The left
+ operand is the dividend and the right operand is the divisor.
+ ECMAScript does not perform integer division. The operands and
+ result of all division operations are double-precision
+ floating-point numbers. The result of division is determined by the
+ specification of IEEE 754 arithmetic:
+ If + either operand is NaN, + the result is NaN.
++ The + sign of the result is positive if both operands have the same + sign, negative if the operands have different signs.
++ Division + of an infinity by an infinity results in NaN.
++ Division + of an infinity by a zero results in an infinity. The sign is + determined by the rule already stated above.
++ Division + of an infinity by a non-zero finite value results in a signed + infinity. The sign is determined by the rule already stated above.
++ Division + of a finite value by an infinity results in zero. The sign is + determined by the rule already stated above.
++ Division + of a zero by a zero results in NaN; + division of zero by any other finite value results in zero, with + the sign determined by the rule already stated above.
++ Division + of a non-zero finite value by a zero results in a signed infinity. + The sign is determined by the rule already stated above.
++ In + the remaining cases, where neither an infinity, nor a zero, nor + NaN + is involved, the quotient is computed and rounded to the nearest + representable value using IEEE 754 round-to-nearest mode. If the + magnitude is too large to represent, the operation overflows; the + result is then an infinity of appropriate sign. If the magnitude + is too small to represent, the operation underflows and the result + is a zero of the appropriate sign. The ECMAScript language + requires support of gradual underflow as defined by IEEE 754.
+
+ The %
+ operator yields the remainder of its operands from an implied
+ division; the left operand is the dividend and the right operand is
+ the divisor.
NOTE In + C and C++, the remainder operator accepts only integral operands; in + ECMAScript, it also accepts floating-point operands.
+
+ The
+ result of a floating-point remainder operation as computed by the %
+ operator is not the same as the “remainder” operation defined by
+ IEEE 754. The IEEE 754 “remainder” operation computes the
+ remainder from a rounding division, not a truncating division, and
+ so its behaviour is not analogous to that of the usual integer
+ remainder operator. Instead the ECMAScript language defines %
+ on floating-point operations to behave in a manner analogous to that
+ of the Java integer remainder operator; this may be compared with
+ the C library function fmod.
The + result of an ECMAScript floating-point remainder operation is + determined by the rules of IEEE arithmetic:
++ If + either operand is NaN, + the result is NaN.
++ The + sign of the result equals the sign of the dividend.
++ If + the dividend is an infinity, or the divisor is a zero, or both, + the result is NaN.
++ If + the dividend is finite and the divisor is an infinity, the result + equals the dividend.
++ If + the dividend is a zero and the divisor is finite, the result is + the same as the dividend.
++ In + the remaining cases, where neither an infinity, nor a zero, nor + NaN + is involved, the floating-point remainder r from a dividend n and + a divisor d is defined by the mathematical relation r = n − + (d * q) where q is an integer that is negative only if n/d is + negative and positive only if n/d is positive, and whose + magnitude is as large as possible without exceeding the magnitude + of the true mathematical quotient of n and d. +r is computed and rounded to the nearest representable value using +IEEE 754 round-to-nearest mode. +
++ Syntax
++ AdditiveExpression :
+
+ MultiplicativeExpression
AdditiveExpression + MultiplicativeExpression
AdditiveExpression - MultiplicativeExpression
+ The + addition operator either performs string concatenation or numeric + addition.
+
+ The
+ production AdditiveExpression
+ : AdditiveExpression
+ +
+ MultiplicativeExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating AdditiveExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating MultiplicativeExpression.
++ Let + rval be GetValue(rref).
++ Let + lprim be ToPrimitive(lval).
++ Let + rprim be ToPrimitive(rval).
++ If + Type(lprim) is String or Type(rprim) is String, then +
+ ++ Return + the result of applying the addition operation to ToNumber(lprim) + and ToNumber(rprim). See the Note below 11.6.3.
+NOTE 1 No hint is provided in the calls to ToPrimitive in steps 5 and 6. + All native ECMAScript objects except Date objects handle the absence + of a hint as if the hint Number were given; Date objects handle the + absence of a hint as if the hint String were given. Host objects may + handle the absence of a hint in some other manner.
+NOTE 2 Step 7 differs from step 3 of the comparison algorithm for the + relational operators (11.8.5), by using the logical-or operation + instead of the logical-and operation.
+
+ The
+ production AdditiveExpression
+ : AdditiveExpression
+ -
+ MultiplicativeExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating AdditiveExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating MultiplicativeExpression.
++ Let + rval be GetValue(rref).
++ Let + lnum be ToNumber(lval).
++ Let + rnum be ToNumber(rval).
++ Return + the result of applying the subtraction operation to lnum and + rnum. See the note below 11.6.3.
+
+ The +
+ operator performs addition when applied to two operands of numeric
+ type, producing the sum of the operands. The -
+ operator performs subtraction, producing the difference of two
+ numeric operands.
+ Addition + is a commutative operation, but not always associative.
+The + result of an addition is determined using the rules of IEEE 754 + binary double-precision arithmetic:
++ If + either operand is NaN, + the result is NaN.
++ The + sum of two infinities of opposite sign is NaN.
++ The + sum of two infinities of the same sign is the infinity of that + sign.
++ The + sum of an infinity and a finite value is equal to the infinite + operand.
++ The + sum of two negative zeros is −0. + The sum of two positive zeros, or of two zeros of opposite sign, + is +0.
++ The + sum of a zero and a nonzero finite value is equal to the nonzero + operand.
++ The + sum of two nonzero finite values of the same magnitude and + opposite sign is +0.
++ In + the remaining cases, where neither an infinity, nor a zero, nor + NaN is involved, and the operands have the same sign or have + different magnitudes, the sum is computed and rounded to the + nearest representable value using IEEE 754 round-to-nearest mode. + If the magnitude is too large to represent, the operation + overflows and the result is then an infinity of appropriate sign. + The ECMAScript language requires support of gradual underflow as + defined by IEEE 754.
+
+ The -
+ operator performs subtraction when applied to two operands of
+ numeric type, producing the difference of its operands; the left
+ operand is the minuend and the right operand is the subtrahend.
+ Given numeric operands a
+ and b, it is
+ always the case that a–b
+ produces the same result as a +(–b).
+ Syntax
++ ShiftExpression :
+
+ AdditiveExpression
ShiftExpression << AdditiveExpression
ShiftExpression >> AdditiveExpression
ShiftExpression >>> AdditiveExpression
+ Performs + a bitwise left shift operation on the left operand by the amount + specified by the right operand.
+
+ The
+ production ShiftExpression
+ : ShiftExpression
+ <<
+ AdditiveExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating ShiftExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating AdditiveExpression.
++ Let + rval be GetValue(rref).
++ Let + lnum be ToInt32(lval).
++ Let + rnum be ToUint32(rval).
++ Let + shiftCount be the result of masking out all but the least + significant 5 bits of rnum, that is, compute rnum & + 0x1F.
++ Return + the result of left shifting lnum by shiftCount bits. + The result is a signed 32-bit integer.
++ Performs + a sign-filling bitwise right shift operation on the left operand by + the amount specified by the right operand.
+
+ The
+ production ShiftExpression
+ : ShiftExpression
+ >>
+ AdditiveExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating ShiftExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating AdditiveExpression.
++ Let + rval be GetValue(rref).
++ Let + lnum be ToInt32(lval).
++ Let + rnum be ToUint32(rval).
++ Let + shiftCount be the result of masking out all but the least + significant 5 bits of rnum, that is, compute rnum & + 0x1F.
++ Return + the result of performing a sign-extending right shift of lnum + by shiftCount bits. The most significant bit is propagated. + The result is a signed 32-bit integer.
++ Performs + a zero-filling bitwise right shift operation on the left operand by + the amount specified by the right operand.
+
+ The
+ production ShiftExpression
+ : ShiftExpression
+ >>>
+ AdditiveExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating ShiftExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating AdditiveExpression.
++ Let + rval be GetValue(rref).
++ Let + lnum be ToUint32(lval).
++ Let + rnum be ToUint32(rval).
++ Let + shiftCount be the result of masking out all but the least + significant 5 bits of rnum, that is, compute rnum & + 0x1F.
++ Return + the result of performing a zero-filling right shift of lnum + by shiftCount bits. Vacated bits are filled with zero. The + result is an unsigned 32-bit integer.
++ Syntax
++ RelationalExpression :
+
+ ShiftExpression
RelationalExpression < ShiftExpression
RelationalExpression > ShiftExpression
RelationalExpression <= ShiftExpression
RelationalExpression >= ShiftExpression
RelationalExpression instanceof ShiftExpression
RelationalExpression in ShiftExpression
+ RelationalExpressionNoIn :
+
+ ShiftExpression
RelationalExpressionNoIn < ShiftExpression
RelationalExpressionNoIn > ShiftExpression
RelationalExpressionNoIn <= ShiftExpression
RelationalExpressionNoIn >= ShiftExpression
RelationalExpressionNoIn instanceof ShiftExpression
NOTE The
+ “NoIn” variants are needed to avoid confusing the in
+ operator in a relational expression with the in
+ operator in a for
+ statement.
+ Semantics
++ The + result of evaluating a relational operator is always of type + Boolean, reflecting whether the relationship named by the operator + holds between its two operands.
++ The + RelationalExpressionNoIn + productions are evaluated in the same manner as the + RelationalExpression + productions except that the contained RelationalExpressionNoIn + is evaluated instead of the contained RelationalExpression.
+
+ The
+ production RelationalExpression
+ : RelationalExpression
+ <
+ ShiftExpression is
+ evaluated as follows:
+ Let + lref be the result of evaluating RelationalExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating ShiftExpression.
++ Let + rval be GetValue(rref).
++ Let + r be the result of performing abstract relational comparison + lval < rval. (see 11.8.5)
++ If + r is undefined, return false. Otherwise, + return r.
+
+ The
+ production RelationalExpression : RelationalExpression
+ >
+ ShiftExpression is
+ evaluated as follows:
+ Let + lref be the result of evaluating RelationalExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating ShiftExpression.
++ Let + rval be GetValue(rref).
++ Let + r be the result of performing abstract relational comparison + rval < lval with LeftFirst equal to false. + (see 11.8.5).
++ If + r is undefined, return false. Otherwise, + return r.
+
+ The
+ production RelationalExpression : RelationalExpression
+ <=
+ ShiftExpression is
+ evaluated as follows:
+ Let + lref be the result of evaluating RelationalExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating ShiftExpression.
++ Let + rval be GetValue(rref).
++ Let + r be the result of performing abstract relational comparison + rval < lval with LeftFirst equal to false. + (see 11.8.5).
++ If + r is true or undefined, return false. + Otherwise, return true.
+
+ The
+ production RelationalExpression : RelationalExpression
+ >=
+ ShiftExpression is
+ evaluated as follows:
+ Let + lref be the result of evaluating RelationalExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating ShiftExpression.
++ Let + rval be GetValue(rref).
++ Let + r be the result of performing abstract relational comparison + lval < rval. (see 11.8.5)
++ If + r is true or undefined, return false. + Otherwise, return true.
++ The + comparison x < + y, where x + and y are values, + produces true, false, or undefined (which + indicates that at least one operand is NaN). In addition to x + and y the + algorithm takes a Boolean flag named LeftFirst + as a parameter. The flag is used to control the order in which + operations with potentially visible side-effects are performed upon + x and y. + It is necessary because ECMAScript specifies left to right + evaluation of expressions. The default value of LeftFirst + is true and indicates that the x + parameter corresponds to an expression that occurs to the left of + the y parameter’s + corresponding expression. If LeftFirst is false, the reverse is the case and operations + must be performed upon y before x. + Such a comparison is performed as follows:
++ If + the LeftFirst flag is true, then
++ Let + px be the result of calling ToPrimitive(x, hint + Number).
++ Let + py be the result of calling ToPrimitive(y, hint + Number).
++ Else + the order of evaluation needs to be reversed to preserve left to + right evaluation
++ Let + py be the result of calling ToPrimitive(y, hint + Number).
++ Let + px be the result of calling ToPrimitive(x, hint + Number).
++ If + it is not the case that both Type(px) is String and Type(py) + is String, then +
++ Let + nx be the result of calling ToNumber(px). Because px and py are primitive values evaluation order is not + important.
++ Let + ny be the result of calling ToNumber(py).
++ If + nx is NaN, return undefined.
++ If + ny is NaN, return undefined.
++ If + nx and ny are the same Number value, return false.
++ If + nx is +0 and ny is −0, + return false.
++ If + nx is −0 + and ny is +0, return false.
++ If + nx is +∞, + return false.
++ If + ny is +∞, + return true.
++ If + ny is −∞, + return false.
++ If + nx is −∞, + return true.
++ If + the mathematical value of nx is less than the mathematical + value of ny —note that these mathematical values are both + finite and not both zero—return true. Otherwise, return + false.
++ Else, + both px and py are Strings
++ If + py is a prefix of px, return false. (A String + value p is a prefix of String value q if q + can be the result of concatenating p and some other String + r. Note that any String is a prefix of itself, because r + may be the empty String.)
++ If + px is a prefix of py, return true.
++ Let + k be the smallest nonnegative integer such that the + character at position k within px is different from + the character at position k within py. (There must + be such a k, for neither String is a prefix of the other.)
++ Let + m be the integer that is the code unit value for the + character at position k within px.
++ Let + n be the integer that is the code unit value for the + character at position k within py.
++ If + m < n, return true. Otherwise, return + false.
+NOTE 1 Step 3 differs from step 7 in the algorithm for the addition
+ operator +
+ (11.6.1) in using and instead of or.
NOTE 2 The comparison of Strings uses a simple lexicographic ordering on + sequences of code unit values. There is no attempt to use the more + complex, semantically oriented definitions of character or string + equality and collating order defined in the Unicode specification. + Therefore String values that are canonically equal according to the + Unicode standard could test as unequal. In effect this algorithm + assumes that both Strings are already in normalised form. + Also, note that for strings containing supplementary characters, + lexicographic ordering on sequences of UTF-16 code unit values + differs from that on sequences of code point values.
+
+ The
+ production RelationalExpression:
+ RelationalExpression
+ instanceof
+ ShiftExpression is
+ evaluated as follows:
+ Let + lref be the result of evaluating RelationalExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating ShiftExpression.
++ Let + rval be GetValue(rref).
++ If + Type(rval) is not Object, throw a TypeError + exception.
++ If + rval does not have a [[HasInstance]] internal method, throw + a TypeError exception.
++ Return + the result of calling the [[HasInstance]] internal method of rval + with argument lval.
+
+ The
+ production RelationalExpression
+ : RelationalExpression
+ in ShiftExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating RelationalExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating ShiftExpression.
++ Let + rval be GetValue(rref).
++ If + Type(rval) is not Object, throw a TypeError + exception.
++ Return + the result of calling the [[HasProperty]] internal method of rval + with argument ToString(lval).
++ Syntax
++ EqualityExpression :
+
+ RelationalExpression
EqualityExpression == RelationalExpression
EqualityExpression != RelationalExpression
EqualityExpression === RelationalExpression
EqualityExpression !== RelationalExpression
+ EqualityExpressionNoIn :
+
+ RelationalExpressionNoIn
EqualityExpressionNoIn == RelationalExpressionNoIn
EqualityExpressionNoIn != RelationalExpressionNoIn
EqualityExpressionNoIn === RelationalExpressionNoIn
EqualityExpressionNoIn !== RelationalExpressionNoIn
+ Semantics
++ The + result of evaluating an equality operator is always of type Boolean, + reflecting whether the relationship named by the operator holds + between its two operands.
++ The + EqualityExpressionNoIn + productions are evaluated in the same manner as the + EqualityExpression + productions except that the contained EqualityExpressionNoIn + and RelationalExpressionNoIn + are evaluated instead of the contained EqualityExpression + and RelationalExpression, + respectively.
+
+ The
+ production EqualityExpression : EqualityExpression
+ ==
+ RelationalExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating EqualityExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating RelationalExpression.
++ Let + rval be GetValue(rref).
++ Return + the result of performing abstract equality comparison rval + == lval. (see 11.9.3).
+
+ The
+ production EqualityExpression : EqualityExpression
+ !=
+ RelationalExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating EqualityExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating RelationalExpression.
++ Let + rval be GetValue(rref).
++ Let + r be the result of performing abstract equality comparison + rval == lval. (see 11.9.3).
++ If + r is true, return false. Otherwise, return + true.
++ The + comparison x == y, + where x and y + are values, produces true or false. Such a comparison + is performed as follows:
++ If + Type(x) is the same as Type(y), then
++ If + Type(x) is Undefined, return true.
++ If + Type(x) is Null, return true.
++ If + Type(x) is Number, then
++ If + x is NaN, return false.
++ If + y is NaN, return false.
++ If + x is the same Number value as y, return true.
++ If + x is +0 and y is −0, + return true.
++ If + x is −0 + and y is +0, return true.
++ Return + false.
++ If + Type(x) is String, then return true if x and + y are exactly the same sequence of characters (same length + and same characters in corresponding positions). Otherwise, return + false.
++ If + Type(x) is Boolean, return true if x and y are both true or both false. Otherwise, return + false.
++ Return + true if x and y refer to the same object. + Otherwise, return false.
++ If + x is null and y is undefined, return + true.
++ If + x is undefined and y is null, return + true.
+
+ If
+ Type(x) is Number and Type(y) is String,
return
+ the result of the comparison x == ToNumber(y).
+ If
+ Type(x) is String and Type(y) is Number,
return
+ the result of the comparison ToNumber(x) == y.
+ If + Type(x) is Boolean, return the result of the comparison + ToNumber(x) == y.
++ If + Type(y) is Boolean, return the result of the comparison x + == ToNumber(y).
+
+ If
+ Type(x) is either String or Number and Type(y) is
+ Object,
return the result of the comparison x ==
+ ToPrimitive(y).
+ If
+ Type(x) is Object and Type(y) is either String or
+ Number,
return the result of the comparison ToPrimitive(x)
+ == y.
+ Return + false.
+NOTE 1 Given the above definition of equality:
+
+ String
+ comparison can be forced by:
+ ""
+ + a == "" + b.
+ Numeric
+ comparison can be forced by:
+ +a
+ == +b.
+ Boolean
+ comparison can be forced by:
+ !a
+ == !b.
NOTE 2 The equality operators maintain the following invariants:
+
+ A
+ !=
+ B
+ is
+ equivalent to
+ !(A
+ ==
+ B).
+ A
+ ==
+ B
+ is
+ equivalent to B
+ ==
+ A,
+ except in the order of evaluation of
+ A
+ and
+ B.
NOTE 3 The
+ equality operator is not always transitive. For example, there might
+ be two distinct String objects, each representing the same String
+ value; each String object would be considered equal to the String
+ value by the ==
+ operator, but the two String objects would not be equal to each
+ other.
NOTE 4 Comparison of Strings uses a simple equality test on sequences of + code unit values. There is no attempt to use the more complex, + semantically oriented definitions of character or string equality + and collating order defined in the Unicode specification. Therefore + Strings values that are canonically equal according to the Unicode + standard could test as unequal. In effect this algorithm assumes + that both Strings are already in normalised form.
+
+ The
+ production EqualityExpression : EqualityExpression
+ ===
+ RelationalExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating EqualityExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating RelationalExpression.
++ Let + rval be GetValue(rref).
++ Return + the result of performing the strict equality comparison rval + === lval. (See 11.9.6)
+
+ The
+ production EqualityExpression : EqualityExpression
+ !==
+ RelationalExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating EqualityExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating RelationalExpression.
++ Let + rval be GetValue(rref).
++ Let + r be the result of performing strict equality comparison + rval === lval. (See 11.9.6)
++ If + r is true, return false. Otherwise, return + true.
++ The + comparison x === + y, where x + and y are values, + produces true or false. Such a comparison is performed + as follows:
++ If + Type(x) is Undefined, return true.
++ If + Type(x) is Null, return true.
++ If + Type(x) is Number, then
++ If + x is NaN, return false.
++ If + y is NaN, return false.
++ If + x is the same Number value as y, return true.
++ If + x is +0 and y is −0, + return true.
++ If + x is −0 + and y is +0, return true.
++ Return + false.
++ If + Type(x) is String, then return true if x and y + are exactly the same sequence of characters (same length and same + characters in corresponding positions); otherwise, return false.
++ If + Type(x) is Boolean, return true if x and y + are both true or both false; otherwise, return false.
++ Return + true if x and y refer to the same object. + Otherwise, return false.
+NOTE This + algorithm differs from the SameValue Algorithm (9.12) in its + treatment of signed zeroes and NaNs.
++ Syntax
++ BitwiseANDExpression :
+
+ EqualityExpression
BitwiseANDExpression & EqualityExpression
+ BitwiseANDExpressionNoIn :
+
+ EqualityExpressionNoIn
BitwiseANDExpressionNoIn & EqualityExpressionNoIn
+ BitwiseXORExpression :
+
+ BitwiseANDExpression
BitwiseXORExpression ^ BitwiseANDExpression
+ BitwiseXORExpressionNoIn :
+
+ BitwiseANDExpressionNoIn
BitwiseXORExpressionNoIn ^ BitwiseANDExpressionNoIn
+ BitwiseORExpression :
+
+ BitwiseXORExpression
BitwiseORExpression | BitwiseXORExpression
+ BitwiseORExpressionNoIn :
+
+ BitwiseXORExpressionNoIn
BitwiseORExpressionNoIn | BitwiseXORExpressionNoIn
+ Semantics
++ The + production A : A @ B, + where @ is one of the bitwise operators in the productions above, is + evaluated as follows:
++ Let + lref be the result of evaluating A.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating B.
++ Let + rval be GetValue(rref).
++ Let + lnum be ToInt32(lval).
++ Let + rnum be ToInt32(rval).
++ Return + the result of applying the bitwise operator @ to lnum and + rnum. The result is a signed 32 bit integer.
++ Syntax
++ LogicalANDExpression :
+
+ BitwiseORExpression
LogicalANDExpression && BitwiseORExpression
+ LogicalANDExpressionNoIn :
+
+ BitwiseORExpressionNoIn
LogicalANDExpressionNoIn && BitwiseORExpressionNoIn
+ LogicalORExpression :
+
+ LogicalANDExpression
LogicalORExpression || LogicalANDExpression
+ LogicalORExpressionNoIn :
+
+ LogicalANDExpressionNoIn
LogicalORExpressionNoIn || LogicalANDExpressionNoIn
+ Semantics
+
+ The
+ production LogicalANDExpression
+ : LogicalANDExpression
+ &&
+ BitwiseORExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating LogicalANDExpression.
++ Let + lval be GetValue(lref).
++ If + ToBoolean(lval) is false, return lval.
++ Let + rref be the result of evaluating BitwiseORExpression.
++ Return + GetValue(rref).
+
+ The
+ production LogicalORExpression
+ : LogicalORExpression
+ ||
+ LogicalANDExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating LogicalORExpression.
++ Let + lval be GetValue(lref).
++ If + ToBoolean(lval) is true, return lval.
++ Let + rref be the result of evaluating LogicalANDExpression.
++ Return + GetValue(rref).
++ The + LogicalANDExpressionNoIn + and LogicalORExpressionNoIn + productions are evaluated in the same manner as the + LogicalANDExpression + and LogicalORExpression + productions except that the contained LogicalANDExpressionNoIn, + BitwiseORExpressionNoIn + and LogicalORExpressionNoIn + are evaluated instead of the contained LogicalANDExpression, + BitwiseORExpression + and LogicalORExpression, + respectively.
+NOTE The
+ value produced by a &&
+ or || operator is
+ not necessarily of type Boolean. The value produced will always be
+ the value of one of the two operand expressions.
+ Syntax
++ ConditionalExpression :
+
+ LogicalORExpression
LogicalORExpression
+ ? AssignmentExpression : AssignmentExpression
+ ConditionalExpressionNoIn :
+
+ LogicalORExpressionNoIn
LogicalORExpressionNoIn
+ ? AssignmentExpression : AssignmentExpressionNoIn
+ Semantics
+
+ The
+ production ConditionalExpression
+ :
+ LogicalORExpression
+ ?
+ AssignmentExpression
+ :
+ AssignmentExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating LogicalORExpression.
++ If + ToBoolean(GetValue(lref)) is true, then
++ Let + trueRef be the result of evaluating the first + AssignmentExpression.
++ Return + GetValue(trueRef).
++ Else
++ Let + falseRef be the result of evaluating the second + AssignmentExpression.
++ Return + GetValue(falseRef).
++ The + ConditionalExpressionNoIn + production is evaluated in the same manner as the + ConditionalExpression + production except that the contained LogicalORExpressionNoIn, + AssignmentExpression + and AssignmentExpressionNoIn + are evaluated instead of the contained LogicalORExpression, + first AssignmentExpression + and second AssignmentExpression, + respectively.
++
NOTE The grammar + for a ConditionalExpression in ECMAScript is a little bit different + from that in C and Java, which each allow the second subexpression + to be an Expression but restrict the third expression to be a + ConditionalExpression. The motivation for this difference in + ECMAScript is to allow an assignment expression to be governed by + either arm of a conditional and to eliminate the confusing and + fairly useless case of a comma expression as the centre expression.
++ Syntax
++ AssignmentExpression :
+
+ ConditionalExpression
LeftHandSideExpression
+ AssignmentOperator AssignmentExpression
+ AssignmentExpressionNoIn :
+
+ ConditionalExpressionNoIn
LeftHandSideExpression
+ AssignmentOperator AssignmentExpressionNoIn
+ AssignmentOperator : + one + of
+|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+ Semantics
++ The + AssignmentExpressionNoIn + productions are evaluated in the same manner as the + AssignmentExpression + productions except that the contained ConditionalExpressionNoIn andAssignmentExpressionNoIn are evaluated instead of the + contained ConditionalExpression + and AssignmentExpression, + respectively.
+
+ The
+ production AssignmentExpression
+ : LeftHandSideExpression
+ =
+ AssignmentExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating LeftHandSideExpression.
++ Let + rref be the result of evaluating AssignmentExpression.
++ Let + rval be GetValue(rref).
++ Throw + a SyntaxError exception if the following conditions are all + true:
++ IsStrictReference(lref) + is true
++ Type(GetBase(lref)) + is Environment Record
+
+ GetReferencedName(lref)
+ is either "eval"
+ or "arguments"
+ Call + PutValue(lref, rval).
++ Return + rval.
+NOTE When + an assignment occurs within strict mode code, its LeftHandSide + must not evaluate to an unresolvable reference. If it does a + ReferenceError exception is thrown upon assignment. The + LeftHandSide also + may not be a reference to a data property with the attribute value + {[[Writable]]:false}, + to an accessor property with the attribute value + {[[Set]]:undefined}, + nor to a non-existent property of an object whose [[Extensible]] + internal property has the value false. In these cases a + TypeError exception is thrown.
+
+ The
+ production AssignmentExpression : LeftHandSideExpression@ = AssignmentExpression,
+ where @ represents one of the operators indicated above, is
+ evaluated as follows:
+ Let + lref be the result of evaluating LeftHandSideExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating AssignmentExpression.
++ Let + rval be GetValue(rref).
++ Let + r be the result of applying operator @ to lval and + rval.
++ Throw + a SyntaxError exception if the following conditions are all + true:
++ IsStrictReference(lref) + is true
++ Type(GetBase(lref)) + is Environment Record
+
+ GetReferencedName(lref)
+ is either "eval"
+ or "arguments"
+ Call + PutValue(lref, r).
++ Return + r.
+NOTE See + NOTE 11.13.1.
++ Syntax
++ Expression :
+
+ AssignmentExpression
Expression , AssignmentExpression
+ ExpressionNoIn :
+
+ AssignmentExpressionNoIn
ExpressionNoIn , AssignmentExpressionNoIn
+ Semantics
+
+ The
+ production Expression
+ : Expression
+ ,
+ AssignmentExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating Expression.
++ Call + GetValue(lref).
++ Let + rref be the result of evaluating AssignmentExpression.
++ Return + GetValue(rref).
++ The + ExpressionNoIn + production is evaluated in the same manner as the Expression + production except that the contained ExpressionNoIn + and AssignmentExpressionNoIn + are evaluated instead of the contained Expression + and AssignmentExpression, + respectively.
++
NOTE GetValue must + be called even though its value is not used because it may have + observable side-effects.
++ Syntax
++ Statement :
+
+ Block
VariableStatement
EmptyStatement
ExpressionStatement
IfStatement
IterationStatement
ContinueStatement
BreakStatement
ReturnStatement
WithStatement
LabelledStatement
SwitchStatement
ThrowStatement
TryStatement
DebuggerStatement
+ Semantics
++ A + Statement can be + part of a LabelledStatement, + which itself can be part of a LabelledStatement, + and so on. The labels introduced this way are collectively referred + to as the “current label set” when describing the semantics of + individual statements. A LabelledStatement + has no semantic meaning other than the introduction of a label to a + label set. The label set of an IterationStatement + or a SwitchStatement + initially contains the single element empty. The label set of + any other statement is initially empty.
+NOTE Several + widely used implementations of ECMAScript are known to support the + use of FunctionDeclaration + as a Statement. However + there are significant and irreconcilable variations among the + implementations in the semantics applied to such + FunctionDeclarations. + Because of these irreconcilable difference, the use of a + FunctionDeclaration + as a Statement + results in code that is not reliably portable among implementations. + It is recommended that ECMAScript implementations either disallow + this usage of FunctionDeclaration + or issue a warning when such a usage is encountered. Future editions + of ECMAScript may define alternative portable means for declaring + functions in a Statement + context.
++ Syntax
++ Block :
+
+ { StatementListopt }
+ StatementList :
+
+ Statement
StatementList
+ Statement
+ Semantics
+
+ The
+ production Block : { }
+ is evaluated as follows:
+ Return + (normal, empty, empty).
+
+ The
+ production Block : {
+ StatementList }is
+ evaluated as follows:
+ Return + the result of evaluating StatementList.
++ The + production StatementList :Statement is evaluated as follows:
++ Let + s be the result of evaluating Statement.
++ If + an exception was thrown, return (throw, + V, empty) where V + is the exception. (Execution now proceeds as if no exception were + thrown.)
++ Return + s.
++ The + production StatementList :StatementList Statement is evaluated as follows:
++ Let + sl be the result of evaluating StatementList.
++ If + sl is an abrupt completion, return sl.
++ Let + s be the result of evaluating Statement.
++ If + an exception was thrown, return (throw, + V, empty) where V + is the exception. (Execution now proceeds as if no exception were + thrown.)
++ If + s.value is empty, let + V = sl.value, otherwise let V = s.value.
++ Return + (s.type, V, s.target).
++ Syntax
++ VariableStatement :
+
+ var VariableDeclarationList ;
+ VariableDeclarationList :
+
+ VariableDeclaration
VariableDeclarationList , VariableDeclaration
+ VariableDeclarationListNoIn :
+
+ VariableDeclarationNoIn
VariableDeclarationListNoIn , VariableDeclarationNoIn
+ VariableDeclaration :
++ Identifier + Initialiseropt
++ VariableDeclarationNoIn :
++ Identifier + InitialiserNoInopt
++ Initialiser :
+
+ = AssignmentExpression
+ InitialiserNoIn :
+
+ = AssignmentExpressionNoIn
+ A + variable statement declares variables that are created as defined in + 10.5. Variables are initialised to undefined when created. A + variable with an Initialiser + is assigned the value of its AssignmentExpression + when the VariableStatement + is executed, not when the variable is created.
++ Semantics
+
+ The
+ production VariableStatement : var VariableDeclarationList ;
+ is evaluated as follows:
+ Evaluate + VariableDeclarationList.
++ Return + (normal, empty, + empty).
++ The + production VariableDeclarationList + : VariableDeclaration + is evaluated as follows:
++ Evaluate + VariableDeclaration.
+
+ The
+ production VariableDeclarationList
+ : VariableDeclarationList
+ ,
+ VariableDeclaration
+ is evaluated as follows:
+ Evaluate + VariableDeclarationList.
++ Evaluate + VariableDeclaration.
++ The + production VariableDeclaration : Identifier is evaluated as follows:
++ Return + a String value containing the same sequence of characters as in the + Identifier.
++ The + production VariableDeclaration + : Identifier + Initialiser is evaluated as follows:
++ Let + lhs be the result of evaluating Identifier as + described in 11.1.2.
++ Let + rhs be the result of evaluating Initialiser.
++ Let + value be GetValue(rhs).
++ Call + PutValue(lhs, value).
++ Return + a String value containing the same sequence of characters as in the + Identifier.
+NOTE The + String value of a VariableDeclaration + is used in the evaluation of for-in statements (12.6.4).
++ If a + VariableDeclaration + is nested within a with statement and the Identifier in the + VariableDeclaration + is the same as a property name of the binding object of the with + statement’s object environment record, then step 4 will assign + value to the property instead of to the VariableEnvironment binding + of the Identifier.
+
+ The
+ production Initialiser : = AssignmentExpression is evaluated as follows:
+ Return + the result of evaluating AssignmentExpression.
++ The + VariableDeclarationListNoIn, + VariableDeclarationNoIn + and InitialiserNoIn + productions are evaluated in the same manner as the + VariableDeclarationList, + VariableDeclaration + and Initialiser + productions except that the contained VariableDeclarationListNoIn, + VariableDeclarationNoIn, + InitialiserNoIn + and AssignmentExpressionNoIn + are evaluated instead of the contained VariableDeclarationList, + VariableDeclaration, + Initialiser and + AssignmentExpression, + respectively.
+
+ It is
+ a SyntaxError if a VariableDeclaration
+ or VariableDeclarationNoIn
+ occurs within strict code and its Identifier
+ is either "eval"
+ or "arguments".
+ Syntax
++ EmptyStatement :
++ ;
++ Semantics
+
+ The
+ production EmptyStatement : ; is
+ evaluated as follows:
+ Return + (normal, + empty, empty).
++ Syntax
++ ExpressionStatement :
+
+ [lookahead
+ ∉
+ {{,
+ function}] Expression ;
NOTE An
+ ExpressionStatement
+ cannot start with an opening curly brace because that might make it
+ ambiguous with a Block.
+ Also, an ExpressionStatement
+ cannot start with the function
+ keyword because that might make it ambiguous with a
+ FunctionDeclaration.
+ Semantics
+
+ The
+ production ExpressionStatement : [lookahead ∉
+ {{,
+ function}]Expression;
+ is evaluated as follows:
+ Let + exprRef be the result of evaluating Expression.
++ Return + (normal, GetValue(exprRef), + empty).
++ Syntax
++ IfStatement :
+
+ if ( Expression ) Statement else Statementif ( Expression ) Statement
+ Each
+ else for which the
+ choice of associated if
+ is ambiguous shall be associated with the nearest possible if
+ that would otherwise have no corresponding else.
+ Semantics
+
+ The
+ production IfStatement : if ( Expression ) Statement else Statement is evaluated as follows:
+ Let + exprRef be the result of evaluating Expression.
++ If + ToBoolean(GetValue(exprRef)) is true, then
++ Return + the result of evaluating the first Statement.
++ Else,
++ Return + the result of evaluating the second Statement.
+
+ The
+ production IfStatement : if ( Expression ) Statement is evaluated as follows:
+ Let + exprRef be the result of evaluating Expression.
++ If + ToBoolean(GetValue(exprRef)) is false, return + (normal, empty, + empty).
++ Return + the result of evaluating Statement.
++ Syntax
++ IterationStatement :
+
+ do
+ Statement
+ while ( Expression ); while ( Expression ) Statementfor ( ExpressionNoInopt; Expressionopt ; Expressionopt ) Statementfor ( var VariableDeclarationListNoIn; Expressionopt ; Expressionopt ) Statementfor ( LeftHandSideExpression in Expression ) Statementfor ( var VariableDeclarationNoIn in Expression ) Statement
+ The
+ production do Statement while ( Expression );
+ is evaluated as follows:
+ Let + V = empty.
++ Let + iterating be true.
++ Repeat, + while iterating is true
++ Let + stmt be the result of evaluating Statement.
++ If + stmt.value is not empty, + let V = stmt.value.
++ If + stmt.type is not continue + || stmt.target is not in the current label set, then
++ If + stmt.type is break + and stmt.target is in the current label set, return + (normal, V, empty).
++ If + stmt is an abrupt completion, return stmt.
++ Let + exprRef be the result of evaluating Expression.
++ If + ToBoolean(GetValue(exprRef)) is false, set iterating + to false.
++ Return + (normal, V, empty);
+
+ The
+ production IterationStatement : while ( Expression ) Statement is evaluated as follows:
+ Let + V = empty.
++ Repeat
++ Let + exprRef be the result of evaluating Expression.
++ If + ToBoolean(GetValue(exprRef)) is false, return + (normal, V, empty).
++ Let + stmt be the result of evaluating Statement.
++ If + stmt.value is not empty, + let V = stmt.value.
++ If + stmt.type is not continue + || stmt.target is not in the current label set, then
++ If + stmt.type is break + and stmt.target is in the current label set, then
++ Return + (normal, V, empty).
++ If + stmt is an abrupt completion, return stmt.
+
+ The
+ production
IterationStatement
+ : for
+ ( ExpressionNoInopt
+ ; Expressionopt
+ ; Expressionopt)
+ Statement
is
+ evaluated as follows:
+ If + ExpressionNoIn is present, then.
++ Let + exprRef be the result of evaluating ExpressionNoIn.
++ Call + GetValue(exprRef). (This value is not used.)
++ Let + V = empty.
++ Repeat
++ If + the first Expression is present, then
+ ++ Let + stmt be the result of evaluating Statement.
++ If + stmt.value is not empty, + let V = stmt.value
++ If + stmt.type is break + and stmt.target is in the current label set, return + (normal, V, empty).
++ If + stmt.type is not continue + || stmt.target is not in the current label set, then
++ If + stmt is an abrupt completion, return stmt.
++ If + the second Expression is present, then
++ Let + incExprRef be the result of evaluating the second + Expression.
++ Call + GetValue(incExprRef). (This value is not used.)
+
+ The
+ production
IterationStatement
+ : for (
+ var
+ VariableDeclarationListNoIn
+ ; Expressionopt ;
+ Expressionopt ) Statement
is
+ evaluated as follows:
+ Evaluate + VariableDeclarationListNoIn.
++ Let + V = empty.
++ Repeat
++ If + the first Expression is present, then
+ ++ Let + stmt be the result of evaluating Statement.
++ If + stmt.value is not empty, + let V = stmt.value.
++ If + stmt.type is break + and stmt.target is in the current label set, return + (normal, V, empty).
++ If + stmt.type is not continue + || stmt.target is not in the current label set, then
++ If + stmt is an abrupt completion, return stmt.
++ If + the second Expression is present, then.
++ Let + incExprRef be the result of evaluating the second + Expression.
++ Call + GetValue(incExprRef). (This value is not used.)
+
+ The
+ production IterationStatement
+ : for (
+ LeftHandSideExpression
+ in Expression
+ ) Statement
+ is evaluated as follows:
+ Let + exprRef be the result of evaluating the Expression.
++ Let + experValue be GetValue(exprRef).
++ If + experValue is null or undefined, return + (normal, empty, + empty).
++ Let + obj be ToObject(experValue).
++ Let + V = empty.
++ Repeat
++ Let + P be the name of the next property of obj whose + [[Enumerable]] attribute is true. If there is no such + property, return (normal, V, + empty).
++ Let + lhsRef be the result of evaluating the + LeftHandSideExpression ( it may be evaluated repeatedly).
++ Call + PutValue(lhsRef, P).
++ Let + stmt be the result of evaluating Statement.
++ If + stmt.value is not empty, + let V = stmt.value.
++ If + stmt.type is break + and stmt.target is in the current label set, return + (normal, V, empty).
++ If + stmt.type is not continue || stmt.target is + not in the current label set, then
++ If + stmt is an abrupt completion, return stmt.
+
+ The
+ production
IterationStatement
+ : for (
+ var
+ VariableDeclarationNoIn
+ in Expression
+ ) Statement
is
+ evaluated as follows:
+ Let + varName be the result of evaluating VariableDeclarationNoIn.
++ Let + exprRef be the result of evaluating the Expression.
++ Let + experValue be GetValue(exprRef).
++ If + experValue is null or undefined, return + (normal, empty, + empty).
++ Let + obj be ToObject(experValue).
++ Let + V = empty.
++ Repeat
++ Let + P be the name of the next property of obj whose + [[Enumerable]] attribute is true. If there is no such + property, return (normal, V, + empty).
++ Let + varRef be the result of evaluating varName as if it + were an Identifier Reference (11.1.2); it may be evaluated + repeatedly.
++ Call + PutValue(varRef, P).
++ Let + stmt be the result of evaluating Statement.
++ If + stmt.value is not empty, + let V = stmt.value.
++ If + stmt.type is break + and stmt.target is in the current label set, return + (normal, V, empty).
++ If + stmt.type is not continue + || stmt.target is not in the current label set, then
++ If + stmt is an abrupt completion, return stmt.
++ The + mechanics and order of enumerating the properties (step 6.a in the + first algorithm, step 7.a in the second) is not specified. + Properties of the object being enumerated may be deleted during + enumeration. If a property that has not yet been visited during + enumeration is deleted, then it will not be visited. If new + properties are added to the object being enumerated during + enumeration, the newly added properties are not guaranteed to be + visited in the active enumeration. + A property name must not be visited more than once in any enumeration. +
+ ++ Enumerating + the properties of an object includes enumerating properties of its + prototype, and the prototype of the prototype, and so on, + recursively; but a property of a prototype is not enumerated if it + is “shadowed” because some previous object in the prototype + chain has a property with the same name. + The values of [[Enumerable]] attributes are not considered when + determining if a property of a prototype object is shadowed by a previous + object on the prototype chain.
+ +NOTE See + NOTE 11.13.1.
++ Syntax
+ ++ ContinueStatement :
+
+ continue ;
+ continue
+ [no LineTerminator here] Identifier;
+ Semantics
++ A + program is considered syntactically incorrect if either of the + following is true:
+
+ The
+ program contains a continue
+ statement without the optional Identifier,
+ which is not nested, directly or indirectly (but not crossing
+ function boundaries), within an IterationStatement.
+ The
+ program contains a continue
+ statement with the optional Identifier,
+ where Identifier does
+ not appear in the label set of an enclosing (but not crossing
+ function boundaries) IterationStatement.
+ A + ContinueStatement + without an Identifier + is evaluated as follows:
++ Return + (continue, empty, + empty).
++ A + ContinueStatement + with the optional Identifier + is evaluated as follows:
++ Return + (continue, empty, + Identifier).
++ Syntax
++ BreakStatement :
+
+ break ;
+ break
+ [no LineTerminator here] Identifier ;
+ Semantics
++ A + program is considered syntactically incorrect if either of the + following is true:
+
+ The
+ program contains a break
+ statement without the optional Identifier,
+ which is not nested, directly or indirectly (but not crossing
+ function boundaries), within an IterationStatement
+ or a SwitchStatement.
+ The
+ program contains a break
+ statement with the optional Identifier,
+ where Identifier does
+ not appear in the label set of an enclosing (but not crossing
+ function boundaries) Statement.
+ A + BreakStatement + without an Identifier + is evaluated as follows:
++ Return + (break, empty, + empty).
++ A + BreakStatement + with an Identifier + is evaluated as follows:
++ Return + (break, empty,Identifier).
++ Syntax
++ ReturnStatement :
+
+ return ;
+ return
+ [no LineTerminator here] Expression ;
+ Semantics
+
+ An
+ ECMAScript program is considered syntactically incorrect if it
+ contains a return
+ statement that is not within a FunctionBody.
+ A return statement
+ causes a function to cease execution and return a value to the
+ caller. If Expression
+ is omitted, the return value is undefined. Otherwise, the
+ return value is the value of Expression.
+ The
+ production ReturnStatement
+ : return
+ [no LineTerminator here]
+ Expressionopt
+ ; is
+ evaluated as:
+ If + the Expression is not present, return (return, + undefined, empty).
++ Let + exprRef be the result of evaluating Expression.
++ Return + (return, GetValue(exprRef), + empty).
++ Syntax
++ WithStatement :
+
+ with ( Expression ) Statement
+ The
+ with statement
+ adds an object environment record for a computed object to the
+ lexical environment of the current execution context. It then
+ executes a statement using this augmented lexical environment.
+ Finally, it restores the original lexical environment.
+ Semantics
+
+ The
+ production WithStatement : with ( Expression ) Statement is evaluated as follows:
+ Let + val be the result of evaluating Expression.
++ Let + oldEnv be the running execution context’s + LexicalEnvironment.
++ Let + newEnv be the result of calling NewObjectEnvironment passing + obj and oldEnv as the arguments
++ Set + the provideThis flag of newEnv to true.
++ Set + the running execution context’s LexicalEnvironment to newEnv.
++ Let + C be the result of evaluating Statement but if an + exception is thrown during the evaluation, let C be (throw, + V, empty), where V + is the exception. (Execution now proceeds as if no exception were + thrown.)
++ Set + the running execution context’s Lexical Environment to oldEnv.
++ Return + C.
++
NOTE No matter how + control leaves the embedded Statement, + whether normally or by some form of abrupt completion or exception, + the LexicalEnvironment is always restored to its former state.
++ Strict + mode code may not include a WithStatement. + The occurrence of a WithStatement + in such a context is treated as a SyntaxError.
++ Syntax
++ SwitchStatement :
+
+ switch ( Expression ) CaseBlock
+ CaseBlock :
+
+ { CaseClausesopt } { CaseClausesoptDefaultClause CaseClausesopt }
+ CaseClauses :
+
+ CaseClause
CaseClauses
+ CaseClause
+ CaseClause :
+
+ case Expression : StatementListopt
+ DefaultClause :
+
+ default : StatementListopt
+ Semantics
+
+ The
+ production SwitchStatement : switch ( Expression ) CaseBlock is evaluated as follows:
+ Let + exprRef be the result of evaluating Expression.
++ Let + R be the result of evaluating CaseBlock, passing it + GetValue(exprRef) as a parameter.
++ If + R.type is break and + R.target is in the current label set, return (normal, + R.value, empty).
++ Return + R.
+
+ The
+ production CaseBlock
+ : {
+ CaseClausesopt
+ }
+ is given an input parameter, input,
+ and is evaluated as follows:
+ Let + V + = empty.
++ Let + A + be the list of CaseClause + items in source text order.
++ Let + searching + be true.
++ Repeat, + while searching + is true
++ Let + C + be the next CaseClause + in A. + If there is no such CaseClause, + return (normal, + V, + empty).
++ Let + clauseSelector + be the result of evaluating C.
+
+ If
+ input
+ is equal to clauseSelector
+ as defined by the ===
+ operator, then
+ Set + searching + to false.
++ IfC + has a StatementList, + then +
++ EvaluateC’s + StatementList + and letR + be the result.
++ IfR + is an abrupt completion, then returnR.
++ LetV + =R.value.
++ Repeat
++ LetC + be the next CaseClause + inA. + If there is no such CaseClause, + return (normal,V, + empty).
++ IfC + has a StatementList, + then +
++ EvaluateC’s + StatementList + and letR + be the result.
++ IfR.value + is not + empty, + then letV + =R.value.
++ IfR + is an abrupt completion, then return (R.type,V,R.target).
+
+ The
+ production CaseBlock
+ : {
+ CaseClausesoptDefaultClause CaseClausesopt
+ }
+ is given an input parameter, input,
+ and is evaluated as follows:
+ Let + V + = empty.
++ Let + A + be the list of CaseClause + items in the first CaseClauses, + in source text order.
++ Let + B + be the list of CaseClause items in the second CaseClauses, in + source text order.
++ Let + found + be false.
++ Repeat + letting C + be in order each CaseClause + in A
++ If + found + is false, + then
++ Let + clauseSelector + be the result of evaluating C.
+
+ If
+ input
+ is equal to clauseSelector
+ as defined by the ===
+ operator, then set found
+ to true.
+ If + found + is true, + then
++ If + C + has a StatementList, then
++ Evaluate + C’s + StatementList + and let R + be the result.
++ IfR.value + is not + empty, + then letV + =R.value.
++ R + is an abrupt completion, then return (R.type,V,R.target).
++ Let + foundInB + be false.
++ If + found + is false, + then +
++ Repeat, + while foundInB + is false + and all elements of B + have not been processed
++ Let + C + be the next CaseClause + in B. + +
++ Let + clauseSelector + be the result of evaluating C.
+
+ If
+ input
+ is equal to clauseSelector
+ as defined by the ===
+ operator, then
+ Set + foundInB + to true.
++ IfC + has a StatementList, + then
++ Evaluate + C’s + StatementList + and let R + be the result.
++ IfR.value + is not + empty, + then letV + =R.value.
++ R + is an abrupt completion, then return (R.type,V,R.target).
++ If + foundInB + is false + and the DefaultClause + has a StatementList, + then
++ Evaluate + the DefaultClause’s + StatementList + and let R + be the result.
++ If + R.value + is not empty, + then let V + = R.value.
++ If + R + is an abrupt completion, then return (R.type, + V, + R.target).
++ Repeat + (Note that if step 7.a.i has been performed this loop does not + start at the beginning of B)
++ Let + C + be the next CaseClause + in B. + If there is no such CaseClause, + return (normal, + V, + empty).
++ If + C + has a StatementList, then +
++ Evaluate + C’s + StatementList and let R + be the result.
++ If + R.value + is not empty, + then let V + = R.value.
++ If + R + is an abrupt completion, then return (R.type, + V, + R.target).
+
+ The
+ production CaseClause
+ : case Expression : StatementListopt is evaluated as follows:
+ Let + exprRef be the result of evaluating Expression.
++ Return + GetValue(exprRef).
+NOTE Evaluating + CaseClause does + not execute the associated StatementList. + It simply evaluates the Expression + and returns the value, which the CaseBlock + algorithm uses to determine which StatementList + to start executing.
++ Syntax
++ LabelledStatement :
+
+ Identifier : Statement
+ Semantics
+
+ A
+ Statement may be
+ prefixed by a label. Labelled statements are only used in
+ conjunction with labelled break
+ and continue
+ statements. ECMAScript has no goto
+ statement.
+ An + ECMAScript program is considered syntactically incorrect if it + contains a LabelledStatement + that is enclosed by a LabelledStatement + with the same Identifier + as label. This does not apply to labels appearing within the body of + a FunctionDeclaration + that is nested, directly or indirectly, within a labelled statement.
+
+ The
+ production Identifier : Statement is evaluated by adding Identifier
+ to the label set of Statement
+ and then evaluating Statement.
+ If the LabelledStatement
+ itself has a non-empty label set, these labels are also added to the
+ label set of Statement
+ before evaluating it. If the result of evaluating Statement
+ is (break, V,
+ L) where L
+ is equal to Identifier,
+ the production results in (normal, V,
+ empty).
+ Prior + to the evaluation of a LabelledStatement, + the contained Statement + is regarded as possessing an empty label set, unless it is an + IterationStatement + or a SwitchStatement, + in which case it is regarded as possessing a label set consisting of + the single element, empty.
++ Syntax
++ ThrowStatement + :
+
+ throw
+ [no LineTerminator here] Expression ;
+ Semantics
+
+ The
+ production ThrowStatement
+ : throw
+ [no LineTerminator here]
+ Expression
+ ; is evaluated as:
+ Let + exprRef be the result of evaluating Expression.
++ Return + (throw, GetValue(exprRef), + empty).
++ Syntax
++ TryStatement :
+
+ try Block Catchtry Block Finallytry Block Catch Finally
+ Catch :
+
+ catch (
+ Identifier
+ ) Block
+ Finally :
+
+ finally Block
+ The
+ try statement
+ encloses a block of code in which an exceptional condition can
+ occur, such as a runtime error or a throw
+ statement. The catch
+ clause provides the exception-handling code. When a catch clause
+ catches an exception, its Identifier
+ is bound to that exception.
+ Semantics
+
+ The
+ production TryStatement
+ : try Block
+ Catch is evaluated
+ as follows:
+ Let + B be the result of evaluating Block.
++ If + B.type is not throw, + return B.
++ Return + the result of evaluating Catch with parameter B.
+
+ The
+ production TryStatement
+ : try Block
+ Finally is
+ evaluated as follows:
+ Let + B be the result of evaluating Block.
++ Let + F be the result of evaluating Finally.
++ If + F.type is normal, + return B.
++ Return + F.
+
+ The
+ production TryStatement
+ : try Block
+ Catch Finally
+ is evaluated as follows:
+ Let + B be the result of evaluating Block.
++ If + B.type is throw, then
++ Let + C be the result of evaluating Catch with parameter + B.
++ Else, + B.type is not throw,
++ Let + C be B.
++ Let + F be the result of evaluating Finally.
++ If + F.type is normal, + return C.
++ Return + F.
+
+ The
+ production Catch :
+ catch (
+ Identifier
+ ) Block
+ is evaluated as follows:
+ Let + C be the parameter that has been passed to this production.
++ Let + oldEnv be the running execution context’s + LexicalEnvironment.
++ Let + catchEnv be the result of calling NewDeclarativeEnvironment + passing oldEnv as the argument. +
++ Call + the CreateMutableBinding concrete method of catchEnv passing + the Identifier String value as the argument.
++ Call + the SetMutableBinding concrete method of catchEnv passing + the Identifier, C, and false as arguments. + Note that the last argument is immaterial in this situation.
++ Set + the running execution context’s LexicalEnvironment to catchEnv.
++ Let + B be the result of evaluating Block.
++ Set + the running execution context’s LexicalEnvironment to oldEnv.
++ Return + B.
+NOTE No + matter how control leaves the Block + the LexicalEnvironment is always restored to its former state.
+
+ The
+ production Finally
+ : finally Block
+ is evaluated as follows:
+ Return + the result of evaluating Block.
+
+ It is
+ an SyntaxError if a TryStatement
+ with a Catch
+ occurs within strict code and the Identifier
+ of the Catch
+ production is either "eval"
+ or "arguments".
+ Syntax
++ DebuggerStatement :
+
+ debugger ;
+ Semantics
++ Evaluating + the DebuggerStatement production may allow an implementation to cause a + breakpoint when run under a debugger. If a debugger is not present + or active this statement has no observable effect.
+
+ The
+ production DebuggerStatement : debugger
+ ; is evaluated as follows:
+ If + an implementation defined debugging facility is available and + enabled, then
++ Perform + an implementation defined debugging action.
++ Let + result be an implementation defined Completion value. +
++ Else
++ Let + result be (normal, + empty, empty).
++ Return + result.
++ Syntax
++ FunctionDeclaration :
+
+ function Identifier ( FormalParameterListopt ) { FunctionBody }
+ FunctionExpression :
+
+ function Identifieropt ( FormalParameterListopt ) { FunctionBody }
+ FormalParameterList :
+
+ Identifier
FormalParameterList , Identifier
+ FunctionBody :
++ SourceElementsopt
++ Semantics
+
+ The
+ production
FunctionDeclaration : function
+ Identifier ( FormalParameterListopt ) {
+ FunctionBody }
is
+ instantiated as follows during Declaration Binding instantiation
+ (10.5):
+ Return + the result of creating a new Function object as specified in 13.2 + with parameters specified by FormalParameterListopt, + and body specified by FunctionBody. + Pass in the VariableEnvironment of the running execution context as + the Scope. + Pass in true + as the Strict + flag if the FunctionDeclaration + is contained in strict code or if its FunctionBody + is strict code.
+
+ The
+ production
FunctionExpression : function
+ ( FormalParameterListopt ) {
+ FunctionBody }
+
is evaluated as follows:
+ Return + the result of creating a new Function object as specified in 13.2 + with parameters specified by FormalParameterListopt + and body specified by FunctionBody. + Pass in the LexicalEnvironment of the running execution context as + the Scope. + Pass in true + as the Strict + flag if the FunctionExpression + is contained in strict code or if its FunctionBody + is strict code.
+
+ The
+ production
FunctionExpression
+ : function
+ Identifier (
+ FormalParameterListopt
+ ) {
+ FunctionBody }
is
+ evaluated as follows:
+ Let + funcEnv be + the result of calling NewDeclarativeEnvironment passing the running + execution context’s Lexical Environment as the argument
++ Let + envRec be + funcEnv’s environment record.
++ Call + the CreateImmutableBinding(N) concrete method of envRec passing the String + value of Identifier + as the argument.
++ Let + closure be + the result of creating a new Function object as specified in 13.2 + with parameters specified by FormalParameterListopt + and body specified by FunctionBody. + Pass in funcEnv as + the Scope. + Pass in true + as the Strict + flag if the FunctionExpression + is contained in strict code or if its FunctionBody + is strict code.
++ Call + the InitializeImmutableBinding(N,V) + concrete method of envRec passing the String + value of Identifier and closure as the arguments.
++ Return + closure.
+NOTE The + Identifier in a FunctionExpression + can be referenced from inside the FunctionExpression's + FunctionBody to + allow the function to call itself recursively. However, unlike in a + FunctionDeclaration, + the Identifier in + a FunctionExpression + cannot be referenced from and does not affect the scope enclosing + the FunctionExpression.
++ The + production FunctionBody :SourceElementsopt is evaluated as follows:
++ The + code of this FunctionBody is strict mode code + if it is part of a FunctionDeclaration + or FunctionExpression + that is contained in strict mode code or if the Directive Prologue + (14.1) of its SourceElements + contains a Use Strict Directive or if any of the conditions in + 10.1.1 apply. If the code of this FunctionBody is strict mode code, + SourceElements + is evaluated in the following steps as strict mode code. Otherwise, + SourceElements + is evaluated in the following steps as non-strict mode code.
++ If + SourceElements + is present return the result of evaluating SourceElements.
++ Else + return (normal, + undefined, + empty).
++ It is + a SyntaxError if any Identifier + value occurs more than once within a FormalParameterList + of a strict mode FunctionDeclaration + or FunctionExpression.
+
+ It is
+ a SyntaxError if the Identifier
+ "eval"
+ or the Identifier "arguments"
+ occurs within a FormalParameterList
+ of a strict mode FunctionDeclaration
+ or FunctionExpression.
+ It is
+ a SyntaxError if the Identifier
+ "eval"
+ or the Identifier "arguments"
+ occurs as the Identifier
+ of a strict mode FunctionDeclaration
+ or FunctionExpression.
+ Given + an optional parameter list specified by FormalParameterList, + a body specified by FunctionBody, + a Lexical Environment specified by Scope, + and a Boolean flag Strict, + a Function object is constructed as follows:
++ Create + a new native ECMAScript object and let F + be that object.
++ Set + all the internal methods, except for [[Get]], of F + as described in 8.12.
+
+ Set
+ the [[Class]] internal property of F
+ to "Function".
+ Set + the [[Prototype]] internal property of F + to the standard built-in Function prototype object as specified in + 15.3.3.1.
++ Set + the [[Get]] internal property of F + as described in 15.3.5.4.
++ Set + the [[Call]] internal property of F + as described in 13.2.1.
++ Set + the [[Construct]] internal property of F + as described in 13.2.2.
++ Set + the [[HasInstance]] internal property of F + as described in 15.3.5.3.
++ Set + the [[Scope]] internal property of F + to the value of Scope.
++ Let + names be + a List containing, in left to right textual order, the Strings + corresponding to the identifiers of FormalParameterList.
++ Set + the [[FormalParameters]] internal property of F to names.
++ Set + the [[Code]] internal property of F to FunctionBody.
++ Set + the [[Extensible]] internal property of F to true.
++ Let + len + be the number of formal parameters specified in + FormalParameterList. + If no parameters are specified, let len + be 0.
+
+ Call
+ the [[DefineOwnProperty]] internal method of F
+ with arguments "length",
+ Property Descriptor {[[Value]]: len,
+ [[Writable]]: false,
+ [[Enumerable]]: false,
+ [[Configurable]]: false},
+ and false.
+
+
+ Let
+ proto
+ be the result of creating a new object as would be constructed by
+ the expression new
+ Object()where Object
+ is the standard built-in constructor with that name.
+ Call
+ the [[DefineOwnProperty]] internal method of proto
+ with arguments "constructor",
+ Property Descriptor {[[Value]]: F,
+ { [[Writable]]: true,
+ [[Enumerable]]: false,
+ [[Configurable]]: true},
+ and false.
+ Call
+ the [[DefineOwnProperty]] internal method of F
+ with arguments "prototype",
+ Property Descriptor {[[Value]]: proto,
+ { [[Writable]]: true,
+ [[Enumerable]]: false,
+ [[Configurable]]: false},
+ and false.
+ If + Strict + is true, + then
++ Let + thrower + be the [[ThrowTypeError]] function Object (13.2.3).
+
+ Call
+ the [[DefineOwnProperty]] internal method of F
+ with arguments "caller",
+ PropertyDescriptor {[[Get]]: thrower,
+ [[Set]]: thrower,
+ [[Enumerable]]: false,
+ [[Configurable]]: false},
+ and false.
+ Call
+ the [[DefineOwnProperty]] internal method of F
+ with arguments "arguments",
+ PropertyDescriptor {[[Get]]: thrower,
+ [[Set]]: thrower,
+ [[Enumerable]]: false,
+ [[Configurable]]: false},
+ and false.
+ Return + F.
+NOTE A
+ prototype
+ property is automatically created for every function, to allow for
+ the possibility that the function will be used as a constructor.
+ When + the [[Call]] internal method for a Function object F + is called with a this value and a list of arguments, the following + steps are taken:
++ Let + funcCtx be the result of establishing a new execution + context for function code using the value of F's + [[FormalParameters]] internal property, the passed arguments List + args, and the this value as described in 10.4.3.
++ Let + result be the result of evaluating the FunctionBody + that is the value of F's [[Code]] internal property. If F + does not have a [[Code]] internal property or if its value is an + empty FunctionBody, then result is (normal, + undefined, empty).
++ Exit + the execution context funcCtx, restoring the previous + execution context.
++ If + result.type is throw + then throw result.value.
++ If + result.type is return + then return result.value.
++ Otherwise + result.type must be normal. + Return undefined.
++ When + the [[Construct]] internal method for a Function object F + is called with a possibly empty list of arguments, the following + steps are taken:
++ Let + obj be + a newly created native ECMAScript object.
++ Set + all the internal methods of obj + as specified in 8.12.
+
+ Set
+ the [[Class]] internal property of obj to "Object".
+ Set + the [[Extensible]] internal property of obj to true.
+
+ Let
+ proto be
+ the value of calling the [[Get]] internal property of F
+ with argument "prototype".
+ If + Type(proto) is Object, set the + [[Prototype]] internal property of obj to proto.
++ If + Type(proto) is not Object, set + the [[Prototype]] internal property of obj to the standard + built-in Object prototype object as described in 15.2.4.
++ Let + result be + the result of calling the [[Call]] internal property of F, + providing obj as + the this + value and providing the argument list passed into [[Construct]] as + args.
++ If + Type(result) + is Object then return result.
++ Return + obj.
++ The + [[ThrowTypeError]] object is a unique function object that is + defined once as follows:
++ Create + a new native ECMAScript object and let F + be that object.
++ Set + all the internal methods of F + as described in 8.12.
+
+ Set
+ the [[Class]] internal property of F
+ to "Function".
+ Set + the [[Prototype]] internal property of F + to the standard built-in Function prototype object as specified in + 15.3.3.1.
++ Set + the [[Call]] internal property of F + as described in 13.2.1.
++ Set + the [[Scope]] internal property of F + to the Global Environment.
++ Set + the [[FormalParameters]] internal property of F to an empty List.
++ Set + the [[Code]] internal property of F to be a FunctionBody + that unconditionally throws a TypeError + exception and performs no other action.
+
+ Call
+ the [[DefineOwnProperty]] internal method of F
+ with arguments "length",
+ Property Descriptor {[[Value]]: 0,
+ [[Writable]]: false,
+ [[Enumerable]]: false,
+ [[Configurable]]: false},
+ and false.
+
+
+ Set + the [[Extensible]] internal property of F to false.
++ Let + [[ThrowTypeError]] be F.
++ Syntax
++ Program :
++ SourceElementsopt
++ SourceElements :
+
+ SourceElement
SourceElements
+ SourceElement
+ SourceElement :
+
+ Statement
FunctionDeclaration
+ Semantics
+
+ The
+ production Program :SourceElementsopt
+ is evaluated as follows:
+ The + code of this Program is strict mode code if the Directive + Prologue (14.1) of its SourceElements contains a Use Strict + Directive or if any of the conditions of 10.1.1 apply. If the code + of this Program is strict mode code, SourceElements + is evaluated in the following steps as strict mode code. Otherwise + SourceElements is evaluated in the following steps as + non-strict mode code.
++ If + SourceElements is not present, return (normal, + empty, empty).
++ Let + progCxt be a new execution context for global code as + described in 10.4.1. +
++ Let + result be the result of evaluating SourceElements.
++ Exit + the execution context progCxt.
++ Return + result.
+NOTE The + processes for initiating the evaluation of a Program + and for dealing with the result of such an evaluation are defined by + an ECMAScript implementation and not by this specification.
++ The + production SourceElements + : SourceElements + SourceElement is + evaluated as follows:
++ Let + headResult be the result of evaluating SourceElements.
++ If + headResult is an abrupt completion, return headResult
++ Let + tailResult be result of evaluating SourceElement.
++ If + tailResult.value is empty, + let V = headResult.value, otherwise let V = + tailResult.value.
++ Return + (tailResult.type, V, tailResult.target) +
++ The + production SourceElement :Statement is evaluated as follows:
++ Return + the result of evaluating Statement.
++ The + production SourceElement :FunctionDeclaration is evaluated as follows:
++ Return + (normal, empty, + empty).
++ A + Directive Prologue is the longest sequence of ExpressionStatement productions occurring as the initial SourceElement + productions of a Program + or FunctionBody + and where each ExpressionStatement in the sequence + consists entirely of a StringLiteral + token followed a semicolon. + The semicolon may appear explicitly or may be inserted by +automatic semicolon insertion. A Directive Prologue may be an empty sequence.
+
+ A Use
+ Strict Directive is an ExpressionStatement
+ in a Directive Prologue whose StringLiteral
+ is either the exact character sequences "use strict"
+ or 'use strict'.
+ A Use Strict Directive may not contain an EscapeSequence
+ or LineContinuation.
+ A + Directive Prologue may contain more than one Use Strict Directive. + However, an implementation may issue a warning if this occurs.
+NOTE The + ExpressionStatement + productions of a Directive Prologue are evaluated normally during + evaluation of the containing SourceElements + production. Implementations may define implementation specific + meanings for ExpressionStatement + productions which are not a Use Strict Directive and which occur in + a Directive Prologue. If an appropriate notification mechanism + exists, an implementation should issue a warning if it encounters in + a Directive Prologue an ExpressionStatement + that is not a Use Strict Directive or which does not have a meaning + defined by the implementation.
++ There + are certain built-in objects available whenever an ECMAScript + program begins execution. One, the global object, is part of the + lexical environment of the executing program. Others are accessible + as initial properties of the global object.
+
+ Unless
+ specified otherwise, the [[Class]] internal property of a built-in
+ object is "Function"
+ if that built-in object has a [[Call]] internal property, or
+ "Object"
+ if that built-in object does not have a [[Call]] internal property.
+ Unless specified otherwise, the [[Extensible]] internal property of
+ a built-in object initially has the value true.
+ Many
+ built-in objects are functions: they can be invoked with arguments.
+ Some of them furthermore are constructors: they are functions
+ intended for use with the new
+ operator. For each built-in function, this specification describes
+ the arguments required by that function and properties of the
+ Function object. For each built-in constructor, this specification
+ furthermore describes properties of the prototype object of that
+ constructor and properties of specific object instances returned by
+ a new expression
+ that invokes that constructor.
+ Unless + otherwise specified in the description of a particular function, if + a function or constructor described in this clause is given fewer + arguments than the function is specified to require, the function or + constructor shall behave exactly as if it had been given sufficient + additional arguments, each such argument being the undefined + value.
++ Unless + otherwise specified in the description of a particular function, if + a function or constructor described in this clause is given more + arguments than the function is specified to allow, the extra + arguments are evaluated by the call and then ignored by the + function. However, an implementation may define implementation + specific behaviour relating to such arguments as long as the + behaviour is not the throwing of a TypeError exception that + is predicated simply on the presence of an extra argument.
+NOTE Implementations + that add additional capabilities to the set of built-in functions + are encouraged to do so by adding new functions rather than adding + new parameters to existing functions.
+
+ Every
+ built-in function and every built-in constructor has the
+ Function prototype object, which is the initial value of the expression
+ Function.prototype
+ (15.3.4), as the value of its [[Prototype]] internal property.
+ Unless
+ otherwise specified every built-in prototype object has the
+ Object prototype object, which is the initial value of the expression
+ Object.prototype
+ (15.2.4), as the value of its [[Prototype]] internal property,
+ except the Object prototype object itself.
+ None
+ of the built-in functions described in this clause that are not
+ constructors shall implement the [[Construct]] internal method
+ unless otherwise specified in the description of a particular
+ function. None of the built-in functions described in this clause
+ shall have a prototype
+ property unless otherwise specified in the description of a
+ particular function.
+ This + clause generally describes distinct behaviours for when a + constructor is “called as a function” and for when it is “called + as part of a new expression”. The “called as a function” + behaviour corresponds to the invocation of the constructor’s + [[Call]] internal method and the “called as part of a new + expression” behaviour corresponds to the invocation of the + constructor’s [[Construct]] internal method. +
+
+ Every
+ built-in Function object described in this clause—whether as a
+ constructor, an ordinary function, or both—has a length
+ property whose value is an integer. Unless otherwise specified, this
+ value is equal to the largest number of named arguments shown in the
+ subclause headings for the function description, including optional
+ parameters.
NOTE For
+ example, the Function object that is the initial value of the slice
+ property of the String prototype object is described under the
+ subclause heading “String.prototype.slice (start, end)” which
+ shows the two named arguments start and end; therefore the value of
+ the length property of
+ that Function object is 2.
+ In
+ every case, the length
+ property of a built-in Function object described in this clause has
+ the attributes { [[Writable]]: false, [[Enumerable]]:
+ false, [[Configurable]]: false }. Every other property
+ described in this clause has the attributes { [[Writable]]: true,
+ [[Enumerable]]: false, [[Configurable]]: true } unless
+ otherwise specified.
+ The + unique global object is created before control enters any + execution context. +
++ Unless + otherwise specified, the standard built-in properties of the global + object have attributes {[[Writable]]: true, [[Enumerable]]: + false, [[Configurable]]: true}.
+
+ The
+ global object does not have a [[Construct]] internal property; it is
+ not possible to use the global object as a constructor with the new
+ operator.
+ The + global object does not have a [[Call]] internal property; it is not + possible to invoke the global object as a function.
++ The + values of the [[Prototype]] and [[Class]] internal properties of the + global object are implementation-dependent.
+
+ In
+ addition to the properties defined in this specification the global
+ object may have additional host defined properties. This may include
+ a property whose value is the global object itself; for example, in
+ the HTML document object model the window
+ property of the global object is the global object itself.
+ The
+ value of NaN is
+ NaN (see 8.5). This property has the attributes {
+ [[Writable]]: false, [[Enumerable]]: false,
+ [[Configurable]]: false }.
+ The
+ value of Infinity
+ is +∞ (see 8.5).
+ This property has the attributes { [[Writable]]: false,
+ [[Enumerable]]: false, [[Configurable]]: false }.
+ The
+ value of undefined
+ is undefined (see 8.1). This property has the attributes {
+ [[Writable]]: false, [[Enumerable]]: false,
+ [[Configurable]]: false }.
+ When
+ the eval function
+ is called with one argument x,
+ the following steps are taken:
+ If + Type(x) + is not String, return x.
++ Let + prog be + the ECMAScript code that is the result of parsing x as a Program. + If the parse fails, throw a SyntaxError + exception (but see also clause 16).
++ Let + evalCtx be + the result of establishing a new execution context (10.4.2) for the + eval code prog.
++ Let + result be + the result of evaluating the program prog.
++ Exit + the running execution context evalCtx, restoring the previous + execution context.
++ If + result.type + is normal and its + completion value is a value V, + then return the value V.
++ If + result.type + is normal and its + completion value is empty, + then return the value undefined.
++ Otherwise, + result.type + must be throw. Throw + result.value + as an exception.
++ A + direct call to the eval function is one that is expressed as a + CallExpression + that meets the following two conditions:
+
+ The
+ Reference that is the result of evaluating the MemberExpression
+ in the CallExpression
+ has an environment record as its base value and its reference name
+ is "eval".
+ The + result of calling the abstract operation GetValue with that + Reference as the argument is the standard built-in function defined + in 15.1.2.1.
+
+ The
+ parseInt function
+ produces an integer value dictated by interpretation of the contents
+ of the string
+ argument according to the specified radix.
+ Leading white space in string
+ is ignored. If radix
+ is undefined or 0, it is assumed to be 10
+ except when the number begins with the character pairs 0x
+ or 0X, in which
+ case a radix of 16 is assumed. If radix
+ is 16, number may also
+ optionally begin with the character pairs 0x
+ or 0X.
+ When
+ the parseInt
+ function is called, the following steps are taken:
+ Let + inputString be ToString(string).
++ Let + S be a newly created substring of inputString + consisting of the first character that is not a StrWhiteSpaceChar + and all characters following that character. (In other words, + remove leading white space.) +If inputString does not contain any such characters, let S be the +empty string.
++ Let + sign be 1.
+
+ If
+ S is not empty and the first character of S is a
+ minus sign -, let
+ sign be −1.
+ If
+ S is not empty and the first character of S is a plus
+ sign + or a minus
+ sign -, then
+ remove the first character from S.
+ Let + R = ToInt32(radix).
++ Let + stripPrefix be true.
++ If + R ≠ 0, then
++ If + R < 2 or R > 36, then return NaN.
++ If + R ≠ 16, let stripPrefix + be false.
++ Else, + R = 0
++ Let + R = 10.
++ If + stripPrefix is true, then
+
+ If
+ the length of S is at least 2 and the first two characters
+ of S are either “0x”
+ or “0X”,
+ then remove the first two characters from S and let R
+ = 16.
+ If + S contains any character that is not a radix-R digit, + then let Z be the substring of S consisting of all + characters before the first such character; otherwise, let Z + be S.
++ If + Z is empty, return NaN.
+
+ Let
+ mathInt be the mathematical integer value that is
+ represented by Z in radix-R notation, using the
+ letters A-Z
+ and a-z
+ for digits with values 10 through 35. (However, if R is 10
+ and Z contains more than 20 significant digits, every
+ significant digit after the 20th may be replaced by a 0
+ digit, at the option of the implementation; and if R
+ is not 2, 4, 8, 10, 16, or 32, then mathInt may be an
+ implementation-dependent approximation to the mathematical integer
+ value that is represented by Z in radix-R notation.)
+ Let + number be the Number value for mathInt.
++ Return + sign × number.
+NOTE parseInt
+ may interpret only a leading portion of string
+ as an integer value; it ignores any characters that cannot be
+ interpreted as part of the notation of an integer, and no indication
+ is given that any such characters were ignored.
+ The
+ parseFloat
+ function produces a Number value dictated by interpretation of the
+ contents of the string
+ argument as a decimal literal.
+ When
+ the parseFloat
+ function is called, the following steps are taken:
+ Let + inputString be ToString(string).
++ Let + trimmedString be a substring of inputString + consisting of the leftmost character that is not a + StrWhiteSpaceChar and all characters to the right of that + character. (In other words, remove leading white space.) +If inputString does not contain any such characters, let +trimmedString be the empty string.
++ If + neither trimmedString nor any prefix of trimmedString + satisfies the syntax of a StrDecimalLiteral (see 9.3.1), + return NaN.
++ Let + numberString be the longest prefix of trimmedString, + which might be trimmedString itself, that satisfies the + syntax of a StrDecimalLiteral.
++ Return + the Number value for the MV of numberString.
+NOTE parseFloat
+ may interpret only a leading portion of string
+ as a Number value; it ignores any characters that cannot be
+ interpreted as part of the notation of an decimal literal, and no
+ indication is given that any such characters were ignored.
+ Returns + true if the argument coerces to NaN, and otherwise + returns false.
++ If + ToNumber(number) is NaN, return true.
++ Otherwise, + return false.
+NOTE A
+ reliable way for ECMAScript code to test if a value X
+ is a NaN is an expression of the form X
+ !== X. The result will be true if and only if X
+ is a NaN.
+ Returns + false if the argument coerces to NaN, +∞, + or −∞, and otherwise + returns true.
++ If + ToNumber(number) is NaN, +∞, + or −∞, return false.
++ Otherwise, + return true.
++ Uniform + Resource Identifiers, or URIs, are Strings that identify resources + (e.g. web pages or files) and transport protocols by which to access + them (e.g. HTTP or FTP) on the Internet. The ECMAScript language + itself does not provide any support for using URIs except for + functions that encode and decode URIs as described in 15.1.3.1, + 15.1.3.2, 15.1.3.3 and 15.1.3.4.
+NOTE Many + implementations of ECMAScript provide additional functions and + methods that manipulate web pages; these functions are beyond the + scope of this standard.
++ A URI + is composed of a sequence of components separated by component + separators. The general form is:
+
+ Scheme
+ :
+ First
+ /
+ Second
+ ;
+ Third
+ ?
+ Fourth
+ where
+ the italicised names represent components and the “:”,
+ “/”, “;”
+ and “?” are
+ reserved characters used as separators. The encodeURI
+ and decodeURI
+ functions are intended to work with complete URIs; they assume that
+ any reserved characters in the URI are intended to have special
+ meaning and so are not encoded. The encodeURIComponent
+ and decodeURIComponent
+ functions are intended to work with the individual
+ component parts of a URI; they assume that any reserved characters
+ represent text and so must be encoded so that they are not
+ interpreted as reserved characters when the component is part of a
+ complete URI.
+ The + following lexical grammar specifies the form of encoded URIs.
++ uri :::
++ uriCharactersopt
++ uriCharacters :::
++ uriCharacter + uriCharactersopt
++ uriCharacter :::
+
+ uriReserved
uriUnescaped
uriEscaped
+ uriReserved ::: one + of
+
+ ;
+ / ? : @ & = + $ ,
+ uriUnescaped :::
+
+ uriAlpha
DecimalDigit
uriMark
+ uriEscaped :::
+
+ % HexDigit HexDigit
+ uriAlpha ::: one + of
+
+ a
+ b c d e f g h i j k l m n o p q r s t u v w x
+ y z
A B C D E F G H I J K L M N O P Q R S T
+ U V W X Y Z
+ uriMark ::: one + of
+
+ -
+ _ . ! ~ * ' ( )
NOTE The above syntax is based upon RFC 2396 + and does not reflect changes introduced by the more recent RFC 3986.
+ +
+ When
+ a character to be included in a URI is not listed above or is not
+ intended to have the special meaning sometimes given to the reserved
+ characters, that character must be encoded. The character is
+ transformed into its UTF-8 encoding, with surrogate pairs first
+ converted from UTF-16 to the corresponding code point value. (Note
+ that for code units in the range [0,127] this results in a single
+ octet with the same value.) The resulting sequence of octets is then
+ transformed into a String with each octet represented by an escape
+ sequence of the form “%xx”.
+ The + encoding and escaping process is described by the abstract operation + Encode taking two String arguments string + and unescapedSet.
++ Let + strLen be the number of characters in string.
++ Let + R be the empty String.
++ Let + k be 0.
++ Repeat
++ If + k equals strLen, return R.
++ Let + C be the character at position k within string.
++ If + C is in unescapedSet, then
++ Let + S be a String containing only the character C.
++ Let + R be a new String value computed by concatenating the + previous value of R and S.
++ Else, + C is not in unescapedSet
++ If + the code unit value of C is not less than 0xDC00 and not + greater than 0xDFFF, throw a URIError exception.
++ If + the code unit value of C is less than 0xD800 or greater + than 0xDBFF, then
++ Let + V be the code unit value of C.
++ Else, + +
++ Increase + k by 1.
++ If + k equals strLen, throw a URIError + exception.
++ Let + kChar be the code unit value of the character at position + k within string.
++ If + kChar is less than 0xDC00 or greater than 0xDFFF, throw a + URIError exception.
++ Let + V be (((the code unit value of C) – 0xD800) * + 0x400 + (kChar – 0xDC00) + 0x10000).
++ Let + Octets be the array of octets resulting by applying the + UTF-8 transformation to V, and let L be the array + size.
++ Let + j be 0.
++ Repeat, + while j < L
++ Let + jOctet be the value at position j within Octets.
+
+ Let
+ S be a String containing three characters “%XY”
+ where XY are two uppercase hexadecimal digits encoding
+ the value of jOctet.
+ Let + R be a new String value computed by concatenating the + previous value of R and S.
++ Increase + j by 1.
++ Increase + k by 1.
++ The + unescaping and decoding process is described by the abstract + operation Decode taking two String arguments string + and reservedSet.
++ Let + strLen be the number of characters in string.
++ Let + R be the empty String.
++ Let + k be 0.
++ Repeat
++ If + k equals strLen, return R.
++ Let + C be the character at position k within string.
+
+ If
+ C is not ‘%’,
+ then
+ Let + S be the String containing only the character C.
+
+ Else,
+ C is ‘%’
+ Let + start be k.
++ If + k + 2 is greater than or equal to strLen, throw a + URIError exception.
++ If + the characters at position (k+1) and (k + 2) within + string do not represent hexadecimal digits, throw a + URIError exception.
++ Let + B be the 8-bit value represented by the two hexadecimal + digits at position (k + 1) and (k + 2).
++ Increment + k by 2.
++ If + the most significant bit in B is 0, then
++ Let + C be the character with code unit value B.
++ If + C is not in reservedSet, then
++ Let + S be the String containing only the character C.
++ Else, + C is in reservedSet
++ Let + S be the substring of string from position start + to position k included.
++ Else, + the most significant bit in B is 1
++ Let + n be the smallest non-negative number such that (B + << n) & 0x80 is equal to 0.
++ If + n equals 1 or n is greater than 4, throw a + URIError exception.
++ Let + Octets be an array of 8-bit integers of size n.
++ Put + B into Octets at position 0.
++ If + k + (3 * (n – 1)) is greater than or equal to + strLen, throw a URIError exception.
++ Let + j be 1.
++ Repeat, + while j < n
++ Increment + k by 1.
++ If + the character at position k is not ‘%’, throw a + URIError exception.
++ If + the characters at position (k +1) and (k + 2) + within string do not represent hexadecimal digits, throw + a URIError exception.
++ Let + B be the 8-bit value represented by the two hexadecimal + digits at position (k + 1) and (k + 2).
++ If + the two most significant bits in B are not 10, throw a + URIError exception.
++ Increment + k by 2.
++ Put + B into Octets at position j.
++ Increment + j by 1.
++ Let + V be the value obtained by applying the UTF-8 + transformation to Octets, that is, from an array of + octets into a 32-bit value. If Octets does not contain a + valid UTF-8 encoding of a Unicode code point throw a URIError + exception.
++ If + V is less than 0x10000, then
++ Let + C be the character with code unit value V.
++ If + C is not in reservedSet, then
++ Let + S be the String containing only the character C.
++ Else, + C is in reservedSet
++ Let + S be the substring of string from position start + to position k included.
++ Else, + V is ≥ 0x10000
++ Let + L be (((V – 0x10000) & 0x3FF) + 0xDC00).
++ Let + H be ((((V – 0x10000) >> 10) & 0x3FF) + + 0xD800).
++ Let + S be the String containing the two characters with code + unit values H and L.
++ Let + R be a new String value computed by concatenating the + previous value of R and S.
++ Increase + k by 1.
+NOTE The + syntax of Uniform Resource Identifiers is given in RFC 2396 and + does not reflect the more recent RFC 3986 which replaces RFC 2396. A + formal description and implementation of UTF-8 is given in RFC 3629.
+ ++ In + UTF-8, characters are encoded using sequences of 1 to 6 octets. The + only octet of a "sequence" of one has the higher-order bit + set to 0, the remaining 7 bits being used to encode the character + value. In a sequence of n octets, n>1, the initial octet has the + n higher-order bits set to 1, followed by a bit set to 0. The + remaining bits of that octet contain bits from the value of the + character to be encoded. The following octets all have the + higher-order bit set to 1 and the following bit set to 0, leaving 6 + bits in each to contain bits from the character to be encoded. The + possible UTF-8 encodings of ECMAScript characters are specified in + Table 21.
+|
+ + Code + Unit Value + |
+
+ + Representation + |
+
+ + 1st + Octet + |
+
+ + 2nd + Octet + |
+
+ + 3rd + Octet + |
+
+ + 4th + Octet + |
+
|
+
+ |
+
+
+ |
+
+
+ |
+ + | ++ | ++ | +
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+ + | ++ | +
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+ + | +
|
+
+ + followed + by +
+ |
+
+
+ + followed + by +
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ + not + followed by +
+ |
+
+
+ |
+ + | ++ | ++ | ++ | +
|
+
+ |
+
+
+ |
+ + | ++ | ++ | ++ | +
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+ + | +
+ Where
+
+ uuuuu
+ =
+ vvvv +
+ 1
+ to + account for the addition of 0x10000 as in Surrogates, section 3.7, + of the Unicode Standard.
++ The + range of code unit values 0xD800-0xDFFF is used to encode surrogate + pairs; the above transformation combines a UTF-16 surrogate pair + into a UTF-32 representation and encodes the resulting 21-bit value + in UTF-8. Decoding reconstructs the surrogate pair.
++ RFC + 3629 prohibits the decoding of invalid UTF-8 octet sequences. For + example, the invalid sequence C0 80 must not decode into the + character U+0000. Implementations of the Decode algorithm are + required to throw a URIError + when encountering such invalid sequences.
+
+ The
+ decodeURI function
+ computes a new version of a URI in which each escape sequence and
+ UTF-8 encoding of the sort that might be introduced by the encodeURI
+ function is replaced with the character that it represents. Escape
+ sequences that could not have been introduced by encodeURI
+ are not replaced.
+ When
+ the decodeURI
+ function is called with one argument encodedURI,
+ the following steps are taken:
+ Let + uriString be ToString(encodedURI).
+
+ Let
+ reservedURISet be a String containing one instance of each
+ character valid in uriReserved plus “#”.
+ Return + the result of calling Decode(uriString, reservedURISet)
+NOTE The
+ character “#”
+ is not decoded from escape sequences even though it is not a
+ reserved URI character.
+ The
+ decodeURIComponent
+ function computes a new version of a URI in which each escape
+ sequence and UTF-8 encoding of the sort that might be introduced by
+ the encodeURIComponent
+ function is replaced with the character that it represents.
+ When
+ the decodeURIComponent
+ function is called with one argument encodedURIComponent,
+ the following steps are taken:
+ Let + componentString be ToString(encodedURIComponent).
++ Let + reservedURIComponentSet be the empty String.
++ Return + the result of calling Decode(componentString, + reservedURIComponentSet)
+
+ The
+ encodeURI function
+ computes a new version of a URI in which each instance of certain
+ characters is replaced by one, two or three escape sequences
+ representing the UTF-8 encoding of the character.
+ When
+ the encodeURI
+ function is called with one argument uri,
+ the following steps are taken:
+ Let + uriString be ToString(uri).
+
+ Let
+ unescapedURISet be a String containing one instance of each
+ character valid in uriReserved and uriUnescaped plus
+ “#”.
+ Return + the result of calling Encode(uriString, unescapedURISet)
+NOTE The
+ character “#”
+ is not encoded to an escape sequence even though it is not a
+ reserved or unescaped URI character.
+ The
+ encodeURIComponent
+ function computes a new version of a URI in which each instance of
+ certain characters is replaced by one, two or three escape sequences
+ representing the UTF-8 encoding of the character.
+ When
+ the encodeURIComponent
+ function is called with one argument uriComponent,
+ the following steps are taken:
+ Let + componentString be ToString(uriComponent).
++ Let + unescapedURIComponentSet be a String containing one instance + of each character valid in uriUnescaped.
++ Return + the result of calling Encode(componentString, + unescapedURIComponentSet)
++ See + 15.9.2.
++ See + 15.11.6.1.
++ See + 15.11.6.2.
++ See + 15.11.6.3.
++ See + 15.11.6.4.
++ See + 15.11.6.5.
++ See + 15.11.6.6.
++ See + 15.8.
++ See + 15.12.
+
+ When
+ Object is called
+ as a function rather than as a constructor, it performs a type
+ conversion.
+ When
+ the Object
+ function is called with no arguments or with one argument value,
+ the following steps are taken:
+ If + value is null, undefined or not supplied, + create and return a new Object object exactly as if the standard + built-in Object constructor had been called with the same arguments + (15.2.2.1).
++ Return + ToObject(value).
+
+ When
+ Object is called
+ as part of a new
+ expression, it is a constructor that may create an object.
+ When
+ the Object
+ constructor is called with no arguments or with one argument value,
+ the following steps are taken:
+ If + value is supplied, then
++ If + Type(value) is Object, then
++ If + the value is a native ECMAScript object, do not create a + new object but simply return value.
++ If + the value is a host object, then actions are taken and a + result is returned in an implementation-dependent manner that may + depend on the host object.
++ Asset: + The argument value was not supplied or its type was Null or + Undefined. +
++ Let + obj be a newly created native ECMAScript object.
++ Set + the [[Prototype]] internal property of obj t to the standard + built-in Object prototype object (15.2.4).
+
+ Set
+ the [[Class]] internal property of obj to "Object".
+ Set + the [[Extensible]] internal property of obj to true.
++ Set + the all the internal methods of obj as specified in 8.12
++ Return + obj.
++ The + value of the [[Prototype]] internal property of the Object + constructor is the standard built-in Function prototype object.
+
+ Besides
+ the internal properties and the length
+ property (whose value is 1), the Object constructor has the
+ following properties:
+ The
+ initial value of Object.prototype
+ is the standard built-in Object prototype object (15.2.4).
+ This + property has the attributes {[[Writable]]: false, [[Enumerable]]: + false, [[Configurable]]: false }.
+
+ When
+ the getPrototypeOf
+ function is called with argument O,
+ the following steps are taken:
+ If + Type(O) is not Object throw a TypeError exception.
++ Return + the value of the [[Prototype]] internal property of O.
++ When + the getOwnPropertyDescriptor function is called, the + following steps are taken:
++ If + Type(O) is not Object throw a TypeError exception.
++ Let + name be ToString(P).
++ Let + desc be the result of calling the [[GetOwnProperty]] + internal method of O with argument name.
++ Return + the result of calling FromPropertyDescriptor(desc) (8.10.4). +
++ When + the getOwnPropertyNames function is called, the following + steps are taken:
++ If + Type(O) is not Object throw a TypeError exception.
+
+ Let
+ array be the result of creating a new object as if by the
+ expression new Array ()
+ where Array is
+ the standard built-in constructor with that name.
+ Let + n be 0.
++ For + each named own property P of O
++ Let + name be the String value that is the name of P.
++ Call + the [[DefineOwnProperty]] internal method of array with + arguments ToString(n), the PropertyDescriptor {[[Value]]: + name, [[Writable]]: true, [[Enumerable]]: true, + [[Configurable]]: true}, and false.
++ Increment + n by 1.
++ Return + array.
+NOTE If + O is a String + instance, the set of own properties processed in step 4 includes the + implicit properties defined in 15.5.5.2 that correspond to character + positions within the object’s [[PrimitiveValue]] String.
++ The + create function creates a new object with a specified + prototype. When the create function is called, the following + steps are taken:
++ If + Type(O) is not Object or Null throw a TypeError + exception.
++ Let + obj be the result of creating a new object as if by the + expression new Object() where Object is the standard built-in + constructor with that name
++ Set + the [[Prototype]] internal property of obj to O.
+
+ If
+ the argument Properties is present and not undefined,
+ add own properties to obj as if by calling the standard
+ built-in function Object.defineProperties
+with arguments obj and Properties.
+ Return + obj.
++ The + defineProperty function is used to add an own property and/or + update the attributes of an existing own property of an object. When + the defineProperty function is called, the following steps + are taken:
++ If + Type(O) is not Object throw a TypeError exception.
++ Let + name be ToString(P).
++ Let + desc be the result of calling ToPropertyDescriptor with + Attributes as the argument.
++ Call + the [[DefineOwnProperty]] internal method of O with + arguments name, desc, and true.
++ Return + O.
++ The + defineProperties function is used to add own properties + and/or update the attributes of existing own properties of an + object. When the defineProperties function is called, the + following steps are taken:
++ Let + props be ToObject(Properties).
++ Let + names be an internal list containing the names of each + enumerable own property of props.
++ Let + descriptors be an empty internal List.
++ For + each element P of names in list order,
++ Let + descObj be the result of calling the [[Get]] internal + method of props with P as the argument.
++ Let + desc be the result of calling ToPropertyDescriptor with + descObj as the argument.
++ Append + desc to the end of descriptors.
+For + each element desc of descriptors in list order,
+Call the [[DefineOwnProperty]] internal method of O with + arguments P, desc, and true.
Return O
++ If an + implementation defines a specific order of enumeration for the + for-in statement, that same enumeration order must be used to order + the list elements in step 3 of this algorithm.
++ When + the seal function is called, the following steps are taken:
++ If + Type(O) is not Object throw a TypeError exception.
++ For + each named own property name P of O,
++ Let + desc be the result of calling the [[GetOwnProperty]] + internal method of O with P.
++ If + desc.[[Configurable]] is true, set + desc.[[Configurable]] to false.
++ Call + the [[DefineOwnProperty]] internal method of O with P, + desc, and true as arguments.
++ Set + the [[Extensible]] internal property of O to false.
++ Return + O.
++ When + the freeze function is called, the following steps are taken:
++ If + Type(O) is not Object throw a TypeError exception.
++ For + each named own property name P of O,
++ Let + desc be the result of calling the [[GetOwnProperty]] + internal method of O with P.
++ If + IsDataDescriptor(desc) is true, then
++ If + desc.[[Writable]] is true, set desc.[[Writable]] + to false.
++ If + desc.[[Configurable]] is true, set + desc.[[Configurable]] to false.
++ Call + the [[DefineOwnProperty]] internal method of O with P, + desc, and true as arguments.
++ Set + the [[Extensible]] internal property of O to false.
++ Return + O.
++ When + the preventExtensions function is called, the following steps + are taken:
++ If + Type(O) is not Object throw a TypeError exception.
++ Set + the [[Extensible]] internal property of O to false.
++ Return + O.
++ When + the isSealed function is called with argument O, + the following steps are taken:
++ If + Type(O) is not Object throw a TypeError exception.
++ For + each named own property name P of O,
++ Let + desc be the result of calling the [[GetOwnProperty]] + internal method of O with P.
++ If + desc.[[Configurable]] is true, then return false.
++ If + the [[Extensible]] internal property of O is false, + then return true.
++ Otherwise, + return false.
++ When + the isFrozen function is called with argument O, + the following steps are taken:
++ If + Type(O) is not Object throw a TypeError exception.
++ For + each named own property name P of O,
++ Let + desc be the result of calling the [[GetOwnProperty]] + internal method of O with P.
++ If + IsDataDescriptor(desc) is true then
++ If + desc.[[Writable]] is true, return false.
++ If + desc.[[Configurable]] is true, then return false.
++ If + the [[Extensible]] internal property of O is false, + then return true.
++ Otherwise, + return false.
++ When + the isExtensible function is called with argument O, + the following steps are taken:
++ If + Type(O) is not Object throw a TypeError exception.
++ Return + the Boolean value of the [[Extensible]] internal property of O.
++ When + the keys function is called with argument O, + the following steps are taken:
++ If + the Type(O) is not Object, throw a TypeError + exception.
++ Let + n be the number of own enumerable properties of O
+
+ Let
+ array be the result of creating a new Object as if by the
+ expression new Array(n)
+ where Array
+ is the standard built-in constructor with that name.
+ Let + index be 0.
++ For + each own enumerable property of O whose name String is P + +
++ Call + the [[DefineOwnProperty]] internal method of array with + arguments ToString(index), the PropertyDescriptor + {[[Value]]: P, [[Writable]]: true, [[Enumerable]]: + true, [[Configurable]]: true}, and false.
++ Increment + index by 1.
++ Return + array.
++ If an + implementation defines a specific order of enumeration for the + for-in statement, that same enumeration order must be used in step 5 + of this algorithm.
+
+ The
+ value of the [[Prototype]] internal property of the Object prototype
+ object is null, the value of the [[Class]] internal property
+ is "Object",
+ and the initial value of the [[Extensible]] internal property is
+ true.
+ The
+ initial value of Object.prototype.constructor
+ is the standard built-in Object
+ constructor.
+ When
+ the toString
+ method is called, the following steps are taken:
If + the this + value is undefined, + return "[object Undefined]".
If + the this + value is null, + return "[object Null]".
Let + O be the result of calling ToObject passing the this value + as the argument.
Let + class be the value of the [[Class]] internal property of O.
Return + the String value that is the result of concatenating the three + Strings "[object ", + class, and "]".
+ When + the toLocaleString method is called, the following steps are + taken:
++ Let + O be the result of calling ToObject passing the this + value as the argument.
++ Let + toString be the result of calling the [[Get]] internal + method of O passing "toString" as the + argument.
++ If + IsCallable(toString) is false, throw a TypeError + exception.
++ Return + the result of calling the [[Call]] internal method of toString + passing O as the this value and no arguments.
+NOTE 1 This function is provided to give all Objects a generic
+ toLocaleString
+ interface, even though not all may use it. Currently, Array,
+ Number, and Date
+ provide their own locale-sensitive toLocaleString
+ methods.
NOTE 2 The first parameter to this function is likely to be used in a + future version of this standard; it is recommended that + implementations do not use this parameter position for anything + else.
++ When + the valueOf method is called, the following steps are taken: +
++ Let + O be the result of calling ToObject passing the this + value as the argument.
++ If + O is the result of calling the Object constructor with a + host object (15.2.2.1), then
++ Return + either O or another value such as the host object + originally passed to the constructor. The specific result that is + returned is implementation-defined.
++ Return + O.
+
+ When
+ the hasOwnProperty
+ method is called with argument V,
+ the following steps are taken:
+ Let + P be ToString(V).
++ Let + O be the result of calling ToObject passing the this + value as the argument.
++ Let + desc be the result of calling the [[GetOwnProperty]] + internal method of O passing P as the argument.
++ If + desc is undefined, return false.
++ Return + true.
+NOTE 1 Unlike [[HasProperty]] (8.12.6), this method does not consider + objects in the prototype chain.
+NOTE 2 The ordering of steps 1 and 2 is chosen to ensure that any + exception that would have been thrown by step 1 in previous editions + of this specification will continue to be thrown even if the this + value is undefined or null.
+
+ When
+ the isPrototypeOf
+ method is called with argument V,
+ the following steps are taken:
+ If + V is not an object, return false.
++ Let + O be the result of calling ToObject passing the this + value as the argument.
++ Repeat
++ Let + V be the value of the [[Prototype]] internal property of V.
++ if + V is null, return false
++ If + O and V refer to the same object, return true.
+NOTE The + ordering of steps 1 and 2 is chosen to preserve the behaviour + specified by previous editions of this specification for the case + where V is not an object and the this value is undefined or null.
+
+ When
+ the propertyIsEnumerable
+ method is called with argument V,
+ the following steps are taken:
+ Let + P be ToString(V).
++ Let + O be the result of calling ToObject passing the this + value as the argument.
++ Let + desc be the result of calling the [[GetOwnProperty]] + internal method of O passing P as the argument.
++ If + desc is undefined, return false.
++ Return + the value of desc.[[Enumerable]].
+NOTE 1 This method does not consider objects in the prototype chain.
+NOTE 2 The ordering of steps 1 and 2 is chosen to ensure that any + exception that would have been thrown by step 1 in previous editions + of this specification will continue to be thrown even if the this + value is undefined or null.
++ Object + instances have no special properties beyond those inherited from the + Object prototype object.
+
+ When
+ Function is called
+ as a function rather than as a constructor, it creates and
+ initialises a new Function object. Thus the function call
+ Function(…)
+ is equivalent to the object creation expression new
+ Function(…)
+ with the same arguments.
+ When
+ the Function
+ function is called with some arguments p1,
+ p2, … , pn,
+ body (where n
+ might be 0, that is,
+ there are no “p”
+ arguments, and where body
+ might also not be provided), the following steps are taken:
+ Create + and return a new Function object as if the standard built-in + constructor Function was used in a new expression with the + same arguments (15.3.2.1).
+
+ When
+ Function is called
+ as part of a new
+ expression, it is a constructor: it initialises the newly created
+ object.
+ The + last argument specifies the body (executable code) of a function; + any preceding arguments specify formal parameters.
+
+ When
+ the Function
+ constructor is called with some arguments p1,
+ p2, … , pn,
+ body (where n
+ might be 0, that is,
+ there are no “p”
+ arguments, and where body
+ might also not be provided), the following steps are taken:
+ Let + argCount be the total number of arguments passed to this + function invocation.
++ Let + P be the empty String.
++ If + argCount = 0, let body be the empty String.
++ Else + if argCount = 1, let body be that argument.
++ Else, + argCount > 1
++ Let + firstArg be the first argument.
++ Let + P be ToString(firstArg).
++ Let + k be 2.
++ Repeat, + while k < argCount
++ Let + nextArg be the k’th argument.
+
+ Let
+ P be the result of concatenating the previous value of P,
+ the String ","
+ (a comma), and ToString(nextArg).
+ Increase + k by 1.
++ Let + body be the k’th argument.
++ Let + body be ToString(body).
++ If + P is not parsable as a FormalParameterListopt + then throw a SyntaxError exception.
++ If + body is not parsable as FunctionBody then throw a + SyntaxError exception.
++ Ifbody is strict mode code (see 10.1.1) then let strict be + true, else let strict be false.
++ If + strict is true, throw any exceptions specified in + 13.1 that apply. +
++ Return + a new Function object created as specified in 13.2 passing P + as the FormalParameterList and body as the + FunctionBody. Pass in the Global Environment as the Scope + parameter and strict as the Strict flag.
+
+ A
+ prototype property
+ is automatically created for every function, to provide for the
+ possibility that the function will be used as a constructor.
+
NOTE It + is permissible but not necessary to have one argument for each + formal parameter to be specified. For example, all three of the + following expressions produce the same result:
+
+ new
+ Function("a", "b", "c", "return
+ a+b+c")
+ new
+ Function("a, b, c", "return a+b+c")
+ new
+ Function("a,b", "c", "return a+b+c")
+ The
+ Function constructor is itself a Function object and its [[Class]]
+ is "Function".
+ The value of the [[Prototype]] internal property of the Function
+ constructor is the standard built-in Function prototype object
+ (15.3.4).
+ The + value of the [[Extensible]] internal property of the Function + constructor is true.
++ The + Function constructor has the following properties:
+
+ The
+ initial value of Function.prototype
+ is the standard built-in Function prototype object (15.3.4).
+ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
++ This + is a data property with a value of 1. This property has the + attributes { [[Writable]]: false, [[Enumerable]]: false, + [[Configurable]]: false }.
+
+ The
+ Function prototype object is itself a Function object (its [[Class]]
+ is "Function")
+ that, when invoked, accepts any arguments and returns undefined.
+ The + value of the [[Prototype]] internal property of the Function + prototype object is the standard built-in Object prototype object + (15.2.4). The initial value of the [[Extensible]] internal property + of the Function prototype object is true.
+
+ The
+ Function prototype object does not have a valueOf
+ property of its own; however, it inherits the valueOf
+ property from the Object prototype Object.
+ The
+ length property of
+ the Function prototype object is 0.
+ The
+ initial value of Function.prototype.constructor
+ is the built-in Function
+ constructor.
+ An + implementation-dependent representation of the function is returned. + This representation has the syntax of a FunctionDeclaration. + Note in particular that the use and placement of white space, line + terminators, and semicolons within the representation String is + implementation-dependent.
+
+ The
+ toString function
+ is not generic; it throws a TypeError exception if its this
+ value is not a Function object. Therefore, it cannot be transferred
+ to other kinds of objects for use as a method.
+ When
+ the apply method
+ is called on an object func
+ with arguments thisArg
+ and argArray, the
+ following steps are taken:
+
+ If + IsCallable(func) is false, then throw a TypeError + exception.
++ If + argArray is null or undefined, then
++ Return + the result of calling the [[Call]] internal method of func, + providing thisArg as the this value and an empty + list of arguments.
++ If + Type(argArray) is not Object, then throw a TypeError + exception.
+
+ Let
+ len be the result of calling the [[Get]] internal method of
+ argArray with argument "length".
+ Let + n be ToUint32(len).
++ Let + argList be an empty List.
++ Let + index be 0.
++ Repeat + while index < n
++ Let + indexName be ToString(index).
++ Let + nextArg be the result of calling the [[Get]] internal + method of argArray with indexName as the argument.
++ Append + nextArg as the last element of argList.
++ Set + index to index + 1.
++ Return + the result of calling the [[Call]] internal method of func, + providing thisArg as the this value and argList + as the list of arguments.
+
+ The
+ length property of
+ the apply method
+ is 2.
NOTE The + thisArg value is passed without modification as the this + value. This is a change from Edition 3, where a undefined or + null thisArg is replaced with the global object and ToObject + is applied to all other values and that result is passed as the this + value.
+
+ When
+ the call method is
+ called on an object func
+ with argument thisArg
+ and optional arguments arg1,
+ arg2 etc, the
+ following steps are taken:
+ If + IsCallable(func) is false, then throw a TypeError + exception.
++ Let + argList be an empty List.
++ If + this method was called with more than one argument then in left to + right order starting with arg1 append each argument as the + last element of argList
++ Return + the result of calling the [[Call]] internal method of func, + providing thisArg as the this value and argList + as the list of arguments.
+
+ The
+ length property of
+ the call method is
+ 1.
NOTE The + thisArg value is passed without modification as the this + value. This is a change from Edition 3, where a undefined or + null thisArg is replaced with the global object and ToObject + is applied to all other values and that result is passed as the this + value.
++ The + bind method takes one or more arguments, thisArg + and (optionally) arg1, + arg2, etc, and + returns a new function object by performing the following steps:
++ Let + Target be the this value.
++ If + IsCallable(Target) is false, throw a TypeError + exception.
++ Let + A be a new (possibly empty) internal list of all of the + argument values provided after thisArg (arg1, arg2 + etc), in order.
++ Let + F be a new native ECMAScript object .
++ Set + all the internal methods, except for [[Get]], of F as + specified in 8.12.
++ Set + the [[Get]] internal property of F as specified in 15.3.5.4.
++ Set + the [[TargetFunction]] internal property of F to Target.
++ Set + the [[BoundThis]] internal property of F to the value of + thisArg.
++ Set + the [[BoundArgs]] internal property of F to A.
++ Set + the [[Class]] internal property of F to "Function".
++ Set + the [[Prototype]] internal property of F to the standard + built-in Function prototype object as specified in 15.3.3.1.
++ Set + the [[Call]] internal property of F as described in + 15.3.4.5.1.
++ Set + the [[Construct]] internal property of F as described in + 15.3.4.5.2.
++ Set + the [[HasInstance]] internal property of F as described in + 15.3.4.5.3.
++ If + the [[Class]] internal property of Target is "Function", + then
++ Let + L be the length property of Target minus the + length of A.
++ Set + the length own property of F to either 0 or + L, whichever is larger. +
++ Else + set the length own property of F to 0.
++ Set + the attributes of the length own property of F to + the values specified in 15.3.5.1.
++ Set + the [[Extensible]] internal property of F to true.
++ Let + thrower be the [[ThrowTypeError]] function Object (13.2.3).
+
+ Call
+ the [[DefineOwnProperty]] internal method of F with
+ arguments "caller",
+ PropertyDescriptor {[[Get]]: thrower, [[Set]]: thrower,
+ [[Enumerable]]: false, [[Configurable]]: false}, and
+ false.
+ Call
+ the [[DefineOwnProperty]] internal method of F with
+ arguments "arguments",
+ PropertyDescriptor {[[Get]]: thrower, [[Set]]: thrower,
+ [[Enumerable]]: false, [[Configurable]]: false}, and
+ false.
+ Return + F.
+
+ The
+ length property of
+ the bind method is
+ 1.
NOTE Function
+ objects created using Function.prototype.bind
+ do not have a prototype
+ property or the [[Code]], [[FormalParameters]], and [[Scope]]
+ internal properties.
+ When + the [[Call]] internal method of a function object, F, + which was created using the bind function is called with a this + value and a list of arguments ExtraArgs, + the following steps are taken:
++ Let + boundArgs be the value of F’s [[BoundArgs]] + internal property.
++ Let + boundThis be the value of F’s [[BoundThis]] + internal property.
++ Let + target be the value of F’s [[TargetFunction]] + internal property.
++ Let + args be a new list containing the same values as the list + boundArgs in the same order followed by the same values as + the list ExtraArgs in the same order.
++ Return + the result of calling the [[Call]] internal method of target + providing boundThis as the this value and providing + args as the arguments.
++ When + the [[Construct]] internal method of a function object, F + that was created using the bind function is called with a list of + arguments ExtraArgs, + the following steps are taken:
++ Let + target be the value of F’s [[TargetFunction]] + internal property.
++ If + target has no [[Construct]] internal method, a TypeError + exception is thrown.
++ Let + boundArgs be the value of F’s [[BoundArgs]] + internal property.
++ Let + args be a new list containing the same values as the list + boundArgs in the same order followed by the same values as + the list ExtraArgs in the same order.
++ Return + the result of calling the [[Construct]] internal method oftarget providing args as the arguments.
++ When + the [[HasInstance]] internal method of a function object F, + that was created using the bind function is called with argument V, + the following steps are taken:
++ Let + target be the value of F’s [[TargetFunction]] + internal property.
++ If + target has no [[HasInstance]] internal method, a TypeError + exception is thrown.
++ Return + the result of calling the [[HasInstance]] internal method oftarget providing V as the argument.
++ In + addition to the required internal properties, every function + instance has a [[Call]] internal property and in most cases use a + different version of the [[Get]] internal property. Depending on how + they are created (see 8.6.2 ,13.2, 15, and 15.3.4.5), function + instances may have a [[HasInstance]] internal property, a [[Scope]] + internal property, a [[Construct]] internal property, a + [[FormalParameters]] internal property, a [[Code]] internal + property, a [[TargetFunction]] internal property, a [[BoundThis]] + internal property, and a [[BoundArgs]] internal property.
++ The + value of the [[Class]] internal property is "Function".
++ Function + instances that correspond to strict mode functions (13.2) and + function instances created using the Function.prototype.bind + method (15.3.4.5) have properties named “caller” and + “arguments” that throw a TypeError exception. An + ECMAScript implementation must not associate any implementation + specific behaviour with accesses of these properties from strict + mode function code. +
+
+ The
+ value of the length
+ property is an integer that indicates the “typical” number of
+ arguments expected by the function. However, the language permits
+ the function to be invoked with some other number of arguments. The
+ behaviour of a function when invoked on a number of arguments other
+ than the number specified by its length
+ property depends on the function. This property has the attributes
+ { [[Writable]]: false,
+ [[Enumerable]]: false,
+ [[Configurable]]: false }.
+ The
+ value of the prototype
+ property is used to initialise the [[Prototype]] internal property
+ of a newly created object before the Function object is invoked as a
+ constructor for that newly created object. This property has the
+ attribute { [[Writable]]: true,
+ [[Enumerable]]: false,
+ [[Configurable]]: false
+ }.
NOTE Function
+ objects created using Function.prototype.bind
+ do not have a prototype
+ property.
+ Assume + F is a Function + object.
++ When + the [[HasInstance]] internal method of F + is called with value V, + the following steps are taken:
++ If + V is not an object, return false.
+
+ Let
+ O be the result of calling the [[Get]] internal method of F
+ with property name "prototype".
+ Repeat
++ Let + V be the value of the [[Prototype]] internal property of V.
+
+ If
+ V is null,
+ return false.
+ If + O and V refer to the same object, return true.
++
NOTE Function
+ objects created using Function.prototype.bind
+ have a different implementation of [[HasInstance]] defined in
+ 15.3.4.5.3.
+ Function + objects use a variation of the [[Get]] internal method used for + other native ECMAScript objects (8.12.3).
++ Assume + F is a Function + object. When the [[Get]] internal method of F + is called with property name P, + the following steps are taken:
++ Let + v be the result of calling the default [[Get]] internal + method (8.12.3) on F passing P as the property name + argument.
+
+ If
+ P is "caller"
+ and v is a strict mode Function object, throw a
+ TypeError exception.
+
+ Return + v.
+NOTE Function
+ objects created using Function.prototype.bind
+ use the default [[Get]] internal method.
+ Array
+ objects give special treatment to a certain class of property names.
+ A property name P
+ (in the form of a String value) is an array index if and only
+ if ToString(ToUint32(P))
+ is equal to P and
+ ToUint32(P)
+ is not equal to 232−1.
+ A property whose property name is an array index is also called an
+ element. Every Array object has a length
+ property whose value is always a nonnegative integer less than 232.
+ The value of the length
+ property is numerically greater than the name of every property
+ whose name is an array index; whenever a property of an Array object
+ is created or changed, other properties are adjusted as necessary to
+ maintain this invariant. Specifically, whenever a property is added
+ whose name is an array index, the length
+ property is changed, if necessary, to be one more than the numeric
+ value of that array index; and whenever the length
+ property is changed, every property whose name is an array index
+ whose value is not smaller than the new length is automatically
+ deleted. This constraint applies only to own properties of an Array
+ object and is unaffected by length
+ or array index properties that may be inherited from its prototypes.
+ An + object, O, is + said to be sparse if the following algorithm returns true:
++ Let + len + be the result of calling the [[Get]] internal method of O + with argument "length".
++ For + each integer i + in the range 0≤i<ToUint32(len)
++ Let + elem + be the result of calling the [[GetOwnProperty]] internal method of + O + with argument ToString(i).
++ If + elem + is undefined, + return true.
++ Return + false.
+
+ When
+ Array is called as
+ a function rather than as a constructor, it creates and initialises
+ a new Array object. Thus the function call Array(…)
+ is equivalent to the object creation expression new Array(…)
+ with the same arguments.
+ When
+ the Array function
+ is called the following steps are taken:
+ Create
+ and return a new Array object exactly as if the standard built-in
+ constructor Array
+ was used in a new
+ expression with the same arguments (15.4.2).
+ When
+ Array is called as
+ part of a new
+ expression, it is a constructor: it initialises the newly created
+ object.
+ This + description applies if and only if the Array constructor is given no + arguments or at least two arguments.
+
+ The
+ [[Prototype]] internal property of the newly constructed object is
+ set to the original Array prototype object, the one that is the
+ initial value of Array.prototype
+ (15.4.3.1).
+ The
+ [[Class]] internal property of the newly constructed object is set
+ to "Array".
+ The + [[Extensible]] internal property of the newly constructed object is + set to true.
+
+ The
+ length property of
+ the newly constructed object is set to the number of arguments.
+ The 0
+ property of the newly constructed object is set to item0
+ (if supplied); the 1
+ property of the newly constructed object is set to item1
+ (if supplied); and, in general, for as many arguments as there are,
+ the k property of
+ the newly constructed object is set to argument k,
+ where the first argument is considered to be argument number 0.
+ These properties all have the attributes {[[Writable]]: true,
+ [[Enumerable]]: true, [[Configurable]]: true}.
+ The
+ [[Prototype]] internal property of the newly constructed object is
+ set to the original Array prototype object, the one that is the
+ initial value of Array.prototype
+ (15.4.3.1). The [[Class]] internal property of the newly constructed
+ object is set to "Array".
+ The [[Extensible]] internal property of the newly constructed object
+ is set to true.
+ If
+ the argument len
+ is a Number and ToUint32(len)
+ is equal to len,
+ then the length
+ property of the newly constructed object is set to ToUint32(len).
+ If the argument len
+ is a Number and ToUint32(len)
+ is not equal to len,
+ a RangeError exception is thrown.
+ If
+ the argument len
+ is not a Number, then the length
+ property of the newly constructed object is set to 1
+ and the 0 property
+ of the newly constructed object is set to len
+ with attributes {[[Writable]]: true, [[Enumerable]]: true,
+ [[Configurable]]: true}..
+ The + value of the [[Prototype]] internal property of the Array + constructor is the Function prototype object (15.3.4).
+
+ Besides
+ the internal properties and the length
+ property (whose value is 1), the Array constructor has the
+ following properties:
+ The
+ initial value of Array.prototype
+ is the Array prototype object (15.4.4).
+ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+
+ The
+ isArray function takes one argument arg,
+ and returns the Boolean value true if the argument is an
+ object whose class internal property is "Array";
+ otherwise it returns false. The following steps are taken:
+ If + Type(arg) is not Object, return false.
+
+ If
+ the value of the [[Class]] internal property of arg is
+ "Array",
+ then return true.
+ Return + false.
++ The + value of the [[Prototype]] internal property of the Array prototype + object is the standard built-in Object prototype object (15.2.4).
+
+ The
+ Array prototype object is itself an array; its [[Class]] is "Array",
+ and it has a length
+ property (whose initial value is +0) and the special
+ [[DefineOwnProperty]] internal method described in 15.4.5.1.
+ In
+ following descriptions of functions that are properties of the Array
+ prototype object, the phrase “this object” refers to the object
+ that is the this value for the invocation of the function. It
+ is permitted for the this to be an object for which the value
+ of the [[Class]] internal property is not "Array".
NOTE The
+ Array prototype object does not have a valueOf
+ property of its own; however, it inherits the valueOf
+ property from the standard built-in Object prototype Object.
+ The
+ initial value of Array.prototype.constructor
+ is the standard built-in Array
+ constructor.
+ When
+ the toString
+ method is called, the following steps are taken:
+ Let + array be the result of calling ToObject on the this + value.
+
+ Let
+ func be the result of calling the [[Get]] internal method of
+ array with argument "join".
+ If + IsCallable(func) is false, then let func be + the standard built-in method Object.prototype.toString (15.2.4.2).
++ Return + the result of calling the [[Call]] internal method of func + providing array as the this value and an empty + arguments list.
++
NOTE The toString
+ function is intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the toString
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ The
+ elements of the array are converted to Strings using their
+ toLocaleString
+ methods, and these Strings are then concatenated, separated by
+ occurrences of a separator String that has been derived in an
+ implementation-defined locale-specific way. The result of calling
+ this function is intended to be analogous to the result of toString,
+ except that the result of this function is intended to be
+ locale-specific.
+ The + result is calculated as follows:
++ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ arrayLen be the result of calling the [[Get]] internal
+ method of array with argument "length".
+ Let + len be ToUint32(arrayLen).
++ Let + separator be the String value for the list-separator String + appropriate for the host environment’s current locale (this is + derived in an implementation-defined way).
++ If + len is zero, return the empty String.
+
+ Let
+ firstElement be the result of calling the [[Get]] internal
+ method of array with argument "0".
+ If + firstElement is undefined or null, then
++ Let + R be the empty String.
++ Else + +
++ Let + elementObj be ToObject(firstElement).
+
+ Let
+ func be the result of calling the [[Get]] internal method
+ of elementObj with argument "toLocaleString".
+ If + IsCallable(func) is false, throw a TypeError + exception.
++ Let + R be the result of calling the [[Call]] internal method of + func providing elementObj as the this value + and an empty arguments list. +
+
+ Let
+ k be 1.
+ Repeat, + while k < len
++ Let + S be a String value produced by concatenating R and + separator.
++ Let + nextElement be the result of calling the [[Get]] internal + method of array with argument ToString(k).
++ If + nextElement is undefined or null, then
++ Let + R be the empty String.
++ Else + +
++ Let + elementObj be ToObject(nextElement).
+
+ Let
+ func be the result of calling the [[Get]] internal method
+ of elementObj with argument "toLocaleString".
+ If + IsCallable(func) is false, throw a TypeError + exception.
++ Let + R be the result of calling the [[Call]] internal method of + func providing elementObj as the this value + and an empty arguments list. +
++ Let + R be a String value produced by concatenating S and + R.
++ Increase + k by 1.
++ Return + R.
+NOTE 1 The first parameter to this function is likely to be used in a + future version of this standard; it is recommended that + implementations do not use this parameter position for anything + else.
+NOTE 2 The toLocaleString
+ function is intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the toLocaleString
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ When
+ the concat method
+ is called with zero or more arguments item1,
+ item2, etc., it
+ returns an array containing the array elements of the object
+ followed by the array elements of each argument in order.
+ The + following steps are taken:
++ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ A be a new array created as if by the expression new
+ Array() where Array
+ is the standard built-in constructor with that name.
+ Let + n be 0.
++ Let + items be an internal List whose first element is O + and whose subsequent elements are, in left to right order, the + arguments that were passed to this function invocation.
++ Repeat, + while items is not empty
++ Remove + the first element from items and let E be the value + of the element.
+
+ If
+ the value of the [[Class]] internal property of E is
+ "Array",
+ then
+ Let + k be 0.
+
+ Let
+ len be the result of calling the [[Get]] internal method
+ of E with argument "length".
+ Repeat, + while k < len
++ Let + P be ToString(k).
++ Let + exists be the result of calling the [[HasProperty]] + internal method of E with P.
++ If + exists is true, then
++ Let + subElement be the result of calling the [[Get]] internal + method of E with argument P.
++ Call + the [[DefineOwnProperty]] internal method of A with + arguments ToString(n), Property Descriptor {[[Value]]: + subElement, [[Writable]]: true, [[Enumerable]]: + true, [[Configurable]]: true}, and false.
++ Increase + n by 1.
++ Increase + k by 1.
++ Else, + E is not an Array
++ Call + the [[DefineOwnProperty]] internal method of A with + arguments ToString(n), Property Descriptor {[[Value]]: E, + [[Writable]]: true, [[Enumerable]]: true, + [[Configurable]]: true}, and false.
++ Increase + n by 1.
++ Return + A.
+
+ The
+ length property of
+ the concat method
+ is 1.
NOTE The
+ concat function is
+ intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the concat
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ The + elements of the array are converted to Strings, and these Strings + are then concatenated, separated by occurrences of the separator. + If no separator is provided, a single comma is used as the + separator.
+
+ The
+ join method takes
+ one argument, separator,
+ and performs the following steps:
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenVal be the result of calling the [[Get]] internal method
+ of O with argument "length".
+ Let + len be ToUint32(lenVal).
+
+ If
+ separator is undefined, let separator be the
+ single-character String ",".
+ Let + sep be ToString(separator).
++ If + len is zero, return the empty String.
+
+ Let
+ element0 be the result of calling the [[Get]] internal
+ method of O with argument "0".
+ If + element0 is undefined or null, let R be + the empty String; otherwise, Let R be ToString(element0).
+
+ Let
+ k be 1.
+ Repeat, + while k < len
++ Let + S be the String value produced by concatenating R + and sep.
++ Let + element be the result of calling the [[Get]] internal + method of O with argument ToString(k).
++ If + element is undefined or null, Let next + be the empty String; otherwise, let next be + ToString(element).
++ Let + R be a String value produced by concatenating S and + next.
++ Increase + k by 1.
++ Return + R.
+
+ The
+ length property of
+ the join method is
+ 1.
NOTE The
+ join function is
+ intentionally generic; it does not require that its this
+ value be an Array object. Therefore, it can be transferred to other
+ kinds of objects for use as a method. Whether the join
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ The + last element of the array is removed from the array and returned.
++ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenVal be the result of calling the [[Get]] internal method
+ of O with argument "length".
+ Let + len be ToUint32(lenVal).
++ If + len is zero, +
+
+ Call
+ the [[Put]] internal method of O with arguments "length",
+ 0, and true.
+ Return + undefined.
++ Else, + len > 0
++ Let + indx be ToString(len–1).
++ Let + element be the result of calling the [[Get]] internal + method of O with argument indx.
++ Call + the [[Delete]] internal method of O with arguments indx + and true.
+
+ Call
+ the [[Put]] internal method of O with arguments "length",
+ indx, and true.
+ Return + element.
+NOTE The
+ pop function is
+ intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the pop
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ The + arguments are appended to the end of the array, in the order in + which they appear. The new length of the array is returned as the + result of the call.
+
+ When
+ the push method is
+ called with zero or more arguments item1,item2, etc., the following steps are taken:
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenVal be the result of calling the [[Get]] internal method
+ of O with argument "length".
+ Let + n be ToUint32(lenVal).
++ Let + items be an internal List whose elements are, in left to + right order, the arguments that were passed to this function + invocation.
++ Repeat, + while items is not empty
++ Remove + the first element from items and let E be the value + of the element.
++ Call + the [[Put]] internal method of O with arguments + ToString(n), E, and true.
++ Increase + n by 1.
+
+ Call
+ the [[Put]] internal method of O with arguments "length",
+ n, and true.
+ Return + n.
+
+ The
+ length property of
+ the push method is
+ 1.
NOTE The
+ push function is
+ intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the push
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ The + elements of the array are rearranged so as to reverse their order. + The object is returned as the result of the call.
++ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenVal be the result of calling the [[Get]] internal method
+ of O with argument "length".
+ Let + len be ToUint32(lenVal).
++ Let + middle be floor(len/2).
++ Letlower be 0.
++ Repeat, + while lower ≠ middle
++ Let + upper be len−lower −1.
++ Let + upperP be ToString(upper).
++ Let + lowerP be ToString(lower).
++ Let + lowerValue be the result of calling the [[Get]] internal + method of O with argument lowerP.
++ Let + upperValue be the result of calling the [[Get]] internal + method of O with argument upperP .
++ Let + lowerExists be the result of calling the [[HasProperty]] + internal method of O with argument lowerP.
++ Let + upperExists be the result of calling the [[HasProperty]] + internal method of O with argument upperP.
++ If + lowerExists is true and upperExists is true, + then
++ Call + the [[Put]] internal method of O with arguments lowerP, + upperValue, and true .
++ Call + the [[Put]] internal method of O with arguments upperP, + lowerValue, and true .
++ Else + if lowerExists is false and upperExists is + true, then
++ Call + the [[Put]] internal method of O with arguments lowerP, + upperValue, and true .
++ Call + the [[Delete]] internal method of O, with arguments upperP + and true.
++ Else + if lowerExists is true and upperExists is + false, then
++ Call + the [[Delete]] internal method of O, with arguments lowerP + and true .
++ Call + the [[Put]] internal method of O with arguments upperP, + lowerValue, and true .
++ Else, + both lowerExists and upperExists are false
++ No + action is required.
++ Increase + lower by 1.
++ Return + O .
+NOTE The
+ reverse function
+ is intentionally generic; it does not require that its this
+ value be an Array object. Therefore, it can be transferred to other
+ kinds of objects for use as a method. Whether the reverse
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ The + first element of the array is removed from the array and returned.
++ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenVal be the result of calling the [[Get]] internal method
+ of O with argument "length".
+ Let + len be ToUint32(lenVal).
++ If + len is zero, then
+
+ Call
+ the [[Put]] internal method of O with arguments "length",
+ 0, and true.
+ Return + undefined.
+
+ Let
+ first be the result of calling the [[Get]] internal method
+ of O with argument "0".
+ Let + k be 1.
++ Repeat, + while k < len
++ Let + from be ToString(k).
++ Let + to be ToString(k–1).
++ Let + fromPresent be the result of calling the [[HasProperty]] + internal method of O with argument from.
++ If + fromPresent is true, then
++ Let + fromVal be the result of calling the [[Get]] internal + method of O with argument from.
++ Call + the [[Put]] internal method of O with arguments to, + fromVal, and true.
++ Else, + fromPresent is false
++ Call + the [[Delete]] internal method of O with arguments to + and true.
++ Increase + k by 1.
++ Call + the [[Delete]] internal method of O with arguments + ToString(len–1) and true.
+
+ Call
+ the [[Put]] internal method of O with arguments "length",
+ (len–1) , and true.
+ Return + first.
+NOTE The
+ shift function is
+ intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the shift
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ The
+ slice method takes
+ two arguments, start
+ and end, and
+ returns an array containing the elements of the array from element
+ start up to, but
+ not including, element end
+ (or through the end of the array if end
+ is undefined). If start
+ is negative, it is treated as length+start
+ where length is
+ the length of the array. If end
+ is negative, it is treated as length+end
+ where length
+ is the length of the array. The following steps are taken:
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ A be a new array created as if by the expression new
+ Array() where Array
+ is the standard built-in constructor with that name.
+ Let
+ lenVal be the result of calling the [[Get]] internal method
+ of O with argument "length".
+ Let + len be ToUint32(lenVal).
++ Let + relativeStart be ToInteger(start).
++ If + relativeStart is negative, let k be max((len +relativeStart),0); else let k be min(relativeStart,len).
++ If + end is undefined, let relativeEnd be len; + else let relativeEnd be ToInteger(end).
++ If + relativeEnd is negative, let final be max((len + + relativeEnd),0); else let final be min(relativeEnd,len).
++ Let + n be 0.
++ Repeat, + while k < final
++ Let + Pk be ToString(k).
++ Let + kPresent be the result of calling the [[HasProperty]] + internal method of O with argument Pk.
++ If + kPresent is true, then
++ Let + kValue be the result of calling the [[Get]] internal + method of O with argument Pk.
++ Call + the [[DefineOwnProperty]] internal method of A with + arguments ToString(n), Property Descriptor {[[Value]]: + kValue, [[Writable]]: true, [[Enumerable]]: true, + [[Configurable]]: true}, and false.
++ Increase + k by 1.
++ Increase + n by 1.
++ Return + A.
+
+ The
+ length property of
+ the slice method
+ is 2.
NOTE The
+ slice function is
+ intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the slice
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ The + elements of this array are sorted. The sort is not necessarily + stable (that is, elements that compare equal do not necessarily + remain in their original order). If comparefn + is not undefined, it should be a function that accepts two + arguments x and y + and returns a negative value if x + < y, + zero if x = + y, or a positive + value if x > + y.
++ Let + obj be the result + of calling ToObject passing the this value as the argument.
+
+ Let
+ len be the result
+ of applying Uint32 to the result of calling the [[Get]] internal
+ method of obj with
+ argument "length".
+ If
+ comparefn is not
+ undefined and is not a consistent comparison function for the
+ elements of this array (see below), the behaviour of sort
+ is implementation-defined.
+ Let
+ proto be the value
+ of the [[Prototype]] internal property of obj.
+ If proto is not
+ null and there exists an integer j
+ such that all of the conditions below are satisfied then the
+ behaviour of sort
+ is implementation-defined:
+ 0 ≤ + j < len
++ The + result of calling the [[HasProperty]] internal method of proto + with argument ToString(j) + is true.
+
+ The
+ behaviour of sort
+ is also implementation defined if obj is sparse and any of the following conditions are true:
+ The + [[Extensible]] internal property of obj + is false.
++ Any + array index property of obj + whose name is a nonnegative integer less than len is a data property whose [[Configurable]] attribute is + false.
+
+ The
+ behaviour of sort
+ is also implementation defined if any array index property of obj
+ whose name is a nonnegative integer less than len
+ is an accessor property or is a data property whose [[Writable]]
+ attribute is false.
+ Otherwise, + the following steps are taken.
++ Perform + an implementation-dependent sequence of calls to the [[Get]] , + [[Put]], and [[Delete]] internal methods of obj and to + SortCompare (described below), where the first argument for each + call to [[Get]], [[Put]], or [[Delete]] is a nonnegative integer + less than len and where the arguments for calls to + SortCompare are results of previous calls to the [[Get]] internal + method. The throw argument to the [[Put]] and [[Delete]] internal + methods will be the value true. If obj is not sparse + then [[Delete]] must not be called.
++ Return + obj.
++ The + returned object must have the following two properties.
+
+ There
+ must be some mathematical permutation π
+ of the nonnegative integers less than len,
+ such that for every nonnegative integer j
+ less than len, if
+ property old[j]
+ existed, then new[π(j)]
+ is exactly the same value as old[j],.
+ But if property old[j]
+ did not exist, then new[π(j)]
+ does not exist.
+ Then
+ for all nonnegative integers j
+ and k, each less
+ than len, if
+ SortCompare(j,k)
+ < 0 (see
+ SortCompare below), then π(j)
+ < π(k).
+ Here + the notation old[j] + is used to refer to the hypothetical result of calling the [[Get]] + internal method of obj + with argument j + before this function is executed, and the notation new[j] + to refer to the hypothetical result of calling the [[Get]] internal + method of obj with + argument j after + this function has been executed.
++ A + function comparefn + is a consistent comparison function for a set of values S + if all of the requirements below are met for all values a, + b, and c + (possibly the same value) in the set S: + The notation a <CF b + means comparefn(a,b) < 0; + a =CF b + means comparefn(a,b) = 0 + (of either sign); and a >CF b + means comparefn(a,b) > 0.
++ Calling + comparefn(a,b) + always returns the same value v + when given a specific pair of values a + and b + as its two arguments. Furthermore, Type(v) + is Number, and v + is not NaN. Note that this implies that exactly one of a <CF b, + a =CF b, + and a >CF b + will be true for a given pair of a + and b.
++ Calling + comparefn(a,b) + does not modify the this + object.
++ a =CF a + (reflexivity)
++ If + a =CF b, + then b =CF a + (symmetry)
++ If + a =CF b + and b =CF c, + then a =CF c + (transitivity of =CF)
++ If + a <CF b + and b <CF c, + then a <CF c + (transitivity of <CF)
++ If + a >CF b + and b >CF c, + then a >CF c + (transitivity of >CF)
+NOTE The + above conditions are necessary and sufficient to ensure that + comparefn divides + the set S into + equivalence classes and that these equivalence classes are totally + ordered.
++ When + the SortCompare abstract operation is called with two arguments j + and k, the + following steps are taken:
++ Let + jString be ToString(j).
++ Let + kString be ToString(k).
++ Let + hasj be the result of calling the [[HasProperty]] internal + method of obj with argument jString.
++ Let + hask be the result of calling the [[HasProperty]] internal + method of obj with argument kString.
++ If + hasj and hask are both false, then + return +0.
++ If + hasj is false, then return 1.
++ If + hask is false, then return –1.
++ Let + x be the result of calling the [[Get]] internal method of + obj with argument jString.
++ Let + y be the result of calling the [[Get]] internal method of + obj with argument kString.
++ If + x and y are both undefined, return +0.
++ If + x is undefined, return 1.
++ If + y is undefined, return −1.
++ If + the argument comparefn is not undefined, then
++ If + IsCallable(comparefn) is false, throw a TypeError + exception.
++ Return + the result of calling the [[Call]] internal method of comparefn + passing undefined as the this value and with + arguments x and y.
++ Let + xString be ToString(x).
++ Let + yString be ToString(y).
++ If + xString < yString, return −1.
++ If + xString > yString, return 1.
++ Return + +0.
+NOTE 1 Because non-existent property values always compare greater than + undefined property values, and undefined always + compares greater than any other value, undefined property values + always sort to the end of the result, followed by non-existent + property values.
+NOTE 2 The sort
+ function is intentionally generic; it does not require that its this
+ value be an Array object. Therefore, it can be transferred to other
+ kinds of objects for use as a method. Whether the sort
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ When
+ the splice method
+ is called with two or more arguments start,
+ deleteCount and
+ (optionally) item1,
+ item2, etc., the
+ deleteCount
+ elements of the array starting at array index start
+ are replaced by the arguments item1,
+ item2, etc. An
+ Array object containing the deleted elements (if any) is returned.
+ The following steps are taken:
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ A be a new array created as if by the expression new
+ Array()where Array
+ is the standard built-in constructor with that name.
+ Let
+ lenVal be the result of calling the [[Get]] internal method
+ of O with argument "length".
+ Let + len be ToUint32(lenVal).
++ Let + relativeStart be ToInteger(start).
++ If + relativeStart is negative, let actualStart be + max((len + relativeStart),0); else let actualStart + be min(relativeStart, len).
++ Let + actualDeleteCount be min(max(ToInteger(deleteCount),0),len – actualStart).
++ Let + k be 0.
++ Repeat, + while k < actualDeleteCount
++ Let + from be ToString(actualStart+k).
++ Let + fromPresent be the result of calling the [[HasProperty]] + internal method of O with argument from.
++ If + fromPresent is true, then
++ Let + fromValue be the result of calling the [[Get]] internal + method of O with argument from.
++ Call + the [[DefineOwnProperty]] internal method of A with + arguments ToString(k), Property Descriptor {[[Value]]: + fromValue, [[Writable]]: true, [[Enumerable]]: + true, [[Configurable]]: true}, and false.
++ Increment + k by 1.
++ Let + items be an internal List whose elements are, in left to + right order, the portion of the actual argument list starting with + item1. The list will be empty if no such items are present.
++ Let + itemCount be the number of elements in items.
++ If + itemCount < actualDeleteCount, then
++ Let + k be actualStart.
++ Repeat, + while k < (len – actualDeleteCount)
++ Let + from be ToString(k+actualDeleteCount).
++ Let + to be ToString(k+itemCount).
++ Let + fromPresent be the result of calling the [[HasProperty]] + internal method of O with argument from.
++ If + fromPresent is true, then
++ Let + fromValue be the result of calling the [[Get]] internal + method of O with argument from.
++ Call + the [[Put]] internal method of O with arguments to, + fromValue, and true.
++ Else, + fromPresent is false
++ Call + the [[Delete]] internal method of O with arguments to + and true.
++ Increase + k by 1.
++ Let + k be len.
++ Repeat, + while k > (len – actualDeleteCount +itemCount) +
++ Call + the [[Delete]] internal method of O with arguments + ToString(k–1) and true.
++ Decrease + k by 1.
++ Else + if itemCount > actualDeleteCount, then
++ Let + k be (len – actualDeleteCount).
++ Repeat, + while k > actualStart
++ Let + from be ToString(k + actualDeleteCount – + 1).
++ Let + to be ToString(k + itemCount – 1)
++ Let + fromPresent be the result of calling the [[HasProperty]] + internal method of O with argument from.
++ If + fromPresent is true, then
++ Let + fromValue be the result of calling the [[Get]] internal + method of O with argument from.
++ Call + the [[Put]] internal method of O with arguments to, + fromValue, and true.
++ Else, + fromPresent is false
++ Call + the [[Delete]] internal method of O with argument to + and true.
++ Decrease + k by 1.
++ Let + k be actualStart.
++ Repeat, + while items is not empty
++ Remove + the first element from items and let E be the value + of that element.
++ Call + the [[Put]] internal method of O with arguments + ToString(k), E, and true.
++ Increase + k by 1.
+
+ Call
+ the [[Put]] internal method of O with arguments "length",
+ (len – actualDeleteCount + itemCount), and
+ true.
+ Return + A.
+
+ The
+ length property of
+ the splice method
+ is 2.
NOTE The
+ splice function is
+ intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the splice
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ The + arguments are prepended to the start of the array, such that their + order within the array is the same as the order in which they appear + in the argument list.
+
+ When
+ the unshift method
+ is called with zero or more arguments item1,item2, etc., the following steps are taken:
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenVal be the result of calling the [[Get]] internal method
+ of O with argument "length".
+ Let + len be ToUint32(lenVal).
++ Let + argCount be the number of actual arguments.
++ Let + k be len.
++ Repeat, + while k > 0, +
++ Let + from be ToString(k–1).
++ Let + to be ToString(k+argCount –1).
++ Let + fromPresent be the result of calling the [[HasProperty]] + internal method of O with argument from.
++ If + fromPresent is true, then
++ Let + fromValue be the result of calling the [[Get]] internal + method of O with argument from.
++ Call + the [[Put]] internal method of O with arguments to, + fromValue, and true.
++ Else, + fromPresent is false
++ Call + the [[Delete]] internal method of O with arguments to, + and true.
++ Decrease + k by 1.
++ Let + j be 0.
++ Let + items be an internal List whose elements are, in left to + right order, the arguments that were passed to this function + invocation.
++ Repeat, + while items is not empty
++ Remove + the first element from items and let E be the value + of that element.
++ Call + the [[Put]] internal method of O with arguments + ToString(j), E, and true.
++ Increase + j by 1.
+
+ Call
+ the [[Put]] internal method of O with arguments "length",
+ len+argCount, and true.
+ Return + len+argCount.
+
+ The
+ length property of
+ the unshift method
+ is 1.
NOTE The
+ unshift function
+ is intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the unshift
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ indexOf
+ compares searchElement
+ to the elements of the array, in ascending order, using the internal
+ Strict Equality Comparison Algorithm (11.9.6), and if found at one
+ or more positions, returns the index of the first such position;
+ otherwise, -1 is returned.
+ The + optional second argument fromIndex + defaults to 0 (i.e. the whole array is searched). If it is greater + than or equal to the length of the array, -1 is returned, i.e. the + array will not be searched. If it is negative, it is used as the + offset from the end of the array to compute fromIndex. + If the computed index is less than 0, the whole array will be + searched.
+
+ When
+ the indexOf method
+ is called with one or two arguments, the following steps are taken:
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenValue be the result of calling the [[Get]] internal
+ method of O with the argument "length".
+ Let + len be ToUint32(lenValue).
++ If + len is 0, return -1.
++ If + argument fromIndex was passed let n be + ToInteger(fromIndex); else let n be 0.
++ If + n ≥ len, return -1.
++ If + n ≥ 0, then +
++ Let + k be n.
++ Else, + n<0
++ Let + k be len - abs(n).
++ If + k is less than 0, then let k be 0.
++ Repeat, + while k<len
++ Let + kPresent be the result of calling the [[HasProperty]] + internal method of O with argument ToString(k).
++ If + kPresent is true, then
++ Let + elementK be the result of calling the [[Get]] internal + method of O with the argument ToString(k).
++ Let + same be the result of applying the Strict Equality + Comparison Algorithm to searchElement and elementK.
++ If + same is true, return k.
++ Increase + k by 1.
++ Return + -1.
+
+ The
+ length property of
+ the indexOf method
+ is 1.
NOTE The
+ indexOf function
+ is intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the indexOf
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ lastIndexOf
+ compares searchElement
+ to the elements of the array in descending order using the internal
+ Strict Equality Comparison Algorithm (11.9.6), and if found at one
+ or more positions, returns the index of the last such position;
+ otherwise, -1 is returned.
+ The + optional second argument fromIndex + defaults to the array's length minus one (i.e. the whole array is searched). + If it is greater than or equal to the length of the array, the whole + array will be searched. If it is negative, it is used as the offset + from the end of the array to compute fromIndex. + If the computed index is less than 0, -1 is returned.
+
+ When
+ the lastIndexOf
+ method is called with one or two arguments, the following steps are
+ taken:
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenValue be the result of calling the [[Get]] internal
+ method of O with the argument "length".
+ Let + len be ToUint32(lenValue).
++ If + len is 0, return -1.
++ If + argument fromIndex was passed let n be + ToInteger(fromIndex); else let n be len.
++ If + n ≥ 0, then let k be min(n, len + – 1).
++ Else, + n < 0
++ Let + k be len - abs(n).
++ Repeat, + while k≥ 0
++ Let + kPresent be the result of calling the [[HasProperty]] + internal method of O with argument ToString(k).
++ If + kPresent is true, then
++ Let + elementK be the result of calling the [[Get]] internal + method of O with the argument ToString(k).
++ Let + same be the result of applying the Strict Equality + Comparision Algorithm to searchElement and elementK.
++ If + same is true, return k.
++ Decrease + k by 1.
++ Return + -1.
+
+ The
+ length property of
+ the lastIndexOf
+ method is 1.
NOTE The
+ lastIndexOf
+ function is intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the lastIndexOf
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ callbackfn should be a function that accepts three arguments and
+ returns a value that is coercible to the Boolean value true
+ or false. every
+ calls callbackfn
+ once for each element present in the array, in ascending order,
+ until it finds one where callbackfn
+ returns false. If such an element is found, every
+ immediately returns false. Otherwise, if callbackfn
+ returned true for all elements, every
+ will return true. callbackfn
+ is called only for elements of the array which actually exist; it is
+ not called for missing elements of the array.
+ If a + thisArg parameter + is provided, it will be used as the this value for each + invocation of callbackfn. + If it is not provided, undefined is used instead.
++ callbackfn + is called with three arguments: the value of the element, the index + of the element, and the object being traversed.
+
+ every
+ does not directly mutate the object on which it is called but the
+ object may be mutated by the calls to callbackfn.
+
+
+ The
+ range of elements processed by every
+ is set before the first call to callbackfn.
+ Elements which are appended to the array after the call to every
+ begins will not be visited by callbackfn.
+ If existing elements of the array are changed, their value as passed
+ to callbackfn will
+ be the value at the time every
+ visits them; elements that are deleted after the call to every
+ begins and before being visited are not visited. every
+ acts like the "for all" quantifier in mathematics. In
+ particular, for an empty array, it returns true.
+ When
+ the every method
+ is called with one or two arguments, the following steps are taken:
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenValue be the result of calling the [[Get]] internal
+ method of O with the argument "length".
+ Let + len be ToUint32(lenValue).
++ If + IsCallable(callbackfn) is false, throw a TypeError + exception.
++ If + thisArg was supplied, let T be thisArg; else + let T be undefined.
++ Let + k be 0.
++ Repeat, + while k < len
++ Let + Pk be ToString(k).
++ Let + kPresent be the result of calling the [[HasProperty]] + internal method of O with argument Pk.
++ If + kPresent is true, then
++ Let + kValue be the result of calling the [[Get]] internal + method of O with argument Pk.
++ Let + testResult be the result of calling the [[Call]] internal + method of callbackfn with T as the this + value and argument list containing kValue, k, and + O.
++ If + ToBoolean(testResult) is false, return false.
++ Increase + k by 1.
++ Return + true.
+
+ The
+ length property of
+ the every method
+ is 1.
NOTE The
+ every function is
+ intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the every
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ callbackfn should be a function that accepts three arguments and
+ returns a value that is coercible to the Boolean value true
+ or false. some
+ calls callbackfn
+ once for each element present in the array, in ascending order,
+ until it finds one where callbackfn
+ returns true. If such an element is found, some
+ immediately returns true. Otherwise, some
+ returns false. callbackfn
+ is called only for elements of the array which actually exist; it is
+ not called for missing elements of the array.
+ If a + thisArg parameter + is provided, it will be used as the this value for each + invocation of callbackfn. + If it is not provided, undefined is used instead.
++ callbackfn + is called with three arguments: the value of the element, the index + of the element, and the object being traversed.
+
+ some
+ does not directly mutate the object on which it is called but the
+ object may be mutated by the calls to callbackfn.
+ The
+ range of elements processed by some
+ is set before the first call to callbackfn.
+ Elements that are appended to the array after the call to some
+ begins will not be visited by callbackfn.
+ If existing elements of the array are changed, their value as passed
+ to callbackfn will
+ be the value at the time that some
+ visits them; elements that are deleted after the call to some
+ begins and before being visited are not visited.
+ some acts like the "exists" quantifier in
+ mathematics. In particular, for an empty array, it returns false.
+ When
+ the some method is
+ called with one or two arguments, the following steps are taken:
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenValue be the result of calling the [[Get]] internal
+ method of O with the argument "length".
+ Let + len be ToUint32(lenValue).
++ If + IsCallable(callbackfn) is false, throw a TypeError + exception.
++ If + thisArg was supplied, let T be thisArg; else + let T be undefined.
++ Let + k be 0.
++ Repeat, + while k < len
++ Let + Pk be ToString(k).
++ Let + kPresent be the result of calling the [[HasProperty]] + internal method of O with argument Pk.
++ If + kPresent is true, then
++ Let + kValue be the result of calling the [[Get]] internal + method of O with argument Pk.
++ Let + testResult be the result of calling the [[Call]] internal + method of callbackfn with T as the this + value and argument list containing kValue, k, and + O.
++ If + ToBoolean(testResult) is true, return true.
++ Increase + k by 1.
++ Return + false.
+
+ The
+ length property of
+ the some method is
+ 1.
NOTE The
+ some function
+ is intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the some
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ callbackfn should be a function that accepts three arguments.
+ forEach calls
+ callbackfn once
+ for each element present in the array, in ascending order.
+ callbackfn is
+ called only for elements of the array which actually exist; it is
+ not called for missing elements of the array.
+ If a + thisArg parameter + is provided, it will be used as the this value for each + invocation of callbackfn. + If it is not provided, undefined is used instead.
++ callbackfn + is called with three arguments: the value of the element, the index + of the element, and the object being traversed. +
+
+ forEach
+ does not directly mutate the object on which it is called but the
+ object may be mutated by the calls to callbackfn.
+
+
+ The
+ range of elements processed by forEach
+ is set before the first call to callbackfn.
+ Elements which are appended to the array after the call to forEach
+ begins will not be visited by callbackfn.
+ If existing elements of the array are changed, their value as passed
+ to callback will be the value at the time forEach
+ visits them; elements that are deleted after the call to forEach
+ begins and before being visited are not visited.
+ When
+ the forEach method
+ is called with one or two arguments, the following steps are taken:
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenValue be the result of calling the [[Get]] internal
+ method of O with the argument "length".
+ Let + len be ToUint32(lenValue).
++ If + IsCallable(callbackfn) is false, throw a TypeError + exception.
++ If + thisArg was supplied, let T be thisArg; else + let T be undefined.
++ Let + k be 0.
++ Repeat, + while k < len
++ Let + Pk be ToString(k).
++ Let + kPresent be the result of calling the [[HasProperty]] + internal method of O with argument Pk.
++ If + kPresent is true, then
++ Let + kValue be the result of calling the [[Get]] internal + method of O with argument Pk.
++ Call + the [[Call]] internal method of callbackfn with T + as the this value and argument list containing kValue, + k, and O.
++ Increase + k by 1.
++ Return undefined.
+
+ The
+ length property of
+ the forEach method
+ is 1.
NOTE The
+ forEach
+ function is intentionally generic; it does not require that its
+ this value be an Array object. Therefore it can be
+ transferred to other kinds of objects for use as a method. Whether
+ the forEach
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ callbackfn should be a function that accepts three arguments. map
+ calls callbackfn
+ once for each element in the array, in ascending order, and
+ constructs a new Array from the results. callbackfn
+ is called only for elements of the array which actually exist; it is
+ not called for missing elements of the array.
+ If a + thisArg parameter + is provided, it will be used as the this value for + each invocation of callbackfn. + If it is not provided, undefined is used instead.
++ callbackfn + is called with three arguments: the value of the element, the index + of the element, and the object being traversed.
+
+ map
+ does not directly mutate the object on which it is called but the
+ object may be mutated by the calls to callbackfn.
+ The
+ range of elements processed by map
+ is set before the first call to callbackfn.
+ Elements which are appended to the array after the call to map
+ begins will not be visited by callbackfn.
+ If existing elements of the array are changed, their value as passed
+ to callbackfn will
+ be the value at the time map
+ visits them; elements that are deleted after the call to map
+ begins and before being visited are not visited.
+ When
+ the map method is
+ called with one or two arguments, the following steps are taken:
+
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenValue be the result of calling the [[Get]] internal
+ method of O with the argument "length".
+ Let + len be ToUint32(lenValue).
++ If + IsCallable(callbackfn) is false, throw a TypeError + exception.
++ If + thisArg was supplied, let T be thisArg; else + let T be undefined.
+
+ Let
+ A be a new array created as if by the expression new
+ Array( len)
+ where Array is
+ the standard built-in constructor with that name and len is
+ the value of len.
+ Let + k be 0.
++ Repeat, + while k < len
++ Let + Pk be ToString(k).
++ Let + kPresent be the result of calling the [[HasProperty]] + internal method of O with argument Pk.
++ If + kPresent is true, then
++ Let + kValue be the result of calling the [[Get]] internal + method of O with argument Pk.
++ Let + mappedValue be the result of calling the [[Call]] internal + method of callbackfn with T as the this + value and argument list containing kValue, k, and + O.
++ Call + the [[DefineOwnProperty]] internal method of A with + arguments Pk, Property Descriptor {[[Value]]: mappedValue, + [[Writable]]: true, [[Enumerable]]: true, + [[Configurable]]: true}, and false.
++ Increase + k by 1.
++ Return + A.
+
+ The
+ length property of
+ the map method is
+ 1.
NOTE The
+ map function
+ is intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the map
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ callbackfn should be a function that accepts three arguments and
+ returns a value that is coercible to the Boolean value true
+ or false. filter
+ calls callbackfn
+ once for each element in the array, in ascending order, and
+ constructs a new array of all the values for which callbackfn
+ returns true. callbackfn
+ is called only for elements of the array which actually exist; it is
+ not called for missing elements of the array.
+ If a + thisArg parameter + is provided, it will be used as the this value for each + invocation of callbackfn. + If it is not provided, undefined is used instead.
++ callbackfn + is called with three arguments: the value of the element, the index + of the element, and the object being traversed.
+
+ filter
+ does not directly mutate the object on which it is called but the
+ object may be mutated by the calls to callbackfn.
+ The
+ range of elements processed by filter
+ is set before the first call to callbackfn.
+ Elements which are appended to the array after the call to filter
+ begins will not be visited by callbackfn.
+ If existing elements of the array are changed their value as passed
+ to callbackfn will
+ be the value at the time filter
+ visits them; elements that are deleted after the call to filter
+ begins and before being visited are not visited.
+ When
+ the filter method
+ is called with one or two arguments, the following steps are taken:
+
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenValue be the result of calling the [[Get]] internal
+ method of O with the argument "length".
+ Let + len be ToUint32(lenValue).
++ If + IsCallable(callbackfn) is false, throw a TypeError + exception.
++ If + thisArg was supplied, let T be thisArg; else + let T be undefined.
+
+ Let
+ A be a new array created as if by the expression new
+ Array() where Array
+ is the standard built-in constructor with that name.
+ Let + k be 0.
++ Let + to be 0.
++ Repeat, + while k < len
++ Let + Pk be ToString(k).
++ Let + kPresent be the result of calling the [[HasProperty]] + internal method of O with argument Pk.
++ If + kPresent is true, then
++ Let + kValue be the result of calling the [[Get]] internal + method of O with argument Pk.
++ Let + selected be the result of calling the [[Call]] internal + method of callbackfn with T as the this + value and argument list containing kValue, k, and + O.
++ If + ToBoolean(selected) is true, then
++ Call + the [[DefineOwnProperty]] internal method of A with + arguments ToString(to), Property Descriptor {[[Value]]: + kValue, [[Writable]]: true, [[Enumerable]]: true, + [[Configurable]]: true}, and false.
++ Increase + to by 1.
++ Increase + k by 1.
++ Return + A.
+
+ The
+ length property of
+ the filter method
+ is 1.
NOTE The
+ filter function
+ is intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the filter
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ callbackfn should be a function that takes four arguments. reduce
+ calls the callback, as a function, once for each element present in
+ the array, in ascending order.
+ callbackfn is called with four arguments: the previousValue
+ (or value from the previous call to callbackfn),
+ the currentValue (value of the current element), the
+ currentIndex, and the object being traversed. The first time
+ that callback is called, the previousValue and currentValue
+ can be one of two values. If an initialValue was provided in the call to reduce,
+ then previousValue will be equal to initialValue and currentValue will be equal to the first value
+ in the array. If no initialValue was provided, then previousValue will be equal to
+ the first value in the array and currentValue will be equal
+ to the second. It is a TypeError if the array contains no
+ elements and initialValue
+ is not provided.
+ reduce
+ does not directly mutate the object on which it is called but the
+ object may be mutated by the calls to callbackfn.
+ The
+ range of elements processed by reduce
+ is set before the first call to callbackfn.
+ Elements that are appended to the array after the call to reduce
+ begins will not be visited by callbackfn.
+ If existing elements of the array are changed, their value as passed
+ to callbackfn will
+ be the value at the time reduce
+ visits them; elements that are deleted after the call to reduce
+ begins and before being visited are not visited.
+ When
+ the reduce method
+ is called with one or two arguments, the following steps are taken:
+
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenValue be the result of calling the [[Get]] internal
+ method of O with the argument "length".
+ Let + len be ToUint32(lenValue ).
++ If + IsCallable(callbackfn) is false, throw a TypeError + exception.
++ If + len is 0 and initialValue is not present, throw a TypeError + exception.
++ Let + k be 0.
++ If + initialValue is present, then
++ Set + accumulator to initialValue.
++ Else, + initialValue is not present
++ Let + kPresent be false.
++ Repeat, + while kPresent is false and k < len
++ Let + Pk be ToString(k).
++ Let + kPresent be the result of calling the [[HasProperty]] + internal method of O with argument Pk.
++ If + kPresent is true, then
++ Let + accumulator be the result of calling the [[Get]] internal + method of O with argument Pk.
++ Increase + k by 1.
++ If + kPresent is false, throw a TypeError + exception.
++ Repeat, + while k < len
++ Let + Pk be ToString(k).
++ Let + kPresent be the result of calling the [[HasProperty]] + internal method of O with argument Pk.
++ If + kPresent is true, then
++ Let + kValue be the result of calling the [[Get]] internal + method of O with argument Pk.
++ Let + accumulator be the result of calling the [[Call]] internal + method of callbackfn with undefined as the this + value and argument list containing accumulator, kValue, + k, and O.
++ Increase + k by 1.
++ Return + accumulator.
+
+ The
+ length property of
+ the reduce method
+ is 1.
NOTE The
+ reduce function
+ is intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the reduce
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ callbackfn should be a function that takes four arguments.
+ reduceRight calls
+ the callback, as a function, once for each element present in the array, in descending order.
+ callbackfn is called with four arguments: the previousValue (or
+ value from the previous call to callbackfn),
+ the currentValue (value of the current element), the currentIndex,
+ and the object being traversed. The first time the function is
+ called, the previousValue and currentValue can be one of two values.
+ If an initialValue was
+ provided in the call to reduceRight,
+ then previousValue will be equal to initialValue
+ and currentValue will be equal to the last value in the array. If no
+ initialValue was
+ provided, then previousValue will be equal to the last value in the
+ array and currentValue will be equal to the second-to-last value. It
+ is a TypeError if the array contains no
+ elements and
+ initialValue is
+ not provided.
+ reduceRight
+ does not directly mutate the object on which it is called
+ but the object may be mutated by the calls to callbackfn.
+ The
+ range of elements processed by reduceRight is set before the first call to callbackfn.
+ Elements that are appended to the array after the call to
+ reduceRight begins
+ will not be visited by callbackfn.
+ If existing elements of the array are changed by callbackfn,
+ their value as passed to callbackfn will be the value at the time reduceRight
+ visits them; elements that are deleted after the call to
+ reduceRight begins and
+ before being visited are not visited.
+ When
+ the reduceRight method
+ is called with one or two arguments, the following steps are taken:
+
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenValue be the result of calling the [[Get]] internal
+ method of O with the argument "length".
+ Let + len be ToUint32(lenValue ).
++ If + IsCallable(callbackfn) is false, throw a TypeError + exception.
++ If + len is 0 and initialValue is not present, throw a TypeError + exception.
++ Let + k be len-1.
++ If + initialValue is present, then
++ Set + accumulator to initialValue.
++ Else, + initialValue is not present
++ Let + kPresent be false.
++ Repeat, + while kPresent is false and k ≥ 0
++ Let + Pk be ToString(k).
++ Let + kPresent be the result of calling the [[HasProperty]] + internal method of O with argument Pk.
++ If + kPresent is true, then
++ Let + accumulator be the result of calling the [[Get]] internal + method of O with argument Pk.
++ Decrease + k by 1.
++ If + kPresent is false, throw a TypeError + exception.
++ Repeat, + while k ≥ 0
++ Let + Pk be ToString(k).
++ Let + kPresent be the result of calling the [[HasProperty]] + internal method of O with argument Pk.
++ If + kPresent is true, then
++ Let + kValue be the result of calling the [[Get]] internal + method of O with argument Pk.
++ Let + accumulator be the result of calling the [[Call]] internal + method of callbackfn with undefined as the this + value and argument list containing accumulator, kValue, + k, and O.
++ Decrease + k by 1.
++ Return + accumulator.
+
+ The
+ length property of
+ the reduceRight
+ method is 1.
NOTE The
+ reduceRight function
+ is intentionally generic; it does not require that its this value be
+ an Array object. Therefore it can be transferred to other kinds of
+ objects for use as a method. Whether the reduceRight
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ Array
+ instances inherit properties from the Array prototype object and
+ their [[Class]] internal property value is "Array".
+ Array instances also have the following properties.
+ Array + objects use a variation of the [[DefineOwnProperty]] internal method + used for other native ECMAScript objects (8.12.9).
++ Assume + A is an Array + object, Desc is a + Property Descriptor, and Throw is a Boolean flag.
++ In + the following algorithm, the term “Reject” + means “If Throw is true, + then throw a TypeError + exception, otherwise return false.”
++ When + the [[DefineOwnProperty]] internal method of A + is called with property P, + Property Descriptor Desc, + and Boolean flag Throw, + the following steps are taken:
+
+ Let
+ oldLenDesc be the result of calling the [[GetOwnProperty]]
+ internal method of A passing "length"
+ as the argument. The result will never be undefined or an
+ accessor descriptor because Array objects are created with a length
+ data property that cannot be deleted or reconfigured.
+ Let + oldLen be oldLenDesc.[[Value]].
+
+ If
+ P is "length",
+ then
+ If + the [[Value]] field of Desc is absent, then
+
+ Return
+ the result of calling the default [[DefineOwnProperty]] internal
+ method (8.12.9) on A passing "length",
+ Desc, and Throw as arguments.
+ Let + newLenDesc be a copy of Desc.
++ Let + newLen be ToUint32(Desc.[[Value]]).
++ If + newLen is not equal to ToNumber( Desc.[[Value]]), + throw a RangeError exception.
++ Set + newLenDesc.[[Value] to newLen.
++ If + newLen ≥oldLen, then
+
+ Return
+ the result of calling the default [[DefineOwnProperty]] internal
+ method (8.12.9) on A passing "length",
+ newLenDesc, and Throw as arguments.
+ Reject + if oldLenDesc.[[Writable]] is false.
++ If + newLenDesc.[[Writable]] is absent or has the value true, + let newWritable be true.
++ Else,
++ Need + to defer setting the [[Writable]] attribute to false in + case any elements cannot be deleted.
++ Let + newWritable be false.
++ Set + newLenDesc.[[Writable] to true.
+
+ Let
+ succeeded be the result of calling the default
+ [[DefineOwnProperty]] internal method (8.12.9) on A passing
+ "length",
+ newLenDesc, and Throw as arguments.
+ If + succeeded is false, return false..
++ While + newLen < oldLen repeat,
++ Set + oldLen to oldLen – 1.
++ Let + deleteSucceeded + be the result of calling the [[Delete]] + internal method of A passing ToString(oldLen) and + false as arguments.
++ If + deleteSucceeded + is false, then
+ ++ If + newWritable is false, then
+
+ Call
+ the default [[DefineOwnProperty]] internal method (8.12.9) on A
+ passing "length",
+ Property Descriptor{[[Writable]]: false}, and false
+ as arguments. This call will always return true.
+ Return + true.
++ Else + if P is an array index (15.4), then
++ Let + index be ToUint32(P).
++ Reject + if index ≥ oldLen and oldLenDesc.[[Writable]] + is false.
++ Let + succeeded be the result of calling the default + [[DefineOwnProperty]] internal method (8.12.9) on A passing + P, Desc, and false as arguments.
++ Reject + if succeeded is false.
++ If + index ≥ oldLen
++ Set + oldLenDesc.[[Value]] to index + 1.
+
+ Call
+ the default [[DefineOwnProperty]] internal method (8.12.9) on A
+ passing "length",
+ oldLenDesc, and false as arguments. This call will
+ always return true.
+ Return + true.
++ Return + the result of calling the default [[DefineOwnProperty]] internal + method (8.12.9) on A passing P, Desc, and + Throw as arguments.
+
+ The
+ length property of
+ this Array object is a data property whose value is always
+ numerically greater than the name of every deletable property whose
+ name is an array index.
+ The
+ length property
+ initially has the attributes {
+ [[Writable]]: true,
+ [[Enumerable]]: false,
+ [[Configurable]]: false
+ }.
NOTE Attempting + to set the length property of an Array object to a value that is + numerically less than or equal to the largest numeric property name + of an existing array indexed non-deletable property of the array + will result in the length being set to a numeric value that is one + greater than that largest numeric property name. See 15.4.5.1.
+
+ When
+ String is called
+ as a function rather than as a constructor, it performs a type
+ conversion.
+ Returns
+ a String value (not a String object) computed by ToString(value).
+ If value is not
+ supplied, the empty String ""
+ is returned.
+ When
+ String is called
+ as part of a new
+ expression, it is a constructor: it initialises the newly created
+ object.
+ The
+ [[Prototype]] internal
+ property of the newly constructed object is set to the standard
+ built-in String prototype object that is the initial value of
+ String.prototype
+ (15.5.3.1).
+ The
+ [[Class]] internal
+ property of the newly constructed object is set to "String".
+ The + [[Extensible]] internal + property of the newly constructed object is set to true.
++ The + [[PrimitiveValue]] internal + property of the newly constructed object is set to ToString(value), + or to the empty String if value + is not supplied.
++ The + value of the [[Prototype]] internal property of the String + constructor is the standard built-in Function prototype object + (15.3.4).
+
+ Besides
+ the internal properties and the length
+ property (whose value is 1), the String constructor has the
+ following properties:
+ The
+ initial value of String.prototype
+ is the standard built-in String prototype object (15.5.4).
+ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
++ Returns + a String value containing as many characters as the number of + arguments. Each argument specifies one character of the resulting + String, with the first argument specifying the first character, and + so on, from left to right. An argument is converted to a character + by applying the operation ToUint16 (9.7) and regarding the resulting + 16-bit integer as the code unit value of a character. If no + arguments are supplied, the result is the empty String.
+
+ The
+ length property of
+ the fromCharCode
+ function is 1.
+ The
+ String prototype object is itself a String object (its [[Class]] is
+ "String")
+ whose value is an empty String.
+ The + value of the [[Prototype]] internal property of the String prototype + object is the standard built-in Object prototype object (15.2.4).
+
+ The
+ initial value of String.prototype.constructor
+ is the built-in String
+ constructor.
+ Returns
+ this String value. (Note that, for a String object, the toString
+ method happens to return the same thing as the valueOf
+ method.)
+ The
+ toString function
+ is not generic; it throws a TypeError exception if its this
+ value is not a String or a String object. Therefore, it cannot be
+ transferred to other kinds of objects for use as a method.
+ Returns + this String value.
+
+ The
+ valueOf function
+ is not generic; it throws a TypeError exception if its this
+ value is not a String or String object. Therefore, it cannot be
+ transferred to other kinds of objects for use as a method.
+ Returns + a String containing the character at position pos + in the String resulting from converting this object to a String. If + there is no character at that position, the result is the empty + String. The result is a String value, not a String object.
+
+ If
+ pos is a value of
+ Number type that is an integer, then the result of x.charAt( pos)
+ is equal to the result of x.substring( pos,
+ pos+1).
+ When
+ the charAt method
+ is called with one argument pos,
+ the following steps are taken:
+ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + S be the result of calling ToString, giving it the this + value as its argument.
++ Let + position be ToInteger(pos).
++ Let + size be the number of characters in S.
++ If + position < 0 or position ≥ size, return + the empty String.
++ Return + a String of length 1, containing one character from S, + namely the character at position position, where the first + (leftmost) character in S is considered to be at position 0, + the next one at position 1, and so on.
+NOTE The
+ charAt function is
+ intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ Returns + a Number (a nonnegative integer less than 216) + representing the code unit value of the character at position pos + in the String resulting from converting this object to a String. If + there is no character at that position, the result is NaN.
+
+ When
+ the charCodeAt
+ method is called with one argument pos,
+ the following steps are taken:
+ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + S be the result of calling ToString, giving it the this + value as its argument.
++ Let + position be ToInteger(pos).
++ Let + size be the number of characters in S.
++ If + position < 0 or position ≥ size, return + NaN.
++ Return + a value of Number type, whose value is the code unit value of the + character at position position in the String S, where + the first (leftmost) character in S is considered to be at + position 0, the next one at position 1, and so on.
+NOTE The
+ charCodeAt
+ function is intentionally generic; it does not require that its this
+ value be a String object. Therefore it can be transferred to other
+ kinds of objects for use as a method.
+ When
+ the concat method
+ is called with zero or more arguments string1,
+ string2, etc., it
+ returns a String consisting of the characters of this object
+ (converted to a String) followed by the characters of each of
+ string1, string2,
+ etc. (where each argument is converted to a String). The result is a
+ String value, not a String object. The following steps are taken:
+ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + S be the result of calling ToString, giving it the this + value as its argument.
++ Let + args be an internal list that is a copy of the argument list + passed to this function.
++ Let + R be S.
++ Repeat, + while args is not empty
++ Remove + the first element from args and let next be the + value of that element.
++ Let + R be the String value consisting of the characters in the + previous value of R followed by the characters of + ToString(next).
++ Return + R.
+
+ The
+ length property of
+ the concat method
+ is 1.
NOTE The
+ concat function is
+ intentionally generic; it does not require that its this
+ value be a String object. Therefore it can be transferred to other
+ kinds of objects for use as a method.
+ If
+ searchString
+ appears as a substring of the result of converting this object to a
+ String, at one or more positions that are greater than or equal to
+ position, then the
+ index of the smallest such position is returned; otherwise, -1
+ is returned. If position
+ is undefined, 0 is assumed, so as to search all of the
+ String.
+ The
+ indexOf method
+ takes two arguments, searchString and position,
+ and performs the following steps:
+ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + S be the result of calling ToString, giving it the this + value as its argument.
++ Let + searchStr be ToString(searchString).
+
+ Let
+ pos be ToInteger(position). (If position is
+ undefined, this step produces the value 0).
+ Let + len be the number of characters in S.
++ Let + start be min(max(pos, 0), len).
++ Let + searchLen be the number of characters in searchStr.
+
+ Return
+ the smallest possible integer k not smaller than start
+ such that k+ searchLen is not greater than len,
+ and for all nonnegative integers j less than searchLen,
+ the character at position k+j of S is the same
+ as the character at position j of searchStr); but if
+ there is no such integer k, then return the value -1.
+ The
+ length property of
+ the indexOf method
+ is 1.
NOTE The
+ indexOf function
+ is intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ If
+ searchString
+ appears as a substring of the result of converting this object to a
+ String at one or more positions that are smaller than or equal to
+ position, then the
+ index of the greatest such position is returned; otherwise, -1
+ is returned. If position
+ is undefined, the length of the String value is assumed, so
+ as to search all of the String.
+ The
+ lastIndexOf method
+ takes two arguments, searchString and position,
+ and performs the following steps:
+ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + S be the result of calling ToString, giving it the this + value as its argument.
++ Let + searchStr be ToString(searchString).
++ Let + numPos be ToNumber(position). (If position is + undefined, this step produces the value NaN).
++ If + numPos is NaN, let pos be +∞; + otherwise, let pos be ToInteger(numPos).
++ Let + len be the number of characters in S.
++ Let + start min(max(pos, 0), len).
++ Let + searchLen be the number of characters in searchStr.
+
+ Return
+ the largest possible nonnegative integer k not larger than
+ start such that k+ searchLen is not greater
+ than len, and for all nonnegative integers j less
+ than searchLen, the character at position k+j
+ of S is the same as the character at position j of
+ searchStr; but if there is no such integer k, then
+ return the value -1.
+ The
+ length property of
+ the lastIndexOf
+ method is 1.
NOTE The
+ lastIndexOf
+ function is intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ When
+ the localeCompare
+ method is called with one argument that,
+ it returns a Number other than NaN that represents the result
+ of a locale-sensitive String comparison of the this value (converted
+ to a String) with that
+ (converted to a String). The two Strings are S
+ and That. The two
+ Strings are compared in an implementation-defined fashion. The
+ result is intended to order String values in the sort order
+ specified by the system default locale, and will be negative, zero,
+ or positive, depending on whether S
+ comes before That
+ in the sort order, the Strings are equal, or S
+ comes after That
+ in the sort order, respectively.
+ Before + perform the comparisons the following steps are performed to prepare + the Strings:
++ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + S be the result of calling ToString, giving it the this + value as its argument.
++ Let + That be ToString(that).
+
+ The
+ localeCompare
+ method, if considered as a function of two arguments this and
+ that, is a
+ consistent comparison function (as defined in 15.4.4.11) on the set
+ of all Strings.
+ The
+ actual return values are implementation-defined to permit
+ implementers to encode additional information in the value, but the
+ function is required to define a total ordering on all Strings and
+ to return 0 when
+ comparing Strings that are considered canonically equivalent by the
+ Unicode standard.
+ If no + language-sensitive comparison at all is available from the host + environment, this function may perform a bitwise comparison.
+NOTE 1 The localeCompare
+ method itself is not directly suitable as an argument to
+ Array.prototype.sort
+ because the latter requires a function of two arguments.
NOTE 2 This function is intended to rely on whatever language-sensitive + comparison functionality is available to the ECMAScript environment + from the host environment, and to compare according to the rules of + the host environment’s current locale. It is strongly recommended + that this function treat Strings that are canonically equivalent + according to the Unicode standard as identical (in other words, + compare the Strings as if they had both been converted to Normalised + Form C or D first). It is also recommended that this function not + honour Unicode compatibility equivalences or decompositions.
+NOTE 3 The second parameter to this function is likely to be used in a + future version of this standard; it is recommended that + implementations do not use this parameter position for anything + else.
+NOTE 4 The localeCompare
+ function is intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ When
+ the match method
+ is called with argument regexp,
+ the following steps are taken:
+ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + S be the result of calling ToString, giving it the this + value as its argument.
+
+ If
+ Type(regexp) is Object and the value of the [[Class]]
+ internal property of regexp is "RegExp",
+ then let rx be regexp;
+ Else,
+ let rx be a new RegExp object created as if by the
+ expression new
+ RegExp( regexp)
+ where RegExp is
+ the standard built-in constructor with that name.
+ Let
+ global be the result of calling the [[Get]] internal method
+ of rx with argument "global".
+ Let
+ exec be the standard built-in function RegExp.prototype.exec
+ (see 15.10.6.2)
+ If + global is not true, then
++ Return + the result of calling the [[Call]] internal method of exec + with rx as the this value and argument list + containing S.
++ Else, + global is true
+
+ Call
+ the [[Put]] internal method of rx with arguments
+ "lastIndex"
+ and 0.
+ Let
+ A be a new array created as if by the expression new
+ Array() where Array
+ is the standard built-in constructor with that name.
+ Let + previousLastIndex be 0.
++ Let + n be 0.
++ Let + lastMatch be true.
++ Repeat, + while lastMatch is true
++ Let + result be the result of calling the [[Call]] internal + method of exec with rx as the this value and + argument list containing S.
++ If + result is null, then set lastMatch to false.
++ Else, + result is not null
+
+ Let
+ thisIndex be the result of calling the [[Get]] internal
+ method of rx with argument "lastIndex".
+ If + thisIndex = previousLastIndex then
+
+ Call
+ the [[Put]] internal method of rx with arguments
+ "lastIndex"
+ and thisIndex+1.
+ Set + previousLastIndex to thisIndex+1.
++ Else, + set previousLastIndex to thisIndex.
+
+ Let
+ matchStr be the result of calling the [[Get]] internal
+ method of result with argument "0".
+ Call + the [[DefineOwnProperty]] internal method of A with + arguments ToString(n), the Property Descriptor + {[[Value]]: matchStr, [[Writable]]: true, + [[Enumerable]]: true, [[configurable]]: true}, and + false.
++ Increment + n.
++ If + n = 0, then return null.
++ Return + A.
+NOTE The
+ match function is
+ intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ First + set string according to the following steps:
++ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + string be the result of calling ToString, giving it the this + value as its argument.
+
+ If
+ searchValue is a
+ regular expression (an object whose [[Class]] internal property is
+ "RegExp"),
+ do the following: If searchValue.global
+ is false, then search string
+ for the first match of the regular expression searchValue.
+ If searchValue.global
+ is true, then search string
+ for all matches of the regular expression searchValue.
+ Do the search in the same manner as in String.prototype.match,
+ including the update of searchValue.lastIndex.
+ Let m be the
+ number of left capturing parentheses in searchValue
+ (using NcapturingParens
+ as specified in 15.10.2.1).
+ If + searchValue is not + a regular expression, let searchString + be ToString(searchValue) + and search string + for the first occurrence of searchString. + Let m be 0.
++ If + replaceValue is a + function, then for each matched substring, call the function with + the following m + + 3 arguments. Argument 1 is the substring that matched. If + searchValue is a + regular expression, the next m + arguments are all of the captures in the MatchResult (see + 15.10.2.1). Argument m + + 2 is the offset within string + where the match occurred, and argument m + + 3 is string. The + result is a String value derived from the original input by + replacing each matched substring with the corresponding return value + of the function call, converted to a String if need be.
+
+ Otherwise,
+ let newstring
+ denote the result of converting replaceValue
+ to a String. The result is a String value derived from the original
+ input String by replacing each matched substring with a String
+ derived from newstring
+ by replacing characters in newstring
+ by replacement text as specified in Table 22. These $
+ replacements are done left-to-right, and, once such a replacement is
+ performed, the new replacement text is not subject to further
+ replacements. For example, "$1,$2".replace(/(\$(\d))/g,
+ "$$1-$1$2") returns "$1-$11,$1-$22".
+ A $ in newstring
+ that does not match any of the forms below is left as is.
|
+ + Characters + |
+
+ + Replacement + text + |
+
|
+
+ |
+
+
+ |
+
|
+
+ |
+
+ + The + matched substring. + |
+
|
+
+ |
+
+ + The + portion of string + that precedes the matched substring. + |
+
|
+
+ |
+
+ + The + portion of string + that follows the matched substring. + |
+
|
+
+ |
+
+
+ The
+ nth
+ capture, where n
+ is a single digit in the range 1
+ to 9 and |
+
|
+
+ |
+
+ + The + nnth + capture, where nn + is a two-digit decimal number in the range 01 + to 99. If nn≤m + and the nnth + capture is undefined, use the empty String instead. If + nn>m, + the result is implementation-defined. + |
+
NOTE The
+ replace function
+ is intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ When + the search method is called with argument regexp, + the following steps are taken:
++ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + string be the result of calling ToString, giving it the this + value as its argument.
+
+ If
+ Type(regexp) is Object and the value of the [[Class]]
+ internal property of regexp is "RegExp",
+ then let rx be regexp;
+ Else,
+ let rx be a new RegExp object created as if by the
+ expression new
+ RegExp( regexp)
+ where RegExp is
+ the standard built-in constructor with that name.
+ Search
+ the value string from its beginning for an occurrence of the
+ regular expression pattern rx. Let result be a Number
+ indicating the offset within string where the pattern
+ matched, or –1 if there was no match. The lastIndex
+ and global
+ properties of regexp are ignored when performing the search. The
+ lastIndex
+ property of regexp is left unchanged.
+ Return + result.
+NOTE The
+ search function is
+ intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ The
+ slice method takes
+ two arguments, start
+ and end, and
+ returns a substring of the result of converting this object to a
+ String, starting from character position start
+ and running to, but not including, character position end
+ (or through the end of the String if end
+ is undefined). If start
+ is negative, it is treated as sourceLength+start where sourceLength
+ is the length of the String. If end
+ is negative, it is treated as sourceLength+end
+ where sourceLength
+ is the length of the String. The result is a String value, not a
+ String object. The following steps are taken:
+ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + S be the result of calling ToString, giving it the this + value as its argument.
++ Let + len be the number of characters in S.
++ Let + intStart be ToInteger(start).
++ If + end is undefined, let intEnd be len; + else let intEnd be ToInteger(end).
++ If + intStart is negative, let from be max(len + intStart,0); else let from be min(intStart,len).
++ If + intEnd is negative, let to be max(len +intEnd,0); else let to be min(intEnd, len).
++ Let + span be max(to – from,0).
++ Return + a String containing span consecutive characters from S + beginning with the character at position from.
+
+ The
+ length property of
+ the slice method
+ is 2.
NOTE The
+ slice function is
+ intentionally generic; it does not require that its this
+ value be a String object. Therefore it can be transferred to other
+ kinds of objects for use as a method.
+ Returns
+ an Array object into which substrings of the result of converting
+ this object to a String have been stored. The substrings are
+ determined by searching from left to right for occurrences of
+ separator; these
+ occurrences are not part of any substring in the returned array, but
+ serve to divide up the String value. The value of separator
+ may be a String of any length or it may be a RegExp object (i.e., an
+ object whose [[Class]] internal property is "RegExp";
+ see 15.10).
+ The
+ value of separator
+ may be an empty String, an empty regular expression, or a regular
+ expression that can match an empty String. In this case, separator
+ does not match the empty substring at the beginning or end of the
+ input String, nor does it match the empty substring at the end of
+ the previous separator match. (For example, if separator
+ is the empty String, the String is split up into individual
+ characters; the length of the result array equals the length of the
+ String, and each substring contains one character.) If separator
+ is a regular expression, only the first match at a given position of
+ the this String is considered, even if backtracking could
+ yield a non-empty-substring match at that position. (For example,
+ "ab".split(/a*?/)
+ evaluates to the array ["a","b"],
+ while "ab".split(/a*/)
+ evaluates to the array["","b"].)
+ If + the this object is (or converts to) the empty String, the + result depends on whether separator + can match the empty String. If it can, the result array contains no + elements. Otherwise, the result array contains one element, which is + the empty String.
+If + separator is a + regular expression that contains capturing parentheses, then each + time separator is + matched the results (including any undefined results) of the + capturing parentheses are spliced into the output array. + For example,
+
+ "A<B>bold</B>and<CODE>coded</CODE>".split(/<(\/)?([^<>]+)>/)
evaluates + to the array
+
+ ["A",
+ undefined, "B", "bold", "/", "B",
+ "and", undefined,
"CODE", "coded",
+ "/", "CODE", ""]
+ If + separator is + undefined, then the result array contains just one String, + which is the this value (converted to a String). If limit + is not undefined, then the output array is truncated so that + it contains no more than limit + elements.
+
+ When
+ the split method
+ is called, the following steps are taken:
+ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + S be the result of calling ToString, giving it the this + value as its argument.
+
+ Let
+ A be a new array created as if by the expression new
+ Array()where Array
+ is the standard built-in constructor with that name.
+ Let + lengthA be 0.
++ If + limit is undefined, let lim = 232–1; + else let lim = ToUint32(limit).
++ Let + s be the number of characters in S.
++ Let + p = 0.
+
+ If
+ separator is a RegExp object (its [[Class]] is "RegExp"),
+ let R = separator; otherwise let R =
+ ToString(separator).
+ If + lim = 0, return A.
++ If + separator is undefined, then
+
+ Call
+ the [[DefineOwnProperty]] internal method of A with
+ arguments "0",
+ Property Descriptor {[[Value]]: S, [[Writable]]: true,
+ [[Enumerable]]: true, [[Configurable]]: true}, and
+ false.
+ Return + A.
++ If + s = 0, then
++ Call + SplitMatch(S, 0, R) and let z be its + MatchResult result.
++ If + z is not failure, return A.
+
+ Call
+ the [[DefineOwnProperty]] internal method of A with
+ arguments "0",
+ Property Descriptor {[[Value]]: S, [[Writable]]: true,
+ [[Enumerable]]: true, [[Configurable]]: true}, and
+ false.
+ Return + A.
++ Let + q = p.
++ Repeat, + while q ≠ s
++ Call + SplitMatch(S, q, R) and let z + be its MatchResult result.
++ If + z is failure, then let q = q+1.
++ Else, + z is not failure
++ z + must be a State. Let e be z's endIndex and + let cap be z's captures array.
++ If + e = p, then let q = q+1.
++ Else, + e ≠ p
++ Let + T be a String value equal to the substring of S + consisting of the characters at positions p (inclusive) + through q (exclusive).
++ Call + the [[DefineOwnProperty]] internal method of A with + arguments ToString(lengthA), Property Descriptor + {[[Value]]: T, [[Writable]]: true, [[Enumerable]]: + true, [[Configurable]]: true}, and false.
++ Increment + lengthA by 1.
++ If + lengthA = lim, return A.
++ Let + p = e.
++ Let + i = 0.
++ Repeat, + while i is not equal to the number of elements in cap.
++ Let + i = i+1.
++ Call + the [[DefineOwnProperty]] internal method of A with + arguments ToString(lengthA), Property Descriptor + {[[Value]]: cap[i], [[Writable]]: true, + [[Enumerable]]: true, [[Configurable]]: true}, + and false.
++ Increment + lengthA by 1.
++ If + lengthA + = lim, return A.
++ Let + q = p.
++ Let + T be a String value equal to the substring of S + consisting of the characters at positions p (inclusive) + through s (exclusive).
++ Call + the [[DefineOwnProperty]] internal method of A with + arguments ToString(lengthA), Property Descriptor {[[Value]]: + T, [[Writable]]: true, [[Enumerable]]: true, + [[Configurable]]: true}, and false.
++ Return + A.
++ The + abstract operation SplitMatch + takes three parameters, a String S, + an integer q, and + a String or RegExp R, + and performs the following in order to return a MatchResult (see + 15.10.2.1):
+
+ If
+ R is a RegExp object (its [[Class]] is "RegExp"),
+ then
+ Call + the [[Match]] internal method of R giving it the arguments + S and q, and return the MatchResult result.
++ Type(R) + must be String. Let r be the number of characters in R.
++ Let + s be the number of characters in S.
++ If + q+r > s then return the MatchResult + failure.
++ If + there exists an integer i between 0 (inclusive) and r + (exclusive) such that the character at position q+i + of S is different from the character at position i of + R, then return failure.
+
+ The
+ length property of
+ the split method
+ is 2.
NOTE 1 The split method
+ ignores the value of separator.global
+ for separators that are RegExp objects.
NOTE 2 The split
+ function is intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ The + substring method takes two arguments, start + and end, and + returns a substring of the result of converting this object to a + String, starting from character position start + and running to, but not including, character position end + of the String (or through the end of the String is end + is undefined). The result is a String value, not a String + object.
++ If + either argument is NaN or negative, it is replaced with zero; + if either argument is larger than the length of the String, it is + replaced with the length of the String.
++ If + start is larger + than end, they are + swapped.
++ The + following steps are taken:
++ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + S be the result of calling ToString, giving it the this + value as its argument.
++ Let + len be the number of characters in S.
++ Let + intStart be ToInteger(start).
++ If + end is undefined, let intEnd be len; + else let intEnd be ToInteger(end).
++ Let + finalStart be min(max(intStart, 0), len).
++ Let + finalEnd be min(max(intEnd, 0), len).
++ Let + from be min(finalStart, finalEnd).
++ Let + to be max(finalStart, finalEnd).
++ Return + a String whose length is to - from, containing + characters from S, namely the characters with indices from + through to −1, in + ascending order.
+
+ The
+ length property of
+ the substring
+ method is 2.
NOTE The
+ substring function
+ is intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ The + following steps are taken:
++ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + S be the result of calling ToString, giving it the this + value as its argument.
++ Let + L be a String where each character of L is either the + Unicode lowercase equivalent of the corresponding character of S + or the actual corresponding character of S if no Unicode + lowercase equivalent exists.
++ Return + L.
++ For + the purposes of this operation, the 16-bit code units of the Strings + are treated as code points in the Unicode Basic Multilingual Plane. + Surrogate code points are directly transferred from S + to L without any + mapping.
+The + result must be derived according to the case mappings in the Unicode + character database (this explicitly includes not only the + UnicodeData.txt file, but also the SpecialCasings.txt file that + accompanies it in Unicode 2.1.8 and later).
+NOTE 1 The case mapping of some characters may produce multiple
+ characters. In this case the result String may not be the same
+ length as the source String. Because both toUpperCase
+ and toLowerCase
+ have context-sensitive behaviour, the functions are not symmetrical.
+ In other words, s.toUpperCase().toLowerCase()
+ is not necessarily equal to s.toLowerCase().
NOTE 2 The toLowerCase
+ function is intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ This
+ function works exactly the same as toLowerCase
+ except that its result is intended to yield the correct result for
+ the host environment’s current locale, rather than a
+ locale-independent result. There will only be a difference in the
+ few cases (such as Turkish) where the rules for that language
+ conflict with the regular Unicode case mappings.
NOTE 1 The first parameter to this function is likely to be used in a + future version of this standard; it is recommended that + implementations do not use this parameter position for anything + else.
+NOTE 2 The toLocaleLowerCase
+ function is intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ This
+ function behaves in exactly the same way as
+ String.prototype.toLowerCase,
+ except that characters are mapped to their uppercase
+ equivalents as specified in the Unicode Character Database.
NOTE The
+ toUpperCase
+ function is intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ This
+ function works exactly the same as toUpperCase
+ except that its result is intended to yield the correct result for
+ the host environment’s current locale, rather than a
+ locale-independent result. There will only be a difference in the
+ few cases (such as Turkish) where the rules for that language
+ conflict with the regular Unicode case mappings.
NOTE 1 The first parameter to this function is likely to be used in a + future version of this standard; it is recommended that + implementations do not use this parameter position for anything + else.
+NOTE 2 The toLocaleUpperCase
+ function is intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ The + following steps are taken:
++ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + S be the result of calling ToString, giving it the this + value as its argument.
++ Let + T be a String value that is a copy of S with both + leading and trailing white space removed. The definition of white + space is the union of WhiteSpace and LineTerminator.
++ Return + T.
+NOTE The
+ trim function is
+ intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ String
+ instances inherit properties from the String prototype object and
+ their [[Class]] internal property value is "String".
+ String instances also have a [[PrimitiveValue]] internal property, a
+ length property,
+ and a set of enumerable properties with array index names.
+ The + [[PrimitiveValue]] internal property is the String value represented + by this String object. The array index named properties correspond + to the individual characters of the String value. A special + [[GetOwnProperty]] internal method is used to specify the number, + values, and attributes of the array index named properties. +
++ The + number of characters in the String value represented by this String + object.
++ Once + a String object is created, this property is unchanging. It has the + attributes { [[Writable]]: false, [[Enumerable]]: false, + [[Configurable]]: false }.
++ String + objects use a variation of the [[GetOwnProperty]] internal method + used for other native ECMAScript objects (8.12.1). + + This special internal method is used to add access for named properties + corresponding to individual characters of String objects.
++ Assume + S is a String + object and P is a + String.
++ When + the [[GetOwnProperty]] internal method of S is called with property name P, + the following steps are taken:
++ Let + desc be the result of calling the default [[GetOwnProperty]] + internal method (8.12.1) on S with argument P.
++ If + desc is not undefined return desc. +
++ If + ToString(abs(ToInteger(P))) + is not + the same value as P, + return undefined.
++ Let + str be the String value of the [[PrimitiveValue]] internal + property of S.
++ Let + index be + ToInteger(P).
+ Let + len be the number of characters in str.
++ If + len ≤ index, return undefined.
++ Let + resultStr be a String of length 1, containing one character + from str, specifically the character at position index, + where the first (leftmost) character in str is considered to + be at position 0, the next one at position 1, and so on.
++ Return + a Property Descriptor { [[Value]]: resultStr, + [[Enumerable]]: true, [[Writable]]: false, + [[Configurable]]: false }
+
+ When
+ Boolean is called
+ as a function rather than as a constructor, it performs a type
+ conversion.
+ Returns + a Boolean value (not a Boolean object) computed by ToBoolean(value).
+
+ When
+ Boolean is called
+ as part of a new
+ expression it is a constructor: it initialises the newly created
+ object.
+ The
+ [[Prototype]] internal property of the newly constructed object is
+ set to the original Boolean prototype object, the one that is the
+ initial value of Boolean.prototype
+ (15.6.3.1).
+ The
+ [[Class]] internal property of the newly constructed Boolean object
+ is set to "Boolean".
+ The + [[PrimitiveValue]] internal property of the newly constructed + Boolean object is set to ToBoolean(value).
++ The + [[Extensible]] internal property of the newly constructed object is + set to true.
++ The + value of the [[Prototype]] internal property of the Boolean + constructor is the Function prototype object (15.3.4).
+
+ Besides
+ the internal properties and the length
+ property (whose value is 1), the Boolean constructor has the
+ following property:
+ The
+ initial value of Boolean.prototype
+ is the Boolean prototype object (15.6.4).
+ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+
+ The
+ Boolean prototype object is itself a Boolean object (its [[Class]]
+ is "Boolean")
+ whose value is false.
+ The + value of the [[Prototype]] internal property of the Boolean + prototype object is the standard built-in Object prototype object + (15.2.4).
+
+ The
+ initial value of Boolean.prototype.constructor
+ is the built-in Boolean
+ constructor.
+ The + following steps are taken:
++ Let + B be the this value.
++ If + Type(B) is Boolean, then let b be B.
+
+ Else
+ if Type(B) is Object and the value of the [[Class]] internal
+ property of B is "Boolean",
+ then let b be the value of the [[PrimitiveValue]] internal
+ property of B.
+ Else + throw a TypeError exception.
+
+ If
+ b is true, then return "true";
+ else return "false".
+ The + following steps are taken:
++ Let + B be the this value.
++ If + Type(B) is Boolean, then let b be B.
+
+ Else
+ if Type(B) is Object and the value of the [[Class]] internal
+ property of B is "Boolean",
+ then let b be the value of the [[PrimitiveValue]] internal
+ property of B.
+ Else + throw a TypeError exception.
++ Return + b.
+
+ Boolean
+ instances inherit properties from the Boolean prototype object and
+ their [[Class]] internal property value is "Boolean".
+ Boolean instances also have a [[PrimitiveValue]] internal property.
+ The + [[PrimitiveValue]] internal property is the Boolean value + represented by this Boolean object.
+
+ When
+ Number is called
+ as a function rather than as a constructor, it performs a type
+ conversion.
+ Returns + a Number value (not a Number object) computed by ToNumber(value) + if value was + supplied, else returns +0.
+
+ When
+ Number is called
+ as part of a new
+ expression it is a constructor: it initialises the newly created
+ object.
+ The
+ [[Prototype]] internal property of the newly constructed object is
+ set to the original Number prototype object, the one that is the
+ initial value of Number.prototype
+ (15.7.3.1).
+ The
+ [[Class]] internal property of the newly constructed object is set
+ to "Number".
+ The + [[PrimitiveValue]] internal property of the newly constructed object + is set to ToNumber(value) + if value was + supplied, else to +0.
++ The + [[Extensible]] internal property of the newly constructed object is + set to true.
++ The + value of the [[Prototype]] internal property of the Number + constructor is the Function prototype object (15.3.4).
+
+ Besides
+ the internal properties and the length
+ property (whose value is 1), the Number constructor has the
+ following property:
+ The
+ initial value of Number.prototype
+ is the Number prototype object (15.7.4).
+ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+
+ The
+ value of Number.MAX_VALUE
+ is the largest positive finite value of the Number type, which is
+ approximately 1.7976931348623157 × 10308.
+ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+
+ The
+ value of Number.MIN_VALUE
+ is the smallest positive value of the Number type, which is
+ approximately 5 × 10 324.
+ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+
+ The
+ value of Number.NaN
+ is NaN.
+ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
++ The + value of Number.NEGATIVE_INFINITY is −∞.
++ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
++ The + value of Number.POSITIVE_INFINITY is +∞.
++ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+
+ The
+ Number prototype object is itself a Number object (its [[Class]] is
+ "Number")
+ whose value is +0.
+ The + value of the [[Prototype]] internal property of the Number prototype + object is the standard built-in Object prototype object (15.2.4).
+
+ Unless
+ explicitly stated otherwise, the methods of the Number prototype
+ object defined below are not generic and the this value passed to
+ them must be either a Number value or an Object for which the value
+ of the [[Class]] internal property is "Number".
+ In
+ the following descriptions of functions that are properties of the
+ Number prototype object, the phrase “this Number object” refers
+ to either the object that is the this value for the
+ invocation of the function or, if Type(this value) is Number,
+ an object that is created as if by the expression new
+ Number(this value)
+ where Number is
+ the standard built-in constructor with that name. Also, the phrase
+ “this Number value” refers to either the Number value
+ represented by this Number object, that is, the value of the
+ [[PrimitiveValue]] internal property of this Number object or the
+ this value if its type is Number. A TypeError
+ exception is thrown if the this value is neither an object
+ for which the value of the [[Class]] internal property is "Number"
+ or a value whose type is Number.
+ The
+ initial value of Number.prototype.constructor
+ is the built-in Number
+ constructor.
+ The + optional radix + should be an integer value in the inclusive range 2 + to 36. If radix + not present or is undefined the Number 10 + is used as the value of radix. + If ToInteger(radix) + is the Number 10 then + this Number value is given as an argument to the ToString abstract + operation; the resulting String value is returned.
+
+ If
+ ToInteger(radix)
+ is not an integer between 2 and 36 inclusive throw a RangeError
+ exception. If ToInteger(radix)
+ is an integer from 2 to 36, but not 10, the result is a String
+ representation of this Number value using the specified radix.
+ Letters a-z
+ are used for digits with values 10 through 35. The precise algorithm
+ is implementation-dependent if the radix is not 10, however the
+ algorithm should be a generalization of that specified in 9.8.1.
+ The
+ toString function
+ is not generic; it throws a TypeError exception if its this
+ value is not a Number or a Number object. Therefore, it cannot be
+ transferred to other kinds of objects for use as a method.
+ Produces
+ a String value that represents this Number value formatted according
+ to the conventions of the host environment’s current locale. This
+ function is implementation-dependent, and it is permissible, but not
+ encouraged, for it to return the same thing as toString.
NOTE The + first parameter to this function is likely to be used in a future + version of this standard; it is recommended that implementations do + not use this parameter position for anything else.
++ Returns + this Number value.
+
+ The
+ valueOf function
+ is not generic; it throws a TypeError exception if its this
+ value is not a Number or a Number object. Therefore, it cannot be
+ transferred to other kinds of objects for use as a method.
+ Return + a String containing this Number value represented in decimal + fixed-point notation with fractionDigits + digits after the decimal point. If fractionDigits + is undefined, 0 is assumed. Specifically, perform the + following steps:
+
+ Let
+ f be ToInteger(fractionDigits). (If fractionDigits
+ is undefined, this step produces the value 0).
+ If + f < 0 or f > 20, throw a RangeError + exception.
++ Let + x be this Number value.
+
+ If
+ x is NaN, return the String "NaN".
+ Let + s be the empty String.
++ If + x < 0, then
+
+ Let
+ s be "-".
+ Let + x = –x.
++ If + x ≥ 1021, + then
++ Let + m = ToString(x).
++ Else, + x < 1021
++ Let + n be an integer for which the exact mathematical value of n + ÷ 10f – x + is as close to zero as possible. If there are two such n, + pick the larger n.
+
+ If
+ n = 0, let m be the String "0".
+ Otherwise, let m be the String consisting of the digits of
+ the decimal representation of n (in order, with no leading
+ zeroes).
+ If + f ≠ 0, then
++ Let + k be the number of characters in m.
++ If + k ≤ f, then
+
+ Let
+ z be the String consisting of f+1–k
+ occurrences of the character ‘0’.
+ Let + m be the concatenation of Strings z and m.
++ Let + k = f + 1.
++ Let + a be the first k–f characters of m, and + let b be the remaining f characters of m.
+
+ Let
+ m be the concatenation of the three Strings a, ".",
+ and b.
+ Return + the concatenation of the Strings s and m.
+
+ The
+ length property of
+ the toFixed method
+ is 1.
+ If
+ the toFixed method
+ is called with more than one argument, then the behaviour is
+ undefined (see clause 15).
+ An
+ implementation is permitted to extend the behaviour of toFixed
+ for values of fractionDigits
+ less than 0 or greater than 20. In this case toFixed
+ would not necessarily throw RangeError for such values.
NOTE The
+ output of toFixed
+ may be more precise than toString
+ for some values because toString only prints enough significant
+ digits to distinguish the number from adjacent number values. For
+ example,
+
(1000000000000000128).toString()
+ returns "1000000000000000100",
while
+ (1000000000000000128).toFixed(0)
+ returns "1000000000000000128".
+ Return + a String containing this Number value represented in decmal + exponential notation with one digit before the significand's decimal + point and fractionDigits + digits after the significand's decimal point. If fractionDigits + is undefined, include as many significand digits as necessary + to uniquely specify the Number (just like in ToString except that in + this case the Number is always output in exponential notation). + Specifically, perform the following steps:
++ Let + x be this Number value.
++ Let + f be ToInteger(fractionDigits).
+
+ If
+ x is NaN, return the String "NaN".
+ Let + s be the empty String.
++ If + x < 0, then
+
+ Let
+ s be "-".
+ Let + x = –x.
++ If + x = +∞, then
+
+ Return
+ the concatenation of the Strings s and "Infinity".
+
+
+ If + fractionDigits is not undefined and (f < 0 + or f > 20), throw a RangeError exception.
++ If + x = 0, then
++ Let + f = 0.
+
+ Let
+ m be the String consisting of f+1 occurrences of the
+ character ‘0’.
+ Let + e = 0.
++ Else, + x ≠ 0
++ If + fractionDigits is not undefined, then
++ Let + e and n be integers such that 10f + ≤ n < 10f+1 + and for which the exact mathematical value of n × + 10e–f – x + is as close to zero as possible. If there are two such sets of e + and n, pick the e and n for which n × + 10e–f is larger.
++ Else, + fractionDigits is undefined +
++ Let + e, n, and f be integers such that f ≥ + 0, 10f ≤ n + < 10f+1, the number value for n × + 10e–f is x, + and f is as small as possible. Note that the decimal + representation of n has f+1 digits, n is not + divisible by 10, and the least significant digit of n is + not necessarily uniquely determined by these criteria.
++ Let + m be the String consisting of the digits of the decimal + representation of n (in order, with no leading zeroes).
++ If + f ≠ 0, then
++ Let + a be the first character of m, and let b be + the remaining f characters of m.
+
+ Let
+ m be the concatenation of the three Strings a, ".",
+ and b.
+ If + e = 0, then +
+
+ Let
+ c = "+".
+ Let
+ d = "0".
+ Else
+
+ If
+ e > 0, then let c = "+".
+ Else, + e ≤ 0
+
+ Let
+ c = "-".
+ Let + e = –e.
++ Let + d be the String consisting of the digits of the decimal + representation of e (in order, with no leading zeroes).
+
+ Let
+ m be the concatenation of the four Strings m, "e",
+ c, and d.
+ Return + the concatenation of the Strings s and m.
+
+ The
+ length property of
+ the toExponential
+ method is 1.
+ If
+ the toExponential
+ method is called with more than one argument, then the behaviour is
+ undefined (see clause 15).
+ An
+ implementation is permitted to extend the behaviour of toExponential
+ for values of fractionDigits
+ less than 0 or greater than 20. In this case toExponential
+ would not necessarily throw RangeError for such values.
NOTE For + implementations that provide more accurate conversions than required + by the rules above, it is recommended that the following alternative + version of step 9.b.i be used as a guideline:
++ Let + e, + n, + and f be + integers such that f + ≥ + 0, 10f + ≤ + n < 10f+1, + the number value for n × + 10e–f + is x, and f + is as small as possible. If there are multiple possibilities for + n, + choose the value of n + for which n + × + 10e–f + is closest in value to x. + If there are two such possible values of n, + choose the one that is even.
++ Return + a String containing this Number value represented either in decimal + exponential notation with one digit before the significand's decimal + point and precision–1 + digits after the significand's decimal point or in decimal fixed + notation with precision + significant digits. If precision + is undefined, call ToString (9.8.1) instead. Specifically, + perform the following steps:
++ Let + x be this Number value.
++ If + precision is undefined, return ToString(x).
++ Let + p be ToInteger(precision).
+
+ If
+ x is NaN, return the String "NaN".
+ Let + s be the empty String.
++ If + x < 0, then
+
+ Let
+ s be "-".
+ Let + x = –x.
++ If + x = +∞, then
+
+ Return
+ the concatenation of the Strings s and "Infinity".
+ If + p < 1 or p > 21, throw a RangeError + exception.
++ If + x = 0, then
+
+ Let
+ m be the String consisting of p occurrences of the
+ character ‘0’.
+ Let + e = 0.
++ Else + x ≠ 0,
++ Let + e and n be integers such that 10p–1 + ≤ n < 10p + and for which the exact mathematical value of n × + 10e–p+1 + – x is as close to zero as possible. If there are two + such sets of e and n, pick the e and n + for which n × 10e–p+1 + is larger.
++ Let + m be the String consisting of the digits of the decimal + representation of n (in order, with no leading zeroes).
++ If + e < –6 or e ≥ + p, then
++ Let + a be the first character of m, and let b be + the remaining p–1 characters of m.
+
+ Let
+ m be the concatenation of the three Strings a, ".",
+ and b.
+ If + e = 0, then
+
+ Let
+ c = "+"
+ and d = "0".
+ Else + e ≠ 0,
++ If + e > 0, then +
+
+ Let
+ c = "+".
+ Else + e < 0,
+
+ Let
+ c = "-".
+ Let + e = –e.
++ Let + d be the String consisting of the digits of the decimal + representation of e (in order, with no leading zeroes).
+
+ Let
+ m be the concatenation of the five Strings s, m,
+ "e",
+ c, and d.
+ If + e = p–1, then return the concatenation of the + Strings s and m.
++ If + e ≥ 0, then
+
+ Let
+ m be the concatenation of the first e+1 characters
+ of m, the character ‘.’,
+ and the remaining p– (e+1) characters of m.
+ Else + e < 0,
+
+ Let
+ m be the concatenation of the String "0.",
+ –(e+1) occurrences of the character ‘0’,
+ and the String m.
+ Return + the concatenation of the Strings s and m.
+
+ The
+ length property of
+ the toPrecision
+ method is 1.
+ If
+ the toPrecision
+ method is called with more than one argument, then the behaviour is
+ undefined (see clause 15).
+ An
+ implementation is permitted to extend the behaviour of toPrecision
+ for values of precision
+ less than 1 or greater than 21. In this case toPrecision
+ would not necessarily throw RangeError for such values.
+ Number
+ instances inherit properties from the Number prototype object and
+ their [[Class]] internal property value is "Number".
+ Number instances also have a [[PrimitiveValue]] internal property.
+ The + [[PrimitiveValue]] internal property is the Number value represented + by this Number object.
++ The + Math object is a single object that has some named properties, some + of which are functions.
+
+ The
+ value of the [[Prototype]] internal property of the Math object is
+ the standard built-in Object prototype object (15.2.4). The value of
+ the [[Class]] internal property of the Math object is "Math".
+ The
+ Math object does not have a [[Construct]] internal property; it is
+ not possible to use the Math object as a constructor with the new
+ operator.
+ The + Math object does not have a [[Call]] internal property; it is not + possible to invoke the Math object as a function.
+NOTE In + this specification, the phrase “the Number value for x” + has a technical meaning defined in 8.5.
++ The + Number value for e, + the base of the natural logarithms, which is approximately + 2.7182818284590452354.
++ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
++ The + Number value for the natural logarithm of 10, which is approximately + 2.302585092994046.
++ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
++ The + Number value for the natural logarithm of 2, which is approximately + 0.6931471805599453.
++ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
++ The + Number value for the base-2 + logarithm of e, + the base of the natural logarithms; this value is approximately + 1.4426950408889634.
++ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+NOTE The
+ value of Math.LOG2E
+ is approximately the reciprocal of the value of Math.LN2.
+ The + Number value for the base-10 + logarithm of e, + the base of the natural logarithms; this value is approximately + 0.4342944819032518.
++ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+NOTE The
+ value of Math.LOG10E
+ is approximately the reciprocal of the value of Math.LN10.
+ The + Number value for π, the ratio of + the circumference of a circle to its diameter, which is + approximately 3.1415926535897932.
++ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
++ The + Number value for the square root of ½, + which is approximately 0.7071067811865476.
++ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+NOTE The
+ value of Math.SQRT1_2
+ is approximately the reciprocal of the value of Math.SQRT2.
+ The + Number value for the square root of 2, + which is approximately 1.4142135623730951.
++ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+
+ Each
+ of the following Math object functions applies the ToNumber abstract operator to each of
+ its arguments (in left-to-right order if there is more than one) and
+ then performs a computation on the resulting Number value(s).
+ In + the function descriptions below, the symbols NaN, −0, + +0, −∞ and +∞ + refer to the Number values described in 8.5.
+NOTE The
+ behaviour of the functions acos,
+ asin, atan,
+ atan2, cos,
+ exp, log,
+ pow, sin,
+ and sqrt is not
+ precisely specified here except to require specific results for
+ certain argument values that represent boundary cases of interest.
+ For other argument values, these functions are intended to compute
+ approximations to the results of familiar mathematical functions,
+ but some latitude is allowed in the choice of approximation
+ algorithms. The general intent is that an implementer should be able
+ to use the same mathematical library for ECMAScript on a given
+ hardware platform that is available to C programmers on that
+ platform.
+ Although
+ the choice of algorithms is left to the implementation, it is
+ recommended (but not specified by this standard) that
+ implementations use the approximation algorithms for IEEE 754
+ arithmetic contained in fdlibm,
+ the freely distributable mathematical library from Sun Microsystems
+ (http://www.netlib.org/fdlibm).
+
+
+ Returns + the absolute value of x; + the result has the same magnitude as x + but has positive sign.
++ If + x + is NaN, the result is NaN.
++ If + x + is −0, + the result is +0.
++ If + x + is −∞, + the result is +∞.
++ Returns + an implementation-dependent approximation to the arc cosine of x. + The result is expressed in radians and ranges from +0 + to +π.
++ If + x + is NaN, the result is NaN.
++ If + x + is greater than 1, the result is NaN.
++ If + x + is less than −1, + the result is NaN.
++ If + x + is exactly 1, the result is +0.
++ Returns + an implementation-dependent approximation to the arc sine of x. + The result is expressed in radians and ranges from −π/2 + to +π/2.
++ If + x + is NaN, the result is NaN.
++ If + x + is greater than 1, the result is NaN.
++ If + x + is less than –1, the result is NaN.
++ If + x + is +0, the result is +0.
++ If + x + is −0, + the result is −0.
++ Returns + an implementation-dependent approximation to the arc tangent of x. + The result is expressed in radians and ranges from −π/2 + to +π/2.
++ If + x + is NaN, the result is NaN.
++ If + x + is +0, the result is +0.
++ If + x + is −0, + the result is −0.
++ If + x + is +∞, + the result is an implementation-dependent approximation to +π/2.
++ If + x + is −∞, + the result is an implementation-dependent approximation to −π/2.
++ Returns + an implementation-dependent approximation to the arc tangent of the + quotient y/x + of the arguments y + and x, where the + signs of y and x + are used to determine the quadrant of the result. Note that it is + intentional and traditional for the two-argument arc tangent + function that the argument named y + be first and the argument named x + be second. The result is expressed in radians and ranges from −π + to +π.
++ If + either x + or y + is NaN, the result is NaN.
++ If + y>0 + and x + is +0, the result is an implementation-dependent approximation to + +π/2.
++ If + y>0 + and x + is −0, + the result is an implementation-dependent approximation to +π/2.
++ If + y + is +0 and x>0, + the result is +0.
++ If + y + is +0 and x + is +0, the result is +0.
++ If + y + is +0 and x + is −0, + the result is an implementation-dependent approximation to +π.
++ If + y + is +0 and x<0, + the result is an implementation-dependent approximation to +π.
++ If + y + is −0 + and x>0, + the result is −0.
++ If + y + is −0 + and x + is +0, the result is −0.
++ If + y + is −0 + and x + is −0, + the result is an implementation-dependent approximation to −π.
++ If + y + is −0 + and x<0, + the result is an implementation-dependent approximation to −π.
++ If + y<0 + and x + is +0, the result is an implementation-dependent approximation to + −π/2.
++ If + y<0 + and x + is −0, + the result is an implementation-dependent approximation to −π/2.
++ If + y>0 + and y + is finite and x + is +∞, + the result is +0.
++ If + y>0 + and y + is finite and x + is −∞, + the result if an implementation-dependent approximation to +π.
++ If + y<0 + and y + is finite and x + is +∞, + the result is −0.
++ If + y<0 + and y + is finite and x + is −∞, + the result is an implementation-dependent approximation to −π.
++ If + y + is +∞ + and x + is finite, the result is an implementation-dependent approximation + to +π/2.
++ If + y + is −∞ + and x + is finite, the result is an implementation-dependent approximation + to −π/2.
++ If + y + is +∞ + and x + is +∞, + the result is an implementation-dependent approximation to +π/4.
++ If + y + is +∞ + and x + is −∞, + the result is an implementation-dependent approximation to +3π/4.
++ If + y + is −∞ + and x + is +∞, + the result is an implementation-dependent approximation to −π/4.
++ If + y + is −∞ + and x + is −∞, + the result is an implementation-dependent approximation to −3π/4.
++ Returns + the smallest (closest to −∞) + Number value that is not less than x + and is equal to a mathematical integer. If x + is already an integer, the result is x.
++ If + x + is NaN, the result is NaN.
++ If + x + is +0, the result is +0.
++ If + x + is −0, + the result is −0.
++ If + x + is +∞, + the result is +∞.
++ If + x + is −∞, + the result is −∞.
++ If + x + is less than 0 but greater than -1, the result is −0.
+
+ The
+ value of Math.ceil(x)
+ is the same as the value of -Math.floor(-x).
+ Returns + an implementation-dependent approximation to the cosine of x. + The argument is expressed in radians.
++ If + x + is NaN, the result is NaN.
++ If + x + is +0, the result is 1.
++ If + x + is −0, + the result is 1.
++ If + x + is +∞, + the result is NaN.
++ If + x + is −∞, + the result is NaN.
++ Returns + an implementation-dependent approximation to the exponential + function of x (e + raised to the power of x, + where e is the + base of the natural logarithms).
++ If + x + is NaN, the result is NaN.
++ If + x + is +0, the result is 1.
++ If + x + is −0, + the result is 1.
++ If + x + is +∞, + the result is +∞.
++ If + x + is −∞, + the result is +0.
++ Returns + the greatest (closest to +∞) + Number value that is not greater than x + and is equal to a mathematical integer. If x + is already an integer, the result is x.
++ If + x + is NaN, the result is NaN.
++ If + x + is +0, the result is +0.
++ If + x + is −0, + the result is −0.
++ If + x + is +∞, + the result is +∞.
++ If + x + is −∞, + the result is −∞.
++ If + x + is greater than 0 but less than 1, the result is +0.
+NOTE The
+ value of Math.floor(x)
+ is the same as the value of -Math.ceil(-x).
+ Returns + an implementation-dependent approximation to the natural logarithm + of x.
++ If + x + is NaN, the result is NaN.
++ If + x + is less than 0, the result is NaN.
++ If + x + is +0 or −0, + the result is −∞.
++ If + x + is 1, the result is +0.
++ If + x + is +∞, + the result is +∞.
++ Given + zero or more arguments, calls ToNumber on each of the arguments and + returns the largest of the resulting values.
++ If + no arguments are given, the result is −∞.
++ If + any value is NaN, the result is NaN.
++ The + comparison of values to determine the largest value is done as in + 11.8.5 except that +0 is considered to be larger than −0.
+
+ The
+ length property of
+ the max method is
+ 2.
+ Given + zero or more arguments, calls ToNumber on each of the arguments and + returns the smallest of the resulting values.
++ If + no arguments are given, the result is +∞.
++ If + any value is NaN, the result is NaN.
++ The + comparison of values to determine the smallest value is done as in + 11.8.5 except that +0 is considered to be larger than −0.
+
+ The
+ length property of
+ the min method is
+ 2.
+ Returns + an implementation-dependent approximation to the result of raising x + to the power y.
++ If + y + is NaN, the result is NaN.
++ If + y + is +0, the result is 1, even if x + is NaN.
++ If + y + is −0, + the result is 1, even if x + is NaN.
++ If + x + is NaN and y + is nonzero, the result is NaN.
++ If + abs(x)>1 + and y + is +∞, + the result is +∞.
++ If + abs(x)>1 + and y + is −∞, + the result is +0.
++ If + abs(x)==1 + and y + is +∞, + the result is NaN.
++ If + abs(x)==1 + and y + is −∞, + the result is NaN.
++ If + abs(x)<1 + and y + is +∞, + the result is +0.
++ If + abs(x)<1 + and y + is −∞, + the result is +∞.
++ If + x + is +∞ + and y>0, + the result is +∞.
++ If + x + is +∞ + and y<0, + the result is +0.
++ If + x + is −∞ + and y>0 + and y + is an odd integer, the result is −∞.
++ If + x + is −∞ + and y>0 + and y + is not an odd integer, the result is +∞.
++ If + x + is −∞ + and y<0 + and y + is an odd integer, the result is −0.
++ If + x + is −∞ + and y<0 + and y + is not an odd integer, the result is +0.
++ If + x + is +0 and y>0, + the result is +0.
++ If + x + is +0 and y<0, + the result is +∞.
++ If + x + is −0 + and y>0 + and y + is an odd integer, the result is −0.
++ If + x + is −0 + and y>0 + and y + is not an odd integer, the result is +0.
++ If + x + is −0 + and y<0 + and y + is an odd integer, the result is −∞.
++ If + x + is −0 + and y<0 + and y + is not an odd integer, the result is +∞.
++ If + x<0 + and x + is finite and y + is finite and y + is not an integer, the result is NaN.
++ Returns + a Number value with positive sign, greater than or equal to 0 but + less than 1, chosen randomly or pseudo randomly with approximately + uniform distribution over that range, using an + implementation-dependent algorithm or strategy. This function takes + no arguments.
++ Returns + the Number value that is closest to x + and is equal to a mathematical integer. If two integer Number values + are equally close to x, + then the result is the Number value that is closer to +∞. + If x is already an + integer, the result is x.
++ If + x + is NaN, the result is NaN.
++ If + x + is +0, the result is +0.
++ If + x + is −0, + the result is −0.
++ If + x + is +∞, + the result is +∞.
++ If + x + is −∞, + the result is −∞.
++ If + x + is greater than 0 but less than 0.5, the result is +0.
++ If + x + is less than 0 but greater than or equal to -0.5, the result is −0.
+NOTE 1 Math.round(3.5)
+ returns 4, but
+ Math.round(–3.5)
+ returns –3.
NOTE 2 The value of Math.round(x)
+ is the same as the value of Math.floor(x+0.5),
+ except when x is
+ −0
+ or is less than 0
+ but greater than or equal to -0.5;
+ for these cases Math.round(x)
+ returns −0,
+ but Math.floor(x+0.5)
+ returns +0.
+ Returns + an implementation-dependent approximation to the sine of x. + The argument is expressed in radians.
++ If + x + is NaN, the result is NaN.
++ If + x + is +0, the result is +0.
++ If + x + is −0, + the result is −0.
++ If + x + is +∞ + or −∞, + the result is NaN.
++ Returns + an implementation-dependent approximation to the square root of x.
++ If + x + is NaN, the result is NaN.
++ If + x + is less than 0, the result is NaN.
++ If + x + is +0, the result is +0.
++ If + x + is −0, + the result is −0.
++ If + x + is +∞, + the result is +∞.
++ Returns + an implementation-dependent approximation to the tangent of x. + The argument is expressed in radians.
++ If + x + is NaN, the result is NaN.
++ If + x + is +0, the result is +0.
++ If + x + is −0, + the result is −0.
++ If + x + is +∞ + or −∞, + the result is NaN.
++ The + following functions are abstract operations that operate on time + values (defined in 15.9.1.1). Note that, in every case, if any + argument to one of these functions is NaN, the result will be + NaN.
++ A + Date object contains a Number indicating a particular instant in + time to within a millisecond. Such a Number is called a time + value. A time value may also be NaN, indicating that the + Date object does not represent a specific instant of time.
++ Time + is measured in ECMAScript in milliseconds since 01 January, 1970 + UTC. In time values leap seconds are ignored. It is assumed that + there are exactly 86,400,000 milliseconds per day. ECMAScript Number + values can represent all integers from –9,007,199,254,740,991 to + 9,007,199,254,740,991; this range suffices to measure times to + millisecond precision for any instant that is within approximately + 285,616 years, either forward or backward, from 01 January, 1970 + UTC.
++ The + actual range of times supported by ECMAScript Date objects is + slightly smaller: exactly –100,000,000 days to 100,000,000 days + measured relative to midnight at the beginning of 01 January, 1970 + UTC. This gives a range of 8,640,000,000,000,000 milliseconds to + either side of 01 January, 1970 UTC.
++ The + exact moment of midnight at the beginning of 01 January, 1970 UTC is + represented by the value +0.
++ A + given time value t belongs to day number
++ Day(t) + = floor(t / msPerDay)
++ where + the number of milliseconds per day is
++ msPerDay + = 86400000
++ The + remainder is called the time within the day:
++ TimeWithinDay(t) + = t modulo msPerDay
++ ECMAScript + uses an extrapolated Gregorian system to map a day number to a year + number and to determine the month and date within that year. In this + system, leap years are precisely those which are (divisible by 4) + and ((not divisible by 100) + or (divisible by 400)). + The number of days in year number y + is therefore defined by
+
+ DaysInYear(y)
+ = 365 if (y modulo 4) ≠
+ 0
= 366 if (y modulo 4) = 0 and (y modulo 100) ≠
+ 0
= 365 if (y modulo 100) = 0 and (y modulo 400) ≠
+ 0
= 366 if (y modulo 400) = 0
+ All + non-leap years have 365 + days with the usual number of days per month and leap years have an + extra day in February. The day number of the first day of year y + is given by:
++ DayFromYear(y) = + 365 × (y−1970) + + floor((y−1969)/4) − + floor((y−1901)/100) + + floor((y−1601)/400)
++ The + time value of the start of a year is:
++ TimeFromYear(y) = + msPerDay × DayFromYear(y)
++ A + time value determines a year by:
++ YearFromTime(t) = + the largest integer y (closest to positive infinity) such + that TimeFromYear(y) ≤ t
++ The + leap-year function is 1 for a time within a leap year and otherwise + is zero:
+
+ InLeapYear(t) =
+ 0 if DaysInYear(YearFromTime(t)) = 365
= 1 if
+ DaysInYear(YearFromTime(t)) = 366
+ Months + are identified by an integer in the range 0 + to 11, inclusive. The + mapping MonthFromTime(t) from a time value t to a + month number is defined by:
+
+ MonthFromTime(t) =
+ 0 if 0 ≤ DayWithinYear(t)
+ < 31
= 1 if 31 ≤
+ DayWithinYear (t) < 59+InLeapYear(t)
=
+ 2 if 59+InLeapYear(t) ≤
+ DayWithinYear (t) < 90+InLeapYear(t)
=
+ 3 if 90+InLeapYear(t) ≤
+ DayWithinYear (t) < 120+InLeapYear(t)
=
+ 4 if 120+InLeapYear(t) ≤
+ DayWithinYear (t) < 151+InLeapYear(t)
=
+ 5 if 151+InLeapYear(t) ≤
+ DayWithinYear (t) < 181+InLeapYear(t)
=
+ 6 if 181+InLeapYear(t) ≤
+ DayWithinYear (t) < 212+InLeapYear(t)
=
+ 7 if 212+InLeapYear(t) ≤
+ DayWithinYear (t) < 243+InLeapYear(t)
=
+ 8 if 243+InLeapYear(t) ≤
+ DayWithinYear (t) < 273+InLeapYear(t)
=
+ 9 if 273+InLeapYear(t) ≤
+ DayWithinYear (t) < 304+InLeapYear(t)
=
+ 10 if 304+InLeapYear(t) ≤
+ DayWithinYear (t) < 334+InLeapYear(t)
=
+ 11 if 334+InLeapYear(t) ≤
+ DayWithinYear (t) < 365+InLeapYear(t)
where
++ DayWithinYear(t) = + Day(t)−DayFromYear(YearFromTime(t))
++ A + month value of 0 + specifies January; 1 + specifies February; 2 + specifies March; 3 + specifies April; 4 specifies + May; 5 specifies June; 6 + specifies July; 7 + specifies August; 8 + specifies September; 9 + specifies October; 10 + specifies November; and 11 + specifies December. Note that MonthFromTime(0) + = 0, corresponding to Thursday, 01 January, 1970.
++ A + date number is identified by an integer in the range 1 + through 31, inclusive. + The mapping DateFromTime(t) from a time value t to a + month number is defined by:
+
+ DateFromTime(t) =
+ DayWithinYear(t)+1 if MonthFromTime(t)=0
=
+ DayWithinYear(t)−30 if
+ MonthFromTime(t)=1
= DayWithinYear(t)−58−InLeapYear(t) if
+ MonthFromTime(t)=2
= DayWithinYear(t)−89−InLeapYear(t) if
+ MonthFromTime(t)=3
=
+ DayWithinYear(t)−119−InLeapYear(t) if
+ MonthFromTime(t)=4
=
+ DayWithinYear(t)−150−InLeapYear(t) if
+ MonthFromTime(t)=5
=
+ DayWithinYear(t)−180−InLeapYear(t) if
+ MonthFromTime(t)=6
=
+ DayWithinYear(t)−211−InLeapYear(t) if
+ MonthFromTime(t)=7
=
+ DayWithinYear(t)−242−InLeapYear(t) if
+ MonthFromTime(t)=8
=
+ DayWithinYear(t)−272−InLeapYear(t) if
+ MonthFromTime(t)=9
=
+ DayWithinYear(t)−303−InLeapYear(t) if
+ MonthFromTime(t)=10
=
+ DayWithinYear(t)−333−InLeapYear(t) if
+ MonthFromTime(t)=11
+ The + weekday for a particular time value t + is defined as
++ WeekDay(t) + = (Day(t) + 4) modulo 7
++ A + weekday value of 0 + specifies Sunday; 1 + specifies Monday; 2 + specifies Tuesday; 3 + specifies Wednesday; 4 specifies + Thursday; 5 specifies + Friday; and 6 specifies + Saturday. Note that WeekDay(0) = + 4, corresponding to Thursday, 01 January, 1970.
++ An + implementation of ECMAScript is expected to determine the local time + zone adjustment. The local time zone adjustment is a value LocalTZA + measured in milliseconds which when added to UTC represents the + local standard time. Daylight saving time is not + reflected by LocalTZA. The value LocalTZA does not vary with time + but depends only on the geographic location.
++ An + implementation of ECMAScript is expected to determine the daylight + saving time algorithm. The algorithm to determine the daylight + saving time adjustment DaylightSavingTA(t), measured in + milliseconds, must depend only on four things:
++ (1) + the time since the beginning of the year
++ t + – TimeFromYear(YearFromTime(t))
++ (2) + whether t is in a + leap year
++ InLeapYear(t)
++ (3) + the week day of the beginning of the year
++ WeekDay(TimeFromYear(YearFromTime(t))
++ and + (4) the geographic location.
++ The + implementation of ECMAScript should not try to determine whether the + exact time was subject to daylight saving time, but just whether + daylight saving time would have been in effect if the current + daylight saving time algorithm had been used at the time. This + avoids complications such as taking into account the years that the + locale observed daylight saving time year round.
++ If + the host environment provides functionality for determining daylight + saving time, the implementation of ECMAScript is free to map the + year in question to an equivalent year (same leap-year-ness and same + starting week day for the year) for which the host environment + provides daylight saving time information. The only restriction is + that all equivalent years should produce the same result.
++ Conversion + from UTC to local time is defined by
++ LocalTime(t) + = t + LocalTZA + DaylightSavingTA(t)
++ Conversion + from local time to UTC is defined by
++ UTC(t) + = t – + LocalTZA – DaylightSavingTA(t + – LocalTZA)
++ Note + that UTC(LocalTime(t)) + is not necessarily always equal to t.
++ The + following functions are useful in decomposing time values:
++ HourFromTime(t) = + floor(t / msPerHour) modulo HoursPerDay
++ MinFromTime(t) = + floor(t / msPerMinute) modulo MinutesPerHour
++ SecFromTime(t) = + floor(t / msPerSecond) modulo SecondsPerMinute
++ msFromTime(t) = + t modulo msPerSecond
++ where
++ HoursPerDay = + 24
++ MinutesPerHour = + 60
++ SecondsPerMinute = + 60
++ msPerSecond = + 1000
++ msPerMinute = + 60000 = msPerSecond × + SecondsPerMinute
++ msPerHour = + 3600000 = msPerMinute × + MinutesPerHour
++ The + operator MakeTime calculates a number of milliseconds from its four + arguments, which must be ECMAScript Number values. This operator + functions as follows:
++ If + hour is not finite or min is not finite or sec + is not finite or ms is not finite, return NaN.
++ Let + h be ToInteger(hour).
++ Let + m be ToInteger(min).
++ Let + s be ToInteger(sec).
++ Let + milli be ToInteger(ms).
+
+ Let
+ t be h *
+ msPerHour + m
+ * msPerMinute +
+ s *
+ msPerSecond +
+ milli, performing the arithmetic according to IEEE 754 rules
+ (that is, as if using the ECMAScript operators *
+ and +).
+ Return + t.
++ The + operator MakeDay calculates a number of days from its three + arguments, which must be ECMAScript Number values. This operator + functions as follows:
++ If + year is not finite or month is not finite or date + is not finite, return NaN.
++ Let + y be ToInteger(year).
++ Let + m be ToInteger(month).
++ Let + dt be ToInteger(date).
++ Let + ym be y + floor(m /12).
++ Let + mn be m modulo 12.
+
+ Find
+ a value t such that YearFromTime(t) ==
+ ym and MonthFromTime(t) ==
+ mn) and DateFromTime(t) ==
+ 1; but if this is not possible (because some argument is out of
+ range), return NaN.
+ Return + Day(t) + dt − 1.
++ The + operator MakeDate calculates a number of milliseconds from its two + arguments, which must be ECMAScript Number values. This operator + functions as follows:
++ If + day is not finite or time is not finite, return NaN.
++ Return + day × msPerDay + time.
++ The + operator TimeClip calculates a number of milliseconds from its + argument, which must be an ECMAScript Number value. This operator + functions as follows:
++ If + time is not finite, return NaN.
++ If + abs(time) > 8.64 x 1015, + return NaN.
++ Return + an implementation-dependent choice of either ToInteger(time) + or ToInteger(time) + (+0). (Adding a positive zero + converts −0 to + +0.)
++
NOTE The point of + step 3 is that an implementation is permitted a choice of internal + representations of time values, for example as a 64-bit signed + integer or as a 64-bit floating-point value. Depending on the + implementation, this internal representation may or may not + distinguish −0 and + +0.
+
+ ECMAScript
+ defines a string interchange format for date-times based upon a
+ simplification of the ISO 8601 Extended Format. The format is as
+ follows: YYYY-MM-DDTHH:mm:ss.sssZ
+ Where + the fields are as follows:
+YYYY | is the decimal digits of the year in the Gregorian calendar. |
- | “:” (hyphen) appears literally twice in the string. |
MM | is the month of the year from 01 (January) to 12 (December). |
DD | is the day of the month from 01 to 31. |
T | “T” appears literally in the string, to indicate the beginning of the time element. |
HH | is the number of complete hours that have passed since midnight as two decimal digits. |
: | “:” (colon) appears literally twice in the string. |
mm | is the number of complete minutes since the start of the hour as two decimal digits. |
ss | is the number of complete seconds since the start of the minute as two decimal digits. |
. | “.” (dot) appears literally in the string. |
sss | is the number of complete milliseconds since the start of the second as three decimal digits. |
Z | is the time zone offset specified as “Z” (for UTC) or either
+ “+” or “-” followed by a time expression hh:mm |
This + format includes date-only forms:
+YYYY
YYYY-MM
YYYY-MM-DD
It also includes “date-time” forms that consist of one of the above
+date-only forms immediately followed by “T”
+and one of the following time forms with an optional time zone offset
+appended:
+ THH:mm
THH:mm:ss
THH:mm:ss.sss
All
+ numbers must be base 10.
+If the MM or DD fields are absent
+“01” is used as the value. If the mm or
+ss fields are absent “00” is used as the value
+and the value of an absent sss file is “000”. The
+value of an absent time zone offset is “Z”.
+ Illegal + values (out-of-bounds as well as syntax errors) in a format string + means that the format string is not a valid instance of this format.
+NOTE 1 As every day both starts and ends with
+ midnight, the two notations 00:00
+ and 24:00
+ are available to distinguish the two midnights that can be
+ associated with one date. This means that the following two
+ notations refer to exactly the same point in time: 1995-02-04T24:00
+ and 1995-02-05T00:00
NOTE 2 There exists no international standard that + specifies abbreviations for civil time zones like CET, EST, etc. and + sometimes the same abbreviation is even used for two very different + time zones. For this reason, ISO 8601 and this format specifies + numeric representations of date and time.
++ ECMAScript + requires the ability to specify 6 + digit years (extended years); approximately 285,616 + years, either forward or backward, from 01 January, 1970 UTC. To + represent years before 0 + or after 9999, ISO 8601 + permits the expansion of the year representation, but only by prior + agreement between the sender and the receiver. In the simplified + ECMAScript format such an expanded year representation shall have 2 + extra year digits and is always prefixed with a + or – sign. The + year 0 is considered + positive and hence prefixed with a + sign.
+
+ When
+ Date is called as
+ a function rather than as a constructor, it returns a String
+ representing the current time (UTC).
NOTE The
+ function call Date(…)
+ is not equivalent to the object creation expression new Date(…)
+ with the same arguments.
+ All
+ of the arguments are optional; any arguments supplied are accepted
+ but are completely ignored. A String is created and returned as if
+ by the expression (new
+ Date()).toString() where Date
+ is the standard built-in constructor with that name and toString
+ is the standard built-in method Date.prototype.toString.
+ When
+ Date is called as
+ part of a new
+ expression, it is a constructor: it initialises the newly created
+ object.
+ When + Date is called with two to seven arguments, it computes the + date from year, month, and (optionally) date, + hours, minutes, seconds and ms.
+
+ The
+ [[Prototype]] internal property of the newly constructed object is
+ set to the original Date prototype object, the one that is the
+ initial value of Date.prototype
+ (15.9.4.1).
+ The
+ [[Class]] internal property of the newly constructed object is set
+ to "Date".
+ The + [[Extensible]] internal property of the newly constructed object is + set to true.
++ The + [[PrimitiveValue]] internal property of the newly constructed object + is set as follows:
++ Let + y be ToNumber(year).
++ Let + m be ToNumber(month).
++ If + date is supplied then let dt be ToNumber(date); + else let dt be 1.
++ If + hours is supplied then let h be ToNumber(hours); + else let h be 0.
++ If + minutes is supplied then let min be + ToNumber(minutes); else let min be 0.
++ If + seconds is supplied then let s be ToNumber(seconds); + else let s be 0.
++ If + ms is supplied then let milli be ToNumber(ms); + else let milli be 0.
++ If y is not NaN and 0 ≤ ToInteger(y) ≤ 99, then + let yr be 1900+ToInteger(y); otherwise, let yr + be y.
++ Let + finalDate be MakeDate(MakeDay(yr, m, dt), + MakeTime(h, min, s, milli)).
++ Set + the [[PrimitiveValue]] internal property of the newly constructed + object to TimeClip(UTC(finalDate)).
+
+ The
+ [[Prototype]] internal property of the newly constructed object is
+ set to the original Date prototype object, the one that is the
+ initial value of Date.prototype
+ (15.9.4.1).
+ The
+ [[Class]] internal property of the newly constructed object is set
+ to "Date".
+ The + [[Extensible]] internal property of the newly constructed object is + set to true.
++ The + [[PrimitiveValue]] internal property of the newly constructed object + is set as follows:
++ Let + v be ToPrimitive(value).
++ If + Type(v) is String, then +
+
+ Parse
+ v as a date, in exactly the same manner as for the parse
+ method (15.9.4.2); let V be the time value for this date.
+ Else, + let V be ToNumber(v).
++ Set + the [[PrimitiveValue]] internal property of the newly constructed + object to TimeClip(V) and return.
+
+ The
+ [[Prototype]] internal property of the newly constructed object is
+ set to the original Date prototype object, the one that is the
+ initial value of Date.prototype
+ (15.9.4.1).
+ The
+ [[Class]] internal property of the newly constructed object is set
+ to "Date".
+ The + [[Extensible]] internal property of the newly constructed object is + set to true.
++ The + [[PrimitiveValue]] internal property of the newly constructed object + is set to the time value (UTC) identifying the current time.
++ The + value of the [[Prototype]] internal property of the Date constructor + is the Function prototype object (15.3.4).
+
+ Besides
+ the internal properties and the length
+ property (whose value is 7),
+ the Date constructor has the following properties:
+ The
+ initial value of Date.prototype
+ is the built-in Date prototype object (15.9.5).
+ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+
+ The
+ parse function
+ applies the ToString operator to its argument and interprets the
+ resulting String as a date and time; it returns a Number, the UTC
+ time value corresponding to the date and time. The String may be
+ interpreted as a local time, a UTC time, or a time in some other
+ time zone, depending on the contents of the String. The function
+ first attempts to parse the format of the String according to the
+ rules called out in Date Time String Format (15.9.1.15). If the
+ String does not conform to that format the function may fall back to
+ any implementation-specific heuristics or implementation-specific
+ date formats. Unrecognizable Strings or dates containing illegal
+ element values in the format String shall cause Date.parse
+ to return NaN.
If + x is any Date + object whose milliseconds amount is zero within a particular + implementation of ECMAScript, then all of the following expressions + should produce the same numeric value in that implementation, if all + the properties referenced have their initial values:
+
+ x.valueOf()
+ Date.parse(x.toString())
+ Date.parse(x.toUTCString())
+ Date.parse(x.toISOString())
However, + the expression
+
+ Date.parse( x.toLocaleString())
+ is
+ not required to produce the same Number value as the preceding three
+ expressions and, in general, the value produced by Date.parse
+ is implementation-dependent when given any String value that does
+ not conform to the Date Time String Format (15.9.1.15) and that
+ could not be produced in that implementation by the toString
+ or toUTCString
+ method.
+ When
+ the UTC function
+ is called with fewer than two arguments, the behaviour is
+ implementation-dependent. When the UTC
+ function is called with two to seven arguments, it computes the date
+ from year, month
+ and (optionally) date,
+ hours, minutes,
+ seconds and ms.
+ The following steps are taken:
+ Let + y be ToNumber(year).
++ Let + m be ToNumber(month).
++ If + date is supplied then let dt be ToNumber(date); + else let dt be 1.
++ If + hours is supplied then let h be ToNumber(hours); + else let h be 0.
++ If + minutes is supplied then let min be + ToNumber(minutes); else let min be 0.
++ If + seconds is supplied then let s be ToNumber(seconds); + else let s be 0.
++ If + ms is supplied then let milli be ToNumber(ms); + else let milli be 0.
++ If y is not NaN and 0 ≤ ToInteger(y) ≤ 99, then + let yr be 1900+ToInteger(y); otherwise, let yr + be y.
++ Return + TimeClip(MakeDate(MakeDay(yr, m, dt), + MakeTime(h, min, s, milli))).
+
+ The
+ length property of
+ the UTC function
+ is 7.
NOTE The
+ UTC function differs from
+ the Date constructor in
+ two ways: it returns a time value as a Number, rather than creating
+ a Date object, and it interprets the arguments in UTC rather than as
+ local time.
+ The
+ now function
+ return a Number value that is the time value designating the UTC
+ date and time of the occurrence of the call to now.
+ The
+ Date prototype object is itself a Date object (its [[Class]] is
+ "Date")
+ whose [[PrimitiveValue]] is NaN.
+ The + value of the [[Prototype]] internal property of the Date prototype + object is the standard built-in Object prototype object (15.2.4).
+
+ In
+ following descriptions of functions that are properties of the Date
+ prototype object, the phrase “this Date object” refers to the
+ object that is the this value for the invocation of the
+ function. Unless explicitly noted otherwise, none of these functions
+ are generic; a TypeError exception is thrown if the this
+ value is not an object for which the value of the [[Class]] internal
+ property is "Date".
+ Also, the phrase “this time value” refers to the Number value
+ for the time represented by this Date object, that is, the value of
+ the [[PrimitiveValue]] internal property of this Date object.
+ The
+ initial value of Date.prototype.constructor
+ is the built-in Date
+ constructor.
+ This + function returns a String value. The contents of the String are + implementation-dependent, but are intended to represent the Date in + the current time zone in a convenient, human-readable form.
+NOTE For
+ any Date value d
+ whose milliseconds amount is zero, the result of
+ Date.parse(d.toString())
+ is equal to d.valueOf().
+ See 15.9.4.2.
+ This + function returns a String value. The contents of the String are + implementation-dependent, but are intended to represent the “date” + portion of the Date in the current time zone in a convenient, + human-readable form.
++ This + function returns a String value. The contents of the String are + implementation-dependent, but are intended to represent the “time” + portion of the Date in the current time zone in a convenient, + human-readable form.
++ This + function returns a String value. The contents of the String are + implementation-dependent, but are intended to represent the Date in + the current time zone in a convenient, human-readable form that + corresponds to the conventions of the host environment’s current + locale.
+NOTE The + first parameter to this function is likely to be used in a future + version of this standard; it is recommended that implementations do + not use this parameter position for anything else.
++ This + function returns a String value. The contents of the String are + implementation-dependent, but are intended to represent the “date” + portion of the Date in the current time zone in a convenient, + human-readable form that corresponds to the conventions of the host + environment’s current locale.
+NOTE The + first parameter to this function is likely to be used in a future + version of this standard; it is recommended that implementations do + not use this parameter position for anything else.
++ This + function returns a String value. The contents of the String are + implementation-dependent, but are intended to represent the “time” + portion of the Date in the current time zone in a convenient, + human-readable form that corresponds to the conventions of the host + environment’s current locale.
+NOTE The + first parameter to this function is likely to be used in a future + version of this standard; it is recommended that implementations do + not use this parameter position for anything else.
+
+ The
+ valueOf function
+ returns a Number, which is this time value.
+ Return + this time value.
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + YearFromTime(LocalTime(t)).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + YearFromTime(t).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + MonthFromTime(LocalTime(t)).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + MonthFromTime(t).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + DateFromTime(LocalTime(t)).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + DateFromTime(t).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + WeekDay(t).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + HourFromTime(LocalTime(t)).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + HourFromTime(t).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + MinFromTime(LocalTime(t)).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + MinFromTime(t).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + SecFromTime(LocalTime(t)).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + SecFromTime(t).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + msFromTime(LocalTime(t)).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + msFromTime(t).
++ Returns + the difference between local time and UTC time in minutes.
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + (t − LocalTime(t)) + / msPerMinute.
++ Set + the [[PrimitiveValue]] internal property of this Date object to v.
++ Return + v.
++ Let + t be the result of LocalTime(this time value).
++ Let + time be MakeTime(HourFromTime(t), MinFromTime(t), + SecFromTime(t), ToNumber(ms)).
++ Set + the [[PrimitiveValue]] internal property of this Date object to u.
++ Return + u.
++ Let + t be this time value.
++ Let + time be MakeTime(HourFromTime(t), MinFromTime(t), + SecFromTime(t), ToNumber(ms)).
++ Set + the [[PrimitiveValue]] internal property of this Date object to v.
++ Return + v.
+
+ If ms
+ is not specified, this behaves as if ms
+ were specified with the value getMilliseconds().
+ Let + t be the result of LocalTime(this time value).
++ Let + s be ToNumber(sec).
++ If + ms is not specified, then let milli be msFromTime(t); + otherwise, let milli be ToNumber(ms).
++ Let + date be MakeDate(Day(t), MakeTime(HourFromTime(t), + MinFromTime(t), s, milli)).
++ Set + the [[PrimitiveValue]] internal property of this Date object to u.
++ Return + u.
+
+ The
+ length property of
+ the setSeconds
+ method is 2.
+ If ms
+ is not specified, this behaves as if ms
+ were specified with the value getUTCMilliseconds().
+ Let + t be this time value.
++ Let + s be ToNumber(sec).
++ If + ms is not specified, then let milli be msFromTime(t); + otherwise, let milli be ToNumber(ms).
++ Let + date be MakeDate(Day(t), MakeTime(HourFromTime(t), + MinFromTime(t), s, milli)).
++ Let + v be TimeClip(date).
++ Set + the [[PrimitiveValue]] internal property of this Date object to v.
++ Return + v.
+
+ The
+ length property of
+ the setUTCSeconds
+ method is 2.
+ If
+ sec is not
+ specified, this behaves as if sec
+ were specified with the value getSeconds().
+ If ms
+ is not specified, this behaves as if ms
+ were specified with the value getMilliseconds().
+ Let + t be the result of LocalTime(this time value).
++ Let + m be ToNumber(min).
++ If + sec is not specified, then let s be SecFromTime(t); + otherwise, let s be ToNumber(sec).
++ If + ms is not specified, then let milli be msFromTime(t); + otherwise, let milli be ToNumber(ms).
++ Let + date be MakeDate(Day(t), MakeTime(HourFromTime(t), + m, s, milli)).
++ Set + the [[PrimitiveValue]] internal property of this Date object to u.
++ Return + u.
+
+ The
+ length property of
+ the setMinutes
+ method is 3.
+ If
+ sec is not
+ specified, this behaves as if sec
+ were specified with the value getUTCSeconds().
+ If ms
+ is not specified, this function behaves as if ms
+ were specified with the value return by getUTCMilliseconds().
+ Let + t be this time value.
++ Let + m be ToNumber(min).
++ If + sec is not specified, then let s be SecFromTime(t); + otherwise, let s be ToNumber(sec).
++ If + ms is not specified, then let milli be msFromTime(t); + otherwise, let milli be ToNumber(ms).
++ Let + date be MakeDate(Day(t), MakeTime(HourFromTime(t), + m, s, milli)).
++ Let + v be TimeClip(date).
++ Set + the [[PrimitiveValue]] internal property of this Date object to v.
++ Return + v.
+
+ The
+ length property of
+ the setUTCMinutes
+ method is 3.
+ If
+ min is not
+ specified, this behaves as if min
+ were specified with the value getMinutes().
+ If
+ sec is not
+ specified, this behaves as if sec
+ were specified with the value getSeconds().
+ If ms
+ is not specified, this behaves as if ms
+ were specified with the value getMilliseconds().
+ Let + t be the result of LocalTime(this time value).
++ Let + h be ToNumber(hour).
++ If + min is not specified, then let m be MinFromTime(t); + otherwise, let m be ToNumber(min).
++ If + If sec is not specified, then let s be + SecFromTime(t); otherwise, let s be ToNumber(sec).
++ If + ms is not specified, then let milli be msFromTime(t); + otherwise, let milli be ToNumber(ms).
++ Let + date be MakeDate(Day(t), MakeTime(h, m, + s, milli)).
++ Set + the [[PrimitiveValue]] internal property of this Date object to u.
++ Return + u.
+
+ The
+ length property of
+ the setHours
+ method is 4.
+ If
+ min is not
+ specified, this behaves as if min
+ were specified with the value getUTCMinutes().
+ If
+ sec is not
+ specified, this behaves as if sec
+ were specified with the value getUTCSeconds().
+ If ms
+ is not specified, this behaves as if ms
+ were specified with the value getUTCMilliseconds().
+ Let + t be this time value.
++ Let + h be ToNumber(hour).
++ If + min is not specified, then let m be MinFromTime(t); + otherwise, let m be ToNumber(min).
++ If + sec is not specified, then let s be SecFromTime(t); + otherwise, let s be ToNumber(sec).
++ If + ms is not specified, then let milli be msFromTime(t); + otherwise, let milli be ToNumber(ms).
++ Let + newDate be MakeDate(Day(t), MakeTime(h, m, + s, milli)).
++ Let + v be TimeClip(newDate).
++ Set + the [[PrimitiveValue]] internal property of this Date object to v.
++ Return + v.
+
+ The
+ length property of
+ the setUTCHours
+ method is 4.
+ Let + t be the result of LocalTime(this time value).
++ Let + dt be ToNumber(date).
++ Let + newDate be MakeDate(MakeDay(YearFromTime(t), + MonthFromTime(t), dt), TimeWithinDay(t)).
++ Set + the [[PrimitiveValue]] internal property of this Date object to u.
++ Return + u.
++ Let + t be this time value.
++ Let + dt be ToNumber(date).
++ Let + newDate be MakeDate(MakeDay(YearFromTime(t), + MonthFromTime(t), dt), TimeWithinDay(t)).
++ Let + v be TimeClip(newDate).
++ Set + the [[PrimitiveValue]] internal property of this Date object to v.
++ Return + v.
+
+ If
+ date is not
+ specified, this behaves as if date
+ were specified with the value getDate().
+ Let + t be the result of LocalTime(this time value).
++ Let + m be ToNumber(month).
++ If + date is not specified, then let dt be + DateFromTime(t); otherwise, let dt be ToNumber(date).
++ Let + newDate be MakeDate(MakeDay(YearFromTime(t), m, + dt), TimeWithinDay(t)).
++ Set + the [[PrimitiveValue]] internal property of this Date object to u.
++ Return + u.
+
+ The
+ length property of
+ the setMonth
+ method is 2.
+ If
+ date is not
+ specified, this behaves as if date
+ were specified with the value getUTCDate().
+ Let + t be this time value.
++ Let + m be ToNumber(month).
++ If + date is not specified, then let dt be + DateFromTime(t); otherwise, let dt be ToNumber(date).
++ Let + newDate be MakeDate(MakeDay(YearFromTime(t), m, + dt), TimeWithinDay(t)).
++ Let + v be TimeClip(newDate).
++ Set + the [[PrimitiveValue]] internal property of this Date object to v.
++ Return + v.
+
+ The
+ length property of
+ the setUTCMonth
+ method is 2.
+ If
+ month is not
+ specified, this behaves as if month
+ were specified with the value getMonth().
+ If
+ date is not
+ specified, this behaves as if date
+ were specified with the value getDate().
+ Let + t be the result of LocalTime(this time value); but if this time value is NaN, let t be +0.
++ Let + y be ToNumber(year).
++ If + month is not specified, then let m be + MonthFromTime(t); otherwise, let m be + ToNumber(month).
++ If + date is not specified, then let dt be + DateFromTime(t); otherwise, let dt be ToNumber(date).
++ Let + newDate be MakeDate(MakeDay(y, m, dt), + TimeWithinDay(t)).
++ Set + the [[PrimitiveValue]] internal property of this Date object to u.
++ Return + u.
+
+ The
+ length property of
+ the setFullYear
+ method is 3.
+ If
+ month is not
+ specified, this behaves as if month
+ were specified with the value getUTCMonth().
+ If
+ date is not
+ specified, this behaves as if date
+ were specified with the value getUTCDate().
+ Let + t be this time value; but if this time value is NaN, + let t be +0.
++ Let + y be ToNumber(year).
++ If + month is not specified, then let m be + MonthFromTime(t); otherwise, let m be + ToNumber(month).
++ If + date is not specified, then let dt be + DateFromTime(t); otherwise, let dt be ToNumber(date).
++ Let + newDate be MakeDate(MakeDay(y, m, dt), + TimeWithinDay(t)).
++ Let + v be TimeClip(newDate).
++ Set + the [[PrimitiveValue]] internal property of this Date object to v.
++ Return + v.
+
+ The
+ length property of
+ the setUTCFullYear
+ method is 3.
+ This + function returns a String value. The contents of the String are + implementation-dependent, but are intended to represent the Date in + a convenient, human-readable form in UTC.
+NOTE The
+ intent is to produce a String representation of a date that is more
+ readable than the format specified in 15.9.1.15. It is not essential
+ that the chosen format be unambiguous or easily machine parsable. If
+ an implementation does not have a preferred human-readable format it
+ is recommended to use the format defined in 15.9.1.15 but with a
+ space rather than a “T”
+ used to separate the date and time elements.
+ This + function returns a String value represent the instance in time + represented by this Date object. The format of the String is the + Date Time string format defined in 15.9.1.15. All fields are present + in the String. The time zone is always UTC, denoted by the suffix Z. + If the time value of this object is not a finite Number a RangeError + exception is thrown.
+
+ This
+ function provides a String representation of a Date object for use
+ by JSON.stringify
+ (15.12.3).
+ When
+ the toJSON method
+ is called with argument key,
+ the following steps are taken:
+ Let + O be the result of calling ToObject, giving it the this + value as its argument.
++ Let + tv be ToPrimitive(O, hint Number).
++ If + tv is a Number and is not finite, return null.
+
+ Let
+ toISO be the result of calling the [[Get]] internal method
+ of O with argument "toISOString".
+ If + IsCallable(toISO) is false, throw a TypeError + exception.
++ Return + the result of calling the [[Call]] internal method of toISO + with O as the this value and an empty argument list.
+NOTE 1 The argument is ignored.
+NOTE 2 The toJSON
+ function is intentionally generic; it does not require that its this
+ value be a Date object. Therefore, it can be transferred to other
+ kinds of objects for use as a method. However, it does require that
+ any such object have a toISOString
+ method. An object is free to use the argument key
+ to filter its stringification.
+
+ Date
+ instances inherit properties from the Date prototype object and
+ their [[Class]] internal property value is "Date".
+ Date instances also have a [[PrimitiveValue]] internal property.
+ The + [[PrimitiveValue]] internal property is time value represented by + this Date object.
++ A + RegExp object contains a regular expression and the associated + flags.
+NOTE The + form and functionality of regular expressions is modelled after the + regular expression facility in the Perl 5 programming language.
+
+ The
+ RegExp constructor
+ applies the following grammar to the input pattern String. An error
+ occurs if the grammar cannot interpret the String as an expansion of
+ Pattern.
+ Syntax
++ Pattern ::
++ Disjunction
++ Disjunction ::
+
+ Alternative
+ Alternative | Disjunction
+ Alternative ::
+
+ [empty]
Alternative
+ Term
+ Term ::
+
+ Assertion
Atom
Atom
+ Quantifier
+ Assertion ::
+
+ ^ $ \
+ b \
+ B
+
(?
+ =
+ Disjunction ) (
+ ?
+ !
+ Disjunction )
+ Quantifier ::
+
+ QuantifierPrefix
QuantifierPrefix
+ ?
+ QuantifierPrefix ::
+
+ *
+? { DecimalDigits } { DecimalDigits
+ ,
+ } { DecimalDigits
+ , DecimalDigits }
+ Atom ::
+
+ PatternCharacter.\
+ AtomEscape
CharacterClass
() (
+ ?
+ :
+ Disjunction )
+ PatternCharacter ::SourceCharacter but + not any + of:
+
+ ^ $
+ \ . * + ? ( ) [ ] { } |
+ AtomEscape ::
+
+ DecimalEscape
CharacterEscape
CharacterClassEscape
+ CharacterEscape ::
+
+ ControlEscapec
+ ControlLetter
HexEscapeSequence
UnicodeEscapeSequence
IdentityEscape
+ ControlEscape :: + one + of
+
+ f
+ n r t v
+ ControlLetter :: + one + of
+
+ a
+ b c d e f g h i j k l m n o p q r s t u v w x
+ y z
A B C D E F G H I J K L M N O P Q R S T
+ U V W X Y Z
+ IdentityEscape ::
+
+ SourceCharacter but
+ not
+ IdentifierPart
<ZWJ>
<ZWNJ>
+ DecimalEscape ::
++ DecimalIntegerLiteral [lookahead + ∉ + DecimalDigit]
++ CharacterClassEscape :: + one + of
+
+ d
+ D s S w W
+ CharacterClass ::
+
+ [
+ [lookahead
+ ∉
+ {^}]
+ ClassRanges
+ ] [
+ ^ ClassRanges
+ ]
+ ClassRanges ::
+
+ [empty]
NonemptyClassRanges
+ NonemptyClassRanges ::
+
+ ClassAtom
ClassAtom
+ NonemptyClassRangesNoDash
ClassAtom
+ - ClassAtom ClassRanges
+ NonemptyClassRangesNoDash ::
+
+ ClassAtom
ClassAtomNoDash
+ NonemptyClassRangesNoDash
ClassAtomNoDash
+ - ClassAtom ClassRanges
+ ClassAtom ::
+
+ -
ClassAtomNoDash
+ ClassAtomNoDash ::
+
+ SourceCharacter but
+ not one
+ of \ or ] or - \
+ ClassEscape
+ ClassEscape ::
+
+ DecimalEscapeb
CharacterEscape
+ A + regular expression pattern is converted into an internal procedure + using the process described below. An implementation is encouraged + to use more efficient algorithms than the ones listed below, as long + as the results are the same. The internal procedure is used as the + value of a RegExp object’s [[Match]] internal property.
++ The + descriptions below use the following variables:
++ Input + is the String being matched by the regular expression pattern. The + notation input[n] + means the nth + character of input, + where n can range + between 0 (inclusive) and InputLength + (exclusive).
++ InputLength + is the number of characters in the Input + String.
+
+ NcapturingParens
+ is the total number of left capturing parentheses (i.e. the total
+ number of times the Atom
+ :: (
+ Disjunction )
+ production is expanded) in the pattern. A left capturing
+ parenthesis is any (
+ pattern character that is matched by the (
+ terminal of the Atom
+ :: (
+ Disjunction )
+ production.
+ IgnoreCase
+ is the setting of the RegExp object's ignoreCase
+ property.
+ Multiline
+ is the setting of the RegExp object’s multiline
+ property.
+ Furthermore, + the descriptions below use the following internal data structures:
++ A + CharSet is a + mathematical set of characters.
++ A + State is an + ordered pair (endIndex, + captures) + where endIndex is + an integer and captures + is an internal array of NcapturingParens + values. States + are used to represent partial match states in the regular + expression matching algorithms. The endIndex + is one plus the index of the last input character matched so far by + the pattern, while captures + holds the results of capturing parentheses. The nth + element of captures + is either a String that represents the value obtained by the nth + set of capturing parentheses or undefined if the nth + set of capturing parentheses hasn’t been reached yet. Due to + backtracking, many States + may be in use at any time during the matching process.
++ A + MatchResult is + either a State or + the special token failure that indicates that the match + failed.
++ A + Continuation + procedure is an internal closure (i.e. an internal procedure with + some arguments already bound to values) that takes one State + argument and returns a MatchResult + result. If an internal closure references variables bound in the + function that creates the closure, the closure uses the values that + these variables had at the time the closure was created. The + Continuation + attempts to match the remaining portion (specified by the closure's + already-bound arguments) of the pattern against the input String, + starting at the intermediate state given by its State + argument. If the match succeeds, the Continuation + returns the final State + that it reached; if the match fails, the Continuation + returns failure.
++ A + Matcher procedure + is an internal closure that takes two arguments -- a State + and a Continuation + -- and returns a MatchResult + result. A Matcher + attempts to match a middle subpattern (specified by the closure's + already-bound arguments) of the pattern against the input String, + starting at the intermediate state given by its State + argument. The Continuation + argument should be a closure that matches the rest of the pattern. + After matching the subpattern of a pattern to obtain a new State, + the Matcher then + calls Continuation + on that new State + to test if the rest of the pattern can match as well. If it can, + the matcher returns the State + returned by Continuation; + if not, the Matcher + may try different choices at its choice points, repeatedly calling + Continuation + until it either succeeds or all possibilities have been exhausted.
++ An + AssertionTester + procedure is an internal closure that takes a State + argument and returns a Boolean result. The assertion tester tests a + specific condition (specified by the closure's already-bound + arguments) against the current place in the input String and + returns true if the condition matched or false if + not.
++ An + EscapeValue is + either a character or an integer. An EscapeValue + is used to denote the interpretation of a DecimalEscape + escape sequence: a character ch + means that the escape sequence is interpreted as the character ch, + while an integer n + means that the escape sequence is interpreted as a backreference to + the nth + set of capturing parentheses.
++ The + production Pattern + :: Disjunction + evaluates as follows:
++ Evaluate + Disjunction to obtain a Matcher m.
++ Return + an internal closure that takes two arguments, a String str + and an integer index, and performs the following:
++ Let + Input be the given String str. This variable will be + used throughout the algorithms in 15.10.2.
++ Let + InputLength be the length of Input. This variable + will be used throughout the algorithms in 15.10.2.
++ Let + c be a Continuation that always returns its State argument + as a successful MatchResult.
++ Let + cap be an internal array of NcapturingParens + undefined values, indexed 1 through NcapturingParens.
++ Let + x be the State (index, cap).
++ Call + m(x, c) and return its result.
+NOTE A
+ Pattern evaluates ("compiles") to an internal procedure
+ value. RegExp.prototype.exec
+ can then apply this procedure to a String and an offset within the
+ String to determine whether the pattern would match starting at
+ exactly that offset within the String, and, if it does match, what
+ the values of the capturing parentheses would be. The algorithms in
+ 15.10.2 are designed so that compiling a pattern may throw a
+ SyntaxError exception; on the other hand, once the pattern is
+ successfully compiled, applying its result internal procedure to
+ find a match in a String cannot throw an exception (except for any
+ host-defined exceptions that can occur anywhere such as
+ out-of-memory).
+ The + production Disjunction + :: Alternative + evaluates by evaluating Alternative + to obtain a Matcher + and returning that Matcher.
+
+ The
+ production Disjunction
+ :: Alternative
+ | Disjunction
+ evaluates as follows:
+ Evaluate + Alternative to obtain a Matcher m1.
++ Evaluate + Disjunction to obtain a Matcher m2.
++ Return + an internal Matcher closure that takes two arguments, a State x + and a Continuation c, and performs the following:
++ Call + m1(x, c) and let r be its result.
++ If + r isn't failure, return r.
++ Call + m2(x, c) and return its result.
++
NOTE The
+ | regular
+ expression operator separates two alternatives. The pattern first
+ tries to match the left Alternative
+ (followed by the sequel of the regular expression); if it fails, it
+ tries to match the right Disjunction
+ (followed by the sequel of the regular expression). If the left
+ Alternative, the
+ right Disjunction,
+ and the sequel all have choice points, all choices in the sequel are
+ tried before moving on to the next choice in the left Alternative.
+ If choices in the left Alternative
+ are exhausted, the right Disjunction
+ is tried instead of the left Alternative.
+ Any capturing parentheses inside a portion of the pattern skipped by
+ | produce
+ undefined values instead of Strings. Thus, for example,
+ /a|ab/.exec("abc")
returns
+ the result "a"
+ and not "ab".
+ Moreover,
+ /((a)|(ab))((c)|(bc))/.exec("abc")
returns + the array
+
+ ["abc",
+ "a", "a", undefined, "bc", undefined,
+ "bc"]
and + not
+
+ ["abc",
+ "ab", undefined, "ab", "c", "c",
+ undefined]
+ The + production Alternative + :: [empty] + evaluates by returning a Matcher that takes two arguments, a State x + and a Continuation c, + and returns the result of calling c(x).
++ The + production Alternative + :: Alternative + Term evaluates as + follows:
++ Evaluate + Alternative to obtain a Matcher m1.
++ Evaluate + Term to obtain a Matcher m2.
++ Return + an internal Matcher closure that takes two arguments, a State x + and a Continuation c, and performs the following:
++ Create + a Continuation d that takes a State argument y and + returns the result of calling m2(y, c).
++ Call + m1(x, d) and return its result.
+NOTE Consecutive + Terms try to + simultaneously match consecutive portions of the input String. If + the left Alternative, + the right Term, + and the sequel of the regular expression all have choice points, all + choices in the sequel are tried before moving on to the next choice + in the right Term, + and all choices in the right Term + are tried before moving on to the next choice in the left + Alternative.
++ The + production Term :: + Assertion + evaluates by returning an internal Matcher closure that takes two + arguments, a State x + and a Continuation c, + and performs the following:
++ Evaluate + Assertion to obtain an AssertionTester t.
++ Call + t(x) and let r be the resulting Boolean value.
++ If + r is false, return failure.
++ Call + c(x) and return its result.
++ The + production Term :: + Atom evaluates + by evaluating Atom + to obtain a Matcher and returning that Matcher.
++ The + production Term :: + Atom + Quantifier + evaluates as follows:
++ Evaluate + Atom to obtain a Matcher m.
++ Evaluate + Quantifier to obtain the three results: an integer min, + an integer (or ∞) max, + and Boolean greedy.
++ If + max is finite and less than min, then throw a + SyntaxError exception.
+
+ Let
+ parenIndex be the number of left capturing parentheses in
+ the entire regular expression that occur to the left of this
+ production expansion's Term. This is the total number of
+ times the Atom :: (
+ Disjunction )
+ production is expanded prior to this production's Term plus
+ the total number of Atom :: (
+ Disjunction )
+ productions enclosing this Term.
+ Let
+ parenCount be the number of left capturing parentheses in
+ the expansion of this production's Atom. This is the total
+ number of Atom :: (
+ Disjunction )
+ productions enclosed by this production's Atom.
+ Return + an internal Matcher closure that takes two arguments, a State x + and a Continuation c, and performs the following:
++ Call + RepeatMatcher(m, min, max, greedy, + x, c, parenIndex, parenCount) and + return its result.
++ The + abstract operation RepeatMatcher takes eight parameters, a + Matcher m, an + integer min, an + integer (or ∞) max, + a Boolean greedy, + a State x, a + Continuation c, an + integer parenIndex, + and an integer parenCount, + and performs the following:
++ If + max is zero, then call c(x) and return its + result.
++ Create + an internal Continuation closure d that takes one State argument y and performs the following:
++ If + min is zero and y's endIndex is equal to + x's endIndex, then return failure.
++ If + min is zero then let min2 be zero; otherwise let + min2 be min–1.
++ If + max is ∞, then let + max2 be ∞; otherwise + let max2 be max–1.
++ Call + RepeatMatcher(m, min2, max2, greedy, + y, c, parenIndex, parenCount) and + return its result.
++ Let + cap be a fresh copy of x's captures internal + array.
++ For + every integer k that satisfies parenIndex < k + and k ≤ + parenIndex+parenCount, set cap[k] to + undefined.
++ Let + e be x's endIndex.
++ Let + xr be the State (e, cap).
++ If + min is not zero, then call m(xr, d) and + return its result.
++ If + greedy is false, then
++ Call + c(x) and let z be its result.
++ If + z is not failure, return z.
++ Call + m(xr, d) and return its result.
++ Call + m(xr, d) and let z be its result.
++ If + z is not failure, return z.
++ Call + c(x) and return its result.
+NOTE An + Atom followed by a + Quantifier is + repeated the number of times specified by the Quantifier. + A Quantifier can + be non-greedy, in which case the Atom + pattern is repeated as few times as possible while still matching + the sequel, or it can be greedy, in which case the Atom + pattern is repeated as many times as possible while still matching + the sequel. The Atom + pattern is repeated rather than the input String that it matches, so + different repetitions of the Atom + can match different input substrings.
+NOTE 2 If the Atom and + the sequel of the regular expression all have choice points, the + Atom is first + matched as many (or as few, if non-greedy) times as possible. All + choices in the sequel are tried before moving on to the next choice + in the last repetition of Atom. + All choices in the last (nth) repetition of Atom + are tried before moving on to the next choice in the next-to-last + (n–1)st repetition of Atom; + at which point it may turn out that more or fewer repetitions of + Atom are now + possible; these are exhausted (again, starting with either as few or + as many as possible) before moving on to the next choice in the + (n-1)st repetition of Atom + and so on.
+Compare
+
+ /a[a-z]{2,4}/.exec("abcdefghi")
which
+ returns "abcde"
+ with
+ /a[a-z]{2,4}?/.exec("abcdefghi")
which
+ returns "abc".
Consider + also
+
+ /(aa|aabaac|ba|b|c)*/.exec("aabaac")
which, + by the choice point ordering above, returns the array
+
+ ["aaba",
+ "ba"]
and + not any of:
+
+ ["aabaac",
+ "aabaac"]
+ ["aabaac",
+ "c"]
The + above ordering of choice points can be used to write a regular + expression that calculates the greatest common divisor of two + numbers (represented in unary notation). The following example + calculates the gcd of 10 and 15:
+
+ "aaaaaaaaaa,aaaaaaaaaaaaaaa".replace(/^(a+)\1*,\1+$/,"$1")
+ which
+ returns the gcd in unary notation "aaaaa".
NOTE 3 Step 4 of the RepeatMatcher clears Atom's + captures each time Atom + is repeated. We can see its behaviour in the regular expression
+
+ /(z)((a+)?(b+)?(c))*/.exec("zaacbbbcac")
which + returns the array
+
+ ["zaacbbbcac",
+ "z", "ac", "a", undefined, "c"]
and + not
+
+ ["zaacbbbcac",
+ "z", "ac", "a", "bbb", "c"]
+ because
+ each iteration of the outermost *
+ clears all captured Strings contained in the quantified Atom,
+ which in this case includes capture Strings numbered 2, 3, and 4.
NOTE 4 Step 1 of the RepeatMatcher's d + closure states that, once the minimum number of repetitions has been + satisfied, any more expansions of Atom + that match the empty String are not considered for further + repetitions. This prevents the regular expression engine from + falling into an infinite loop on patterns such as:
+
+ /(a*)*/.exec("b")
or + the slightly more complicated:
+
+ /(a*)b\1+/.exec("baaaac")
which + returns the array
+
+ ["b",
+ ""]
+ The
+ production Assertion
+ :: ^
+ evaluates by returning an internal AssertionTester closure that
+ takes a State argument x
+ and performs the following:
+ Let + e be x's endIndex.
++ If + e is zero, return true.
++ If + Multiline is false, return false.
++ If + the character Input[e–1] is one of LineTerminator, + return true.
++ Return + false.
+
+ The
+ production Assertion
+ :: $
+ evaluates by returning an internal AssertionTester closure that
+ takes a State argument x
+ and performs the following:
+ Let + e be x's endIndex.
++ If + e is equal to InputLength, return true.
++ If + multiline is false, return false.
++ If + the character Input[e] is one of LineTerminator, + return true.
++ Return + false.
+
+ The
+ production Assertion
+ :: \ b
+ evaluates by returning an internal AssertionTester closure that
+ takes a State argument x
+ and performs the following:
+ Let + e be x's endIndex.
++ Call + IsWordChar(e–1) and let a be the Boolean + result.
++ Call + IsWordChar(e) and let b be the Boolean result.
++ If + a is true and b is false, return true.
++ If + a is false and b is true, return true.
++ Return + false.
+
+ The
+ production Assertion
+ :: \ B
+ evaluates by returning an internal AssertionTester closure that
+ takes a State argument x
+ and performs the following:
+ Let + e be x's endIndex.
++ Call + IsWordChar(e–1) and let a be the Boolean + result.
++ Call + IsWordChar(e) and let b be the Boolean result.
++ If + a is true and b is false, return false.
++ If + a is false and b is true, return false.
++ Return + true.
+
+ The
+ production Assertion
+ :: ( ? = Disjunction
+ ) evaluates as follows:
+ Evaluate + Disjunction to obtain a Matcher m.
++ Return + an internal Matcher closure that takes two arguments, a State x + and a Continuation c, and performs the following steps:
++ Let + d be a Continuation that always returns its State argument as a successful MatchResult.
++ Call + m(x, d) and let r be its result.
++ If + r is failure, return failure.
++ Let + y be r's State.
++ Let + cap be y's captures internal array.
++ Let + xe be x's endIndex.
++ Let + z be the State (xe, cap).
++ Call + c(z) and return its result.
+
+ The
+ production Assertion ::
+ ( ? ! Disjunction
+ ) evaluates as follows:
+ Evaluate + Disjunction to obtain a Matcher m.
++ Return + an internal Matcher closure that takes two arguments, a State x + and a Continuation c, and performs the following steps:
++ Let + d be a Continuation that always returns its State argument as a successful MatchResult.
++ Call + m(x, d) and let r be its result.
++ If + r isn't failure, return failure.
++ Call + c(x) and return its result.
++ The + abstract operation IsWordChar + takes an integer parameter e + and performs the following:
++ If + e == –1 or e == InputLength, return false.
++ Let + c be the character Input[e].
++ If + c is one of the sixty-three characters below, return true.
+|
+
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+ + | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | +
+ Return + false.
++ The + production Quantifier + :: QuantifierPrefix + evaluates as follows:
++ Evaluate + QuantifierPrefix to obtain the two results: an integer min + and an integer (or ∞) max.
++ Return + the three results min , max, and true.
+
+ The
+ production Quantifier
+ :: QuantifierPrefix
+ ? evaluates as follows:
+ Evaluate + QuantifierPrefix to obtain the two results: an integer min + and an integer (or ∞) max.
++ Return + the three results min , max, and false.
+
+ The
+ production QuantifierPrefix
+ :: *
+ evaluates by returning the two results 0 and ∞.
+ The
+ production QuantifierPrefix
+ :: +
+ evaluates by returning the two results 1 and ∞.
+ The
+ production QuantifierPrefix
+ :: ?
+ evaluates by returning the two results 0 and 1.
+ The
+ production QuantifierPrefix
+ :: { DecimalDigits
+ } evaluates as follows:
+ The
+ production QuantifierPrefix
+ :: { DecimalDigits
+ , } evaluates as follows:
+ Let + i be the MV of DecimalDigits.
++ Return + the two results i and ∞.
+
+ The
+ production QuantifierPrefix
+ :: { DecimalDigits
+ , DecimalDigits
+ } evaluates as follows:
+ Let + i be the MV of the first DecimalDigits.
++ Let + j be the MV of the second DecimalDigits.
++ Return + the two results i and j.
++ The + production Atom :: + PatternCharacter + evaluates as follows:
++ Let + ch be the character represented by PatternCharacter.
++ Let + A be a one-element CharSet containing the character ch.
++ Call + CharacterSetMatcher(A, false) and return its + Matcher result.
+
+ The
+ production Atom ::
+ . evaluates as
+ follows:
+ Let + A be the set of all characters except LineTerminator.
++ Call + CharacterSetMatcher(A, false) and return its + Matcher result.
+
+ The
+ production Atom ::
+ \ AtomEscape
+ evaluates by evaluating AtomEscape
+ to obtain a Matcher and returning that Matcher.
+ The + production Atom :: + CharacterClass + evaluates as follows:
++ Evaluate + CharacterClass to obtain a CharSet A and a Boolean + invert.
++ Call + CharacterSetMatcher(A, invert) and return its + Matcher result.
+
+ The
+ production Atom ::
+ ( Disjunction
+ ) evaluates as follows:
+ Evaluate + Disjunction to obtain a Matcher m.
+
+ Let
+ parenIndex be the number of left capturing parentheses in
+ the entire regular expression that occur to the left of this
+ production expansion's initial left parenthesis. This is the total
+ number of times the Atom :: ( Disjunction )
+ production is expanded prior to this production's Atom plus
+ the total number of Atom :: ( Disjunction )
+ productions enclosing this Atom.
+ Return + an internal Matcher closure that takes two arguments, a State x + and a Continuation c, and performs the following steps:
++ Create + an internal Continuation closure d that takes one State argument y and performs the following steps:
++ Let + cap be a fresh copy of y's captures + internal array.
++ Let + xe be x's endIndex.
++ Let + ye be y's endIndex.
++ Let + s be a fresh String whose characters are the + characters of Input at positions xe (inclusive) + through ye (exclusive).
++ Set + cap[parenIndex+1] to s.
++ Let + z be the State (ye, cap).
++ Call + c(z) and return its result.
++ Call + m(x, d) and return its result.
+
+ The
+ production Atom ::
+ ( ? : Disjunction
+ ) evaluates by evaluating Disjunction
+ to obtain a Matcher and returning that Matcher.
+ The + abstract operation CharacterSetMatcher takes two arguments, a CharSet A + and a Boolean flag invert, + and performs the following:
++ Return + an internal Matcher closure that takes two arguments, a State x + and a Continuation c, and performs the following steps:
++ Let + e be x's endIndex.
++ If + e == InputLength, return failure.
++ Let + ch be the character Input[e].
++ Let + cc be the result of Canonicalize(ch).
++ If + invert is false, then
++ If + there does not exist a member a of set A such + that Canonicalize(a) == cc, return + failure.
++ Else + invert is true,
++ If + there exists a member a of set A such that + Canonicalize(a) == cc, return failure.
++ Let + cap be x's captures internal array.
++ Let + y be the State (e+1, cap).
++ Call + c(y) and return its result.
++ The + abstract operation Canonicalize takes a character parameter ch + and performs the following steps:
++ If + IgnoreCase is false, return ch.
+
+ Let
+ u be ch converted to upper case as if by calling the
+ standard built-in method String.prototype.toUpperCase
+ on the one-character String ch.
+ If + u does not consist of a single character, return ch.
++ Let + cu be u's character.
++ If + ch's code unit value is greater than or equal to decimal 128 + and cu's code unit value is less than decimal 128, then + return ch.
++ Return + cu.
+NOTE 1 Parentheses of the form (
+ Disjunction
+ ) serve both to group the components of the Disjunction
+ pattern together and to save the result of the match. The result can
+ be used either in a backreference (\
+ followed by a nonzero decimal number), referenced in a replace
+ String, or returned as part of an array from the regular expression
+ matching internal procedure. To inhibit the capturing behaviour of
+ parentheses, use the form (?:
+ Disjunction
+ ) instead.
NOTE 2 The form (?= Disjunction
+ ) specifies a zero-width positive lookahead. In order for
+ it to succeed, the pattern inside Disjunction
+ must match at the current position, but the current position is not
+ advanced before matching the sequel. If Disjunction
+ can match at the current position in several ways, only the first
+ one is tried. Unlike other regular expression operators, there is no
+ backtracking into a (?=
+ form (this unusual behaviour is inherited from Perl). This only
+ matters when the Disjunction
+ contains capturing parentheses and the sequel of the pattern
+ contains backreferences to those captures.
For + example,
+
+ /(?=(a+))/.exec("baaabac")
matches
+ the empty String immediately after the first b
+ and therefore returns the array:
+ ["",
+ "aaa"]
To + illustrate the lack of backtracking into the lookahead, consider:
+
+ /(?=(a+))a*b\1/.exec("baaabac")
This + expression returns
+
+ ["aba",
+ "a"]
and + not:
+
+ ["aaaba",
+ "a"]
NOTE 3 The form (?! Disjunction
+ ) specifies a zero-width negative lookahead. In order for
+ it to succeed, the pattern inside Disjunction
+ must fail to match at the current position. The current position is
+ not advanced before matching the sequel. Disjunction
+ can contain capturing parentheses, but backreferences to them only
+ make sense from within Disjunction
+ itself. Backreferences to these capturing parentheses from elsewhere
+ in the pattern always return undefined because the negative
+ lookahead must fail for the pattern to succeed. For example,
+ /(.*?)a(?!(a+)b\2c)\2(.*)/.exec("baaabaac")
looks
+ for an a not
+ immediately followed by some positive number n of a's,
+ a b, another n a's
+ (specified by the first \2)
+ and a c. The
+ second \2 is
+ outside the negative lookahead, so it matches against undefined
+ and therefore always succeeds. The whole expression returns the
+ array:
+ ["baaabaac",
+ "ba", undefined, "abaac"]
+ In
+ case-insignificant matches all characters are implicitly converted
+ to upper case immediately before they are compared. However, if
+ converting a character to upper case would expand that character
+ into more than one character (such as converting "ß"
+ (\u00DF)
+ into "SS"),
+ then the character is left as-is instead. The character is also left
+ as-is if it is not an ASCII character but converting it to upper
+ case would make it into an ASCII character. This prevents Unicode
+ characters such as \u0131
+ and \u017F
+ from matching regular expressions such as /[a z]/i,
+ which are only intended to match ASCII letters. Furthermore, if
+ these conversions were allowed, then /[^\W]/i
+ would match each of a,
+ b,
+ …, h,
+ but not i
+ or s.
+ The + production AtomEscape + :: DecimalEscape + evaluates as follows:
++ Evaluate + DecimalEscape to obtain an EscapeValue E.
++ If + E is a character, then
++ Let + ch be E's character.
++ Let + A be a one-element CharSet containing the character ch.
++ Call + CharacterSetMatcher(A, false) and return its + Matcher result.
++ E + must be an integer. Let n be that integer.
++ If + n=0 or n>NCapturingParens then throw a + SyntaxError exception.
++ Return + an internal Matcher closure that takes two arguments, a State x + and a Continuation c, and performs the following:
++ Let + cap be x's captures internal array.
++ Let + s be cap[n].
++ If + s is undefined, then call c(x) and + return its result.
++ Let + e be x's endIndex.
++ Let + len be s's length.
++ Let + f be e+len.
++ If + f>InputLength, return failure.
++ If + there exists an integer i between 0 (inclusive) and len + (exclusive) such that Canonicalize(s[i]) is + not the same character as Canonicalize(Input + [e+i]), then return failure.
++ Let + y be the State (f, cap).
++ Call + c(y) and return its result.
++ The + production AtomEscape + :: CharacterEscape + evaluates as follows:
++ Evaluate + CharacterEscape to obtain a character ch.
++ Let + A be a one-element CharSet containing the character ch.
++ Call + CharacterSetMatcher(A, false) and return its + Matcher result.
++ The + production AtomEscape + :: CharacterClassEscape + evaluates as follows:
++ Evaluate + CharacterClassEscape to obtain a CharSet A.
++ Call + CharacterSetMatcher(A, false) and return its + Matcher result.
+NOTE An
+ escape sequence of the form \
+ followed by a nonzero decimal number n
+ matches the result of the nth
+ set of capturing parentheses (see 15.10.2.11). It is an error if the
+ regular expression has fewer than n
+ capturing parentheses. If the regular expression has n
+ or more capturing parentheses but the nth
+ one is undefined because it has not captured anything, then
+ the backreference always succeeds.
+ The + production CharacterEscape + :: ControlEscape + evaluates by returning the character according to Table 23 +
+|
+ + ControlEscape + + + |
+
+ + Code + Unit + |
+
+ + Name + |
+
+ + Symbol + |
+
|
+
+ |
+
+
+ |
+
+ + horizontal + tab + |
+
+ + <HT> + |
+
|
+
+ |
+
+
+ |
+
+ + line + feed (new line) + |
+
+ + <LF> + |
+
|
+
+ |
+
+
+ |
+
+ + vertical + tab + |
+
+ + <VT> + |
+
|
+
+ |
+
+
+ |
+
+ + form + feed + |
+
+ + <FF> + |
+
|
+
+ |
+
+
+ |
+
+ + carriage + return + |
+
+ + <CR> + |
+
+ The
+ production CharacterEscape
+ :: c ControlLetter
+ evaluates as follows:
+ Let + ch be the character represented by ControlLetter.
++ Let + i be ch's code unit value.
++ Let + j be the remainder of dividing i by 32.
++ Return + the code unit numbered j.
++ The + production CharacterEscape + :: HexEscapeSequence + evaluates by evaluating the CV of the HexEscapeSequence + (see 7.8.4) and returning its character result.
++ The + production CharacterEscape + :: UnicodeEscapeSequence + evaluates by evaluating the CV of the UnicodeEscapeSequence + (see 7.8.4) and returning its character result.
++ The + production CharacterEscape + :: IdentityEscape + evaluates by returning the character represented by IdentityEscape.
++ The + production DecimalEscape + :: DecimalIntegerLiteral + [lookahead ∉ + DecimalDigit] + evaluates as follows.
++ Let + i be the MV of DecimalIntegerLiteral.
++ If + i is zero, return the EscapeValue consisting of a <NUL> + character (Unicode value 0000).
++ Return + the EscapeValue consisting of the integer i.
++ The + definition of “the MV of DecimalIntegerLiteral” + is in 7.8.3.
+NOTE If
+ \ is followed by a
+ decimal number n
+ whose first digit is not 0,
+ then the escape sequence is considered to be a backreference. It is
+ an error if n is
+ greater than the total number of left capturing parentheses in the
+ entire regular expression. \0
+ represents the <NUL> character and cannot be followed by a
+ decimal digit.
+ The
+ production CharacterClassEscape
+ :: d
+ evaluates by returning the ten-element set of characters containing
+ the characters 0
+ through 9
+ inclusive.
+ The
+ production CharacterClassEscape
+ :: D
+ evaluates by returning the set of all characters not included in the
+ set returned by CharacterClassEscape
+ :: d.
+ The
+ production CharacterClassEscape
+ :: s
+ evaluates by returning the set of characters containing the
+ characters that are on the right-hand side of the WhiteSpace
+ (7.2) or LineTerminator
+ (7.3) productions.
+ The
+ production CharacterClassEscape
+ :: S
+ evaluates by returning the set of all characters not included in the
+ set returned by CharacterClassEscape
+ :: s.
+ The
+ production CharacterClassEscape
+ :: w
+ evaluates by returning the set of characters containing the
+ sixty-three characters:
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+ + | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | +
+ The
+ production CharacterClassEscape
+ :: W
+ evaluates by returning the set of all characters not included in the
+ set returned by CharacterClassEscape
+ :: w.
+ The
+ production CharacterClass
+ :: [ [lookahead
+ ∉
+ {^}]
+ ClassRanges
+ ] evaluates by evaluating ClassRanges
+ to obtain a CharSet and returning that CharSet and the Boolean
+ false.
+ The
+ production CharacterClass
+ :: [ ^ ClassRanges
+ ] evaluates by evaluating ClassRanges
+ to obtain a CharSet and returning that CharSet and the Boolean true.
+ The
+ production ClassRanges
+ :: [empty]
+ evaluates by returning the empty CharSet.
+ The
+ production ClassRanges
+ :: NonemptyClassRanges
+ evaluates by evaluating NonemptyClassRanges
+ to obtain a CharSet and returning that CharSet.
+ The + production NonemptyClassRanges + :: ClassAtom + evaluates by evaluating ClassAtom + to obtain a CharSet and returning that CharSet.
++ The + production NonemptyClassRanges :: ClassAtom + NonemptyClassRangesNoDash evaluates as follows:
++ Evaluate + ClassAtom to obtain a CharSet A.
++ Evaluate + NonemptyClassRangesNoDash to obtain a CharSet B.
++ Return + the union of CharSets A and B.
+
+ The
+ production NonemptyClassRanges :: ClassAtom
+ - ClassAtom ClassRanges evaluates as follows:
+ Evaluate + the first ClassAtom to obtain a CharSet A.
++ Evaluate + the second ClassAtom to obtain a CharSet B.
++ Evaluate + ClassRanges to obtain a CharSet C.
++ Call + CharacterRange(A, B) and let D be the + resulting CharSet.
++ Return + the union of CharSets D and C.
++ The + abstract operation CharacterRange + takes two CharSet parameters A + and B and performs + the following:
++ If + A does not contain exactly one character or B does + not contain exactly one character then throw a SyntaxError + exception.
++ Let + a be the one character in CharSet A.
++ Let + b be the one character in CharSet B.
++ Let + i be the code unit value of character a.
++ Let + j be the code unit value of character b.
++ If + i > j then throw a SyntaxError exception.
++ Return + the set containing all characters numbered i through j, + inclusive.
++ The + production NonemptyClassRangesNoDash + :: ClassAtom + evaluates by evaluating ClassAtom + to obtain a CharSet and returning that CharSet.
++ The + production NonemptyClassRangesNoDash + :: ClassAtomNoDash + NonemptyClassRangesNoDash + evaluates as follows:
++ Evaluate + ClassAtomNoDash to obtain a CharSet A.
++ Evaluate + NonemptyClassRangesNoDash to obtain a CharSet B.
++ Return + the union of CharSets A and B.
+
+ The
+ production NonemptyClassRangesNoDash
+ :: ClassAtomNoDash
+ - ClassAtom
+ ClassRanges
+ evaluates as follows:
+ Evaluate + ClassAtomNoDash to obtain a CharSet A.
++ Evaluate + ClassAtom to obtain a CharSet B.
++ Evaluate + ClassRanges to obtain a CharSet C.
++ Call + CharacterRange(A, B) and let D be the + resulting CharSet.
++ Return + the union of CharSets D and C.
+NOTE 1 ClassRanges can
+ expand into single ClassAtoms
+ and/or ranges of two ClassAtoms
+ separated by dashes. In the latter case the ClassRanges
+ includes all characters between the first ClassAtom
+ and the second ClassAtom,
+ inclusive; an error occurs if either ClassAtom
+ does not represent a single character (for example, if one is \w)
+ or if the first ClassAtom's
+ code unit value is greater than the second ClassAtom's
+ code unit value.
NOTE 2 Even if the pattern ignores case, the case of the two ends of a
+ range is significant in determining which characters belong to the
+ range. Thus, for example, the pattern /[E-F]/i
+ matches only the letters E,
+ F, e,
+ and f, while the
+ pattern /[E-f]/i
+ matches all upper and lower-case ASCII letters as well as the
+ symbols [, \,
+ ], ^,
+ _, and `.
NOTE 3 A -
+ character can be treated literally or it can denote a range. It is
+ treated literally if it is the first or last character of
+ ClassRanges,
+ the beginning or end limit of a range specification, or immediately
+ follows a range specification.
+ The
+ production ClassAtom
+ :: -
+ evaluates by returning the CharSet containing the one character -.
+ The + production ClassAtom + :: ClassAtomNoDash + evaluates by evaluating ClassAtomNoDash + to obtain a CharSet and returning that CharSet.
+
+ The
+ production ClassAtomNoDash
+ :: SourceCharacter
+ but not one of \
+ or ] or -
+ evaluates by returning a one-element CharSet containing
+ the character represented by SourceCharacter.
+ The
+ production ClassAtomNoDash
+ :: \ ClassEscape
+ evaluates by evaluating ClassEscape
+ to obtain a CharSet and returning that CharSet.
+ The + production ClassEscape + :: DecimalEscape + evaluates as follows:
++ Evaluate + DecimalEscape to obtain an EscapeValue E.
++ If + E is not a character then throw a SyntaxError + exception.
++ Let + ch be E's character.
++ Return + the one-element CharSet containing the character ch.
+
+ The
+ production ClassEscape
+ :: b
+ evaluates by returning the CharSet containing the one character <BS>
+ (Unicode value 0008).
+ The + production ClassEscape + :: CharacterEscape + evaluates by evaluating CharacterEscape + to obtain a character and returning a one-element CharSet containing + that character.
++ The + production ClassEscape + :: CharacterClassEscape + evaluates by evaluating CharacterClassEscape + to obtain a CharSet and returning that CharSet.
+NOTE A
+ ClassAtom can use
+ any of the escape sequences that are allowed in the rest of the
+ regular expression except for \b,
+ \B, and
+ backreferences. Inside a CharacterClass,
+ \b means the
+ backspace character, while \B
+ and backreferences raise errors. Using a backreference inside a
+ ClassAtom causes
+ an error.
+ If
+ pattern is an
+ object R whose
+ [[Class]] internal property is "RegExp"
+ and flags is
+ undefined, then return R
+ unchanged. Otherwise call the standard built-in RegExp
+ constructor (15.10.4.1) as if by the expression new
+ RegExp( pattern,
+ flags)
+ and return the object constructed by that constructor.
+ When
+ RegExp is called
+ as part of a new
+ expression, it is a constructor: it initialises the newly created
+ object.
+ If
+ pattern is an
+ object R whose
+ [[Class]] internal property is "RegExp"
+ and flags is
+ undefined, then let P
+ be the pattern
+ used to construct R
+ and let F be the
+ flags used to construct R.
+ If pattern is an
+ object R whose
+ [[Class]] internal property is "RegExp"
+ and flags is not
+ undefined, then throw a TypeError exception.
+ Otherwise, let P
+ be the empty String if pattern
+ is undefined and ToString(pattern)
+ otherwise, and let F
+ be the empty String if flags
+ is undefined and ToString(flags)
+ otherwise.
+ If + the characters of P + do not have the syntactic form Pattern, + then throw a SyntaxError + exception. Otherwise let the newly constructed object have a + [[Match]] internal property obtained by + evaluating ("compiling") the characters of P + as a Pattern + as described in 15.10.2. +
+
+ If
+ F
+ contains any character other than "g",
+ "i",
+ or "m",
+ or if it contains the same character more than once, then throw a
+ SyntaxError
+ exception.
+
+ If + a SyntaxError + exception is not thrown, then: +
++ Let + S + be a String in the form of a Pattern + equivalent to P, + in which certain characters are escaped as described below. S + may or may not be identical to P + or pattern; + however, the internal procedure that would result from evaluating S + as a Pattern + must behave identically to the internal procedure given by the + constructed object's [[Match]] internal property. + +
+
+ The
+ characters /
+ or backslash
+ \
+ occurring in the pattern shall be escaped in S
+ as necessary to ensure that the String value formed by concatenating
+ the Strings "/",
+ S,
+ "/",
+ and F
+ can be parsed (in an appropriate lexical context) as a
+ RegularExpressionLiteral
+ that behaves identically to the constructed regular expression. For
+ example, if P
+ is "/",
+ then S
+ could be "\/"
+ or "\u002F",
+ among other possibilities, but not "/",
+ because ///
+ followed by F
+ would be parsed as a SingleLineComment
+ rather than a RegularExpressionLiteral.
+ If P
+ is the empty String, this specification can be met by letting S
+ be "(?:)".
+
+
+ The + following properties of the newly constructed object are data + properties with the attributes that are specified in 15.10.7. The + [[Value]] of each property is set as follows:
+
+ The
+ source property of
+ the newly constructed object is set to S.
+ The
+ global property of
+ the newly constructed object is set to a Boolean value that is true
+ if F contains the
+ character "g"
+ and false otherwise.
+ The
+ ignoreCase
+ property of the newly constructed object is set to a Boolean value
+ that is true if F
+ contains the character "i"
+ and false otherwise.
+ The
+ multiline property
+ of the newly constructed object is set to a Boolean value that is
+ true if F
+ contains the character "m"
+ and false otherwise.
+ The
+ lastIndex property
+ of the newly constructed object is set to 0.
+ The + [[Prototype]] internal property of the newly constructed object is + set to the standard built-in RegExp prototype object as specified in + 15.10.6.
+
+ The
+ [[Class]] internal property of the newly constructed object is set
+ to "RegExp".
NOTE If
+ pattern is a StringLiteral,
+ the usual escape sequence substitutions are performed before the
+ String is processed by RegExp. If pattern must contain an escape
+ sequence to be recognised by RegExp, any
+ backslash \
+ characters must be escaped within the StringLiteral
+ to prevent them being removed when the contents of the StringLiteral
+ are formed.
+
+ The + value of the [[Prototype]] internal property of the RegExp + constructor is the standard built-in Function prototype object + (15.3.4).
+
+ Besides
+ the internal properties and the length
+ property (whose value is 2), the RegExp constructor has the
+ following properties:
+ The
+ initial value of RegExp.prototype
+ is the RegExp prototype object (15.10.6).
+ This + property shall have the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+
+ The
+ value of the [[Prototype]] internal property of the RegExp prototype
+ object is the standard built-in Object prototype object (15.2.4).
+ The RegExp prototype object is itself a regular expression object;
+ its [[Class]] is "RegExp".
+ The initial values of the RegExp prototype object’s data
+ properties (15.10.7) are set as if the object was created by the
+ expression new RegExp()
+ where RegExp is
+ that standard built-in constructor with that name.
+ The
+ RegExp prototype object does not have a valueOf
+ property of its own; however, it inherits the valueOf
+ property from the Object prototype object.
+ In
+ the following descriptions of functions that are properties of the
+ RegExp prototype object, the phrase “this RegExp object” refers
+ to the object that is the this value for the invocation of
+ the function; a TypeError exception is thrown if the this
+ value is not an object or an object for which the value of the
+ [[Class]] internal property is not "RegExp".
+ The
+ initial value of RegExp.prototype.constructor
+ is the standard built-in RegExp
+ constructor.
+ Performs + a regular expression match of string + against the regular expression and returns an Array object + containing the results of the match, or null if string + did not match.
++ The + String ToString(string) + is searched for an occurrence of the regular expression pattern as + follows:
++ Let + R be this RegExp object.
++ Let + S be the value of ToString(string).
++ Let + length be the length of S.
+
+ Let
+ lastIndex be the result of calling the [[Get]] internal
+ method of R with argument "lastIndex"..
+ Let + i be the value of ToInteger(lastIndex).
+
+ Let
+ global be the result of calling the [[Get]] internal method
+ of R with argument "global".
+ If + global is false, then let i = 0.
++ Let + matchSucceeded be false.
++ Repeat, + while matchSucceeded is false
++ If + i < 0 or i > length, then
+
+ Call
+ the [[Put]] internal method of R with arguments
+ "lastIndex",
+ 0, and true.
+ Return
+ null.
+ Call + the [[Match]] internal method of R with arguments S + and i.
++ If + [[Match]] returned failure, then +
++ Let + i = i+1.
++ else + +
++ Let + r be the State result of the call to [[Match]].
++ Set + matchSucceeded to true.
++ Let + e be r's endIndex value.
++ If + global is true,
+
+ Call
+ the [[Put]] internal method of R with arguments
+ "lastIndex",
+ e, and true.
+ Let + n be the length of r's captures array. (This + is the same value as 15.10.2.1's NCapturingParens.)
+
+ Let
+ A be a new array created as if by the expression new
+ Array() where Array
+ is the standard built-in constructor with that name.
+ Let + matchIndex be the position of the matched substring within + the complete String S.
+
+ Call
+ the [[DefineOwnProperty]] internal method of A with
+ arguments "index",
+ Property Descriptor {[[Value]]: matchIndex, [[Writable]:
+ true, [[Enumerable]]: true, [[Configurable]]: true},
+ and true.
+ Call
+ the [[DefineOwnProperty]] internal method of A with
+ arguments "input",
+ Property Descriptor {[[Value]]: S, [[Writable]: true,
+ [[Enumerable]]: true, [[Configurable]]: true}, and
+ true.
+ Call
+ the [[DefineOwnProperty]] internal method of A with
+ arguments "length",
+ Property Descriptor {[[Value]]: n + 1}, and true.
+ Let + matchedSubstr be the matched substring (i.e. the portion of + S between offset i inclusive and offset e + exclusive).
+
+ Call
+ the [[DefineOwnProperty]] internal method of A with
+ arguments "0",
+ Property Descriptor {[[Value]]: matchedSubstr, [[Writable]:
+ true, [[Enumerable]]: true, [[Configurable]]: true},
+ and true.
+ For + each integer i such that I > 0 and I ≤ + n
++ Let + captureI be ith element of r's + captures array.
++ Call + the [[DefineOwnProperty]] internal method of A with + arguments ToString(i), Property Descriptor {[[Value]]: + captureI, [[Writable]: true, [[Enumerable]]: true, + [[Configurable]]: true}, and true.
++ Return + A.
++ The + following steps are taken:
+
+ Let
+ match be the result of evaluating the RegExp.prototype.exec
+ (15.10.6.2) algorithm upon this RegExp object using string
+ as the argument.
+ If + match is not null, then return true; else return + false.
+
+ Return
+ the String value formed by concatenating the Strings "/",
+ the String value of the source property of this RegExp
+ object, and "/";
+ plus "g"
+ if the global
+ property is true, "i"
+ if the ignoreCase
+ property is true, and "m"
+ if the multiline
+ property is true.
NOTE The + returned String has the form of a + RegularExpressionLiteral + that evaluates to another RegExp object with the same + behaviour as this object. +
+
+ RegExp
+ instances inherit properties from the RegExp prototype object and
+ their [[Class]] internal property value is "RegExp".
+ RegExp instances also have a [[Match]] internal property and a
+ length property.
+ The + value of the [[Match]] internal property is an implementation + dependent representation of the Pattern + of the RegExp object.
++ RegExp + instances also have the following properties.
+
+ The
+ value of the source
+ property is a String in the form of a Pattern
+ representing the current regular expression. This property shall
+ have the attributes { [[Writable]]: false,
+ [[Enumerable]]: false, [[Configurable]]: false }.
+ The
+ value of the global
+ property is a Boolean value indicating whether the flags contained
+ the character “g”.
+ This property shall have the attributes { [[Writable]]: false,
+ [[Enumerable]]: false, [[Configurable]]: false }.
+ The
+ value of the ignoreCase
+ property is a Boolean value indicating whether the flags contained
+ the character “i”.
+ This property shall have the attributes { [[Writable]]: false,
+ [[Enumerable]]: false, [[Configurable]]: false }.
+ The
+ value of the multiline
+ property is a Boolean value indicating whether the flags contained
+ the character “m”.
+ This property shall have the attributes { [[Writable]]: false,
+ [[Enumerable]]: false, [[Configurable]]: false }.
+ The
+ value of the lastIndex
+ property specifies the String position at which to start the next
+ match. It is coerced to an integer when used (see
+ 15.10.6.2). This property shall have the attributes
+ { [[Writable]]: true, [[Enumerable]]: false,
+ [[Configurable]]: false }.
NOTE Unlike
+ the other standard built-in properties of RegExp instances,
+ lastIndex is
+ writable.
+ Instances + of Error objects are thrown as exceptions when runtime errors occur. + The Error objects may also serve as base objects for user-defined + exception classes.
+
+ When
+ Error is
+ called as a function rather than as a constructor, it creates and
+ initialises a new Error object. Thus the function call Error(…)
+ is equivalent to the object creation expression new
+ Error(…)
+ with the same arguments.
+ The
+ [[Prototype]] internal property of the newly constructed object is
+ set to the original Error prototype object, the one that is the
+ initial value of Error.prototype
+ (15.11.3.1).
+ The
+ [[Class]] internal property of the newly constructed object is set
+ to "Error".
+ The + [[Extensible]] internal property of the newly constructed object is + set to true.
+
+ If
+ the argument message
+ is not undefined, the message
+ own property of the newly constructed object is set to
+ ToString(message).
+ When
+ Error is called as
+ part of a new
+ expression, it is a constructor: it initialises the newly created
+ object.
+ The
+ [[Prototype]] internal property of the newly constructed object is
+ set to the original Error prototype object, the one that is the
+ initial value of Error.prototype
+ (15.11.3.1).
+ The
+ [[Class]] internal property of the newly constructed Error object is
+ set to "Error".
+ The + [[Extensible]] internal property of the newly constructed object is + set to true.
+
+ If
+ the argument message
+ is not undefined, the message
+ own property of the newly constructed object is set to
+ ToString(message).
+ The + value of the [[Prototype]] internal property of the Error + constructor is the Function prototype object (15.3.4).
+
+ Besides
+ the internal properties and the length
+ property (whose value is 1), the Error constructor has the
+ following property:
+ The
+ initial value of Error.prototype
+ is the Error prototype object (15.11.4).
+ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+
+ The
+ Error prototype object is itself an Error object (its [[Class]] is
+ "Error").
+ The + value of the [[Prototype]] internal property of the Error prototype + object is the standard built-in Object prototype object (15.2.4).
+
+ The
+ initial value of Error.prototype.constructor
+ is the built-in Error
+ constructor.
+ The
+ initial value of Error.prototype.name
+ is "Error".
+ The
+ initial value of Error.prototype.message
+ is the empty String.
+ The + following steps are taken:
++ Let + O be the this value.
+
+ Let
+ name be the result of calling the [[Get]] internal method of
+ O with argument "name".
+ If
+ name is undefined, then let name be "Error";
+ else let name be ToString(name).
+ Let
+ msg be the result of calling the [[Get]] internal method of
+ O with argument "message".
If + msg is undefined, then let + msg + be + the empty String; else let msg be ToString(msg).
If name and msg are both the empty String, return "Error".
If name is the empty String, return msg.
If msg is the empty String, return name.
Return the result of concatenating name, ":", a single space
+ character, and msg.
+ Error
+ instances inherit properties from the Error prototype object and
+ their [[Class]] internal property value is "Error".
+ Error instances have no special properties.
+ One + of the NativeError objects below is thrown when a runtime + error is detected. All of these objects share the same structure, as + described in 15.11.7.
++ This + exception is not currently used within this specification. This + object remains for compatibility with previous editions of this + specification.
++ Indicates + a numeric value has exceeded the allowable range. See 15.4.2.2, + 15.4.5.1, 15.7.4.2, 15.7.4.5, 15.7.4.6, and 15.7.4.7, 15.9.5.43.
++ Indicate + that an invalid reference value has been detected. See 8.7.1, 8.7.2, + 10.2.1, 10.2.1.1.4, 10.2.1.2.4, and 11.13.1.
++ Indicates + that a parsing error has occurred. See 11.1.5, 11.3.1, 11.3.2, + 11.4.1, 11.4.4, 11.4.5, 11.13.1, 11.13.2, 12.2.1, 12.10.1, 12.14.1, + 13.1, 15.1.2.1, 15.3.2.1, 15.10.2.2, 15.10.2.5, 15.10.2.9, + 15.10.2.15, 15.10.2.19, 15.10.4.1, and 15.12.2.
++ Indicates + the actual type of an operand is different than the expected type. + See 8.6.2, 8.7.2, 8.10.5, 8.12.5, 8.12.7, 8.12.8, 8.12.9, 9.9, 9.10, + 10.2.1, 10.2.1.1.3, 10.6, 11.2.2, 11.2.3, 11.4.1, 11.8.6, 11.8.7, + 11.3.1, 13.2, 13.2.3, 15, 15.2.3.2, 15.2.3.3, 15.2.3.4, 15.2.3.5, + 15.2.3.6, 15.2.3.7, 15.2.3.8, 15.2.3.9, 15.2.3.10, 15.2.3.11, + 15.2.3.12, 15.2.3.13, 15.2.3.14, 15.2.4.3, 15.3.4.2, 15.3.4.3, + 15.3.4.4, 15.3.4.5, 15.3.4.5.2, 15.3.4.5.3, 15.3.5, 15.3.5.3, + 15.3.5.4, 15.4.4.3, 15.4.4.11, 15.4.4.16, 15.4.4.17, 15.4.4.18, + 15.4.4.19, 15.4.4.20, 15.4.4.21, 15.4.4.22, 15.4.5.1, 15.5.4.2, + 15.5.4.3, 15.6.4.2, 15.6.4.3, 15.7.4, 15.7.4.2, 15.7.4.4, 15.7.4.8 [?], + 15.9.5, 15.9.5.44, 15.10.4.1, 15.10.6, 15.11.4.4 and 15.12.3.
++ Indicates + that one of the global URI handling functions was used in a way that + is incompatible with its definition. See 15.1.3.
+
+ When
+ an ECMAScript implementation detects a runtime error, it throws an
+ instance of one of the NativeError objects defined in
+ 15.11.6. Each of these objects has the structure described below,
+ differing only in the name used as the constructor name instead of
+ NativeError, in the name property of the prototype
+ object, and in the implementation-defined message
+ property of the prototype object.
+ For + each error object, references to NativeError in the + definition should be replaced with the appropriate error object name + from 15.11.6.
++ When + a NativeError constructor is called as a function rather than + as a constructor, it creates and initialises a new object. A call + of the object as a function is equivalent to calling it as a + constructor with the same arguments.
+
+ The
+ [[Prototype]] internal property of the newly constructed object is
+ set to the prototype object for this error constructor. The
+ [[Class]] internal property of the newly constructed object is set
+ to "Error".
+ The [[Extensible]] internal property of the newly constructed object
+ is set to true.
+ If
+ the argument message
+ is not undefined, the message
+ own property of the newly constructed object is set to
+ ToString(message).
+ When
+ a NativeError constructor is called as part of a new
+ expression, it is a constructor: it initialises the newly created
+ object.
+ The
+ [[Prototype]] internal property of the newly constructed object is
+ set to the prototype object for this NativeError constructor.
+ The [[Class]] internal property of the newly constructed object is
+ set to "Error".
+ The [[Extensible]] internal property of the newly constructed object
+ is set to true.
+ If
+ the argument message
+ is not undefined, the message
+ property of the newly constructed object is set to
+ ToString(message).
+ The + value of the [[Prototype]] internal property of a NativeError + constructor is the Function prototype object (15.3.4).
+
+ Besides
+ the internal properties and the length
+ property (whose value is 1), each NativeError
+ constructor has the following property:
+ The
+ initial value of NativeError.prototype
+ is a NativeError prototype object (15.11.7.7). Each
+ NativeError constructor has a separate prototype object.
+ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+
+ Each
+ NativeError prototype object is an Error object (its
+ [[Class]] is "Error").
+ The + value of the [[Prototype]] internal property of each NativeError + prototype object is the standard built-in Error prototype object + (15.11.4).
+
+ The
+ initial value of the constructor
+ property of the prototype for a given NativeError constructor
+ is the NativeError constructor function itself (15.11.7).
+ The
+ initial value of the name
+ property of the prototype for a given NativeError constructor
+ is the name of the constructor (the name used instead of
+ NativeError).
+ The
+ initial value of the message
+ property of the prototype for a given NativeError constructor
+ is the empty String.
NOTE The
+ prototypes for the NativeError constructors do not themselves
+ provide a toString function,
+ but instances of errors will inherit it from the Error prototype
+ object.
+ NativeError
+ instances inherit properties from their NativeError prototype
+ object and their [[Class]] internal property value is "Error".
+ NativeError instances have no special properties.
+ The + JSON object is a single object that contains two functions, + parse and stringify, that are used to parse and + construct JSON texts. The JSON Data Interchange Format is described + in RFC 4627 <http://www.ietf.org/rfc/rfc4627.txt>. The JSON + interchange format used in this specification is exactly that + described by RFC 4627 with two exceptions:
++ The + top level JSONText + production of the ECMAScript JSON grammar may consist of any + JSONValue rather + than being restricted to being a JSONObject + or a JSONArray as + specified by RFC 4627. +
++ Conforming + implementations of JSON.parse and JSON.stringify must + support the exact interchange format described in this + specification without any deletions or extensions to the format. + This differs from RFC 4627 which permits a JSON parser to accept + non-JSON forms and extensions.
+
+ The
+ value of the [[Prototype]] internal property of the JSON object is
+ the standard built-in Object prototype object (15.2.4). The value of
+ the [[Class]] internal property of the JSON object is "JSON".
+ The value of the [[Extensible]] internal property of the JSON object
+ is set to true.
+ The
+ JSON object does not have a [[Construct]] internal property; it is
+ not possible to use the JSON object as a constructor with the new
+ operator.
+ The + JSON object does not have a [[Call]] internal property; it is not + possible to invoke the JSON object as a function.
++ JSON.stringify + produces a String that conforms to the following JSON grammar. + JSON.parse accepts a String that conforms to the JSON grammar.
++ JSON + is similar to ECMAScript source text in that it consists of a + sequence of characters conforming to the rules of SourceCharacter. + The JSON Lexical Grammar defines the tokens that make up a JSON text + similar to the manner that the ECMAScript lexical grammar defines + the tokens of an ECMAScript source test. The JSON Lexical grammar + only recognizes the white space character specified by the + production JSONWhiteSpace. + The JSON lexical grammar shares some productions with the + ECMAScript lexical grammar. All nonterminal symbols of the grammar + that do not begin with the characters “JSON” are defined by + productions of the ECMAScript lexical grammar.
++ Syntax
++ JSONWhiteSpace ::
+
+ <TAB>
<CR>
<LF>
<SP>
+ JSONString ::
+
+ " JSONStringCharactersopt "
+ JSONStringCharacters ::
++ JSONStringCharacter + JSONStringCharactersopt +
++ JSONStringCharacter ::
+
+ SourceCharacter but
+ not double-quote " orbackslash \
+ orU+0000 thru U+001F
+ \ JSONEscapeSequence
+ JSONEscapeSequence ::
++ JSONEscapeCharacter
++ UnicodeEscapeSequence +
++ JSONEscapeCharacter :: one + of
+
+ "
+ / \ b f n r t
+ JSONNumber ::
+
+ -optDecimalIntegerLiteral JSONFractionoptExponentPartopt
+ JSONFraction ::
+
+ . DecimalDigits
+ JSONNullLiteral ::
++ NullLiteral
++ JSONBooleanLiteral ::
++ BooleanLiteral
++ The + JSON Syntactic Grammar defines a valid JSON text in terms of tokens + defined by the JSON lexical grammar. The goal symbol of the grammar + is JSONText. +
++ Syntax
++ JSONText : +
++ JSONValue
++ JSONValue : +
+
+ JSONNullLiteral
JSONBooleanLiteral
JSONObject
JSONArray
JSONString
JSONNumber
+ JSONObject :
+
+ {
+ } { JSONMemberList }
+ JSONMember :
+
+ JSONString : JSONValue
+ JSONMemberList :
+
+ JSONMember
+
JSONMemberList ,
+ JSONMember
+
+ JSONArray :
+
+ [
+ ] [ JSONElementList
+ ]
+ JSONElementList :
+
+ JSONValue
JSONElementList
+ , JSONValue
+ The
+ parse function
+ parses a JSON text (a JSON-formatted String) and produces an
+ ECMAScript value. The JSON format is a restricted form of ECMAScript
+ literal. JSON objects are realized as ECMAScript objects. JSON
+ arrays are realized as ECMAScript arrays. JSON strings, numbers,
+ booleans, and null are realized as ECMAScript Strings, Numbers,
+ Booleans, and null. JSON uses a more limited set of white
+ space characters than WhiteSpace
+ and allows Unicode code points U+2028 and U+2029 to directly appear
+ in JSONString
+ literals without using an escape sequence. The process of parsing is
+ similar to 11.1.4 and 11.1.5 as constrained by the JSON grammar.
+ The + optional reviver parameter is a function that takes two + parameters, (key and value). It can filter and + transform the results. It is called with each of the key/value + pairs produced by the parse, and its return value is used instead of + the original value. If it returns what it received, the structure is + not modified. If it returns undefined then the property is + deleted from the result.
++ Let + JText be ToString(text).
++ Parse + JText using the grammars in 15.12.1. Throw a SyntaxError + exception if JText did not conform to the JSON grammar for + the goal symbol JSONText. +
++ Let + unfiltered be the result of parsing and evaluating JText + as if it was the source text of an ECMAScript Program but + using JSONString in place of StringLiteral. + Note that since JText conforms to the JSON grammar this + result will be either a primitive value or an object that is + defined by either an ArrayLiteral or an ObjectLiteral.
++ If + IsCallable(reviver) is true, then
+
+ Let
+ root be a new object created as if by the expression new
+ Object(), where Object
+ is the standard built-in constructor with that name.
+ Call + the [[DefineOwnProperty]] internal method of root with the + empty String, the PropertyDescriptor {[[Value]]: unfiltered, + [[Writable]]: true, [[Enumerable]]: true, + [[Configurable]]: true}, and false as arguments.
++ Return + the result of calling the abstract operation Walk, passing root + and the empty String. The abstract operation Walk is described + below.
++ Else
++ Return + unfiltered.
++ The + abstract operation Walk is a recursive abstract operation that takes + two parameters: a holder + object and the String name + of a property in that object. Walk uses the value of reviver + that was originally passed to the above parse function.
++ Let + val be the result of calling the [[Get]] internal method of + holder with argument name.
++ If + val is an object, then
+
+ If
+ the [[Class]] internal property of val is "Array"
+ Set + I to 0.
+
+ Let
+ len be the result of calling the [[Get]] internal method
+ of val with argument "length".
+ Repeat + while I < len, +
++ Let + newElement be the result of calling the abstract + operation Walk, passing val and ToString(I).
++ If + newElement is undefined, then
++ Call + the [[Delete]] internal method of val with ToString(I) + and false as arguments. +
++ Else
++ Call + the [[DefineOwnProperty]] internal method of val with + arguments ToString(I), the Property Descriptor + {[[Value]]: newElement, [[Writable]]: true, + [[Enumerable]]: true, [[Configurable]]: true}, and false.
++ Add + 1 to I.
++ Else
++ Let + keys be an internal List of String values consisting of + the names of all the own properties of val whose + [[Enumerable]] attribute is true. The ordering of the + Strings should be the same as that used by the + Object.keys + standard built-in function.
++ For + each String P in keys do, +
++ Let + newElement be the result of calling the abstract + operation Walk, passing val and P. +
++ If + newElement is undefined, then
++ Call + the [[Delete]] internal method of val with P and + false as arguments. +
++ Else
++ Call + the [[DefineOwnProperty]] internal method of val with + arguments P, the Property Descriptor {[[Value]]: + newElement, [[Writable]]: true, [[Enumerable]]: + true, [[Configurable]]: true}, and false.
++ Return + the result of calling the [[Call]] internal method of reviver + passing holder as the this value and with an argument + list consisting of name and val.
+
+ It is
+ not permitted for a conforming implementation of JSON.parse
+ to extend the JSON grammars. If an implementation wishes to support
+ a modified or extended JSON interchange format it must do so by
+ defining a different parse function.
+
NOTE In + the case where there are duplicate name Strings within an object, + lexically preceding values for the same key shall be overwritten.
+
+ The
+ stringify function
+ returns a String in JSON format representing an ECMAScript value. It
+ can take three parameters. The first parameter is required. The
+ value parameter is
+ an ECMAScript value, which is usually an object or array, although
+ it can also be a String, Boolean, Number or null. The
+ optional replacer
+ parameter is either a function that alters the way objects and
+ arrays are stringified, or an array of Strings and Numbers that acts
+ as a white list for selecting the object properties that will be
+ stringified. The optional space
+ parameter is a String or Number that allows the result to have white
+ space injected into it to improve human readability.
+ These + are the steps in stringifying an object:
++ Let + stack be an empty List.
++ Let + indent be the empty String.
++ Let + PropertyList and ReplacerFunction be undefined.
++ If + Type(replacer) is Object, then
++ If + IsCallable(replacer) is true, then
++ Let + ReplacerFunction be replacer.
+
+ Else
+ if the [[Class]] internal property of replacer is "Array",
+ then
+ Let + PropertyList be an empty internal List
++ For + each value v of a property of replacer that has an + array index property name. The properties are enumerated in the + ascending array index order of their names.
++ Let + item be undefined.
++ If + Type(v) is String then let item be v.
++ Else + if Type(v) is Object then,
+
+ If
+ the [[Class]] internal property of v is "String"
+ or "Number"
+ then let item be ToString(v).
+ If + item is not undefined and item is not currently an + element of PropertyList then,
++ Append + item to the end of PropertyList.
++ If + Type(space) is Object then,
+ ++ If + Type(space) is Number
++ Let + space be min(10, ToInteger(space)).
++ Set + gap to a String containing space space characters. + This will be the empty String if space is less than 1.
++ Else + if Type(space) is String
++ If + the number of characters in space is 10 or less, set gap + to space otherwise set gap to a String consisting of + the first 10 characters of space.
++ Else
++ Set + gap to the empty String.
+
+ Let
+ wrapper be a new object created as if by the expression new
+ Object(), where Object
+ is the standard built-in constructor with that name.
+ Call + the [[DefineOwnProperty]] internal method of wrapper with + arguments the empty String, the Property Descriptor {[[Value]]: + value, [[Writable]]: true, [[Enumerable]]: true, + [[Configurable]]: true}, and false.
++ Return + the result of calling the abstract operation Str with the + empty String and wrapper.
+
+ The
+ abstract operation Str(key,
+ holder)
+ has access to ReplacerFunction from the invocation of the stringify
+ method. Its algorithm is as follows:
+ Let + value be the result of calling the [[Get]] internal method + of holder with argument key.
++ If + Type(value) is Object, then
+
+ Let
+ toJSON be the result of calling the [[Get]] internal method
+ of value with argument "toJSON".
+ If + IsCallable(toJSON) is true
++ Let + value be the result of calling the [[Call]] internal + method of toJSON passing value as the this + value and with an argument list consisting of key.
++ If + ReplacerFunction is not undefined, then
++ Let + value be the result of calling the [[Call]] internal method + of ReplacerFunction passing holder as the this + value and with an argument list consisting of key and + value.
++ If + Type(value) is Object then,
+
+ If
+ the [[Class]] internal property of value is "Number"
+ then,
+ Let + value be ToNumber(value).
+
+ Else
+ if the [[Class]] internal property of value is "String"
+ then,
+ Let + value be ToString(value).
+
+ Else
+ if the [[Class]] internal property of value is "Boolean"
+ then,
+ Let + value be the value of the [[PrimitiveValue]] internal + property of value.
+
+ If
+ value is null then return "null".
+ If
+ value is true then return "true".
+ If
+ value is false then return "false".
+ If + Type(value) is String, then return the result of calling the + abstract operation Quote with argument value.
++ If + Type(value) is Number
++ If + value is finite then return ToString(value).
+
+ Else,
+ return "null".
+ If + Type(value) is Object, and IsCallable(value) is false
+ ++ Return + undefined.
++ The + abstract operation Quote(value) + wraps a String value in double quotes and escapes characters within + it. +
++ Let + product be the double quote character.
++ For + each character C in value
++ If + C is the double quote character or the backslash character
++ Let + product be the concatenation of product and the + backslash character.
++ Let + product be the concatenation of product and C.
++ Else + if C is backspace, formfeed, newline, carriage return, or + tab
++ Let + product be the concatenation of product and the + backslash character.
++ Let + abbrev be the character corresponding to the value of C + as follows:
+backspace "b"
formfeed "f"
newline "n"
carriage return "r"
tab "t"
+ Let + product be the concatenation of product and abbrev.
++ Else + if C is a control character having a code unit value less + than the space character
++ Let + product be the concatenation of product and the + backslash character.
+
+ Let
+ product be the concatenation of product and "u".
+ Let + hex be the result of converting the numeric code unit + value of C to a String of four hexadecimal digits.
++ Let + product be the concatenation of product and hex.
++ Else
++ Let + product be the concatenation of product and C.
++ Let + product be the concatenation of product and the + double quote character.
++ Return + product.
++ The + abstract operation JO(value) + serializes an object. It has access to the stack, + indent, gap, + PropertyList, + ReplacerFunction, + and space of the + invocation of the stringify method.
++ If + stack contains value then throw a TypeError + exception because the structure is cyclical.
++ Append + value to stack.
++ Let + stepback be indent.
++ Let + indent be the concatenation of indent and gap.
++ If + PropertyList is not undefined, then
++ Let + K be PropertyList.
++ Else
++ Let + K be an internal List of Strings consisting of the names of + all the own properties of value whose [[Enumerable]] + attribute is true. The ordering of the Strings should be + the same as that used by the Object.keys standard built-in + function.
++ Let + partial be an empty List.
++ For + each element P of K.
++ Let + strP be the result of calling the abstract operation Str + with arguments P and value.
++ If + strP is not undefined
++ Let + member be the result of calling the abstract operation + Quote with argument P.
++ Let + member be the concatenation of member and the colon + character.
++ If + gap is not the empty String
++ Let + member be the concatenation of member and the + space character.
++ Let + member be the concatenation of member and strP.
++ Append + member to partial.
++ If + partial is empty, then
+
+ Let
+ final be "{}".
+ Else
++ If + gap is the empty String
++ Let + properties be a String formed by concatenating all the + element Strings of partial with each adjacent pair of + Strings separated with the comma character. A comma is not + inserted either before the first String or after the last String. + +
+
+ Let
+ final be the result of concatenating "{",
+ properties, and "}".
+ Else + gap is not the empty String
++ Let + separator be the result of concatenating the comma + character, the line feed character, and indent.
++ Let + properties be a String formed by concatenating all the + element Strings of partial with each adjacent pair of + Strings separated with separator. The separator + String is not inserted either before the first String or after + the last String.
+
+ Let
+ final be the result of concatenating "{",
+ the line feed character, indent, properties, the
+ line feed character, stepback, and "}".
+ Remove + the last element of stack.
++ Let + indent be stepback.
++ Return + final.
+
+ The
+ abstract operation JA(value)
+ serializes an array. It has access to the stack,
+ indent, gap,
+ and space of the
+ invocation of the stringify method. The representation of arrays
+ includes only the elements between zero and array.length
+ – 1 inclusive. Named
+ properties are excluded from the stringification. An array is
+ stringified as an open left bracket, elements separated by comma,
+ and a closing right bracket.
+ If + stack contains value then throw a TypeError + exception because the structure is cyclical.
++ Append + value to stack.
++ Let + stepback be indent.
++ Let + indent be the concatenation of indent and gap.
++ Let + partial be an empty List.
+
+ Let
+ len be the result of calling the [[Get]] internal method of
+ value with argument "length".
+ Let + index be 0.
++ Repeat + while index < len
++ Let + strP be the result of calling the abstract operation Str + with arguments ToString(index) and value. +
++ If + strP is undefined
+
+ Append
+ "null"
+ to partial.
+ Else
++ Append + strP to partial.
++ Increment + index by 1.
++ If + partial is empty ,then
+
+ Let
+ final be "[]".
+ Else
++ If + gap is the empty String
++ Let + properties be a String formed by concatenating all the + element Strings of partial with each adjacent pair of + Strings separated with the comma character. A comma is not + inserted either before the first String or after the last String. + +
+
+ Let
+ final be the result of concatenating "[",
+ properties, and "]".
+ Else
++ Let + separator be the result of concatenating the comma + character, the line feed character, and indent.
++ Let + properties be a String formed by concatenating all the + element Strings of partial with each adjacent pair of + Strings separated with separator. The separator + String is not inserted either before the first String or after + the last String.
+
+ Let
+ final be the result of concatenating "[",
+ the line feed character, indent, properties, the
+ line feed character, stepback, and "]".
+ Remove + the last element of stack.
++ Let + indent be stepback.
++ Return + final.
+NOTE 1 JSON structures are allowed to be nested to any depth, but they + must be acyclic. If value + is or contains a cyclic structure, then the stringify function must + throw a TypeError exception. This is an example of a value + that cannot be stringified:
+a = [];
a[0] = a;
my_text = JSON.stringify(a); // This must throw an TypeError.
NOTE 2 Symbolic primitive values are rendered as follows:
+The
+ null value is rendered in JSON text as the String null.
The + undefined value is not rendered.
+The
+ true value is rendered in JSON text as the String true.
The
+ false value is rendered in JSON text as the String false.
NOTE 3 String values are wrapped in double quotes. The characters "
+ and \ are escaped
+ with \ prefixes.
+ Control characters are replaced with escape sequences \uHHHH,
+ or with the shorter forms, \b
+ (backspace), \f
+ (formfeed), \n
+ (newline), \r
+ (carriage return), \t
+ (tab).
NOTE 4 Finite numbers are stringified as if by calling ToString(number).
+ NaN and Infinity regardless of sign are represented as the
+ String null.
NOTE 5 Values that do not have a JSON representation (such as undefined
+ and functions) do not produce a String. Instead they produce the
+ undefined value. In arrays these values are represented as the
+ String null.
+ In objects an unrepresentable value causes the property to be
+ excluded from stringification.
NOTE 6 An object is rendered as an opening left brace followed by zero or + more properties, separated with commas, closed with a right brace. A + property is a quoted String representing the key or property name, a + colon, and then the stringified property value. An array is rendered + as an opening left bracket followed by zero or more values, + separated with commas, closed with a right bracket.
+
+ An
+ implementation must report most errors at the time the relevant
+ ECMAScript language construct is evaluated. An early error is
+ an error that can be detected and reported prior to the evaluation
+ of any construct in the Program
+ containing the error. An implementation must report early errors in
+ a Program prior to
+ the first evaluation of that Program.
+ Early errors in eval code are reported at the time eval
+ is called but prior to evaluation of any construct within the eval
+ code. All errors that are not early errors are runtime errors.
+ An + implementation must treat any instance of the following kinds of + errors as an early error:
++ Any + syntax error.
++ Attempts + to define an ObjectLiteral that has multiple get property assignments with + the same name or multiple set property assignments with the + same name.
++ Attempts + to define an ObjectLiteral + that has both a data property assignment and a get or + set property assignment with the same name.
++ Errors + in regular expression literals that are not implementation-defined + syntax extensions.
++ Attempts + in strict mode code to define an ObjectLiteral + that has multiple data property assignments with the same name.
++ The + occurrence of a WithStatement + in strict mode code.
++ The + occurrence of an Identifier + value appearing more than once within a FormalParameterList + of an individual strict mode FunctionDeclaration + or FunctionExpression.
+
+ Improper
+ uses of return,
+ break, and
+ continue.
+ Attempts
+ to call PutValue on any value for which an early determination can
+ be made that the value is not a Reference (for example, executing
+ the assignment statement 3=4).
+ An + implementation shall not treat other kinds of errors as early errors + even if the compiler can prove that a construct cannot execute + without error under any circumstances. An implementation may issue + an early warning in such a case, but it should not report the error + until the relevant construct is actually executed. +
++ An + implementation shall report all errors as specified, except for the + following:
+
+ An
+ implementation may extend program syntax and regular expression
+ pattern or flag syntax. To permit this, all operations (such as
+ calling eval,
+ using a regular expression literal, or using the Function
+ or RegExp
+ constructor) that are allowed to throw SyntaxError
+ are permitted to exhibit implementation-defined behaviour instead
+ of throwing SyntaxError
+ when they encounter an implementation-defined extension to the
+ program syntax or regular expression pattern or flag syntax.
+ An + implementation may provide additional types, values, objects, + properties, and functions beyond those described in this + specification. This may cause constructs (such as looking up a + variable in the global scope) to have implementation-defined + behaviour instead of throwing an error (such as ReferenceError).
+
+ An
+ implementation may define behaviour other than throwing RangeError
+ for toFixed,
+ toExponential,
+ and toPrecision
+ when the fractionDigits
+ or precision
+ argument is outside the specified range.
+
++ SourceCharacter ::See clause 6
++ any + Unicode code unit
++ InputElementDiv ::See clause 7
+
+ WhiteSpace
LineTerminator
Comment
Token
DivPunctuator
+ InputElementRegExp ::See clause 7
+
+ WhiteSpace
LineTerminator
Comment
Token
RegularExpressionLiteral
+ WhiteSpace ::See 7.2
+
+ <TAB>
<VT>
<FF>
<SP>
<#x0a>
<BOM>
<USP>
+ LineTerminator ::See 7.3
+
+ <LF>
<CR>
<LS>
<PS>
+ LineTerminatorSequence ::See 7.3
+
+ <LF>
<CR>
+ [lookahead
+ ∉
+ <LF>
+ ]
<LS>
<PS>
<CR>
+ <LF>
+ Comment ::See 7.4
+
+ MultiLineComment
SingleLineComment
+ MultiLineComment ::See 7.4
+
+ /* MultiLineCommentCharsopt */
+ MultiLineCommentChars ::See 7.4
+
+ MultiLineNotAsteriskChar
+ MultiLineCommentCharsopt* PostAsteriskCommentCharsopt
+ PostAsteriskCommentChars ::See 7.4
+
+ MultiLineNotForwardSlashOrAsteriskChar
+ MultiLineCommentCharsopt* PostAsteriskCommentCharsopt
+ MultiLineNotAsteriskChar ::See 7.4
+
+ SourceCharacter but
+ not asterisk *
+ MultiLineNotForwardSlashOrAsteriskChar ::See 7.4
+
+ SourceCharacter but
+ not forward-slash /
+ orasterisk *
+ SingleLineComment ::See 7.4
+
+ // SingleLineCommentCharsopt
+ SingleLineCommentChars ::See 7.4
++ SingleLineCommentChar + SingleLineCommentCharsopt
++ SingleLineCommentChar ::See 7.4
++ SourceCharacter + but + not + LineTerminator
++ Token ::See 7.5
+
+ IdentifierName
Punctuator
NumericLiteral
StringLiteral
+ Identifier ::See 7.6
++ IdentifierName but + not ReservedWord
++ IdentifierName ::See 7.6
+
+ IdentifierStart
IdentifierName
+ IdentifierPart
+ IdentifierStart ::See 7.6
+
+ UnicodeLetter$
_\ UnicodeEscapeSequence
+ IdentifierPart ::See 7.6
+
+ IdentifierStart
UnicodeCombiningMark
UnicodeDigit
UnicodeConnectorPunctuation
<ZWNJ>
<ZWJ>
+ UnicodeLetter See 7.6
++ any + character in the Unicode categories “Uppercase letter (Lu)”, + “Lowercase letter (Ll)”, “Titlecase letter (Lt)”, “Modifier + letter (Lm)”, “Other letter (Lo)”, or “Letter number (Nl)”.
++ UnicodeCombiningMark See 7.6
++ any + character in the Unicode categories “Non-spacing mark (Mn)” or + “Combining spacing mark (Mc)”
++ UnicodeDigit See 7.6
++ any + character in the Unicode category “Decimal number (Nd)”
++ UnicodeConnectorPunctuation See 7.6
++ any + character in the Unicode category “Connector punctuation (Pc)”
++ ReservedWord ::See 7.6.1
+
+ Keyword
FutureReservedWord
NullLiteral
BooleanLiteral
+ Keyword :: one + ofSee 7.6.1.1
+|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+ + | +
|
+
+ |
+
+
+ |
+
+
+ |
+ + | +
+ FutureReservedWord + :: + one + ofSee 7.6.1.2
+|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+ + | +
|
+
+ |
+ |||
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+ + | ++ | ++ | +
+ Punctuator :: one + ofSee 7.7
+|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+ + | +
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+ + | +
+ DivPunctuator :: + one + ofSee 7.7
+|
+
+ |
+
+
+ |
+ + | ++ | ++ | ++ | +
+ Literal ::See 7.8
+
+ NullLiteral
BooleanLiteral
NumericLiteral
StringLiteral
RegularExpressionLiteral
+ NullLiteral ::See 7.8.1
+
+ null
+ BooleanLiteral ::See 7.8.2
+
+ true
false
+ NumericLiteral ::See 7.8.3
+
+ DecimalLiteral
HexIntegerLiteral
+ DecimalLiteral ::See 7.8.3
+
+ DecimalIntegerLiteral . DecimalDigitsopt
+ ExponentPartopt. DecimalDigits ExponentPartopt
DecimalIntegerLiteral
+ ExponentPartopt
+ DecimalIntegerLiteral ::See 7.8.3
+
+ 0
NonZeroDigit
+ DecimalDigitsopt
+ DecimalDigits ::See 7.8.3
+
+ DecimalDigit
DecimalDigits
+ DecimalDigit
+ DecimalDigit :: + one + ofSee 7.8.3
+
+ 0
+ 1 2 3 4 5 6 7 8 9
+ NonZeroDigit:: + one + ofSee 7.8.3
+
+ 1 2 3 4 5 6 7 8 9
+ ExponentPart:: + See 7.8.3
+ExponentIndicator SignedInteger
++ ExponentIndicator :: + one + ofSee 7.8.3
+
+ e
+ E
+ SignedInteger ::See 7.8.3
+
+ DecimalDigits+ DecimalDigits- DecimalDigits
+ HexIntegerLiteral ::See 7.8.3
+
+ 0x HexDigit0X HexDigit
HexIntegerLiteral HexDigit
+ HexDigit :: + one + ofSee 7.8.3
+
+ 0
+ 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F
+ StringLiteral ::See 7.8.4
+
+ "DoubleStringCharactersopt
+ "'SingleStringCharactersopt
+ '
+ DoubleStringCharacters ::See 7.8.4
++ DoubleStringCharacter + DoubleStringCharactersopt
++ SingleStringCharacters ::See 7.8.4
++ SingleStringCharacter + SingleStringCharactersopt
++ DoubleStringCharacter ::See 7.8.4
+
+ SourceCharacter but
+ not double-quote "
+ or
+ backslash \ or
+ LineTerminator\
+ EscapeSequence
LineContinuation
+ SingleStringCharacter ::See 7.8.4
+
+ SourceCharacter but
+ not single-quote '
+ orbackslash \ or
+ LineTerminator\
+ EscapeSequence
LineContinuation
+ LineContinuation ::See 7.8.4
+
+ \
+ LineTerminatorSequence
+ EscapeSequence ::See 7.8.4
+
+ CharacterEscapeSequence0 [lookahead
+ ∉DecimalDigit]
HexEscapeSequence
UnicodeEscapeSequence
+ CharacterEscapeSequence ::See 7.8.4
+
+ SingleEscapeCharacter
NonEscapeCharacter
+ SingleEscapeCharacter :: one + ofSee 7.8.4
+
+ '
+ " \ b f n r t v
+ NonEscapeCharacter ::See 7.8.4
++ SourceCharacter + but + notEscapeCharacter or + LineTerminator
++ EscapeCharacter ::See 7.8.4
+
+ SingleEscapeCharacter
DecimalDigitxu
+ HexEscapeSequence ::See 7.8.4
+
+ x
+ HexDigit HexDigit
+ UnicodeEscapeSequence ::See 7.8.4
+
+ u HexDigit HexDigit HexDigit HexDigit
+ RegularExpressionLiteral ::See 7.8.5
+
+ / RegularExpressionBody /
+ RegularExpressionFlags
+ RegularExpressionBody ::See 7.8.5
++ RegularExpressionFirstChar + RegularExpressionChars
++ RegularExpressionChars ::See 7.8.5
+
+ [empty]
RegularExpressionChars
+ RegularExpressionChar
+ RegularExpressionFirstChar ::See 7.8.5
+
+ RegularExpressionNonTerminator but
+ not *
+ or
+ \ or
+ /
+ or
+ [
RegularExpressionBackslashSequence
RegularExpressionClass
+ RegularExpressionChar ::See 7.8.5
+
+ RegularExpressionNonTerminator but
+ not \
+ or
+ /
+ or
+ [
RegularExpressionBackslashSequence
RegularExpressionClass
+ RegularExpressionBackslashSequence ::See 7.8.5
+
+ \ RegularExpressionNonTerminator
+ RegularExpressionNonTerminator ::See 7.8.5
++ SourceCharacter but + not + LineTerminator
++ RegularExpressionClass ::See 7.8.5
+
+ [
+ RegularExpressionClassChars
+ ]
+ RegularExpressionClassChars
+ ::See 7.8.5
+ [empty]
RegularExpressionClassChars
+ RegularExpressionClassChar
+ RegularExpressionClassChar
+ ::See 7.8.5
+ RegularExpressionNonTerminator
+ but
+ not ]
+ or
+ \
RegularExpressionBackslashSequence
+ RegularExpressionFlags ::See 7.8.5
+
+ [empty]
RegularExpressionFlags
+ IdentifierPart
+ StringNumericLiteral :::See 9.3.1
+
+ StrWhiteSpaceopt
StrWhiteSpaceoptStrNumericLiteral StrWhiteSpaceopt
+ StrWhiteSpace :::See 9.3.1
++ StrWhiteSpaceChar + StrWhiteSpaceopt
++ StrWhiteSpaceChar :::See 9.3.1
+
+ WhiteSpace
LineTerminator
+ StrNumericLiteral :::See 9.3.1
+
+ StrDecimalLiteral
HexIntegerLiteral
+ StrDecimalLiteral :::See 9.3.1
+
+ StrUnsignedDecimalLiteral+
+ StrUnsignedDecimalLiteral-
+ StrUnsignedDecimalLiteral
+ StrUnsignedDecimalLiteral :::See 9.3.1
+
+ Infinity
DecimalDigits . DecimalDigitsopt
+ ExponentPartopt. DecimalDigits ExponentPartopt
DecimalDigits
+ ExponentPartopt
+ DecimalDigits :::See 9.3.1
+
+ DecimalDigit
DecimalDigits
+ DecimalDigit
+ DecimalDigit ::: one + ofSee 9.3.1
+
+ 0
+ 1 2 3 4 5 6 7 8 9
+ ExponentPart :::See 9.3.1
++ ExponentIndicator + SignedInteger
++ ExponentIndicator ::: + one + ofSee 9.3.1
+
+ e
+ E
+ SignedInteger :::See 9.3.1
+
+ DecimalDigits+
+ DecimalDigits-
+ DecimalDigits
+ HexIntegerLiteral :::See 9.3.1
+
+ 0x HexDigit0X HexDigit
HexIntegerLiteral HexDigit
+ HexDigit ::: + one + ofSee 9.3.1
+
+ 0
+ 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F
+ PrimaryExpression :See 11.1
+
+ this
Identifier
Literal
ArrayLiteral
ObjectLiteral( Expression )
+ ArrayLiteral :See 11.1.4
+
+ [
+ Elisionopt
+ ] ElementList
[
+
+ ] ElementList ,
+ Elisionopt
[
+
+ ]
+ ElementList :See 11.1.4
+
+ Elisionopt
+ AssignmentExpression
ElementList
+ ,
+ Elisionopt
+ AssignmentExpression
+ Elision :See 11.1.4
+
+ ,
Elision
+ ,
+ ObjectLiteral :See 11.1.5
+
+ {
+ } {
+ PropertyNameAndValueList
+ } PropertyNameAndValueList
{
+
+ , }
+ PropertyNameAndValueList :See 11.1.5
+
+ PropertyAssignment
PropertyNameAndValueList
+ , PropertyAssignment
+ PropertyAssignment :See 11.1.5
+
+ PropertyName
+ :
+ AssignmentExpressionget
+ PropertyName()
+ { FunctionBody } PropertyName
set
+ (
+ PropertySetParameterList
+ ) { FunctionBody }
+ PropertyName :See 11.1.5
+
+ IdentifierName
StringLiteral
NumericLiteral
+ PropertySetParameterList :See 11.1.5
++ Identifier
++ MemberExpression :See 11.2
+
+ PrimaryExpression
FunctionExpression
MemberExpression [ Expression ] MemberExpression . IdentifierNamenew MemberExpression
+ Arguments
+ NewExpression :See 11.2
+
+ MemberExpression
new
+ CallExpression :See 11.2
+
+ MemberExpression
+ Arguments
+ Arguments[ Expression ] CallExpression . IdentifierName
+ Arguments :See 11.2
+
+ ( ) ArgumentList
()
+ ArgumentList :See 11.2
+
+ AssignmentExpression
ArgumentList , AssignmentExpression
+ LeftHandSideExpression :See 11.2
+
+ NewExpression
CallExpression
+ PostfixExpression :See 11.3
+
+ LeftHandSideExpression
LeftHandSideExpression
+ [noLineTerminator here]
+ ++
LeftHandSideExpression
+ [noLineTerminator here]
+ --
+ UnaryExpression :See 11.4
+
+ PostfixExpression
delete
+ void
+ UnaryExpressiontypeof
+ UnaryExpression
++-- UnaryExpression+ UnaryExpression- UnaryExpression~ UnaryExpression! UnaryExpression
+ MultiplicativeExpression :See 11.5
+
+ UnaryExpression
MultiplicativeExpression * UnaryExpression
MultiplicativeExpression / UnaryExpression
MultiplicativeExpression % UnaryExpression
+ AdditiveExpression :See 11.6
+
+ MultiplicativeExpression
AdditiveExpression + MultiplicativeExpression
AdditiveExpression - MultiplicativeExpression
+ ShiftExpression :See 11.7
+
+ AdditiveExpression
ShiftExpression << AdditiveExpression
ShiftExpression >> AdditiveExpression
ShiftExpression >>> AdditiveExpression
+ RelationalExpression :See 11.8
+
+ ShiftExpression
RelationalExpression < ShiftExpression
RelationalExpression > ShiftExpression
RelationalExpression <= ShiftExpression
RelationalExpression >= ShiftExpression
RelationalExpression instanceof ShiftExpression
RelationalExpression in ShiftExpression
+ RelationalExpressionNoIn :See 11.8
+
+ ShiftExpression
RelationalExpressionNoIn < ShiftExpression
RelationalExpressionNoIn > ShiftExpression
RelationalExpressionNoIn <= ShiftExpression
RelationalExpressionNoIn >= ShiftExpression
RelationalExpressionNoIn instanceof ShiftExpression
+ EqualityExpression :See 11.9
+
+ RelationalExpression
EqualityExpression == RelationalExpression
EqualityExpression != RelationalExpression
EqualityExpression === RelationalExpression
EqualityExpression !== RelationalExpression
+ EqualityExpressionNoIn :See 11.9
+
+ RelationalExpressionNoIn
EqualityExpressionNoIn == RelationalExpressionNoIn
EqualityExpressionNoIn != RelationalExpressionNoIn
EqualityExpressionNoIn === RelationalExpressionNoIn
EqualityExpressionNoIn !== RelationalExpressionNoIn
+ BitwiseANDExpression :See 11.10
+
+ EqualityExpression
BitwiseANDExpression & EqualityExpression
+ BitwiseANDExpressionNoIn :See 11.10
+
+ EqualityExpressionNoIn
BitwiseANDExpressionNoIn & EqualityExpressionNoIn
+ BitwiseXORExpression :See 11.10
+
+ BitwiseANDExpression
BitwiseXORExpression ^ BitwiseANDExpression
+ BitwiseXORExpressionNoIn :See 11.10
+
+ BitwiseANDExpressionNoIn
BitwiseXORExpressionNoIn ^ BitwiseANDExpressionNoIn
+ BitwiseORExpression :See 11.10
+
+ BitwiseXORExpression
BitwiseORExpression | BitwiseXORExpression
+ BitwiseORExpressionNoIn :See 11.10
+
+ BitwiseXORExpressionNoIn
BitwiseORExpressionNoIn | BitwiseXORExpressionNoIn
+ LogicalANDExpression :See 11.11
+
+ BitwiseORExpression
LogicalANDExpression && BitwiseORExpression
+ LogicalANDExpressionNoIn :See 11.11
+
+ BitwiseORExpressionNoIn
LogicalANDExpressionNoIn && BitwiseORExpressionNoIn
+ LogicalORExpression :See 11.11
+
+ LogicalANDExpression
LogicalORExpression || LogicalANDExpression
+ LogicalORExpressionNoIn :See 11.11
+
+ LogicalANDExpressionNoIn
LogicalORExpressionNoIn || LogicalANDExpressionNoIn
+ ConditionalExpression :See 11.12
+
+ LogicalORExpression
LogicalORExpression
+ ? AssignmentExpression : AssignmentExpression
+ ConditionalExpressionNoIn :See 11.12
+
+ LogicalORExpressionNoIn
LogicalORExpressionNoIn
+ ? AssignmentExpressionNoIn : AssignmentExpressionNoIn
+ AssignmentExpression :See 11.13
+
+ ConditionalExpression
LeftHandSideExpression
+ AssignmentOperator AssignmentExpression
+ AssignmentExpressionNoIn :See 11.13
+
+ ConditionalExpressionNoIn
LeftHandSideExpression
+ AssignmentOperator AssignmentExpressionNoIn
+ AssignmentOperator : + one + ofSee 11.13
+|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+ Expression :See 11.14
+
+ AssignmentExpression
Expression , AssignmentExpression
+ ExpressionNoIn :See 11.14
+
+ AssignmentExpressionNoIn
ExpressionNoIn , AssignmentExpressionNoIn
+ Statement :See clause 12
+
+ Block
VariableStatement
EmptyStatement
ExpressionStatement
IfStatement
IterationStatement
ContinueStatement
BreakStatement
ReturnStatement
WithStatement
LabelledStatement
SwitchStatement
ThrowStatement
TryStatement
DebuggerStatement
+ Block :See 12.1
+
+ { StatementListopt }
+ StatementList :See 12.1
+
+ Statement
StatementList
+ Statement
+ VariableStatement :See 12.2
+
+ var VariableDeclarationList ;
+ VariableDeclarationList :See 12.2
+
+ VariableDeclaration
VariableDeclarationList , VariableDeclaration
+ VariableDeclarationListNoIn :See 12.2
+
+ VariableDeclarationNoIn
VariableDeclarationListNoIn , VariableDeclarationNoIn
+ VariableDeclaration :See 12.2
++ Identifier + Initialiseropt
++ VariableDeclarationNoIn :See 12.2
++ Identifier + InitialiserNoInopt
++ Initialiser :See 12.2
+
+ = AssignmentExpression
+ InitialiserNoIn :See 12.2
+
+ = AssignmentExpressionNoIn
+ EmptyStatement :See 12.3
+
+ ;
+ ExpressionStatement :See 12.4
+
+ [lookahead
+ ∉
+ {{,
+ function}]Expression ;
+ IfStatement :See 12.5
+
+ if ( Expression ) Statement else Statementif ( Expression ) Statement
+ IterationStatement :See 12.6
+
+ do
+ Statement
+ while ( Expression ); while ( Expression ) Statementfor ( ExpressionNoInopt; Expressionopt ; Expressionopt ) Statementfor ( var VariableDeclarationListNoIn; Expressionopt ; Expressionopt ) Statementfor ( LeftHandSideExpression in Expression ) Statementfor ( var VariableDeclarationNoIn in Expression ) Statement
+ ContinueStatement :See 12.7
+
+ continue
+ [noLineTerminator here]Identifieropt ;
+ BreakStatement :See 12.8
+
+ break
+ [noLineTerminator here]Identifieropt ;
+ ReturnStatement :See 12.9
+
+ return
+ [noLineTerminator here]Expressionopt ;
+ WithStatement :See 12.10
+
+ with ( Expression ) Statement
+ SwitchStatement :See 12.11
+
+ switch ( Expression ) CaseBlock
+ CaseBlock :See 12.11
+
+ { CaseClausesopt } { CaseClausesoptDefaultClause CaseClausesopt }
+ CaseClauses :See 12.11
+
+ CaseClause
CaseClauses
+ CaseClause
+ CaseClause :See 12.11
+
+ case Expression : StatementListopt
+ DefaultClause :See 12.11
+
+ default : StatementListopt
+ LabelledStatement :See 12.12
+
+ Identifier : Statement
+ ThrowStatement :See 12.13
+
+ throw
+ [noLineTerminator here]
+ Expression ;
+ TryStatement :See 12.14
+
+ try Block Catchtry Block Finallytry Block Catch Finally
+ Catch :See 12.14
+
+ catch (
+ Identifier ) Block
+ Finally :See 12.14
+
+ finally Block
+ DebuggerStatement :See 12.15
+
+ debugger ;
+ FunctionDeclaration :See clause 13
+
+ function Identifier ( FormalParameterListopt ) { FunctionBody }
+ FunctionExpression :See clause 13
+
+ function Identifieropt ( FormalParameterListopt ) { FunctionBody }
+ FormalParameterList :See clause 13
+
+ Identifier
FormalParameterList , Identifier
+ FunctionBody :See clause 13
++ SourceElementsopt
++ Program :See clause 14
++ SourceElementsopt
++ SourceElements :See clause 14
+
+ SourceElement
SourceElements
+ SourceElement
+ SourceElement :See clause 14
+
+ Statement
FunctionDeclaration
+ uri :::See 15.1.3
++ uriCharactersopt
++ uriCharacters :::See 15.1.3
++ uriCharacter + uriCharactersopt
++ uriCharacter :::See 15.1.3
+
+ uriReserved
uriUnescaped
uriEscaped
+ uriReserved ::: + one + ofSee 15.1.3
+
+ ;
+ / ? : @ & = + $ ,
+ uriUnescaped :::See 15.1.3
+
+ uriAlpha
DecimalDigit
uriMark
+ uriEscaped :::See 15.1.3
+
+ % HexDigit HexDigit
+ uriAlpha ::: + one + ofSee 15.1.3
+
+ a
+ b c d e f g h i j k l m n o p q r s t u v w x
+ y z
A B C D E F G H I J K L M N O P Q R S T
+ U V W X Y Z
+ uriMark ::: + one + ofSee 15.1.3
+
+ -
+ _ . ! ~ * ‘ ( )
+ Pattern ::See 15.10.1
++ Disjunction
++ Disjunction ::See 15.10.1
+
+ Alternative
+ Alternative | Disjunction
+ Alternative ::See 15.10.1
+
+ [empty]
Alternative
+ Term
+ Term ::See 15.10.1
+
+ Assertion
Atom
Atom
+ Quantifier
+ Assertion ::See 15.10.1
+
+ ^ $ \
+ b \
+ B (
+ ?
+ =
+ Disjunction ) (
+ ?
+ !
+ Disjunction )
+ Quantifier ::See 15.10.1
+
+ QuantifierPrefix
QuantifierPrefix
+ ?
+ QuantifierPrefix ::See 15.10.1
+
+ *
+? { DecimalDigits } { DecimalDigits
+ ,
+ } { DecimalDigits
+ , DecimalDigits }
+ Atom ::See 15.10.1
+
+ PatternCharacter.\
+ AtomEscape
CharacterClass
() (
+ ?
+ :
+ Disjunction )
+ PatternCharacter :: SourceCharacter but + not any + of:See 15.10.1
+
+ ^
+ $ \ . * + ? ( ) [ ] { } |
+ AtomEscape ::See 15.10.1
+
+ DecimalEscape
CharacterEscape
CharacterClassEscape
+ CharacterEscape ::See 15.10.1
+
+ ControlEscapec ControlLetter
HexEscapeSequence
UnicodeEscapeSequence
IdentityEscape
+ ControlEscape :: one + ofSee 15.10.1
+
+ f
+ n r t v
+ ControlLetter :: one + ofSee 15.10.1
+
+ a
+ b c d e f g h i j k l m n o p q r s t u v w x
+ y z
A B C D E F G H I J K L M N O P Q R S T
+ U V W X Y Z
+ IdentityEscape ::See 15.10.1
+
+ SourceCharacter but
+ not
+ IdentifierPart
<ZWJ>
<ZWNJ>
+ DecimalEscape ::See 15.10.1
++ DecimalIntegerLiteral [lookahead + ∉ + DecimalDigit]
++
++ CharacterClassEscape :: + one + ofSee 15.10.1
+
+ d
+ D s S w W
+ CharacterClass ::See 15.10.1
+
+ [
+ [lookahead
+ ∉
+ {^}]
+ ClassRanges
+ ] [
+ ^ ClassRanges
+ ]
+ ClassRanges ::See 15.10.1
+
+ [empty]
NonemptyClassRanges
+ NonemptyClassRanges ::See 15.10.1
+
+ ClassAtom
ClassAtom
+ NonemptyClassRangesNoDash
ClassAtom
+ – ClassAtom ClassRanges
+ NonemptyClassRangesNoDash ::See 15.10.1
+
+ ClassAtom
ClassAtomNoDash
+ NonemptyClassRangesNoDash
ClassAtomNoDash
+ – ClassAtom ClassRanges
+ ClassAtom ::See 15.10.1
+
+ -
ClassAtomNoDash
+ ClassAtomNoDash ::See 15.10.1
+
+ SourceCharacter but
+ not one
+ of \ or ]
+ or - \
+ ClassEscape
+ ClassEscape ::See 15.10.1
+
+ DecimalEscapeb
CharacterEscape
+ JSONWhiteSpace ::See 15.12.1.1
+
+ <TAB>
<CR>
<LF>
<SP>
+ JSONString ::See 15.12.1.1
+
+ "
+ JSONStringCharactersopt "
+ JSONStringCharacters ::See 15.12.1.1
++ JSONStringCharacter + JSONStringCharactersopt +
++ JSONStringCharacter ::See 15.12.1.1
+
+ SourceCharacter but
+ not double-quote " or backslash \
+ or U+0000 thru
+ U+001F
+ \ JSONEscapeSequence
+ JSONEscapeSequence ::See 15.12.1.1
++ JSONEscapeCharacter
++ UnicodeEscapeSequence +
++ JSONEscapeCharacter :: + one + ofSee 15.12.1.1
+
+ "
+ / \ b f n r t
+ JSONNumber ::See 15.12.1.1
+
+ -optDecimalIntegerLiteral JSONFractionoptExponentPartopt
+ JSONFraction ::See 15.12.1.1
+
+ . DecimalDigits
+ JSONNullLiteral ::See 15.12.1.1
++ NullLiteral
++ JSONBooleanLiteral ::See 15.12.1.1
++ BooleanLiteral
++ JSONText :See 15.12.1.2
++ JSONValue
++ JSONValue :See 15.12.1.2 +
+
+ JSONNullLiteral
JSONBooleanLiteral
JSONObject
JSONArray
JSONString
JSONNumber
+ JSONObject :See 15.12.1.2
+
+ {
+ } { JSONMemberList }
+ JSONMember :See 15.12.1.2
+
+ JSONString : JSONValue
+ JSONMemberList :See 15.12.1.2
+
+ JSONMember
+
JSONMemberList ,
+ JSONMember
+
+ JSONArray :See 15.12.1.2
+
+ [
+ ] [ JSONElementList
+ ]
+ JSONElementList :See 15.12.1.2
+
+ JSONValue
JSONElementList
+ , JSONValue
+ Past + editions of ECMAScript have included additional syntax and semantics + for specifying octal literals and octal escape sequences. These have + been removed from this edition of ECMAScript. This non-normative + annex presents uniform syntax and semantics for octal literals and + octal escape sequences for compatibility with some older ECMAScript + programs.
++ The + syntax and semantics of 7.8.3 can be extended as follows except that + this extension is not allowed for strict mode code:
++ Syntax
++ NumericLiteral ::
+
+ DecimalLiteral
HexIntegerLiteral
OctalIntegerLiteral
+ OctalIntegerLiteral ::
+
+ 0 OctalDigit
OctalIntegerLiteral OctalDigit
+ OctalDigit :: one + of
+
+ 0
+ 1
+ 2
+ 3
+ 4
+ 5
+ 6
+ 7
+ Semantics
++ The + MV of NumericLiteral + :: + OctalIntegerLiteral is + the MV of OctalIntegerLiteral.
+
+ The
+ MV of OctalDigit ::
+ 0
+ is 0.
+ The
+ MV of OctalDigit ::
+ 1
+ is 1.
+ The
+ MV of OctalDigit ::
+ 2
+ is 2.
+ The
+ MV of OctalDigit ::
+ 3
+ is 3.
+ The
+ MV of OctalDigit ::
+ 4
+ is 4.
+ The
+ MV of OctalDigit ::
+ 5
+ is 5.
+ The
+ MV of OctalDigit ::
+ 6
+ is 6.
+ The
+ MV of OctalDigit ::
+ 7
+ is 7.
+ The
+ MV of OctalIntegerLiteral ::
+ 0
+ OctalDigit is the MV
+ of OctalDigit.
+ The + MV of OctalIntegerLiteral :: + OctalIntegerLiteral + OctalDigit is (the MV + of OctalIntegerLiteral + times 8) plus the MV of OctalDigit.
++ The + syntax and semantics of 7.8.4 can be extended as follows except that + this extension is not allowed for strict mode code:
++ Syntax
++ EscapeSequence ::
+
+ CharacterEscapeSequence
OctalEscapeSequence
HexEscapeSequence
UnicodeEscapeSequence
+ OctalEscapeSequence ::
+
+ OctalDigit [lookahead
+ ∉
+ DecimalDigit]
ZeroToThree
+ OctalDigit [lookahead
+ ∉DecimalDigit]
FourToSeven
+ OctalDigit
ZeroToThree OctalDigit OctalDigit
+ ZeroToThree :: one + of
+
+ 0
+ 1 2 3
+ FourToSeven :: + one + of
++ 4 + 5 6 7
++ Semantics
++ The + CV of EscapeSequence :: + OctalEscapeSequence + is the CV of the OctalEscapeSequence.
++ The + CV of OctalEscapeSequence + :: + OctalDigit [lookahead + ∉ + DecimalDigit] + is the character whose code unit value is the MV of the + OctalDigit.
++ The + CV of OctalEscapeSequence + :: + ZeroToThree + OctalDigit [lookahead + ∉ + DecimalDigit] + is the character whose code unit value is (8 times the MV of the + ZeroToThree) plus the + MV of the OctalDigit.
++ The + CV of OctalEscapeSequence + :: + FourToSeven + OctalDigit is the + character whose code unit value is (8 times the MV of the + FourToSeven) plus the + MV of the OctalDigit.
++ The + CV of OctalEscapeSequence + :: + ZeroToThree + OctalDigit OctalDigit + is the character whose code unit value is (64 (that is, 82) + times the MV of the ZeroToThree) + plus (8 times the MV of the first OctalDigit) + plus the MV of the second OctalDigit.
+
+ The
+ MV of ZeroToThree ::
+ 0
+ is 0.
+ The
+ MV of ZeroToThree ::
+ 1
+ is 1.
+ The
+ MV of ZeroToThree ::
+ 2
+ is 2.
+ The
+ MV of ZeroToThree ::
+ 3
+ is 3.
+ The
+ MV of FourToSeven ::
+ 4
+ is 4.
+ The
+ MV of FourToSeven ::
+ 5
+ is 5.
+ The
+ MV of FourToSeven ::
+ 6
+ is 6.
+ The
+ MV of FourToSeven ::
+ 7
+ is 7.
+ Some + implementations of ECMAScript have included additional properties + for some of the standard native objects. This non-normative annex + suggests uniform semantics for such properties without making the + properties or their semantics part of this standard.
+
+ The
+ escape function is
+ a property of the global object. It computes a new version of a
+ String value in which certain characters have been replaced by a
+ hexadecimal escape sequence.
+ For
+ those characters being replaced whose code unit value is 0xFF
+ or less, a two-digit escape sequence of the form % xx
+ is used. For those characters being replaced whose code unit value
+ is greater than 0xFF,
+ a four-digit escape sequence of the form %u xxxx
+ is used
+ When
+ the escape
+ function is called with one argument string,
+ the following steps are taken:
+ Call + ToString(string).
++ Compute + the number of characters in Result(1).
++ Let + R be the empty string.
++ Let + k be 0.
++ If + k equals Result(2), return R.
++ Get + the character (represented as a 16-bit unsigned integer) at + position k within Result(1).
+
+ If
+ Result(6) is one of the 69 nonblank
+ characters“ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789@*_+-./”then
+ go to step 13.
+ If + Result(6), is less than 256, go to step 11.
+
+ Let
+ S be a String containing six characters “%u wxyz”
+ where wxyz are four hexadecimal digits encoding the value of
+ Result(6).
+ Go + to step 14.
+
+ Let
+ S be a String containing three characters “% xy”
+ where xy are two hexadecimal digits encoding the value of
+ Result(6).
+ Go + to step 14.
++ Let + S be a String containing the single character Result(6).
++ Let + R be a new String value computed by concatenating the + previous value of R and S.
++ Increase + k by 1.
++ Go + to step 5.
+NOTE The + encoding is partly based on the encoding described in RFC 1738, but + the entire encoding specified in this standard is described above + without regard to the contents of RFC 1738. This encoding does not + reflect changes to RFC 1738 made by RFC 3986.
+ +
+ The
+ unescape function
+ is a property of the global object. It computes a new version of a
+ String value in which each escape sequence of the sort that might be
+ introduced by the escape
+ function is replaced with the character that it represents.
+ When
+ the unescape
+ function is called with one argument string,
+ the following steps are taken:
+ Call + ToString(string).
++ Compute + the number of characters in Result(1).
++ Let + R be the empty String.
++ Let + k be 0.
++ If + k equals Result(2), return R.
++ Let + c be the character at position k within Result(1).
+
+ If
+ c is not %,
+ go to step 18.
+ If + k is greater than Result(2)−6, + go to step 14.
+
+ If
+ the character at position k+1 within Result(1) is not u,
+ go to step 14.
+ If + the four characters at positions k+2, k+3, k+4, + and k+5 within Result(1) are not all hexadecimal digits, go + to step 14.
++ Let + c be the character whose code unit value is the integer + represented by the four hexadecimal digits at positions k+2,k+3, k+4, and k+5 within Result(1).
++ Increase + k by 5.
++ Go + to step 18.
++ If + k is greater than Result(2)−3, + go to step 18.
++ If + the two characters at positions k+1 and k+2 within + Result(1) are not both hexadecimal digits, go to step 18.
++ Let + c be the character whose code unit value is the integer + represented by two zeroes plus the two hexadecimal digits at + positions k+1 and k+2 within Result(1).
++ Increase + k by 2.
++ Let + R be a new String value computed by concatenating the + previous value of R and c.
++ Increase + k by 1.
++ Go + to step 5.
+
+ The
+ substr method
+ takes two arguments, start
+ and length, and
+ returns a substring of the result of converting the this object to a
+ String, starting from character position start
+ and running for length
+ characters (or through the end of the String if length
+ is undefined). If start
+ is negative, it is treated as (sourceLength+start)
+ where sourceLength
+ is the length of the String. The result is a String value, not a
+ String object. The following steps are taken:
+ Call + ToString, giving it the this value as its argument.
++ Call + ToInteger(start).
++ If + length is undefined, use +∞; + otherwise call ToInteger(length).
++ Compute + the number of characters in Result(1).
++ If + Result(2) is positive or zero, use Result(2); else use + max(Result(4)+Result(2),0).
++ Compute + min(max(Result(3),0), Result(4)–Result(5)).
++ If + Result(6) ≤ 0, return the empty + String “”.
++ Return + a String containing Result(6) consecutive characters from Result(1) + beginning with the character at position Result(5).
+
+ The
+ length property of
+ the substr method
+ is 2.
NOTE The
+ substr function is
+ intentionally generic; it does not require that its this
+ value be a String object. Therefore it can be transferred to other
+ kinds of objects for use as a method.
NOTE The
+ getFullYear method
+ is preferred for nearly all purposes, because it avoids the “year
+ 2000 problem.”
+ When + the getYear method is called with no arguments, the following + steps are taken:
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + YearFromTime(LocalTime(t)) − + 1900.
+NOTE The
+ setFullYear method
+ is preferred for nearly all purposes, because it avoids the “year
+ 2000 problem.”
+ When + the setYear method is called with one argument year, + the following steps are taken:
++ Let + t be the result of LocalTime(this time value); but if this time value is NaN, let t be +0.
++ Call + ToNumber(year).
++ If + Result(2) is NaN, set the [[PrimitiveValue]] internal + property of the this value to NaN and return NaN.
++ If + Result(2) is not NaN and 0 ≤ + ToInteger(Result(2)) ≤ 99 then + Result(4) is ToInteger(Result(2)) + 1900. Otherwise, Result(4) + is Result(2).
++ Compute + MakeDay(Result(4), MonthFromTime(t), DateFromTime(t)).
++ Compute + UTC(MakeDate(Result(5), TimeWithinDay(t))).
++ Set + the [[PrimitiveValue]] internal property of the this value + to TimeClip(Result(6)).
++ Return + the value of the [[PrimitiveValue]] internal property of the this + value.
+NOTE The
+ property toUTCString
+ is preferred. The toGMTString
+ property is provided principally for compatibility with old code. It
+ is recommended that the toUTCString
+ property be used in new ECMAScript code.
+ The
+ Function object that is the initial value of
+ Date.prototype.toGMTString
+ is the same Function object that is the initial value of
+ Date.prototype.toUTCString.
+ The + strict mode restriction and exceptions
+implements", "interface",
+"let", "package", "private",
+"protected", "public", "static", and
+"yield" are classified as FutureReservedWord tokens
+within strict mode code. (7.6.12 [?]).+ A + conforming implementation, when processing strict mode code, may + not extend the syntax of NumericLiteral + (7.8.3) to include OctalIntegerLiteral + as described in B.1.1.
++ A + conforming implementation, when + processing strict mode code (see 10.1.1), may not extend the syntax + of EscapeSequence to + include OctalEscapeSequence + as described in B.1.2.
+
+ Assignment
+ to an undeclared identifier or otherwise unresolvable reference
+ does not create a property in the global object. When a simple
+ assignment occurs within strict mode code, its LeftHandSide must not evaluate to an
+ unresolvable Reference. If it does a ReferenceError
+ exception is thrown (8.7.2). The LeftHandSide also
+ may not be a reference to a data property with the attribute value
+ {[[Writable]]:false},
+ to an accessor property with the attribute value
+ {[[Set]]:undefined},
+ nor to a non-existent
+ property of an object whose [[Extensible]] internal property has
+ the value false.
+ In these cases a TypeError
+ exception is thrown (11.13.1).
+ The
+ identifier eval
+ or arguments
+ may not appear as the LeftHandSideExpression
+ of an Assignment operator (11.13) or of a PostfixExpression
+ (11.3) or as the UnaryExpression
+ operated upon by a Prefix Increment (11.4.4) or a Prefix Decrement
+ (11.4.5) operator.
+
+ Arguments
+ objects for strict mode functions define non-configurable accessor
+ properties named "caller"
+ and "callee"
+ which throw a TypeError exception on access
+ (10.6).
+ Arguments + objects for strict mode functions do not dynamically share their + array indexed property values with the corresponding formal + parameter bindings of their functions. (10.6).
+
+ For
+ strict mode functions, if an arguments object is created the
+ binding of the local identifier arguments
+ to the arguments object is immutable and hence may not be the
+ target of an assignment expression. (10.5).
+ It + is a SyntaxError + if strict mode code contains an + ObjectLiteral with + more than one definition of any data property (11.1.5).
+
+ It
+ is a SyntaxError
+ if the Identifier
+ "eval"
+ or the Identifier "arguments"
+ occurs as the Identifier
+ in a PropertySetParameterList
+ of a
+ PropertyAssignment
+ that is contained in strict code or
+ if its FunctionBody is
+ strict code (11.1.5).
+ Strict + mode eval code cannot instantiate variables or functions in the + variable environment of the caller to eval. Instead, a new variable + environment is created and that environment is used for declaration + binding instantiation for the eval code (10.4.2).
+
+ If
+ this
+ is evaluated within strict mode code, then the this
+ value is not coerced to
+ an object. A this
+ value of null
+ or undefined
+ is not converted to the global object and primitive values are not
+ converted to wrapper objects. The this
+ value passed via a function call (including calls made using
+ Function.prototype.apply
+ and Function.prototype.call)
+ do not coerce the passed this value to an object (10.4.3, 11.1.1,
+ 15.3.4.3, 15.3.4.4).
+ When
+ a delete
+ operator occurs within strict mode code,
+ a SyntaxError is thrown if its
+ UnaryExpression is a
+ direct reference to a variable, function argument, or function
+ name(11.4.1).
+ When
+ a delete
+ operator occurs within strict mode code, a TypeError
+is thrown if the property to
+ be deleted has the attribute { [[Configurable]]:false
+ } (11.4.1).
+ It
+ is a SyntaxError
+ if a VariableDeclaration
+ or VariableDeclarationNoIn
+ occurs within strict code and its Identifier
+ is eval
+ or
+ arguments
+ (12.2.1).
+ Strict + mode code may not include a WithStatement. + The occurrence of a WithStatement + in such a context is an SyntaxError + (12.10).
+
+ It
+ is a SyntaxError if a TryStatement
+ with a Catch
+ occurs within strict code and the Identifier
+ of the Catch
+ production is eval
+ or arguments
+ (12.14.1)
+ It
+ is a SyntaxError if the identifier eval
+ or arguments
+ appears within a FormalParameterList
+ of a strict mode FunctionDeclaration
+ or FunctionExpression
+ (13.1)
+ A
+ strict mode function may not have two or more formal parameters
+ that have the same name. An attempt to create such a function using
+ a FunctionDeclaration,
+ FunctionExpression, or
+ Function
+ constructor is a SyntaxError
+ (13.1, 15.3.2).
+ An
+ implementation may not extend, beyond that defined in this specification,
+ meanings within strict mode functions of properties named caller
+ or arguments
+ of function instances. ECMAScript code may not create or modify
+ properties with these names on function objects that correspond to
+ strict mode functions
+ (10.6, 13.2, 15.3.4.5.3).
+ It
+ is a SyntaxError
+ to use within strict mode code the identifiers eval
+ or arguments
+ as the Identifier of a
+ FunctionDeclaration or
+ FunctionExpression or
+ as a formal parameter name (13.1). Attempting to dynamically define
+ such a strict mode function using the Function
+ constructor (15.3.2) will throw a SyntaxError
+ exception.
+ Throughout:
+ In the Edition 3 specification the meaning of phrases such as “as
+ if by the expression new
+ Array()” are subject to misinterpretation. In the
+ Edition 5 specification text for all internal references and
+ invocations of standard built-in objects and methods has been
+ clarified by making it explicit that the intent is that the actual
+ built-in object is to be used rather than the current dynamic value
+ of the correspondingly named property.
+
+ 11.8.2, + 11.8.3, 11.8.5: ECMAScript generally uses a left to right evaluation + order, however the Edition 3 specification language for the > and + <= operators resulted in a partial right to left order. The + specification has been corrected for these operators such that it + now specifies a full left to right evaluation order. However, this + change of order is potentially observable if side-effects occur + during the evaluation process.
++ 11.1.4: + Edition 5 clarifies the fact that a trailing comma at the end of an + ArrayInitialiser + does not add to the length of the array. This is not a semantic + change from Edition 3 but some implementations may have previously + misinterpreted this.
++ 11.2.3: + Edition 5 reverses the order of steps 2 and 3 of the algorithm. The + original order as specified in Editions 1 through 3 was incorrectly + specified such that side-effects of evaluating Arguments + could affect the result of evaluating MemberExpression.
+
+ 12.4:
+ In Edition 3, an object is created, as if by new
+ Object()to serve as the scope for resolving the name of
+ the exception parameter passed to a catch
+ clause of a try
+ statement. If the actual exception object is a function and it is
+ called from within the catch
+ clause, the scope object will be passed as the this value of
+ the call. The body of the function can then define new properties on
+ its this value and those property names become visible
+ identifiers bindings within the scope of the catch clause
+ after the function returns. In Edition 5, when an exception
+ parameter is called as a function, undefined is passed as the
+ this value.
+ 13:.
+ In Edition 3, the algorithm for the production FunctionExpression
+ with an Identifier
+ adds an object created as if by new
+ Object() to the scope chain to serve as a scope for
+ looking up the name of the function. The identifier resolution rules
+ (10.1.4 in Edition 3) when applied to such an object will, if
+ necessary, follow the object’s prototype chain when attempting to
+ resolve an identifier. This means all the properties of
+ Object.prototype are visible as identifiers within that scope. In
+ practice most implementations of Edition 3 have not implemented this
+ semantics. Edition 5 changes the specified semantics by using a
+ Declarative Environment Record to bind the name of the function.
+ 14:.
+ In Edition 3, the algorithm for the production SourceElements : SourceElements
+ SourceElement did not correctly propagate statement
+ result values in the same manner as Block.
+ This could result in the eval function producing an incorrect result when evaluating a Program
+ text. In practice most implementations of Edition 3 have implemented
+ the correct propagation rather than what was specified in Edition 3.
+ 15.10.6: + RegExp.prototype is now a RegExp object rather than an instance of + Object. The value of its [[Class]] internal property which is + observable using Object.prototype.toString + is now “RegExp” rather than “Object”.
++ 7.1: + Unicode format control characters are no longer stripped from + ECMAScript source text before processing. In Edition 5, if such a + character appears in a StringLiteral + or RegularExpressionLiteral + the character will be incorporated into the literal where in Edition + 3 the character would not be incorporated into the literal.
++ 7.2: + Unicode character <BOM> is now treated as whitespace and its + presence in the middle of what appears to be an identifier could + result in a syntax error which would not have occurred in Edition 3
++ 7.3: + Line terminator characters that are preceded by an escape sequence + are now allowed within a string literal token. In Edition 3 a + syntax error would have been produced.
++ 7.8.5: + Regular expression literals now return a unique object each time the + literal is evaluated. This change is detectable by any programs that + test the object identity of such literal values or that are + sensitive to the shared side effects.
++ 7.8.5: + Edition 5 requires early reporting of any possible RegExp + constructor errors that would be produced when converting a + RegularExpressionLiteral + to a RegExp object. Prior to Edition 5 implementations were + permitted to defer the reporting of such errors until the actual + execution time creation of the object.
++ 7.8.5: + In Edition 5 unescaped “/” characters may appear as a + CharacterClass in + a regular expression literal. In Edition 3 such a character would + have been interpreted as the final character of the literal.
+
+ 10.4.2:
+ In Edition 5, indirect calls to the eval function use the global environment as both the variable environment
+ and lexical environment for the eval code. In Edition 3, the
+ variable and lexical environments of the caller of an indirect eval
+ was used as the environments for the eval code.
+ 15.4.4:
+ In Edition 5 all methods of Array.prototype
+ are intentionally generic. In Edition 3 toString
+ and toLocaleString
+ were not generic and would throw a TypeError
+ exception if applied to objects that were not instances of Array.
+ 10.6: + In Edition 5 the array indexed properties of argument objects that + correspond to actual formal parameters are enumerable. In Edition + 3, such properties were not enumerable.
+
+ 10.6:
+ In Edition 5 the value of the [[Class]] internal property of an
+ arguments object is "Arguments".
+ In Edition 3, it was "Object".
+ This is observable if toString
+ is called as a method of an arguments object.
+
+ 12.6.4:
+ for-in statements no longer throw a TypeError if the in
+ expression evaluates to null or undefined. Instead,
+ the statement behaves as if the value of the expression was an
+ object with no enumerable properties.
+ 15:
+ In Edition 5, the following new properties are defined on built-in
+ objects that exist in Edition 3:
+Object.getPrototypeOf,
+Object.getOwnPropertyDescriptor,
+Object.getOwnPropertyNames,
+Object.create,
+Object.defineProperty,
+ Object.defineProperties,
+ Object.seal,
+ Object.freeze,
+ Object.preventExtensions,
+ Object.isSealed,
+ Object.isFrozen,
+ Object.isExtensible,
+ Object.keys,
+ Function.prototype.bind,
+ Array.prototype.indexOf,
+ Array.prototype.lastIndexOf,
+ Array.prototype.every,
+ Array.prototype.some,
+ Array.prototype.forEach,
+ Array.prototype.map,
+ Array.prototype.filter,
+ Array.prototype.reduce,
+ Array.prototype.reduceRight,
+ String.prototype.trim,
+ Date.now,
+ Date.prototype.toISOString,
+ Date.prototype.toJSON.
+
+ 15: + Implementations are now required to ignore extra arguments to + standard built-in methods unless otherwise explicitly specified. In + Edition 3 the handling of extra arguments was unspecified and + implementations were explicitly allowed to throw a TypeError + exception.
++ 15.1.1: + The value properties NaN, Infinity, and undefined + of the Global Object have been changed to be read-only properties.
++ 15.1.2.1. + Implementations are no longer permitted to restrict the use of eval + in ways that are not a direct call. In addition, any invocation of + eval that is not a direct call uses the global environment as its + variable environment rather than the caller’s variable + environment.
+
+ 15.1.2.2:
+ The specification of the function parseInt
+ no longer allows implementations to treat Strings beginning with a 0
+ character as octal values.
+ 15.3.4.3:
+ In Edition 3, a TypeError is thrown if the second argument
+ passed to Function.prototype.apply
+ is neither an array object nor an arguments object. In Edition 5,
+ the second argument may be any kind of generic array-like object
+ that has a valid length
+ property.
+ 15.3.4.3, 15.3.4.4:
+ In Edition 3 passing undefined or null as the first
+ argument to either Function.prototype.apply
+ or Function.prototype.call
+ causes the global object to be passed to the indirectly invoked
+ target function as the this value. If the first argument is a
+ primitive value the result of calling ToObject on the primitive value is passed as the this value. In Edition 5, these
+ transformations are not performed and the actual first argument
+ value is passed as the this value. This difference will
+ normally be unobservable to existing ECMAScript Edition 3 code
+ because a corresponding transformation takes place upon activation
+ of the target function. However, depending upon the implementation,
+ this difference may be observable by host object functions called
+ using apply or
+ call. In addition,
+ invoking a standard built-in function in this manner with null
+ or undefined passed as the this value will in many cases
+ cause behaviour in Edition 5 implementations that differ from
+ Edition 3 behaviour. In particular, in Edition 5 built-in functions
+ that are specified to actually use the passed this value as
+ an object typically throw a TypeError exception if passed
+ null or undefined as the this value.
+ 15.3.5.2:
+ In Edition 5, the prototype
+ property of Function instances is not enumerable. In Edition 3, this
+ property was enumerable.
+ 15.5.5.2: + In Edition 5, the individual characters of a String object’s + [[PrimitiveValue] may be accessed as array indexed properties of the + String object. These properties are non-writable and + non-configurable and shadow any inherited properties with the same + names. In Edition 3, these properties did not exist and ECMAScript + code could dynamically add and remove writable properties with such + names and could access inherited properties with such names. +
+
+ 15.9.4.2:
+ Date.parse is now
+ required to first attempt to parse its argument as an ISO format
+ string. Programs that use this format but depended upon
+ implementation specific behaviour (including failure) may behave
+ differently.
+ 15.10.2.12:
+ In Edition 5, \s
+ now additionally matches <BOM>.
+ 15.10.4.1:
+ In Edition 3, the exact form of the String value of the source
+ property of an object created by the RegExp
+ constructor is implementation defined. In Edition 5, the String must
+ conform to certain specified requirements and hence may be different
+ from that produced by an Edition 3 implementation.
+ 15.10.6.4:
+ In Edition 3, the result of RegExp.prototype.toString
+ need not be derived from the value of the RegExp object’s source
+ property. In Edition 5 the result must be derived from the source
+ property in a specified manner and hence may be different from the
+ result produced by an Edition 3 implementation.
+ 15.11.2.1,
+ 15.11.4.3: In Edition 5, if an initial value for the message
+ property of an Error object is not specified via the Error
+ constructor the initial value of the property is the empty String.
+ In Edition 3, such an initial value is implementation defined.
+ 15.11.4.4:
+ In Edition 3, the result of Error.prototype.toString
+ is implementation defined. In Edition 5, the result is fully
+ specified and hence may differ from some Edition 3 implementations.
+ 15.12:
+ In Edition 5, the name JSON
+ is defined in the global environment. In Edition 3, testing for the
+ presence of that name will show it to be undefined unless it is
+ defined by the program or implementation.
+ ANSI/IEEE + Std 754-1985: IEEE Standard for Binary Floating-Point Arithmetic. + Institute of Electrical and Electronic Engineers, New York (1985)
++ The + Unicode Consortium. The Unicode Standard, Version 3.0, defined by: + The Unicode Standard, Version 3.0 (Boston, MA, Addison-Wesley, + 2000. ISBN 0-201-61635-5)
++ Unicode + Inc. (1998), Unicode Technical Report #15: Unicode Normalization + Forms
+ISO 8601:2004(E) Data elements and interchange +formats – Information interchange -- Representation of dates and times
RFC 1738 “Uniform Resource Locators (URL)”, available at +<http://tools.ietf.org/html/rfc1738>
RFC 2396 “Uniform Resource Identifiers (URI): Generic Syntax”, +available at +<http://tools.ietf.org/html/rfc2396>
RFC 3629 “UTF-8, a transformation format of ISO 10646”, available at +<http://tools.ietf.org/html/rfc3629>
RFC 4627 “The application/json Media Type for JavaScript Object +Notation (JSON)“ , available at +<http://tools.ietf.org/html/rfc4627>
‟Ex igne vita”
+ ++ This + Standard defines the ECMAScript scripting language.
+ \ No newline at end of file diff --git a/x10.html b/x10.html new file mode 100644 index 0000000..b8e3859 --- /dev/null +++ b/x10.html @@ -0,0 +1,1719 @@ + +‟Ex igne vita”
+ ++ There + are three types of ECMAScript executable code:
+Global code is source text that + is treated as an ECMAScript Program. + The global code of a particular Program + does not include any source text that is parsed as part of a + FunctionBody.
+Eval code is the source text
+ supplied to the built-in eval function. More precisely, if the parameter to the built-in eval function is a String, it is treated as an ECMAScript Program.
+ The eval code for a particular invocation of eval
+ is the global code portion of that Program.
Function code is source text that
+ is parsed as part of a FunctionBody.
+ The function code
+ of a particular FunctionBody
+ does not include any source text that is parsed as part of a nested
+ FunctionBody. Function
+ code also denotes the
+ source text supplied when using the built-in Function object as a constructor. More precisely, the last parameter
+ provided to the Function
+ constructor is converted to a String and treated as the
+ FunctionBody. If more
+ than one parameter is provided to the Function
+ constructor, all parameters except the last one are converted to
+ Strings and concatenated together, separated by commas. The
+ resulting String is interpreted as the FormalParameterList
+ for the FunctionBody
+ defined by the last parameter. The function code for a particular
+ instantiation of a Function
+ does not include any source text that is parsed as part of a nested
+ FunctionBody.
+ An + ECMAScript Program + syntactic unit may be processed using either unrestricted or strict + mode syntax and semantics. When processed using strict mode the + three types of ECMAScript code are referred to as strict global + code, strict eval code, and strict function code. Code is + interpreted as strict mode code in the following situations:
++ Global code is strict global code if it begins with a Directive Prologue + that contains a Use Strict Directive (see 14.1).
++ Eval code is strict eval code if it begins with a Directive Prologue + that contains a Use Strict Directive or if the call to eval is a + direct call (see 15.1.2.1.1) to the eval function that is contained + in strict mode code. +
++ Function code that is part of a FunctionDeclaration, + FunctionExpression, + or accessor PropertyAssignment + is strict function code if its FunctionDeclaration, + FunctionExpression, + or PropertyAssignment + is contained in strict mode code or if the function code begins + with a Directive Prologue that contains a Use Strict Directive.
++ Function code that is supplied as the last argument to the built-in Function + constructor is strict function code if the last argument is a + String that when processed as a FunctionBody + begins with a Directive Prologue that contains a Use Strict + Directive.
++ A + Lexical Environment is a specification type used to define + the association of Identifiers + to specific variables and functions based upon the lexical nesting + structure of ECMAScript code. A Lexical Environment consists of an + Environment Record and a possibly null reference to an outer + Lexical Environment. Usually a Lexical Environment is associated + with some specific syntactic structure of ECMAScript code such as a + FunctionDeclaration, + a WithStatement, + or a Catch clause + of a TryStatement + and a new Lexical Environment is created each time such code is + evaluated.
++ An + Environment Record records the identifier bindings that are + created within the scope of its associated Lexical Environment.
++ The + outer environment reference is used to model the logical nesting of + Lexical Environment values. The outer reference of a (inner) Lexical + Environment is a reference to the Lexical Environment that logically + surrounds the inner Lexical Environment. An outer Lexical + Environment may, of course, have its own outer Lexical Environment. + A Lexical Environment may serve as the outer environment for + multiple inner Lexical Environments. For example, if a + FunctionDeclaration + contains two nested FunctionDeclarations + then the Lexical Environments of each of the nested functions will + have as their outer Lexical Environment the Lexical Environment of + the current execution of the surrounding function.
++ Lexical + Environments and Environment Record values are purely specification + mechanisms and need not correspond to any specific artefact of an + ECMAScript implementation. It is impossible for an ECMAScript + program to directly access or manipulate such values.
++ There + are two kinds of Environment Record values used in this + specification: declarative environment records and object + environment records. Declarative environment records are used + to define the effect of ECMAScript language syntactic elements such + as FunctionDeclarations, + VariableDeclarations, + and Catch clauses + that directly associate identifier bindings with ECMAScript + language values. Object environment records are used to define the + effect of ECMAScript elements such as Program + and WithStatement + that associate identifier bindings with the properties of + some object.
++ For + specification purposes Environment Record values can be thought of + as existing in a simple object-oriented hierarchy where Environment + Record is an abstract class with two concrete subclasses, + declarative environment record + and object environment record. The + abstract class includes the abstract specification methods defined + in Table 17. These abstract methods have distinct concrete + algorithms for each of the concrete subclasses. +
+|
+ + Method + |
+
+ + Purpose + |
+
|
+ + HasBinding(N) + |
+
+ + Determine + if an environment record has a binding for an identifier. Return + true if it + does and false + if it does not. The String value N + is the text of the identifier. + |
+
|
+ + CreateMutableBinding(N, + D) + |
+
+ + Create + a new mutable binding in an environment record. The String value + N is the text + of the bound name. If the optional Boolean argument D + is true the binding is may be subsequently deleted. + + |
+
|
+ + SetMutableBinding(N,V, + S) + |
+
+ + Set + the value of an already existing mutable binding in an + environment record. The String value N + is the text of the bound name. V + is the value for the binding and may be a value of any + ECMAScript language type. S + is a Boolean flag. If S + is true and + the binding cannot be set throw a TypeError exception. S + is used to identify strict mode references. + |
+
|
+ + GetBindingValue(N,S) + |
+
+ + Returns + the value of an already existing binding from an environment + record. The String value N + is the text of the bound name. S + is used to identify strict mode references. If S + is true and + the binding does not exist or is uninitialized throw a + ReferenceError exception. + + |
+
|
+ + DeleteBinding(N) + |
+
+ + Delete + a binding from an environment record. The String value N + is the text of the bound name If a binding for N + exists, remove the binding and return true. If the + binding exists but cannot be removed return false. If the + binding does not exist return true. + |
+
|
+ ImplicitThisValue() + |
+
+ Returns + the value to use as the this value on calls to function + objects that are obtained as binding values from this + environment record. + + |
+
+ Each + declarative environment record is associated with an ECMAScript + program scope containing variable and/or function declarations. A + declarative environment record binds the set of identifiers defined + by the declarations contained within its scope.
++ In + addition to the mutable bindings supported by all Environment + Records, declarative environment records also provide for immutable + bindings. An immutable binding is one where the association between + an identifier and a value may not be modified once it has been + established. Creation and initialization of immutable binding are + distinct steps so it is possible for such bindings to exist in + either an initialized or uninitialized state. Declarative + environment records support the methods listed in Table 18 in + addition to the Environment Record abstract specification methods:
+|
+ + Method + |
+
+ + Purpose + |
+
| + + | +
+ + Create + a new but uninitialized immutable binding in an environment + record. The String value N + is the text of the bound name. + |
+
| + + | +
+ Set + the value of an already existing but uninitialized immutable binding in an environment record. The String value N + is the text of the bound name. V + is the value for the binding and is a value of any ECMAScript + language type. + + |
+
+ The + behaviour of the concrete specification methods for Declarative + Environment Records are defined by the following algorithms.
++ The + concrete environment record method HasBinding for declarative + environment records simply determines if the argument identifier is + one of the identifiers bound by the record:
++ Let + envRec be the declarative environment record for which the + method was invoked.
++ If + envRec has a binding for the name that is the value of N, + return true.
++ If + it does not have such a binding, return false
++ The + concrete Environment Record method CreateMutableBinding for + declarative environment records creates a new mutable binding for + the name N that is + initialized to the value undefined. A binding must not + already exist in this Environment Record for N. + If Boolean argument D + is provided and has the value true the new binding is marked + as being subject to deletion.
++ Let + envRec be the declarative environment record for which the + method was invoked.
++ Assert: + envRec does not already have a binding for N.
++ Create + a mutable binding in envRec for N and set its bound + value to undefined. If D is true record that the + newly created binding may be deleted by a subsequent DeleteBinding + call.
++ The + concrete Environment Record method SetMutableBinding for declarative + environment records attempts to change the bound value of the + current binding of the identifier whose name is the value of the + argument N to the + value of argument V. + A binding for N + must already exist. If the binding is an immutable binding, a + TypeError is + thrown + if S is true. +
+ ++ Let + envRec be the declarative environment record for which the + method was invoked.
++ Assert: + envRec must have a binding for N.
++ If + the binding for N in envRec is a mutable binding, + change its bound value to V.
++ Else + this must be an attempt to change the value of an immutable binding + so + if S is true + throw a + TypeError + exception.
++ The + concrete Environment Record method GetBindingValue for declarative + environment records simply returns the value of its bound identifier + whose name is the value of the argument N. + The binding must already exist. If S + is true and the binding is an uninitialized immutable binding + throw a ReferenceError exception.
++ Let + envRec be the declarative environment record for which the + method was invoked.
++ Assert: + envRec has a binding for N.
++ If + the binding for N in envRec is an uninitialized + immutable binding, then
++ If + S is false, return the value undefined, + otherwise throw a ReferenceError exception.
++ Else, + return the value currently bound to N in envRec.
++ The + concrete Environment Record method DeleteBinding for declarative + environment records can only delete bindings that have been + explicitly designated as being subject to deletion.
++ Let + envRec be the declarative environment record for which the + method was invoked.
++ If + envRec does not have a binding for the name that is the + value of N, return true.
++ If + the binding for N in envRec is cannot be deleted, + return false.
++ Remove + the binding for N from envRec.
++ Return + true.
++ Declarative + Environment Records always return undefined as their + ImplicitThisValue.
++ Return + undefined.
++ The + concrete Environment Record method CreateImmutableBinding for + declarative environment records creates a new immutable binding for + the name N that is + initialized to the value undefined. A binding must not + already exist in this environment record for N.
++ Let + envRec be the declarative environment record for which the + method was invoked.
++ Assert: + envRec does not already have a binding for N.
++ Create + an immutable binding in envRec for N and record that + it is uninitialized.
++ The + concrete Environment Record method InitializeImmutableBinding for + declarative environment records is used to set the bound value of + the current binding of the identifier whose name is the value of the + argument N to the + value of argument V. + An uninitialized immutable binding for N + must already exist. +
++ Let + envRec be the declarative environment record for which the + method was invoked.
++ Assert: + envRec must have an uninitialized immutable binding for N.
++ Set + the bound value for N in envRec to V.
++ Record + that the immutable binding for N in envRec has been + initialized.
++ Each + object environment record is associated with an object called its + binding object. An object environment record binds the set of + identifier names that directly correspond to the property names of + its binding object. Property names that are not an IdentifierName are not included in the set of bound identifiers. Both + own and inherited properties are included in the set regardless of + the setting of their [[Enumerable]] attribute. Because properties + can be dynamically added and deleted from objects, the set of + identifiers bound by an object environment record may potentially + change as a side-effect of any operation that adds or deletes + properties. Any bindings that are created as a result of such a + side-effect are considered to be a mutable binding even if the + Writable attribute of the corresponding property has the value + false. Immutable bindings do not exist for object environment + records.
++ Object + environment records can be configured to provide their binding + object as an implicit this value for use in function calls. This + capability is used to specify the behaviour of With Statement + (12.10) induced bindings. The capability is controlled by a + provideThis + Boolean value that is associated with each object environment + record. By default, the value of provideThis + is false for any object environment record.
++ The + behaviour of the concrete specification methods for Object + Environment Records is defined by the following algorithms.
++ The + concrete Environment Record method HasBinding for object environment + records determines if its associated binding object has a property + whose name is the value of the argument N:
++ Let + envRec be the object environment record for which the method + was invoked.
++ Let + bindings be the binding object for envRec.
++ Return + the result of calling the [[HasProperty]] internal method of + bindings, passing N as the property name.
++ The + concrete Environment Record method CreateMutableBinding for object + environment records creates in an environment record’s associated + binding object a property whose name is the String value and + initializes it to the value undefined. A property named N + must not already exist in the binding object. If Boolean argument D + is provided and has the value true the new property’s + [[Configurable]] attribute is set to true, otherwise it is + set to false.
++ Let + envRec be the object environment record for which the method + was invoked.
++ Let + bindings be the binding object for envRec.
++ Assert: + The result of calling the [[HasProperty]] internal method of + bindings, passing N as the property name, is false.
++ If + D is true then let configValue be true + otherwise let configValue be false.
++ Call + the [[DefineOwnProperty]] internal method of bindings, + passing N, Property Descriptor {[[Value]]:undefined, + [[Writable]]: true, [[Enumerable]]: true , + [[Configurable]]: configValue}, and + true + as + arguments.
++ The + concrete Environment Record method SetMutableBinding for object + environment records attempts to set the value of the environment + record’s associated binding object’s property whose name is the + value of the argument N + to the value of argument V. + A property named N + should already exist but if it does not or is not currently + writable, error handling is determined by the value of the Boolean + argument S.
++ Let + envRec be the object environment record for which the method + was invoked.
++ Let + bindings be the binding object for envRec.
++ Call + the [[Put]] internal method of bindings with arguments N, + V, and S.
++ The + concrete Environment Record method GetBindingValue for object + environment records returns the value of its associated binding object’s property whose name is the String value of the argument + identifier N. The + property should already exist but if it does not the result depends + upon the value of the S + argument:
++ Let + envRec be the object environment record for which the method + was invoked.
++ Let + bindings be the binding object for envRec.
++ Let + value be the result of calling the [[HasProperty]] internal + method of bindings, passing N as the property name.
++ If + value is false, then
++ If + S is false, return the value undefined, + otherwise throw a ReferenceError exception.
++ Return + the result of calling the [[Get]] internal method of bindings, + passing N for the argument.
++ The + concrete Environment Record method DeleteBinding for object + environment records can only delete bindings that correspond to + properties of the environment object whose [[Configurable]] + attribute have the value true.
++ Let + envRec be the object environment record for which the method + was invoked.
++ Let + bindings be the binding object for envRec.
++ Return + the result of calling the [[Delete]] internal method of bindings, + passing N and false as arguments.
++ Object + Environment Records return undefined as their + ImplicitThisValue unless their provideThis + flag is true.
++ Let + envRec be the object environment record for which the method + was invoked.
++ If + the provideThis flag of envRec is true, return + the binding object for envRec.
++ Otherwise, + return undefined.
++ The + following abstract operations are used in this specification to + operate upon lexical environments:
++ The + abstract operation GetIdentifierReference is called with a Lexical Environment lex, + an identifier String name, + and a Boolean flag strict. The value of lex may be null. When called, the following steps are + performed:
++ If + lex is the value null, then
++ Return + a value of type Reference whose base value is undefined, + whose referenced name is name, and whose strict mode flag + is strict.
++ Let + envRec be lex’s environment record.
++ Let + exists be the result of calling the HasBinding(N) + concrete method of envRec passing name as the + argument N.
+
+ If
+ exists is true,
+ then
+ Return + a value of type Reference whose base value is envRec, whose + referenced name is name, and whose strict mode flag is + strict.
++ Else
++ Let + outer be the value of lex’s outer environment reference.
++ Return + the result of calling GetIdentifierReference passing outer, + name, and strict as arguments.
++ When + the abstract operation NewDeclarativeEnvironment is called with + either a Lexical Environment or null as argument E the following steps are performed:
++ Let + env be a new Lexical Environment.
++ Let + envRec be a new declarative environment record containing no + bindings.
++ Set + env’s environment record to be envRec.
++ Set + the outer lexical environment reference of env to E.
++ Return + env.
++ When + the abstract operation NewObjectEnvironmentis called with an Object + O and a Lexical Environment E (or + null) as arguments, the following steps are performed:
++ Let + env be a new Lexical Environment.
++ Let + envRec be a new object environment record containing O + as the binding object.
++ Set + env’s environment record to be envRec.
++ Set + the outer lexical environment reference of env to E.
++ Return + env.
++ The + global environment is a unique Lexical Environment which is + created before any ECMAScript code is executed. The global + environment’s Environment Record is an object environment record + whose binding object is the global object (15.1). The global + environment’s outer environment reference is null.
++ As + ECMAScript code is executed, additional properties may be added to + the global object and the initial properties may be modified. + +
++ When + control is transferred to ECMAScript executable code, control is + entering an execution context. Active execution contexts + logically form a stack. The top execution context on this logical + stack is the running execution context. A new execution context is + created whenever control is transferred from the executable code + associated with the currently running execution context to + executable code that is not associated with that execution context. + The newly created execution context is pushed onto the stack and + becomes the running execution context.
++ An + execution context contains whatever state is necessary to track the + execution progress of its associated code. In addition, each + execution context has the state components listed in Table 19.
+|
+ + Component + |
+
+ + Purpose + |
+
|
+ + LexicalEnvironment + |
+
+ + Identifies + the Lexical Environment used to resolve identifier references + made by code within this execution context. + |
+
|
+ + VariableEnvironment + |
+
+ + Identifies + the Lexical Environment whose environment record holds bindings + created by VariableStatements + and FunctionDeclarations + within this execution context. + |
+
|
+ ThisBinding + |
+
+ The
+ value associated with the |
+
+ The + LexicalEnvironment and VariableEnvironment components of an + execution context are always Lexical Environments. When an execution + context is created its LexicalEnvironment and VariableEnvironment + components initially have the same value. The value of the + VariableEnvironment component never changes while the value of the + LexicalEnvironment component may change during execution of code + within an execution context.
++ In + most situations only the running execution context (the top of the + execution context stack) is directly manipulated by algorithms + within this specification. Hence when the terms + “LexicalEnvironment”, “VariableEnvironment” and + “ThisBinding” are used without qualification they are in + reference to those components of the running execution context.
++ An + execution context is purely a specification mechanism and need not + correspond to any particular artefact of an ECMAScript + implementation. It is impossible for an ECMAScript program to + access an execution context. +
++ Identifier + resolution is the process of determining the binding of an + Identifier using + the LexicalEnvironment of the running execution context. During + execution of ECMAScript code, the syntactic production + PrimaryExpression + : + Identifier is + evaluated using the following algorithm:
++ Let + env be the running execution context’s LexicalEnvironment.
++ If + the syntactic production that is being evaluated is contained in a + strict mode code, then let strict be true, else let + strict be false.
++ Return + the result of calling GetIdentifierReference function passing env, + Identifier, and strict as arguments.
++ The + result of evaluating an identifier is always a value of type + Reference with its referenced name component equal to the Identifier + String.
++ Evaluation + of global code or code using the eval function (15.1.2.1) + establishes and enters a new execution context. Every invocation of + an ECMAScript code function (13.2.1) also establishes and enters a + new execution context, even if a function is calling itself + recursively. Every return exits an execution context. A thrown + exception may also exit one or more execution contexts.
++ When + control enters an execution context, the execution context’s + ThisBinding is set, its VariableEnvironment and initial + LexicalEnvironment are defined, and declaration binding + instantiation (10.5) is performed. The exact manner in which these + actions occur depend on the type of code being entered.
++ The + following steps are performed when control enters the execution + context for global code:
++ Initialize + the execution context using the global code as described in + 10.4.1.1.
++ Perform + Declaration Binding Instantiation as described in 10.5 using the + global code.
++ The + following steps are performed to initialize a global execution + context for ECMAScript code C:
++ Set + the VariableEnvironment to the Global Environment.
++ Set + the LexicalEnvironment to the Global Environment.
++ Set + the ThisBinding to the global object.
++ The + following steps are performed when control enters the execution + context for eval code:
++ If + there is no calling context or if the eval code is not being + evaluated by a direct call (15.1.2.1.1) to the eval function then,
++ Else,
++ Set + the ThisBinding to the same value as the ThisBinding of the + calling execution context.
++ Set + the LexicalEnvironment to the same value as the LexicalEnvironment + of the calling execution context.
++ Set + the VariableEnvironment to the same value as the + VariableEnvironment of the calling execution context.
++ If + the eval code is strict code, then
++ Let + strictVarEnv be the result of calling + NewDeclarativeEnvironment passing the LexicalEnvironment as the + argument.
++ Set + the LexicalEnvironment to strictVarEnv.
++ Set + the VariableEnvironment to strictVarEnv.
++ Perform + Declaration Binding Instantiation as described in 10.5 using the + eval code.
++ The + eval code cannot instantiate variable or function bindings in the + variable environment of the calling context that invoked the eval if + either the code of the calling context or the eval code is strict code. Instead such bindings are instantiated in a new + VariableEnvironment that is only accessible to the eval code.
++ The + following steps are performed when control enters the execution + context for function code contained in function object F, + a caller provided thisArg, + and a caller provided argumentsList:
++ If + the function code is strict code, set the ThisBinding to thisArg.
++ Else + if thisArg is null or undefined, set the + ThisBinding to the global object.
++ Else + if Type(thisArg) is not Object, set the ThisBinding to + ToObject(thisArg).
++ Else + set the ThisBinding to thisArg.
++ Let + localEnv be the result of calling NewDeclarativeEnvironment + passing the value of the [[Scope]] internal property of F as + the argument.
++ Set + the LexicalEnvironment to localEnv.
++ Set + the VariableEnvironment to localEnv.
++ Let + code be the value of F’s [[Code]] internal + property.
++ Perform + Declaration Binding Instantiation using the function code code + and argumentList as described in 10.5.
++ Every + execution context has an associated VariableEnvironment. Variables + and functions declared in ECMAScript code evaluated in an execution + context are added as bindings in that VariableEnvironment’s + Environment Record. For function code, parameters are also added as + bindings to that Environment Record.
++ Which + Environment Record is used to bind a declaration and its kind + depends upon the type of ECMAScript code executed by the execution + context, but the remainder of the behaviour is generic. On entering + an execution context, bindings are created in the + VariableEnvironment as follows using the caller provided code and, if it is function code, argument List args:
++ Let + env be the environment record component of the running + execution context’s VariableEnvironment.
++ If + code is eval code, then let configurableBindings be + true else let configurableBindings be false.
++ If + code is strict mode code, then let strict be true + else let strict be false.
++ If + code is function code, then
++ Let + func be the function whose [[Call]] internal method + initiated execution of code. Let names be the value + of func’s [[FormalParameters]] internal property. +
++ Let + argCount be the number of elements in args.
++ Let + n be the number 0.
++ For + each String argName in names, in list order do
++ Let + n be the current value of n plus 1.
++ If + n is greater than argCount, let v be + undefined otherwise let v be the value of the n’th + element of args.
++ Let + argAlreadyDeclared be the result of calling env’s + HasBinding concrete method passing argName as the + argument.
++ If + argAlreadyDeclared is false, call env’s + CreateMutableBinding concrete method passing argName as + the argument.
++ Call + env’s SetMutableBinding concrete method passing argName, + v, and strict as the arguments.
++ For each + FunctionDeclaration f in code, in source text + order do
+Let + fn be the Identifier in FunctionDeclaration + f.
+Let + fo be the result of instantiating FunctionDeclaration f + as described in Clause 13.
+Let + funcAlreadyDeclared be the result of calling env’s + HasBinding concrete method passing fn as the argument.
+If + funcAlreadyDeclared is false, call env’s + CreateMutableBinding concrete method passing fn and + configurableBindings as the arguments.
+Else + if env + is the environment record component of the global environment then
+Let + go + be the global object.
+Let + existingProp + be the resulting of calling the [[GetProperty]] internal method + of go + with argument fn.
+If + existingProp + .[[Configurable]] is true, + then
+Call + the [[DefineOwnProperty]] internal method of go, + passing fn, + Property Descriptor {[[Value]]: + undefined, + [[Writable]]: true, + [[Enumerable]]: true + , [[Configurable]]: configurableBindings + }, and true + as arguments.
+Else + if IsAccessorDescrptor(existingProp) + or existingProp + does not have attribute values {[[Writable]]: true, + [[Enumerable]]: true}, + then
+Throw + a TypeError exception.
+Call + env’s SetMutableBinding concrete method passing fn, + fo, and strict as the arguments.
+
+ Let
+ argumentsAlreadyDeclared be the result of calling env’s
+ HasBinding concrete method passing "arguments"
+ as the argument
+ If + code is function code and argumentsAlreadyDeclared is + false, then
++ Let + argsObj be the result of calling the abstract operation + CreateArgumentsObject (10.6) passing func, names, args, + env and strict as arguments.
++ If + strict is true, then +
+
+ Call
+ env’s CreateImmutableBinding concrete method passing the
+ String "arguments"
+ as the argument.
+ Call
+ env’s InitializeImmutableBinding concrete method passing
+ "arguments"
+ and argsObj as arguments.
+ Else,
+
+ Call
+ env’s CreateMutableBinding concrete method passing the
+ String "arguments"
+ as the argument.
+ Call
+ env’s SetMutableBinding concrete method passing
+ "arguments",
+ argsObj, and false as arguments.
+ For + each VariableDeclaration and VariableDeclarationNoIn + d in code, in source text order do
++ Let + dn be the Identifier in d.
++ Let + varAlreadyDeclared be the result of calling env’s + HasBinding concrete method passing dn as the argument.
++ If + varAlreadyDeclared is false, then
++ Call + env’s CreateMutableBinding concrete method passing dn and configurableBindings as the arguments.
++ Call + env’s SetMutableBinding concrete method passing dn, + undefined, and strict as the arguments.
+
+ When
+ control enters an execution context for function code, an arguments
+ object is created unless (as specified in 10.5) the identifier
+ arguments occurs
+ as an Identifier
+ in the function’s FormalParameterList
+ or occurs as the Identifier
+ of a VariableDeclaration
+ or FunctionDeclaration
+ contained in the function code.
+ The + arguments object is created by calling the abstract operation + CreateArgumentsObject with arguments func + the function object whose code is to be evaluated, + names a List containing the function’s formal parameter + names, args the + actual arguments passed to the [[Call]] internal method, env the variable environment for the function code, and + strict a Boolean + that indicates whether or not the function code is strict code. When + CreateArgumentsObject is called the following steps are performed:
++ Let + len be the number of elements in args.
++ Let + obj be the result of creating a new ECMAScript object.
++ Set + all the internal methods of obj as specified in 8.12.
+
+ Set
+ the [[Class]] internal property of obj to "Arguments".
+ Let + Object be the standard built-in Object constructor (15.2.2).
++ Set + the [[Prototype]] internal property of obj to the standard + built-in Object prototype object (15.2.4).
+
+ Call
+ the [[DefineOwnProperty]] internal method on obj passing
+ "length",
+ the Property Descriptor {[[Value]]: len, [[Writable]]: true,
+ [[Enumerable]]: false, [[Configurable]]: true}, and
+ false as arguments.
+ Let
+ map be the result of creating a new object as if by the
+ expression new Object()
+ where Object is
+ the standard built-in constructor with that name
+ Let + mappedNames be an empty List.
++ Let + indx = len - 1.
++ Repeat + while indx >= 0, +
++ Let + val be the element of args at 0-origined list + position indx.
++ Call + the [[DefineOwnProperty]] internal method on obj passing + ToString(indx), the property descriptor {[[Value]]: val, + [[Writable]]: true, [[Enumerable]]: true, + [[Configurable]]: true}, and false as arguments.
++ If + indx is less than the number of elements in names, + then
++ Let + name be the element of names at 0-origined list + position indx.
++ If + strict is false and name is not an element + of mappedNames, then
++ Add + name as an element of the list mappedNames.
++ Let + g be the result of calling the MakeArgGetter + abstract operation with arguments name and env.
++ Let + p be the result of calling the MakeArgSetter + abstract operation with arguments name and env.
++ Call + the [[DefineOwnProperty]] internal method of map passing + ToString(indx), the Property Descriptor {[[Set]]: p, + [[Get]]: g, [[Configurable]]: true}, and false + as arguments.
++ Let + indx = indx - 1
++ If + mappedNames is not empty, then
++ Set + the [[ParameterMap]] internal property of obj to map.
++ Set + the [[Get]], [[GetOwnProperty]], [[DefineOwnProperty]], and + [[Delete]] internal methods of obj to the definitions + provided below.
++ If + strict is false, then
+
+ Call
+ the [[DefineOwnProperty]] internal method on obj passing
+ "callee",
+ the property descriptor {[[Value]]: func, [[Writable]]:
+ true, [[Enumerable]]: false, [[Configurable]]:
+ true}, and false as arguments.
+ Else, + strict is true so
++ Let + thrower be the [[ThrowTypeError]] function Object (13.2.3).
+
+ Call
+ the [[DefineOwnProperty]] internal method of obj with
+ arguments "caller",
+ PropertyDescriptor {[[Get]]: thrower, [[Set]]: thrower,
+ [[Enumerable]]: false, [[Configurable]]: false}, and
+ false.
+ Call
+ the [[DefineOwnProperty]] internal method of obj with
+ arguments "callee",
+ PropertyDescriptor {[[Get]]: thrower, [[Set]]: thrower,
+ [[Enumerable]]: false, [[Configurable]]: false}, and
+ false.
+ Return + obj
++ The + abstract operation MakeArgGetter called with String name + and environment record env + creates a function object that when executed returns the value bound + for name in env. + It performs the following steps:
+
+ Let
+ body be the result of concatenating the Strings "return
+ ", name, and ";"
+ Return + the result of creating a function object as described in 13.2 using + no FormalParameterList, body for FunctionBody, + env as Scope, and true for Strict.
++ The + abstract operation MakeArgSetter called with String name + and environment record env + creates a function object that when executed sets the value bound + for name in env. + It performs the following steps:
+
+ Let
+ param be the String name concatenated with the String
+ "_arg"
+ Let
+ body be the String "<name> =
+ <param>;"
+ with <name> replaced by the value of name and
+ <param> replaced by the value of param.
+ Return + the result of creating a function object as described in 13.2 using + a List containing the single String param as + FormalParameterList, body for FunctionBody, + env as Scope, and true for Strict.
++ The + [[Get]] internal method of an arguments object for a non-strict mode + function with formal parameters when called with a property name P + performs the following steps:
++ Let + map be the value of the [[ParameterMap]] internal property + of the arguments object.
++ Let + isMapped be the result of calling the [[GetOwnProperty]] + internal method of map passing P as the argument.
++ If + the value of isMapped is undefined, then
++ Else, + map contains a formal parameter mapping for P so, +
++ Return + the result of calling the [[Get]] internal method of map + passing P as the argument.
++ The + [[GetOwnProperty]] internal method of an arguments object for a + non-strict mode function with formal parameters when called with a + property name P + performs the following steps:
++ Let + desc be the result of calling the default [[GetOwnProperty]] + internal method (8.12.1) on the arguments object passing P + as the argument.
++ If + desc is undefined then return desc.
++ Let + map be the value of the [[ParameterMap]] internal property + of the arguments object.
++ Let + isMapped be the result of calling the [[GetOwnProperty]] + internal method of map passing P as the argument.
++ If + the value of isMapped is not undefined, then
++ Set + desc.[[Value]] to the result of calling the [[Get]] + internal method of map passing P as the argument.
++ Return + desc. +
++ The + [[DefineOwnProperty]] internal method of an arguments object for a + non-strict mode function with formal parameters when called with a + property name P, + Property Descriptor Desc, + and Boolean flag Throw + performs the following steps:
++ Let + map be the value of the [[ParameterMap]] internal property + of the arguments object.
++ Let + isMapped be the result of calling the [[GetOwnProperty]] + internal method of map passing P as the argument.
++ Let + allowed be the result of calling the default + [[DefineOwnProperty]] internal method (8.12.9) on the arguments + object passing P, Desc, and false as the + arguments.
++ If + allowed is false, then
++ If + Throw is true then throw a TypeError exception, + otherwise return false.
++ If + the value of isMapped is not undefined, then
++ If + IsAccessorDescriptor(Desc) is true, then
++ Call + the [[Delete]] internal method of map passing P, + and false as the arguments.
++ Else
++ If + Desc.[[Value]] is present, then
++ Call + the [[Put]] internal method of map passing P, + Desc.[[Value]], and Throw as the arguments.
++ If + Desc.[[Writable]] is present and its value is false, + then
++ Call + the [[Delete]] internal method of map passing P and + false as arguments.
++ Return + true.
++ The + [[Delete]] internal method of an arguments object for a non-strict + mode function with formal parameters when called with a property + name P and Boolean + flag Throw + performs the following steps:
++ Let + map be the value of the [[ParameterMap]] internal property + of the arguments object.
++ Let + isMapped be the result of calling the [[GetOwnProperty]] + internal method of map passing P as the argument.
++ Let + result be the result of calling the default [[Delete]] + internal method (8.12.7) on the arguments object passing P and + Throw as the arguments.
++ If + result is true and the value of isMapped is + not undefined, then
++ Call + the [[Delete]] internal method of map passing P, and + false as the arguments.
++ Return + result.
+NOTE 1 For non-strict mode functions the array index (defined in 15.4) + named data properties of an arguments object whose numeric name + values are less than the number of formal parameters of the + corresponding function object initially share their values with the + corresponding argument bindings in the function’s execution + context. This means that changing the property changes the + corresponding value of the argument binding and vice-versa. This + correspondence is broken if such a property is deleted and then + redefined or if the property is changed into an accessor property. + For strict mode functions, the values of the arguments object‘s + properties are simply a copy of the arguments passed to the function + and there is no dynamic linkage between the property values and the + formal parameter values.
+NOTE 2 The ParameterMap object and its property values are used as a + device for specifying the arguments object correspondence to + argument bindings. The ParameterMap object and the objects that are + the values of its properties are not directly accessible from + ECMAScript code. An ECMAScript implementation does not need to + actually create or use such objects to implement the specified + semantics.
+NOTE 3 Arguments objects for strict mode functions define
+ non-configurable accessor properties named "caller"
+ and "callee"
+ which throw a TypeError exception on access. The "callee"
+ property has a more specific meaning for non-strict mode functions
+ and a "caller"
+ property has historically been provided as an implementation-defined
+ extension by some ECMAScript implementations. The strict mode
+ definition of these properties exists to ensure that neither of them
+ is defined in any other manner by conforming ECMAScript
+ implementations.
‟Ex igne vita”
+ ++ Syntax + +
++ PrimaryExpression :
+
+ this
Identifier
Literal
ArrayLiteral
ObjectLiteral( Expression )
+ The
+ this keyword
+ evaluates to the value of the ThisBinding of the current execution
+ context.
+ An + Identifier is + evaluated by performing Identifier Resolution as specified in + 10.3.1. The result of evaluating an Identifier + is always a value of type Reference.
++ A + Literal is + evaluated as described in 7.8.
++ An + array initialiser is an expression describing the initialisation of + an Array object, written in a form of a literal. It is a list of + zero or more expressions, each of which represents an array element, + enclosed in square brackets. The elements need not be literals; they + are evaluated each time the array initialiser is evaluated.
++ Array elements may be elided at the beginning, middle or end of the + element list. Whenever a comma in the element list is not preceded + by an AssignmentExpression + (i.e., a comma at the beginning or after another comma), the missing + array element contributes to the length of the Array and increases + the index of subsequent elements. Elided array elements are not + defined. If an element is elided at the end of an array, that + element does not contribute to the length of the Array.
++ Syntax
++ ArrayLiteral :
+
+ [
+ Elisionopt
+ ] ElementList
[
+
+ ] ElementList , Elisionopt
[
+
+ ]
+ ElementList :
+
+ Elisionopt
+ AssignmentExpression
ElementList , Elisionopt
+ AssignmentExpression
+ Elision :
+
+ ,
Elision ,
+ Semantics
+
+ The
+ production ArrayLiteral
+ : [ Elisionopt
+ ] is
+ evaluated as follows:
+ Let
+ array be the result of creating a new object as if by the
+ expression new Array() where
+ Array is the standard built-in constructor with that
+ name.
+ Let + pad be the result of evaluating Elision; if not + present, use the numeric value zero.
+
+ Call
+ the [[Put]] internal method of array with arguments
+ "length",
+ pad, and false.
+ Return + array.
+
+ The
+ production ArrayLiteral
+ : [ ElementList
+ ] is
+ evaluated as follows:
+ Return + the result of evaluating ElementList.
+
+ The
+ production ArrayLiteral
+ : [ ElementList
+ , Elisionopt
+ ] is
+ evaluated as follows:
+ Let + array be the result of evaluating ElementList.
++ Let + pad be the result of evaluating Elision; if not + present, use the numeric value zero.
+
+ Let
+ len be the result of calling the [[Get]] internal method of
+ array with argument "length".
+ Call
+ the [[Put]] internal method of array with arguments
+ "length",
+ ToUint32(pad+len), and false.
+ Return + array.
+
+ The
+ production ElementList
+ : Elisionopt
+ AssignmentExpression
+ is evaluated as follows:
+ Let
+ array be the result of creating a new object as if by the
+ expression new Array() where
+ Array is the standard built-in constructor with that
+ name.
+ Let + firstIndex be the result of evaluating Elision; if + not present, use the numeric value zero.
++ Let + initResult be the result of evaluating AssignmentExpression.
++ Let + initValue be GetValue(initResult).
++ Call + the [[DefineOwnProperty]] internal method of array with + arguments ToString(firstIndex), the Property Descriptor { + [[Value]]: initValue, [[Writable]]: true, + [[Enumerable]]: true, [[Configurable]]: true}, and + false.
++ Return + array.
+
+ The
+ production ElementList
+ : ElementList
+ , Elisionopt
+ AssignmentExpression
+ is evaluated as follows:
+ Let + array be the result of evaluating ElementList.
++ Let + pad be the result of evaluating Elision; if not + present, use the numeric value zero.
++ Let + initResult be the result of evaluating AssignmentExpression.
++ Let + initValue be GetValue(initResult).
+
+ Let
+ len be the result of calling the [[Get]] internal method of
+ array with argument "length".
+ Call + the [[DefineOwnProperty]] internal method of array with + arguments ToString(ToUint32((pad+len)) and the + Property Descriptor { [[Value]]: initValue, [[Writable]]: + true, [[Enumerable]]: true, [[Configurable]]: true}, + and false.
++ Return + array.
++ The + production Elision + : , is evaluated as follows:
++ Return + the numeric value 1.
++ The + production Elision + : Elision + , is evaluated as follows:
++ Let + preceding be the result of evaluating Elision.
++ Return + preceding+1.
++
NOTE + [[DefineOwnProperty]] is used to ensure that own properties are + defined for the array even if the standard built-in Array prototype + object has been modified in a manner that would preclude the + creation of new own properties using [[Put]].
++ An + object initialiser is an expression describing the initialisation of + an Object, written in a form resembling a literal. It is a list of + zero or more pairs of property names and associated values, enclosed + in curly braces. The values need not be literals; they are evaluated + each time the object initialiser is evaluated.
++ Syntax
++ ObjectLiteral :
+
+ {
+ } {
+ PropertyNameAndValueList
+ } PropertyNameAndValueList
{
+
+ , }
+ PropertyNameAndValueList :
+
+ PropertyAssignment
PropertyNameAndValueList
+ ,
+ PropertyAssignment
+ PropertyAssignment + :
+
+ PropertyName : AssignmentExpressionget
+ PropertyName (
+ ) { FunctionBody } set
+ PropertyName (
+ PropertySetParameterList )
+ { FunctionBody }
+ PropertyName :
+
+ IdentifierName
StringLiteral
NumericLiteral
+ PropertySetParameterList + :
++ Identifier
++ Semantics
+
+ The
+ production ObjectLiteral
+ : {
+ } is
+ evaluated as follows:
+ Return
+ a new object created as if by the expression new
+ Object() where Object
+ is the standard built-in constructor with that name.
+ The
+ productions ObjectLiteral
+ : {
+ PropertyNameAndValueList
+ }
+ and
ObjectLiteral
+ : {
+ PropertyNameAndValueList
+ ,}
+ are evaluated as follows:
+ Return + the result of evaluating PropertyNameAndValueList.
++ The + production PropertyNameAndValueList + : PropertyAssignment + is evaluated as follows:
+
+ Let
+ obj be the result of creating a new object as if by the
+ expression new Object()
+ where Object
+ is the standard built-in constructor with that name.
+ Let + propId be the result of evaluating PropertyAssignment.
++ Call + the [[DefineOwnProperty]] internal method of obj with + arguments propId.name, propId.descriptor, and false.
++ Return + obj.
+
+ The
+ production
PropertyNameAndValueList
+ : PropertyNameAndValueList
+ , PropertyAssignment
is
+ evaluated as follows:
+ Let + obj be the result of evaluating PropertyNameAndValueList.
++ Let + propId be the result of evaluating PropertyAssignment.
++ Let + previous be the result of calling the [[GetOwnProperty]] + internal method of obj with argument propId.name.
++ If + previous is not undefined then throw a SyntaxError + exception if any of the following conditions are true
++ This + production is contained in strict code and + IsDataDescriptor(previous) is true and + IsDataDescriptor(propId.descriptor) is true.
++ IsDataDescriptor(previous) + is true and IsAccessorDescriptor(propId.descriptor) + is true.
++ IsAccessorDescriptor(previous) + is true and IsDataDescriptor(propId.descriptor) is + true.
++ IsAccessorDescriptor(previous) + is true and IsAccessorDescriptor(propId.descriptor) + is true and either both previous and + propId.descriptor have [[Get]] fields or both previous + and propId.descriptor have [[Set]] fields
++ Call + the [[DefineOwnProperty]] internal method of obj with + arguments propId.name, propId.descriptor, and false.
++ Return + obj.
++ If + the above steps would throw a SyntaxError then an + implementation must treat the error as an early error (Clause 16).
+
+ The
+ production PropertyAssignment
+ : PropertyName
+ :
+ AssignmentExpression
+ is evaluated as follows:
+ Let + propName be the result of evaluating PropertyName.
++ Let + exprValue be the result of evaluating AssignmentExpression.
++ Let + propValue be GetValue(exprValue).
++ Let + desc be the Property Descriptor{[[Value]]: propValue, + [[Writable]]: true, [[Enumerable]]: true, + [[Configurable]]: true}
++ Return + Property Identifier (propName, desc).
+
+ The
+ production PropertyAssignment
+ : get
+ PropertyName (
+ ) { FunctionBody
+ } is
+ evaluated as follows:
+ Let + propName be the result of evaluating PropertyName.
++ Let + closure be the result of creating a new Function object as + specified in 13.2 with an empty parameter list and body specified + by FunctionBody. Pass in the LexicalEnvironment of the + running execution context as the Scope. Pass in true + as the Strict flag if the PropertyAssignment + is contained in strict code or if its FunctionBody is strict code.
++ Let + desc be the Property Descriptor{[[Get]]: closure, + [[Enumerable]]: true, [[Configurable]]: true}
++ Return + Property Identifier (propName, desc).
+
+ The
+ production PropertyAssignment
+ : set
+ PropertyName (
+ PropertySetParameterList
+ ) {
+ FunctionBody
+ } is evaluated as
+ follows:
+ Let + propName be the result of evaluating PropertyName.
++ Let + closure be the result of creating a new Function object as + specified in 13.2 with parameters specified by + PropertySetParameterList and body specified by FunctionBody. + Pass in the LexicalEnvironment of the running execution context as + the Scope. Pass in true as the Strict flag if + the PropertyAssignment + is contained in strict code or if its FunctionBody is strict code.
++ Let + desc be the Property Descriptor{[[Set]]: closure, + [[Enumerable]]: true, [[Configurable]]: true}
++ Return + Property Identifier (propName, desc).
+
+ It is
+ a SyntaxError if the Identifier
+ "eval"
+ or the Identifier "arguments"
+ occurs as the Identifier
+ in a PropertySetParameterList
+ of a
+ PropertyAssignment
+ that is contained in strict code
+ or if its FunctionBody
+ is strict code.
+ The + production PropertyName + : IdentifierName + is evaluated as follows:
++ Return + the String value containing the same sequence of characters as the + IdentifierName.
++ The + production PropertyName + : StringLiteral + is evaluated as follows:
++ Return + the SV of the StringLiteral.
++ The + production PropertyName + : NumericLiteral + is evaluated as follows:
++ Let + nbr be the result of forming the value of the + NumericLiteral.
++ Return + ToString(nbr).
+
+ The
+ production PrimaryExpression
+ : (
+ Expression )
+ is evaluated as follows:
+ Return + the result of evaluating Expression. This may be of type + Reference.
++
NOTE This
+ algorithm does not apply GetValue to the result of evaluating
+ Expression. The principal motivation for this is so that operators
+ such as delete and
+ typeof may be
+ applied to parenthesised expressions.
+ Syntax
++ MemberExpression :
+
+ PrimaryExpression
FunctionExpression
MemberExpression [ Expression ] MemberExpression . IdentifierNamenew MemberExpression
+ Arguments
+ NewExpression :
+
+ MemberExpression
new
+ CallExpression :
+
+ MemberExpression
+ Arguments
+ Arguments[ Expression ] CallExpression . IdentifierName
+ Arguments :
+
+ ( ) ArgumentList
()
+ ArgumentList :
+
+ AssignmentExpression
ArgumentList , AssignmentExpression
+ LeftHandSideExpression :
+
+ NewExpression
CallExpression
+ Properties + are accessed by name, using either the dot notation:
+
+ MemberExpression . IdentifierName
CallExpression . IdentifierName
+ or + the bracket notation:
+
+ MemberExpression [ Expression ]
CallExpression [ Expression ]
+ The + dot notation is explained by the following syntactic conversion:
+
+ MemberExpression . IdentifierName
+ is + identical in its behaviour to
+
+ MemberExpression [ <identifier-name-string> ]
+ and + similarly
+
+ CallExpression . IdentifierName
+ is + identical in its behaviour to
+
+ CallExpression [ <identifier-name-string> ]
+ where + <identifier-name-string> + is a string literal containing the same sequence of characters after + processing of Unicode escape sequences as the IdentifierName.
+
+ The
+ production MemberExpression
+ : MemberExpression
+ [ Expression
+ ] is evaluated as
+ follows:
+ Let + baseReference be the result of evaluating MemberExpression.
++ Let + baseValue be GetValue(baseReference).
++ Let + propertyNameReference be the result of evaluating + Expression.
++ Let + propertyNameValue be GetValue(propertyNameReference).
++ Call + CheckObjectCoercible(baseValue).
++ Let + propertyNameString be ToString(propertyNameValue).
++ If + the syntactic production that is being evaluated is contained in + strict mode code, let strict be true, else let strict + be false.
++ Return + a value of type Reference whose base value is baseValue and + whose referenced name is propertyNameString, and whose + strict mode flag is strict.
+
+ The
+ production CallExpression
+ : CallExpression [ Expression ] is evaluated
+ in exactly the same manner, except that the contained CallExpression
+ is evaluated in step 1.
+ The
+ production NewExpression : new NewExpression is evaluated as follows:
+ Let + ref be the result of evaluating NewExpression.
++ Let + constructor be GetValue(ref).
++ If + Type(constructor) is not Object, throw a TypeError + exception.
++ If + constructor does not implement the [[Construct]] internal + method, throw a TypeError exception.
++ Return + the result of calling the [[Construct]] internal method on + constructor, providing no arguments (that is, an empty list + of arguments).
+
+ The
+ production MemberExpression
+ : new
+ MemberExpression
+ Arguments is
+ evaluated as follows:
+ Let + ref be the result of evaluating MemberExpression.
++ Let + constructor be GetValue(ref).
++ Let + argList be the result of evaluating Arguments, + producing an internal list of argument values (11.2.4).
++ If + Type(constructor) is not Object, throw a TypeError + exception.
++ If + constructor does not implement the [[Construct]] internal + method, throw a TypeError exception.
++ Return + the result of calling the [[Construct]] internal method on + constructor, providing the list argList as the + argument values.
++ The + production CallExpression + : MemberExpression + Arguments is + evaluated as follows:
++ Let + ref be the result of evaluating MemberExpression.
++ Let + func be GetValue(ref).
++ Let + argList be the result of evaluating Arguments, + producing an internal list of argument values (see 11.2.4).
++ If + Type(func) is not Object, throw a TypeError + exception.
++ If + IsCallable(func) is false, throw a TypeError + exception.
++ If + Type(ref) is Reference, then
++ If + IsPropertyReference(ref) is true, then
++ Let + thisValue be GetBase(ref).
++ Else, + the base of ref is an Environment Record
++ Let + thisValue be the result of calling the ImplicitThisValue + concrete method of GetBase(ref).
++ Else, + Type(ref) is not Reference.
++ Let + thisValue be undefined.
++ Return + the result of calling the [[Call]] internal method on func, + providing thisValue as the this value and providing + the list argList as the argument values.
++ The + production CallExpression + : CallExpression + Arguments is + evaluated in exactly the same manner, except that the contained + CallExpression is + evaluated in step 1.
++
NOTE The returned + result will never be of type Reference if func + is a native ECMAScript object. Whether calling a host object can + return a value of type Reference is implementation-dependent. If a + value of type Reference is returned, it must be a non-strict + Property Reference.
++ The + evaluation of an argument list produces a List of values (see 8.8).
+
+ The
+ production Arguments :
+ ( ) is evaluated
+ as follows:
+ Return + an empty List.
+
+ The
+ production Arguments : (
+ ArgumentList
+ ) is evaluated as follows:
+ Return + the result of evaluating ArgumentList.
+
+ The
+ production ArgumentList :
+ AssignmentExpression
+ is evaluated as follows:
+ Let + ref be the result of evaluating AssignmentExpression.
++ Let + arg be GetValue(ref).
++ Return + a List whose sole item is arg.
+
+ The
+ production ArgumentList : ArgumentList
+ , AssignmentExpression
+ is evaluated as follows:
+ Let + precedingArgs be the result of evaluating ArgumentList.
++ Let + ref be the result of evaluating AssignmentExpression.
++ Let + arg be GetValue(ref).
++ Return + a List whose length is one greater than the length of precedingArgs + and whose items are the items of precedingArgs, in order, + followed at the end by arg which is the last item of the new + list.
++ The + production MemberExpression + : FunctionExpression + is evaluated as follows:
++ Return + the result of evaluating FunctionExpression.
++ Syntax
++ PostfixExpression :
+
+ LeftHandSideExpression
LeftHandSideExpression
+ [no LineTerminator here]
+ ++
LeftHandSideExpression
+ [no LineTerminator here]
+ --
+ The
+ production PostfixExpression
+ : LeftHandSideExpression
+ [no LineTerminator here] ++
+ is evaluated as follows:
+ Let + lhs be the result of evaluating LeftHandSideExpression.
++ Throw + a SyntaxError exception if the following conditions are all + true:
++ IsStrictReference(lhs) + is true
++ Type(GetBase(lhs)) + is Environment Record
+
+ GetReferencedName(lhs)
+ is either "eval"
+ or "arguments"
+ Let
+ newValue be the result of adding the value 1
+ to oldValue, using the same rules as for the +
+ operator (see 11.6.3).
+ Call + PutValue(lhs, newValue).
++ Return + oldValue.
+
+ The
+ production PostfixExpression
+ : LeftHandSideExpression
+ [no LineTerminator here]
+ -- is
+ evaluated as follows:
+ Let + lhs be the result of evaluating LeftHandSideExpression.
++ Throw + a SyntaxError exception if the following conditions are all + true:
++ IsStrictReference(lhs) + is true
++ Type(GetBase(lhs)) + is Environment Record
+
+ GetReferencedName(lhs)
+ is either "eval"
+ or "arguments"
+ Let
+ newValue be the result of subtracting the value 1
+ from oldValue, using the same rules as for the -
+ operator (11.6.3).
+ Call + PutValue(lhs, newValue).
++ Return + oldValue.
++ Syntax
++ UnaryExpression :
+
+ PostfixExpression
delete
+ void
+ UnaryExpressiontypeof
+ UnaryExpression
++-- UnaryExpression+ UnaryExpression- UnaryExpression~ UnaryExpression! UnaryExpression
+ The
+ production UnaryExpression
+ : delete UnaryExpression is evaluated as follows:
+ Let + ref be the result of evaluating UnaryExpression.
++ If + IsUnresolvableReference(ref) then,
++ If + IsStrictReference(ref) is true, throw a SyntaxError + exception.
++ Else, + return true.
++ If + IsPropertyReference(ref) is true, then
++ Return + the result of calling the [[Delete]] internal method on + ToObject(GetBase(ref)) providing GetReferencedName(ref) + and IsStrictReference(ref) as the arguments.
++ Else, + ref is a Reference to an Environment Record binding, so
++ If + IsStrictReference(ref) is true, throw a SyntaxError + exception.
++ Let + bindings be GetBase(ref).
++ Return + the result of calling the DeleteBinding concrete method of + bindings, providing GetReferencedName(ref) as the + argument.
+NOTE When
+ a delete operator
+ occurs within strict mode code, a SyntaxError exception is
+ thrown if its UnaryExpression
+ is a direct reference to a variable, function argument, or function
+ name. In addition, if a delete
+ operator occurs within strict mode code and the property to be
+ deleted has the attribute { [[Configurable]]: false }, a
+ TypeError exception is thrown.
+ The
+ production UnaryExpression
+ : void
+ UnaryExpression is
+ evaluated as follows:
+ Let + expr be the result of evaluating UnaryExpression.
++ Call + GetValue(expr).
++ Return + undefined.
+NOTE GetValue + must be called even though its value is not used because it may have + observable side-effects.
+
+ The
+ production UnaryExpression
+ : typeof UnaryExpression
+ is evaluated as follows:
+ Let + val be the result of evaluating UnaryExpression.
++ If + Type(val) is Reference, then
+
+ If
+ IsUnresolvableReference(val) is true, return
+ "undefined".
+ Let + val be GetValue(val).
++ Return + a String determined by Type(val) according to Table 20.
+|
+ + Type + of val + |
+
+ + Result + |
+
|
+ + Undefined + |
+
+
+ |
+
|
+ + Null + |
+
+
+ |
+
|
+ + Boolean + |
+
+
+ |
+
|
+ + Number + |
+
+
+ |
+
|
+ + String + |
+
+
+ |
+
|
+ + Object + (native and does not implement [[Call]]) + |
+
+
+ |
+
|
+ Object + (native or host and does implement [[Call]]) + |
+
+
|
+
|
+ Object + (host and does not implement [[Call]]) + |
+
+
+ Implementation-defined
+ except may not be |
+
+ The
+ production UnaryExpression : ++
+ UnaryExpression
+ is evaluated as follows:
+ Let + expr be the result of evaluating UnaryExpression.
++ Throw + a SyntaxError exception if the following conditions are all + true:
++ IsStrictReference(expr) + is true
++ Type(GetBase(expr)) + is Environment Record
+
+ GetReferencedName(expr)
+ is either "eval"
+ or "arguments"
+ Let
+ newValue be the result of adding the value 1
+ to oldValue, using the same rules as for the +
+ operator (see 11.6.3).
+ Call + PutValue(expr, newValue).
++ Return + newValue.
+
+ The
+ production UnaryExpression : --
+ UnaryExpression
+ is evaluated as follows:
+ Let + expr be the result of evaluating UnaryExpression.
++ Throw + a SyntaxError exception if the following conditions are all + true:
++ IsStrictReference(expr) + is true
++ Type(GetBase(expr)) + is Environment Record
+
+ GetReferencedName(expr)
+ is either "eval"
+ or "arguments"
+ Let
+ newValue be the result of subtracting the value 1
+ from oldValue, using the same rules as for the -
+ operator (see 11.6.3).
+ Call + PutValue(expr, newValue).
++ Return + newValue.
++ The + unary + operator converts its operand to Number type.
+
+ The
+ production UnaryExpression : +
+ UnaryExpression is
+ evaluated as follows:
+ Let + expr be the result of evaluating UnaryExpression.
+
+ The
+ unary - operator
+ converts its operand to Number type and then negates it. Note that
+ negating +0 produces −0,
+ and negating −0
+ produces +0.
+ The
+ production UnaryExpression : -
+ UnaryExpression is
+ evaluated as follows:
+ Let + expr be the result of evaluating UnaryExpression.
++ If + oldValue is NaN, return NaN.
++ Return + the result of negating oldValue; that is, compute a Number + with the same magnitude but opposite sign.
+
+ The
+ production UnaryExpression : ~
+ UnaryExpression is
+ evaluated as follows:
+ Let + expr be the result of evaluating UnaryExpression.
++ Return + the result of applying bitwise complement to oldValue. The + result is a signed 32-bit integer.
+
+ The
+ production UnaryExpression : !
+ UnaryExpression is
+ evaluated as follows:
+ Let + expr be the result of evaluating UnaryExpression.
++ If + oldValue is true, return false.
++ Return + true.
++ Syntax
++ MultiplicativeExpression :
+
+ UnaryExpression
MultiplicativeExpression * UnaryExpression
MultiplicativeExpression / UnaryExpression
MultiplicativeExpression % UnaryExpression
+ Semantics
++ The + production MultiplicativeExpression : MultiplicativeExpression@ UnaryExpression, + where @ stands for one of the operators in the above definitions, is + evaluated as follows:
++ Let + left be the result of evaluating MultiplicativeExpression.
++ Let + leftValue be GetValue(left).
++ Let + right be the result of evaluating UnaryExpression.
++ Let + rightValue be GetValue(right).
++ Let + leftNum be ToNumber(leftValue).
++ Let + rightNum be ToNumber(rightValue).
++ Return + the result of applying the specified operation (*, /, or %) to + leftNum and rightNum. See the Notes below 11.5.1, + 11.5.2, 11.5.3.
+
+ The *
+ operator performs multiplication, producing the product of its
+ operands. Multiplication is commutative. Multiplication is not
+ always associative in ECMAScript, because of finite precision.
The + result of a floating-point multiplication is governed by the rules + of IEEE 754 binary double-precision arithmetic:
++ If + either operand is NaN, + the result is NaN.
++ The + sign of the result is positive if both operands have the same + sign, negative if the operands have different signs.
++ Multiplication + of an infinity by a zero results in NaN.
++ Multiplication + of an infinity by an infinity results in an infinity. The sign is + determined by the rule already stated above.
++ Multiplication + of an infinity by a finite non-zero value results in a signed + infinity. The sign is determined by the rule already stated above.
++ In + the remaining cases, where neither an infinity or NaN is involved, + the product is computed and rounded to the nearest representable + value using IEEE 754 round-to-nearest mode. If the magnitude is + too large to represent, the result is then an infinity of + appropriate sign. If the magnitude is too small to represent, the + result is then a zero of appropriate sign. The ECMAScript language + requires support of gradual underflow as defined by IEEE 754.
+The
+ / operator
+ performs division, producing the quotient of its operands. The left
+ operand is the dividend and the right operand is the divisor.
+ ECMAScript does not perform integer division. The operands and
+ result of all division operations are double-precision
+ floating-point numbers. The result of division is determined by the
+ specification of IEEE 754 arithmetic:
+ If + either operand is NaN, + the result is NaN.
++ The + sign of the result is positive if both operands have the same + sign, negative if the operands have different signs.
++ Division + of an infinity by an infinity results in NaN.
++ Division + of an infinity by a zero results in an infinity. The sign is + determined by the rule already stated above.
++ Division + of an infinity by a non-zero finite value results in a signed + infinity. The sign is determined by the rule already stated above.
++ Division + of a finite value by an infinity results in zero. The sign is + determined by the rule already stated above.
++ Division + of a zero by a zero results in NaN; + division of zero by any other finite value results in zero, with + the sign determined by the rule already stated above.
++ Division + of a non-zero finite value by a zero results in a signed infinity. + The sign is determined by the rule already stated above.
++ In + the remaining cases, where neither an infinity, nor a zero, nor + NaN + is involved, the quotient is computed and rounded to the nearest + representable value using IEEE 754 round-to-nearest mode. If the + magnitude is too large to represent, the operation overflows; the + result is then an infinity of appropriate sign. If the magnitude + is too small to represent, the operation underflows and the result + is a zero of the appropriate sign. The ECMAScript language + requires support of gradual underflow as defined by IEEE 754.
+
+ The %
+ operator yields the remainder of its operands from an implied
+ division; the left operand is the dividend and the right operand is
+ the divisor.
NOTE In + C and C++, the remainder operator accepts only integral operands; in + ECMAScript, it also accepts floating-point operands.
+
+ The
+ result of a floating-point remainder operation as computed by the %
+ operator is not the same as the “remainder” operation defined by
+ IEEE 754. The IEEE 754 “remainder” operation computes the
+ remainder from a rounding division, not a truncating division, and
+ so its behaviour is not analogous to that of the usual integer
+ remainder operator. Instead the ECMAScript language defines %
+ on floating-point operations to behave in a manner analogous to that
+ of the Java integer remainder operator; this may be compared with
+ the C library function fmod.
The + result of an ECMAScript floating-point remainder operation is + determined by the rules of IEEE arithmetic:
++ If + either operand is NaN, + the result is NaN.
++ The + sign of the result equals the sign of the dividend.
++ If + the dividend is an infinity, or the divisor is a zero, or both, + the result is NaN.
++ If + the dividend is finite and the divisor is an infinity, the result + equals the dividend.
++ If + the dividend is a zero and the divisor is finite, the result is + the same as the dividend.
++ In + the remaining cases, where neither an infinity, nor a zero, nor + NaN + is involved, the floating-point remainder r from a dividend n and + a divisor d is defined by the mathematical relation r = n − + (d * q) where q is an integer that is negative only if n/d is + negative and positive only if n/d is positive, and whose + magnitude is as large as possible without exceeding the magnitude + of the true mathematical quotient of n and d. +r is computed and rounded to the nearest representable value using +IEEE 754 round-to-nearest mode. +
++ Syntax
++ AdditiveExpression :
+
+ MultiplicativeExpression
AdditiveExpression + MultiplicativeExpression
AdditiveExpression - MultiplicativeExpression
+ The + addition operator either performs string concatenation or numeric + addition.
+
+ The
+ production AdditiveExpression
+ : AdditiveExpression
+ +
+ MultiplicativeExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating AdditiveExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating MultiplicativeExpression.
++ Let + rval be GetValue(rref).
++ Let + lprim be ToPrimitive(lval).
++ Let + rprim be ToPrimitive(rval).
++ If + Type(lprim) is String or Type(rprim) is String, then +
++ Return + the result of applying the addition operation to ToNumber(lprim) + and ToNumber(rprim). See the Note below 11.6.3.
+NOTE 1 No hint is provided in the calls to ToPrimitive in steps 5 and 6. + All native ECMAScript objects except Date objects handle the absence + of a hint as if the hint Number were given; Date objects handle the + absence of a hint as if the hint String were given. Host objects may + handle the absence of a hint in some other manner.
+NOTE 2 Step 7 differs from step 3 of the comparison algorithm for the + relational operators (11.8.5), by using the logical-or operation + instead of the logical-and operation.
+
+ The
+ production AdditiveExpression
+ : AdditiveExpression
+ -
+ MultiplicativeExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating AdditiveExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating MultiplicativeExpression.
++ Let + rval be GetValue(rref).
++ Let + lnum be ToNumber(lval).
++ Let + rnum be ToNumber(rval).
++ Return + the result of applying the subtraction operation to lnum and + rnum. See the note below 11.6.3.
+
+ The +
+ operator performs addition when applied to two operands of numeric
+ type, producing the sum of the operands. The -
+ operator performs subtraction, producing the difference of two
+ numeric operands.
+ Addition + is a commutative operation, but not always associative.
+The + result of an addition is determined using the rules of IEEE 754 + binary double-precision arithmetic:
++ If + either operand is NaN, + the result is NaN.
++ The + sum of two infinities of opposite sign is NaN.
++ The + sum of two infinities of the same sign is the infinity of that + sign.
++ The + sum of an infinity and a finite value is equal to the infinite + operand.
++ The + sum of two negative zeros is −0. + The sum of two positive zeros, or of two zeros of opposite sign, + is +0.
++ The + sum of a zero and a nonzero finite value is equal to the nonzero + operand.
++ The + sum of two nonzero finite values of the same magnitude and + opposite sign is +0.
++ In + the remaining cases, where neither an infinity, nor a zero, nor + NaN is involved, and the operands have the same sign or have + different magnitudes, the sum is computed and rounded to the + nearest representable value using IEEE 754 round-to-nearest mode. + If the magnitude is too large to represent, the operation + overflows and the result is then an infinity of appropriate sign. + The ECMAScript language requires support of gradual underflow as + defined by IEEE 754.
+
+ The -
+ operator performs subtraction when applied to two operands of
+ numeric type, producing the difference of its operands; the left
+ operand is the minuend and the right operand is the subtrahend.
+ Given numeric operands a
+ and b, it is
+ always the case that a–b
+ produces the same result as a +(–b).
+ Syntax
++ ShiftExpression :
+
+ AdditiveExpression
ShiftExpression << AdditiveExpression
ShiftExpression >> AdditiveExpression
ShiftExpression >>> AdditiveExpression
+ Performs + a bitwise left shift operation on the left operand by the amount + specified by the right operand.
+
+ The
+ production ShiftExpression
+ : ShiftExpression
+ <<
+ AdditiveExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating ShiftExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating AdditiveExpression.
++ Let + rval be GetValue(rref).
++ Let + lnum be ToInt32(lval).
++ Let + rnum be ToUint32(rval).
++ Let + shiftCount be the result of masking out all but the least + significant 5 bits of rnum, that is, compute rnum & + 0x1F.
++ Return + the result of left shifting lnum by shiftCount bits. + The result is a signed 32-bit integer.
++ Performs + a sign-filling bitwise right shift operation on the left operand by + the amount specified by the right operand.
+
+ The
+ production ShiftExpression
+ : ShiftExpression
+ >>
+ AdditiveExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating ShiftExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating AdditiveExpression.
++ Let + rval be GetValue(rref).
++ Let + lnum be ToInt32(lval).
++ Let + rnum be ToUint32(rval).
++ Let + shiftCount be the result of masking out all but the least + significant 5 bits of rnum, that is, compute rnum & + 0x1F.
++ Return + the result of performing a sign-extending right shift of lnum + by shiftCount bits. The most significant bit is propagated. + The result is a signed 32-bit integer.
++ Performs + a zero-filling bitwise right shift operation on the left operand by + the amount specified by the right operand.
+
+ The
+ production ShiftExpression
+ : ShiftExpression
+ >>>
+ AdditiveExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating ShiftExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating AdditiveExpression.
++ Let + rval be GetValue(rref).
++ Let + lnum be ToUint32(lval).
++ Let + rnum be ToUint32(rval).
++ Let + shiftCount be the result of masking out all but the least + significant 5 bits of rnum, that is, compute rnum & + 0x1F.
++ Return + the result of performing a zero-filling right shift of lnum + by shiftCount bits. Vacated bits are filled with zero. The + result is an unsigned 32-bit integer.
++ Syntax
++ RelationalExpression :
+
+ ShiftExpression
RelationalExpression < ShiftExpression
RelationalExpression > ShiftExpression
RelationalExpression <= ShiftExpression
RelationalExpression >= ShiftExpression
RelationalExpression instanceof ShiftExpression
RelationalExpression in ShiftExpression
+ RelationalExpressionNoIn :
+
+ ShiftExpression
RelationalExpressionNoIn < ShiftExpression
RelationalExpressionNoIn > ShiftExpression
RelationalExpressionNoIn <= ShiftExpression
RelationalExpressionNoIn >= ShiftExpression
RelationalExpressionNoIn instanceof ShiftExpression
NOTE The
+ “NoIn” variants are needed to avoid confusing the in
+ operator in a relational expression with the in
+ operator in a for
+ statement.
+ Semantics
++ The + result of evaluating a relational operator is always of type + Boolean, reflecting whether the relationship named by the operator + holds between its two operands.
++ The + RelationalExpressionNoIn + productions are evaluated in the same manner as the + RelationalExpression + productions except that the contained RelationalExpressionNoIn + is evaluated instead of the contained RelationalExpression.
+
+ The
+ production RelationalExpression
+ : RelationalExpression
+ <
+ ShiftExpression is
+ evaluated as follows:
+ Let + lref be the result of evaluating RelationalExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating ShiftExpression.
++ Let + rval be GetValue(rref).
++ Let + r be the result of performing abstract relational comparison + lval < rval. (see 11.8.5)
++ If + r is undefined, return false. Otherwise, + return r.
+
+ The
+ production RelationalExpression : RelationalExpression
+ >
+ ShiftExpression is
+ evaluated as follows:
+ Let + lref be the result of evaluating RelationalExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating ShiftExpression.
++ Let + rval be GetValue(rref).
++ Let + r be the result of performing abstract relational comparison + rval < lval with LeftFirst equal to false. + (see 11.8.5).
++ If + r is undefined, return false. Otherwise, + return r.
+
+ The
+ production RelationalExpression : RelationalExpression
+ <=
+ ShiftExpression is
+ evaluated as follows:
+ Let + lref be the result of evaluating RelationalExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating ShiftExpression.
++ Let + rval be GetValue(rref).
++ Let + r be the result of performing abstract relational comparison + rval < lval with LeftFirst equal to false. + (see 11.8.5).
++ If + r is true or undefined, return false. + Otherwise, return true.
+
+ The
+ production RelationalExpression : RelationalExpression
+ >=
+ ShiftExpression is
+ evaluated as follows:
+ Let + lref be the result of evaluating RelationalExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating ShiftExpression.
++ Let + rval be GetValue(rref).
++ Let + r be the result of performing abstract relational comparison + lval < rval. (see 11.8.5)
++ If + r is true or undefined, return false. + Otherwise, return true.
++ The + comparison x < + y, where x + and y are values, + produces true, false, or undefined (which + indicates that at least one operand is NaN). In addition to x + and y the + algorithm takes a Boolean flag named LeftFirst + as a parameter. The flag is used to control the order in which + operations with potentially visible side-effects are performed upon + x and y. + It is necessary because ECMAScript specifies left to right + evaluation of expressions. The default value of LeftFirst + is true and indicates that the x + parameter corresponds to an expression that occurs to the left of + the y parameter’s + corresponding expression. If LeftFirst is false, the reverse is the case and operations + must be performed upon y before x. + Such a comparison is performed as follows:
++ If + the LeftFirst flag is true, then
++ Let + px be the result of calling ToPrimitive(x, hint + Number).
++ Let + py be the result of calling ToPrimitive(y, hint + Number).
++ Else + the order of evaluation needs to be reversed to preserve left to + right evaluation
++ Let + py be the result of calling ToPrimitive(y, hint + Number).
++ Let + px be the result of calling ToPrimitive(x, hint + Number).
++ If + it is not the case that both Type(px) is String and Type(py) + is String, then +
++ Let + nx be the result of calling ToNumber(px). Because px and py are primitive values evaluation order is not + important.
++ Let + ny be the result of calling ToNumber(py).
++ If + nx is NaN, return undefined.
++ If + ny is NaN, return undefined.
++ If + nx and ny are the same Number value, return false.
++ If + nx is +0 and ny is −0, + return false.
++ If + nx is −0 + and ny is +0, return false.
++ If + nx is +∞, + return false.
++ If + ny is +∞, + return true.
++ If + ny is −∞, + return false.
++ If + nx is −∞, + return true.
++ If + the mathematical value of nx is less than the mathematical + value of ny —note that these mathematical values are both + finite and not both zero—return true. Otherwise, return + false.
++ Else, + both px and py are Strings
++ If + py is a prefix of px, return false. (A String + value p is a prefix of String value q if q + can be the result of concatenating p and some other String + r. Note that any String is a prefix of itself, because r + may be the empty String.)
++ If + px is a prefix of py, return true.
++ Let + k be the smallest nonnegative integer such that the + character at position k within px is different from + the character at position k within py. (There must + be such a k, for neither String is a prefix of the other.)
++ Let + m be the integer that is the code unit value for the + character at position k within px.
++ Let + n be the integer that is the code unit value for the + character at position k within py.
++ If + m < n, return true. Otherwise, return + false.
+NOTE 1 Step 3 differs from step 7 in the algorithm for the addition
+ operator +
+ (11.6.1) in using and instead of or.
NOTE 2 The comparison of Strings uses a simple lexicographic ordering on + sequences of code unit values. There is no attempt to use the more + complex, semantically oriented definitions of character or string + equality and collating order defined in the Unicode specification. + Therefore String values that are canonically equal according to the + Unicode standard could test as unequal. In effect this algorithm + assumes that both Strings are already in normalised form. + Also, note that for strings containing supplementary characters, + lexicographic ordering on sequences of UTF-16 code unit values + differs from that on sequences of code point values.
+
+ The
+ production RelationalExpression:
+ RelationalExpression
+ instanceof
+ ShiftExpression is
+ evaluated as follows:
+ Let + lref be the result of evaluating RelationalExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating ShiftExpression.
++ Let + rval be GetValue(rref).
++ If + Type(rval) is not Object, throw a TypeError + exception.
++ If + rval does not have a [[HasInstance]] internal method, throw + a TypeError exception.
++ Return + the result of calling the [[HasInstance]] internal method of rval + with argument lval.
+
+ The
+ production RelationalExpression
+ : RelationalExpression
+ in ShiftExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating RelationalExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating ShiftExpression.
++ Let + rval be GetValue(rref).
++ If + Type(rval) is not Object, throw a TypeError + exception.
++ Return + the result of calling the [[HasProperty]] internal method of rval + with argument ToString(lval).
++ Syntax
++ EqualityExpression :
+
+ RelationalExpression
EqualityExpression == RelationalExpression
EqualityExpression != RelationalExpression
EqualityExpression === RelationalExpression
EqualityExpression !== RelationalExpression
+ EqualityExpressionNoIn :
+
+ RelationalExpressionNoIn
EqualityExpressionNoIn == RelationalExpressionNoIn
EqualityExpressionNoIn != RelationalExpressionNoIn
EqualityExpressionNoIn === RelationalExpressionNoIn
EqualityExpressionNoIn !== RelationalExpressionNoIn
+ Semantics
++ The + result of evaluating an equality operator is always of type Boolean, + reflecting whether the relationship named by the operator holds + between its two operands.
++ The + EqualityExpressionNoIn + productions are evaluated in the same manner as the + EqualityExpression + productions except that the contained EqualityExpressionNoIn + and RelationalExpressionNoIn + are evaluated instead of the contained EqualityExpression + and RelationalExpression, + respectively.
+
+ The
+ production EqualityExpression : EqualityExpression
+ ==
+ RelationalExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating EqualityExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating RelationalExpression.
++ Let + rval be GetValue(rref).
++ Return + the result of performing abstract equality comparison rval + == lval. (see 11.9.3).
+
+ The
+ production EqualityExpression : EqualityExpression
+ !=
+ RelationalExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating EqualityExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating RelationalExpression.
++ Let + rval be GetValue(rref).
++ Let + r be the result of performing abstract equality comparison + rval == lval. (see 11.9.3).
++ If + r is true, return false. Otherwise, return + true.
++ The + comparison x == y, + where x and y + are values, produces true or false. Such a comparison + is performed as follows:
++ If + Type(x) is the same as Type(y), then
++ If + Type(x) is Undefined, return true.
++ If + Type(x) is Null, return true.
++ If + Type(x) is Number, then
++ If + x is NaN, return false.
++ If + y is NaN, return false.
++ If + x is the same Number value as y, return true.
++ If + x is +0 and y is −0, + return true.
++ If + x is −0 + and y is +0, return true.
++ Return + false.
++ If + Type(x) is String, then return true if x and + y are exactly the same sequence of characters (same length + and same characters in corresponding positions). Otherwise, return + false.
++ If + Type(x) is Boolean, return true if x and y are both true or both false. Otherwise, return + false.
++ Return + true if x and y refer to the same object. + Otherwise, return false.
++ If + x is null and y is undefined, return + true.
++ If + x is undefined and y is null, return + true.
+
+ If
+ Type(x) is Number and Type(y) is String,
return
+ the result of the comparison x == ToNumber(y).
+ If
+ Type(x) is String and Type(y) is Number,
return
+ the result of the comparison ToNumber(x) == y.
+ If + Type(x) is Boolean, return the result of the comparison + ToNumber(x) == y.
++ If + Type(y) is Boolean, return the result of the comparison x + == ToNumber(y).
+
+ If
+ Type(x) is either String or Number and Type(y) is
+ Object,
return the result of the comparison x ==
+ ToPrimitive(y).
+ If
+ Type(x) is Object and Type(y) is either String or
+ Number,
return the result of the comparison ToPrimitive(x)
+ == y.
+ Return + false.
+NOTE 1 Given the above definition of equality:
+
+ String
+ comparison can be forced by:
+ ""
+ + a == "" + b.
+ Numeric
+ comparison can be forced by:
+ +a
+ == +b.
+ Boolean
+ comparison can be forced by:
+ !a
+ == !b.
NOTE 2 The equality operators maintain the following invariants:
+
+ A
+ !=
+ B
+ is
+ equivalent to
+ !(A
+ ==
+ B).
+ A
+ ==
+ B
+ is
+ equivalent to B
+ ==
+ A,
+ except in the order of evaluation of
+ A
+ and
+ B.
NOTE 3 The
+ equality operator is not always transitive. For example, there might
+ be two distinct String objects, each representing the same String
+ value; each String object would be considered equal to the String
+ value by the ==
+ operator, but the two String objects would not be equal to each
+ other.
NOTE 4 Comparison of Strings uses a simple equality test on sequences of + code unit values. There is no attempt to use the more complex, + semantically oriented definitions of character or string equality + and collating order defined in the Unicode specification. Therefore + Strings values that are canonically equal according to the Unicode + standard could test as unequal. In effect this algorithm assumes + that both Strings are already in normalised form.
+
+ The
+ production EqualityExpression : EqualityExpression
+ ===
+ RelationalExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating EqualityExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating RelationalExpression.
++ Let + rval be GetValue(rref).
++ Return + the result of performing the strict equality comparison rval + === lval. (See 11.9.6)
+
+ The
+ production EqualityExpression : EqualityExpression
+ !==
+ RelationalExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating EqualityExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating RelationalExpression.
++ Let + rval be GetValue(rref).
++ Let + r be the result of performing strict equality comparison + rval === lval. (See 11.9.6)
++ If + r is true, return false. Otherwise, return + true.
++ The + comparison x === + y, where x + and y are values, + produces true or false. Such a comparison is performed + as follows:
++ If + Type(x) is Undefined, return true.
++ If + Type(x) is Null, return true.
++ If + Type(x) is Number, then
++ If + x is NaN, return false.
++ If + y is NaN, return false.
++ If + x is the same Number value as y, return true.
++ If + x is +0 and y is −0, + return true.
++ If + x is −0 + and y is +0, return true.
++ Return + false.
++ If + Type(x) is String, then return true if x and y + are exactly the same sequence of characters (same length and same + characters in corresponding positions); otherwise, return false.
++ If + Type(x) is Boolean, return true if x and y + are both true or both false; otherwise, return false.
++ Return + true if x and y refer to the same object. + Otherwise, return false.
+NOTE This + algorithm differs from the SameValue Algorithm (9.12) in its + treatment of signed zeroes and NaNs.
++ Syntax
++ BitwiseANDExpression :
+
+ EqualityExpression
BitwiseANDExpression & EqualityExpression
+ BitwiseANDExpressionNoIn :
+
+ EqualityExpressionNoIn
BitwiseANDExpressionNoIn & EqualityExpressionNoIn
+ BitwiseXORExpression :
+
+ BitwiseANDExpression
BitwiseXORExpression ^ BitwiseANDExpression
+ BitwiseXORExpressionNoIn :
+
+ BitwiseANDExpressionNoIn
BitwiseXORExpressionNoIn ^ BitwiseANDExpressionNoIn
+ BitwiseORExpression :
+
+ BitwiseXORExpression
BitwiseORExpression | BitwiseXORExpression
+ BitwiseORExpressionNoIn :
+
+ BitwiseXORExpressionNoIn
BitwiseORExpressionNoIn | BitwiseXORExpressionNoIn
+ Semantics
++ The + production A : A @ B, + where @ is one of the bitwise operators in the productions above, is + evaluated as follows:
++ Let + lref be the result of evaluating A.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating B.
++ Let + rval be GetValue(rref).
++ Let + lnum be ToInt32(lval).
++ Let + rnum be ToInt32(rval).
++ Return + the result of applying the bitwise operator @ to lnum and + rnum. The result is a signed 32 bit integer.
++ Syntax
++ LogicalANDExpression :
+
+ BitwiseORExpression
LogicalANDExpression && BitwiseORExpression
+ LogicalANDExpressionNoIn :
+
+ BitwiseORExpressionNoIn
LogicalANDExpressionNoIn && BitwiseORExpressionNoIn
+ LogicalORExpression :
+
+ LogicalANDExpression
LogicalORExpression || LogicalANDExpression
+ LogicalORExpressionNoIn :
+
+ LogicalANDExpressionNoIn
LogicalORExpressionNoIn || LogicalANDExpressionNoIn
+ Semantics
+
+ The
+ production LogicalANDExpression
+ : LogicalANDExpression
+ &&
+ BitwiseORExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating LogicalANDExpression.
++ Let + lval be GetValue(lref).
++ If + ToBoolean(lval) is false, return lval.
++ Let + rref be the result of evaluating BitwiseORExpression.
++ Return + GetValue(rref).
+
+ The
+ production LogicalORExpression
+ : LogicalORExpression
+ ||
+ LogicalANDExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating LogicalORExpression.
++ Let + lval be GetValue(lref).
++ If + ToBoolean(lval) is true, return lval.
++ Let + rref be the result of evaluating LogicalANDExpression.
++ Return + GetValue(rref).
++ The + LogicalANDExpressionNoIn + and LogicalORExpressionNoIn + productions are evaluated in the same manner as the + LogicalANDExpression + and LogicalORExpression + productions except that the contained LogicalANDExpressionNoIn, + BitwiseORExpressionNoIn + and LogicalORExpressionNoIn + are evaluated instead of the contained LogicalANDExpression, + BitwiseORExpression + and LogicalORExpression, + respectively.
+NOTE The
+ value produced by a &&
+ or || operator is
+ not necessarily of type Boolean. The value produced will always be
+ the value of one of the two operand expressions.
+ Syntax
++ ConditionalExpression :
+
+ LogicalORExpression
LogicalORExpression
+ ? AssignmentExpression : AssignmentExpression
+ ConditionalExpressionNoIn :
+
+ LogicalORExpressionNoIn
LogicalORExpressionNoIn
+ ? AssignmentExpression : AssignmentExpressionNoIn
+ Semantics
+
+ The
+ production ConditionalExpression
+ :
+ LogicalORExpression
+ ?
+ AssignmentExpression
+ :
+ AssignmentExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating LogicalORExpression.
++ If + ToBoolean(GetValue(lref)) is true, then
++ Let + trueRef be the result of evaluating the first + AssignmentExpression.
++ Return + GetValue(trueRef).
++ Else
++ Let + falseRef be the result of evaluating the second + AssignmentExpression.
++ Return + GetValue(falseRef).
++ The + ConditionalExpressionNoIn + production is evaluated in the same manner as the + ConditionalExpression + production except that the contained LogicalORExpressionNoIn, + AssignmentExpression + and AssignmentExpressionNoIn + are evaluated instead of the contained LogicalORExpression, + first AssignmentExpression + and second AssignmentExpression, + respectively.
++
NOTE The grammar + for a ConditionalExpression in ECMAScript is a little bit different + from that in C and Java, which each allow the second subexpression + to be an Expression but restrict the third expression to be a + ConditionalExpression. The motivation for this difference in + ECMAScript is to allow an assignment expression to be governed by + either arm of a conditional and to eliminate the confusing and + fairly useless case of a comma expression as the centre expression.
++ Syntax
++ AssignmentExpression :
+
+ ConditionalExpression
LeftHandSideExpression
+ AssignmentOperator AssignmentExpression
+ AssignmentExpressionNoIn :
+
+ ConditionalExpressionNoIn
LeftHandSideExpression
+ AssignmentOperator AssignmentExpressionNoIn
+ AssignmentOperator : + one + of
+|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+ Semantics
++ The + AssignmentExpressionNoIn + productions are evaluated in the same manner as the + AssignmentExpression + productions except that the contained ConditionalExpressionNoIn andAssignmentExpressionNoIn are evaluated instead of the + contained ConditionalExpression + and AssignmentExpression, + respectively.
+
+ The
+ production AssignmentExpression
+ : LeftHandSideExpression
+ =
+ AssignmentExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating LeftHandSideExpression.
++ Let + rref be the result of evaluating AssignmentExpression.
++ Let + rval be GetValue(rref).
++ Throw + a SyntaxError exception if the following conditions are all + true:
++ IsStrictReference(lref) + is true
++ Type(GetBase(lref)) + is Environment Record
+
+ GetReferencedName(lref)
+ is either "eval"
+ or "arguments"
+ Call + PutValue(lref, rval).
++ Return + rval.
+NOTE When + an assignment occurs within strict mode code, its LeftHandSide + must not evaluate to an unresolvable reference. If it does a + ReferenceError exception is thrown upon assignment. The + LeftHandSide also + may not be a reference to a data property with the attribute value + {[[Writable]]:false}, + to an accessor property with the attribute value + {[[Set]]:undefined}, + nor to a non-existent property of an object whose [[Extensible]] + internal property has the value false. In these cases a + TypeError exception is thrown.
+
+ The
+ production AssignmentExpression : LeftHandSideExpression@ = AssignmentExpression,
+ where @ represents one of the operators indicated above, is
+ evaluated as follows:
+ Let + lref be the result of evaluating LeftHandSideExpression.
++ Let + lval be GetValue(lref).
++ Let + rref be the result of evaluating AssignmentExpression.
++ Let + rval be GetValue(rref).
++ Let + r be the result of applying operator @ to lval and + rval.
++ Throw + a SyntaxError exception if the following conditions are all + true:
++ IsStrictReference(lref) + is true
++ Type(GetBase(lref)) + is Environment Record
+
+ GetReferencedName(lref)
+ is either "eval"
+ or "arguments"
+ Call + PutValue(lref, r).
++ Return + r.
+NOTE See + NOTE 11.13.1.
++ Syntax
++ Expression :
+
+ AssignmentExpression
Expression , AssignmentExpression
+ ExpressionNoIn :
+
+ AssignmentExpressionNoIn
ExpressionNoIn , AssignmentExpressionNoIn
+ Semantics
+
+ The
+ production Expression
+ : Expression
+ ,
+ AssignmentExpression
+ is evaluated as follows:
+ Let + lref be the result of evaluating Expression.
++ Call + GetValue(lref).
++ Let + rref be the result of evaluating AssignmentExpression.
++ Return + GetValue(rref).
++ The + ExpressionNoIn + production is evaluated in the same manner as the Expression + production except that the contained ExpressionNoIn + and AssignmentExpressionNoIn + are evaluated instead of the contained Expression + and AssignmentExpression, + respectively.
++
NOTE GetValue must + be called even though its value is not used because it may have + observable side-effects.
+ \ No newline at end of file diff --git a/x12.html b/x12.html new file mode 100644 index 0000000..1cd4d78 --- /dev/null +++ b/x12.html @@ -0,0 +1,1685 @@ + +‟Ex igne vita”
+ ++ Syntax
++ Statement :
+
+ Block
VariableStatement
EmptyStatement
ExpressionStatement
IfStatement
IterationStatement
ContinueStatement
BreakStatement
ReturnStatement
WithStatement
LabelledStatement
SwitchStatement
ThrowStatement
TryStatement
DebuggerStatement
+ Semantics
++ A + Statement can be + part of a LabelledStatement, + which itself can be part of a LabelledStatement, + and so on. The labels introduced this way are collectively referred + to as the “current label set” when describing the semantics of + individual statements. A LabelledStatement + has no semantic meaning other than the introduction of a label to a + label set. The label set of an IterationStatement + or a SwitchStatement + initially contains the single element empty. The label set of + any other statement is initially empty.
+NOTE Several + widely used implementations of ECMAScript are known to support the + use of FunctionDeclaration + as a Statement. However + there are significant and irreconcilable variations among the + implementations in the semantics applied to such + FunctionDeclarations. + Because of these irreconcilable difference, the use of a + FunctionDeclaration + as a Statement + results in code that is not reliably portable among implementations. + It is recommended that ECMAScript implementations either disallow + this usage of FunctionDeclaration + or issue a warning when such a usage is encountered. Future editions + of ECMAScript may define alternative portable means for declaring + functions in a Statement + context.
++ Syntax
++ Block :
+
+ { StatementListopt}
+ StatementList :
+
+ Statement
StatementList
+ Statement
+ Semantics
+
+ The
+ production Block : { }
+ is evaluated as follows:
+ Return + (normal, empty, empty).
+
+ The
+ production Block : {
+ StatementList }is
+ evaluated as follows:
+ Return + the result of evaluating StatementList.
++ The + production StatementList :Statement is evaluated as follows:
++ Let + s be the result of evaluating Statement.
++ If + an exception was thrown, return (throw, + V, empty) where V + is the exception. (Execution now proceeds as if no exception were + thrown.)
++ Return + s.
++ The + production StatementList :StatementList Statement is evaluated as follows:
++ Let + sl be the result of evaluating StatementList.
++ If + sl is an abrupt completion, return sl.
++ Let + s be the result of evaluating Statement.
++ If + an exception was thrown, return (throw, + V, empty) where V + is the exception. (Execution now proceeds as if no exception were + thrown.)
++ If + s.value is empty, let + V = sl.value, otherwise let V = s.value.
++ Return + (s.type, V, s.target).
++ Syntax
++ VariableStatement :
+
+ var VariableDeclarationList ;
+ VariableDeclarationList :
+
+ VariableDeclaration
VariableDeclarationList , VariableDeclaration
+ VariableDeclarationListNoIn :
+
+ VariableDeclarationNoIn
VariableDeclarationListNoIn , VariableDeclarationNoIn
+ VariableDeclaration :
++ Identifier + Initialiseropt
++ VariableDeclarationNoIn :
++ Identifier + InitialiserNoInopt
++ Initialiser :
+
+ = AssignmentExpression
+ InitialiserNoIn :
+
+ = AssignmentExpressionNoIn
+ A + variable statement declares variables that are created as defined in + 10.5. Variables are initialised to undefined when created. A + variable with an Initialiser + is assigned the value of its AssignmentExpression + when the VariableStatement + is executed, not when the variable is created.
++ Semantics
+
+ The
+ production VariableStatement : var VariableDeclarationList ;
+ is evaluated as follows:
+ Evaluate + VariableDeclarationList.
++ Return + (normal, empty, + empty).
++ The + production VariableDeclarationList + : VariableDeclaration + is evaluated as follows:
++ Evaluate + VariableDeclaration.
+
+ The
+ production VariableDeclarationList
+ : VariableDeclarationList
+ ,
+ VariableDeclaration
+ is evaluated as follows:
+ Evaluate + VariableDeclarationList.
++ Evaluate + VariableDeclaration.
++ The + production VariableDeclaration : Identifier is evaluated as follows:
++ Return + a String value containing the same sequence of characters as in the + Identifier.
++ The + production VariableDeclaration + : Identifier + Initialiser is evaluated as follows:
++ Let + lhs be the result of evaluating Identifier as + described in 11.1.2.
++ Let + rhs be the result of evaluating Initialiser.
++ Let + value be GetValue(rhs).
++ Call + PutValue(lhs, value).
++ Return + a String value containing the same sequence of characters as in the + Identifier.
+NOTE The + String value of a VariableDeclaration + is used in the evaluation of for-in statements (12.6.4).
++ If a + VariableDeclaration + is nested within a with statement and the Identifier in the + VariableDeclaration + is the same as a property name of the binding object of the with + statement’s object environment record, then step 4 will assign + value to the property instead of to the VariableEnvironment binding + of the Identifier.
+
+ The
+ production Initialiser : = AssignmentExpression is evaluated as follows:
+ Return + the result of evaluating AssignmentExpression.
++ The + VariableDeclarationListNoIn, + VariableDeclarationNoIn + and InitialiserNoIn + productions are evaluated in the same manner as the + VariableDeclarationList, + VariableDeclaration + and Initialiser + productions except that the contained VariableDeclarationListNoIn, + VariableDeclarationNoIn, + InitialiserNoIn + and AssignmentExpressionNoIn + are evaluated instead of the contained VariableDeclarationList, + VariableDeclaration, + Initialiser and + AssignmentExpression, + respectively.
+
+ It is
+ a SyntaxError if a VariableDeclaration
+ or VariableDeclarationNoIn
+ occurs within strict code and its Identifier
+ is either "eval"
+ or "arguments".
+ Syntax
++ EmptyStatement :
++ ;
++ Semantics
+
+ The
+ production EmptyStatement : ; is
+ evaluated as follows:
+ Return + (normal, + empty, empty).
++ Syntax
++ ExpressionStatement :
+
+ [lookahead
+ ∉
+ {{,
+ function}] Expression ;
NOTE An
+ ExpressionStatement
+ cannot start with an opening curly brace because that might make it
+ ambiguous with a Block.
+ Also, an ExpressionStatement
+ cannot start with the function
+ keyword because that might make it ambiguous with a
+ FunctionDeclaration.
+ Semantics
+
+ The
+ production ExpressionStatement : [lookahead ∉
+ {{,
+ function}]Expression;
+ is evaluated as follows:
+ Let + exprRef be the result of evaluating Expression.
++ Return + (normal, GetValue(exprRef), + empty).
++ Syntax
++ IfStatement :
+
+ if ( Expression ) Statement else Statementif ( Expression ) Statement
+ Each
+ else for which the
+ choice of associated if
+ is ambiguous shall be associated with the nearest possible if
+ that would otherwise have no corresponding else.
+ Semantics
+
+ The
+ production IfStatement : if ( Expression ) Statement else Statement is evaluated as follows:
+ Let + exprRef be the result of evaluating Expression.
++ If + ToBoolean(GetValue(exprRef)) is true, then
++ Return + the result of evaluating the first Statement.
++ Else,
++ Return + the result of evaluating the second Statement.
+
+ The
+ production IfStatement : if ( Expression ) Statement is evaluated as follows:
+ Let + exprRef be the result of evaluating Expression.
++ If + ToBoolean(GetValue(exprRef)) is false, return + (normal, empty, + empty).
++ Return + the result of evaluating Statement.
++ Syntax
++ IterationStatement :
+
+ do
+ Statement
+ while ( Expression ); while ( Expression ) Statementfor ( ExpressionNoInopt; Expressionopt; Expressionopt) Statementfor ( var VariableDeclarationListNoIn; Expressionopt; Expressionopt) Statementfor ( LeftHandSideExpression in Expression ) Statementfor ( var VariableDeclarationNoIn in Expression ) Statement
+ The
+ production do Statement while ( Expression );
+ is evaluated as follows:
+ Let + V = empty.
++ Let + iterating be true.
++ Repeat, + while iterating is true
++ Let + stmt be the result of evaluating Statement.
++ If + stmt.value is not empty, + let V = stmt.value.
++ If + stmt.type is not continue + || stmt.target is not in the current label set, then
++ If + stmt.type is break + and stmt.target is in the current label set, return + (normal, V, empty).
++ If + stmt is an abrupt completion, return stmt.
++ Let + exprRef be the result of evaluating Expression.
++ If + ToBoolean(GetValue(exprRef)) is false, set iterating + to false.
++ Return + (normal, V, empty);
+
+ The
+ production IterationStatement : while ( Expression ) Statement is evaluated as follows:
+ Let + V = empty.
++ Repeat
++ Let + exprRef be the result of evaluating Expression.
++ If + ToBoolean(GetValue(exprRef)) is false, return + (normal, V, empty).
++ Let + stmt be the result of evaluating Statement.
++ If + stmt.value is not empty, + let V = stmt.value.
++ If + stmt.type is not continue + || stmt.target is not in the current label set, then
++ If + stmt.type is break + and stmt.target is in the current label set, then
++ Return + (normal, V, empty).
++ If + stmt is an abrupt completion, return stmt.
+
+ The
+ production
IterationStatement
+ : for
+ ( ExpressionNoInopt; Expressionopt; Expressionopt)
+ Statement
is
+ evaluated as follows:
+ If + ExpressionNoIn is present, then.
++ Let + exprRef be the result of evaluating ExpressionNoIn.
++ Call + GetValue(exprRef). (This value is not used.)
++ Let + V = empty.
++ Repeat
++ If + the first Expression is present, then
++ Let + stmt be the result of evaluating Statement.
++ If + stmt.value is not empty, + let V = stmt.value
++ If + stmt.type is break + and stmt.target is in the current label set, return + (normal, V, empty).
++ If + stmt.type is not continue + || stmt.target is not in the current label set, then
++ If + stmt is an abrupt completion, return stmt.
++ If + the second Expression is present, then
++ Let + incExprRef be the result of evaluating the second + Expression.
++ Call + GetValue(incExprRef). (This value is not used.)
+
+ The
+ production
IterationStatement
+ : for (
+ var
+ VariableDeclarationListNoIn
+ ; Expressionopt;
+ Expressionopt) Statement
is
+ evaluated as follows:
+ Evaluate + VariableDeclarationListNoIn.
++ Let + V = empty.
++ Repeat
++ If + the first Expression is present, then
++ Let + stmt be the result of evaluating Statement.
++ If + stmt.value is not empty, + let V = stmt.value.
++ If + stmt.type is break + and stmt.target is in the current label set, return + (normal, V, empty).
++ If + stmt.type is not continue + || stmt.target is not in the current label set, then
++ If + stmt is an abrupt completion, return stmt.
++ If + the second Expression is present, then.
++ Let + incExprRef be the result of evaluating the second + Expression.
++ Call + GetValue(incExprRef). (This value is not used.)
+
+ The
+ production IterationStatement
+ : for (
+ LeftHandSideExpression
+ in Expression
+ ) Statement
+ is evaluated as follows:
+ Let + exprRef be the result of evaluating the Expression.
++ Let + experValue be GetValue(exprRef).
++ If + experValue is null or undefined, return + (normal, empty, + empty).
++ Let + obj be ToObject(experValue).
++ Let + V = empty.
++ Repeat
++ Let + P be the name of the next property of obj whose + [[Enumerable]] attribute is true. If there is no such + property, return (normal, V, + empty).
++ Let + lhsRef be the result of evaluating the + LeftHandSideExpression ( it may be evaluated repeatedly).
++ Call + PutValue(lhsRef, P).
++ Let + stmt be the result of evaluating Statement.
++ If + stmt.value is not empty, + let V = stmt.value.
++ If + stmt.type is break + and stmt.target is in the current label set, return + (normal, V, empty).
++ If + stmt.type is not continue || stmt.target is + not in the current label set, then
++ If + stmt is an abrupt completion, return stmt.
+
+ The
+ production
IterationStatement
+ : for (
+ var
+ VariableDeclarationNoIn
+ in Expression
+ ) Statement
is
+ evaluated as follows:
+ Let + varName be the result of evaluating VariableDeclarationNoIn.
++ Let + exprRef be the result of evaluating the Expression.
++ Let + experValue be GetValue(exprRef).
++ If + experValue is null or undefined, return + (normal, empty, + empty).
++ Let + obj be ToObject(experValue).
++ Let + V = empty.
++ Repeat
++ Let + P be the name of the next property of obj whose + [[Enumerable]] attribute is true. If there is no such + property, return (normal, V, + empty).
++ Let + varRef be the result of evaluating varName as if it + were an Identifier Reference (11.1.2); it may be evaluated + repeatedly.
++ Call + PutValue(varRef, P).
++ Let + stmt be the result of evaluating Statement.
++ If + stmt.value is not empty, + let V = stmt.value.
++ If + stmt.type is break + and stmt.target is in the current label set, return + (normal, V, empty).
++ If + stmt.type is not continue + || stmt.target is not in the current label set, then
++ If + stmt is an abrupt completion, return stmt.
++ The + mechanics and order of enumerating the properties (step 6.a in the + first algorithm, step 7.a in the second) is not specified. + Properties of the object being enumerated may be deleted during + enumeration. If a property that has not yet been visited during + enumeration is deleted, then it will not be visited. If new + properties are added to the object being enumerated during + enumeration, the newly added properties are not guaranteed to be + visited in the active enumeration. + A property name must not be visited more than once in any enumeration. +
+ ++ Enumerating + the properties of an object includes enumerating properties of its + prototype, and the prototype of the prototype, and so on, + recursively; but a property of a prototype is not enumerated if it + is “shadowed” because some previous object in the prototype + chain has a property with the same name. + The values of [[Enumerable]] attributes are not considered when + determining if a property of a prototype object is shadowed by a previous + object on the prototype chain.
+ +NOTE See + NOTE 11.13.1.
++ Syntax
+ ++ ContinueStatement :
+
+ continue ;
+ continue
+ [no LineTerminator here] Identifier;
+ Semantics
++ A + program is considered syntactically incorrect if either of the + following is true:
+
+ The
+ program contains a continue
+ statement without the optional Identifier,
+ which is not nested, directly or indirectly (but not crossing
+ function boundaries), within an IterationStatement.
+ The
+ program contains a continue
+ statement with the optional Identifier,
+ where Identifier does
+ not appear in the label set of an enclosing (but not crossing
+ function boundaries) IterationStatement.
+ A + ContinueStatement + without an Identifier + is evaluated as follows:
++ Return + (continue, empty, + empty).
++ A + ContinueStatement + with the optional Identifier + is evaluated as follows:
++ Return + (continue, empty, + Identifier).
++ Syntax
++ BreakStatement :
+
+ break ;
+ break
+ [no LineTerminator here] Identifier ;
+ Semantics
++ A + program is considered syntactically incorrect if either of the + following is true:
+
+ The
+ program contains a break
+ statement without the optional Identifier,
+ which is not nested, directly or indirectly (but not crossing
+ function boundaries), within an IterationStatement
+ or a SwitchStatement.
+ The
+ program contains a break
+ statement with the optional Identifier,
+ where Identifier does
+ not appear in the label set of an enclosing (but not crossing
+ function boundaries) Statement.
+ A + BreakStatement + without an Identifier + is evaluated as follows:
++ Return + (break, empty, + empty).
++ A + BreakStatement + with an Identifier + is evaluated as follows:
++ Return + (break, empty,Identifier).
++ Syntax
++ ReturnStatement :
+
+ return ;
+ return
+ [no LineTerminator here] Expression ;
+ Semantics
+
+ An
+ ECMAScript program is considered syntactically incorrect if it
+ contains a return
+ statement that is not within a FunctionBody.
+ A return statement
+ causes a function to cease execution and return a value to the
+ caller. If Expression
+ is omitted, the return value is undefined. Otherwise, the
+ return value is the value of Expression.
+ The
+ production ReturnStatement
+ : return
+ [no LineTerminator here]
+ Expressionopt; is
+ evaluated as:
+ If + the Expression is not present, return (return, + undefined, empty).
++ Let + exprRef be the result of evaluating Expression.
++ Return + (return, GetValue(exprRef), + empty).
++ Syntax
++ WithStatement :
+
+ with ( Expression ) Statement
+ The
+ with statement
+ adds an object environment record for a computed object to the
+ lexical environment of the current execution context. It then
+ executes a statement using this augmented lexical environment.
+ Finally, it restores the original lexical environment.
+ Semantics
+
+ The
+ production WithStatement : with ( Expression ) Statement is evaluated as follows:
+ Let + val be the result of evaluating Expression.
++ Let + oldEnv be the running execution context’s + LexicalEnvironment.
++ Let + newEnv be the result of calling NewObjectEnvironment passing + obj and oldEnv as the arguments
++ Set + the provideThis flag of newEnv to true.
++ Set + the running execution context’s LexicalEnvironment to newEnv.
++ Let + C be the result of evaluating Statement but if an + exception is thrown during the evaluation, let C be (throw, + V, empty), where V + is the exception. (Execution now proceeds as if no exception were + thrown.)
++ Set + the running execution context’s Lexical Environment to oldEnv.
++ Return + C.
++
NOTE No matter how + control leaves the embedded Statement, + whether normally or by some form of abrupt completion or exception, + the LexicalEnvironment is always restored to its former state.
++ Strict + mode code may not include a WithStatement. + The occurrence of a WithStatement + in such a context is treated as a SyntaxError.
++ Syntax
++ SwitchStatement :
+
+ switch ( Expression ) CaseBlock
+ CaseBlock :
+
+ { CaseClausesopt} { CaseClausesoptDefaultClause CaseClausesopt}
+ CaseClauses :
+
+ CaseClause
CaseClauses
+ CaseClause
+ CaseClause :
+
+ case Expression : StatementListopt
+ DefaultClause :
+
+ default : StatementListopt
+ Semantics
+
+ The
+ production SwitchStatement : switch ( Expression ) CaseBlock is evaluated as follows:
+ Let + exprRef be the result of evaluating Expression.
++ Let + R be the result of evaluating CaseBlock, passing it + GetValue(exprRef) as a parameter.
++ If + R.type is break and + R.target is in the current label set, return (normal, + R.value, empty).
++ Return + R.
+
+ The
+ production CaseBlock
+ : {
+ CaseClausesopt}
+ is given an input parameter, input,
+ and is evaluated as follows:
+ Let + V + = empty.
++ Let + A + be the list of CaseClause + items in source text order.
++ Let + searching + be true.
++ Repeat, + while searching + is true
++ Let + C + be the next CaseClause + in A. + If there is no such CaseClause, + return (normal, + V, + empty).
++ Let + clauseSelector + be the result of evaluating C.
+
+ If
+ input
+ is equal to clauseSelector
+ as defined by the ===
+ operator, then
+ Set + searching + to false.
++ IfC + has a StatementList, + then +
++ EvaluateC’s + StatementList + and letR + be the result.
++ IfR + is an abrupt completion, then returnR.
++ LetV + =R.value.
++ Repeat
++ LetC + be the next CaseClause + inA. + If there is no such CaseClause, + return (normal,V, + empty).
++ IfC + has a StatementList, + then +
++ EvaluateC’s + StatementList + and letR + be the result.
++ IfR.value + is not + empty, + then letV + =R.value.
++ IfR + is an abrupt completion, then return (R.type,V,R.target).
+
+ The
+ production CaseBlock
+ : {
+ CaseClausesoptDefaultClause CaseClausesopt}
+ is given an input parameter, input,
+ and is evaluated as follows:
+ Let + V + = empty.
++ Let + A + be the list of CaseClause + items in the first CaseClauses, + in source text order.
++ Let + B + be the list of CaseClause items in the second CaseClauses, in + source text order.
++ Let + found + be false.
++ Repeat + letting C + be in order each CaseClause + in A
++ If + found + is false, + then
++ Let + clauseSelector + be the result of evaluating C.
+
+ If
+ input
+ is equal to clauseSelector
+ as defined by the ===
+ operator, then set found
+ to true.
+ If + found + is true, + then
++ If + C + has a StatementList, then
++ Evaluate + C’s + StatementList + and let R + be the result.
++ IfR.value + is not + empty, + then letV + =R.value.
++ R + is an abrupt completion, then return (R.type,V,R.target).
++ Let + foundInB + be false.
++ If + found + is false, + then +
++ Repeat, + while foundInB + is false + and all elements of B + have not been processed
++ Let + C + be the next CaseClause + in B. + +
++ Let + clauseSelector + be the result of evaluating C.
+
+ If
+ input
+ is equal to clauseSelector
+ as defined by the ===
+ operator, then
+ Set + foundInB + to true.
++ IfC + has a StatementList, + then
++ Evaluate + C’s + StatementList + and let R + be the result.
++ IfR.value + is not + empty, + then letV + =R.value.
++ R + is an abrupt completion, then return (R.type,V,R.target).
++ If + foundInB + is false + and the DefaultClause + has a StatementList, + then
++ Evaluate + the DefaultClause’s + StatementList + and let R + be the result.
++ If + R.value + is not empty, + then let V + = R.value.
++ If + R + is an abrupt completion, then return (R.type, + V, + R.target).
++ Repeat + (Note that if step 7.a.i has been performed this loop does not + start at the beginning of B)
++ Let + C + be the next CaseClause + in B. + If there is no such CaseClause, + return (normal, + V, + empty).
++ If + C + has a StatementList, then +
++ Evaluate + C’s + StatementList and let R + be the result.
++ If + R.value + is not empty, + then let V + = R.value.
++ If + R + is an abrupt completion, then return (R.type, + V, + R.target).
+
+ The
+ production CaseClause
+ : case Expression : StatementListopt is evaluated as follows:
+ Let + exprRef be the result of evaluating Expression.
++ Return + GetValue(exprRef).
+NOTE Evaluating + CaseClause does + not execute the associated StatementList. + It simply evaluates the Expression + and returns the value, which the CaseBlock + algorithm uses to determine which StatementList + to start executing.
++ Syntax
++ LabelledStatement :
+
+ Identifier : Statement
+ Semantics
+
+ A
+ Statement may be
+ prefixed by a label. Labelled statements are only used in
+ conjunction with labelled break
+ and continue
+ statements. ECMAScript has no goto
+ statement.
+ An + ECMAScript program is considered syntactically incorrect if it + contains a LabelledStatement + that is enclosed by a LabelledStatement + with the same Identifier + as label. This does not apply to labels appearing within the body of + a FunctionDeclaration + that is nested, directly or indirectly, within a labelled statement.
+
+ The
+ production Identifier : Statement is evaluated by adding Identifier
+ to the label set of Statement
+ and then evaluating Statement.
+ If the LabelledStatement
+ itself has a non-empty label set, these labels are also added to the
+ label set of Statement
+ before evaluating it. If the result of evaluating Statement
+ is (break, V,
+ L) where L
+ is equal to Identifier,
+ the production results in (normal, V,
+ empty).
+ Prior + to the evaluation of a LabelledStatement, + the contained Statement + is regarded as possessing an empty label set, unless it is an + IterationStatement + or a SwitchStatement, + in which case it is regarded as possessing a label set consisting of + the single element, empty.
++ Syntax
++ ThrowStatement + :
+
+ throw
+ [no LineTerminator here] Expression ;
+ Semantics
+
+ The
+ production ThrowStatement
+ : throw
+ [no LineTerminator here]
+ Expression
+ ; is evaluated as:
+ Let + exprRef be the result of evaluating Expression.
++ Return + (throw, GetValue(exprRef), + empty).
++ Syntax
++ TryStatement :
+
+ try Block Catchtry Block Finallytry Block Catch Finally
+ Catch :
+
+ catch (
+ Identifier
+ ) Block
+ Finally :
+
+ finally Block
+ The
+ try statement
+ encloses a block of code in which an exceptional condition can
+ occur, such as a runtime error or a throw
+ statement. The catch
+ clause provides the exception-handling code. When a catch clause
+ catches an exception, its Identifier
+ is bound to that exception.
+ Semantics
+
+ The
+ production TryStatement
+ : try Block
+ Catch is evaluated
+ as follows:
+ Let + B be the result of evaluating Block.
++ If + B.type is not throw, + return B.
++ Return + the result of evaluating Catch with parameter B.
+
+ The
+ production TryStatement
+ : try Block
+ Finally is
+ evaluated as follows:
+ Let + B be the result of evaluating Block.
++ Let + F be the result of evaluating Finally.
++ If + F.type is normal, + return B.
++ Return + F.
+
+ The
+ production TryStatement
+ : try Block
+ Catch Finally
+ is evaluated as follows:
+ Let + B be the result of evaluating Block.
++ If + B.type is throw, then
++ Let + C be the result of evaluating Catch with parameter + B.
++ Else, + B.type is not throw,
++ Let + C be B.
++ Let + F be the result of evaluating Finally.
++ If + F.type is normal, + return C.
++ Return + F.
+
+ The
+ production Catch :
+ catch (
+ Identifier
+ ) Block
+ is evaluated as follows:
+ Let + C be the parameter that has been passed to this production.
++ Let + oldEnv be the running execution context’s + LexicalEnvironment.
++ Let + catchEnv be the result of calling NewDeclarativeEnvironment + passing oldEnv as the argument. +
++ Call + the CreateMutableBinding concrete method of catchEnv passing + the Identifier String value as the argument.
++ Call + the SetMutableBinding concrete method of catchEnv passing + the Identifier, C, and false as arguments. + Note that the last argument is immaterial in this situation.
++ Set + the running execution context’s LexicalEnvironment to catchEnv.
++ Let + B be the result of evaluating Block.
++ Set + the running execution context’s LexicalEnvironment to oldEnv.
++ Return + B.
+NOTE No + matter how control leaves the Block + the LexicalEnvironment is always restored to its former state.
+
+ The
+ production Finally
+ : finally Block
+ is evaluated as follows:
+ Return + the result of evaluating Block.
+
+ It is
+ an SyntaxError if a TryStatement
+ with a Catch
+ occurs within strict code and the Identifier
+ of the Catch
+ production is either "eval"
+ or "arguments".
+ Syntax
++ DebuggerStatement :
+
+ debugger ;
+ Semantics
++ Evaluating + the DebuggerStatement production may allow an implementation to cause a + breakpoint when run under a debugger. If a debugger is not present + or active this statement has no observable effect.
+
+ The
+ production DebuggerStatement : debugger
+ ; is evaluated as follows:
+ If + an implementation defined debugging facility is available and + enabled, then
++ Perform + an implementation defined debugging action.
++ Let + result be an implementation defined Completion value. +
++ Else
++ Let + result be (normal, + empty, empty).
++ Return + result.
+‟Ex igne vita”
+ ++ Syntax
++ FunctionDeclaration :
+
+ function Identifier ( FormalParameterListopt) { FunctionBody }
+ FunctionExpression :
+
+ function Identifieropt( FormalParameterListopt) { FunctionBody }
+ FormalParameterList :
+
+ Identifier
FormalParameterList , Identifier
+ FunctionBody :
++ SourceElementsopt
++ Semantics
+
+ The
+ production
FunctionDeclaration : function
+ Identifier ( FormalParameterListopt) {
+ FunctionBody }
is
+ instantiated as follows during Declaration Binding instantiation
+ (10.5):
+ Return + the result of creating a new Function object as specified in 13.2 + with parameters specified by FormalParameterListopt, + and body specified by FunctionBody. + Pass in the VariableEnvironment of the running execution context as + the Scope. + Pass in true + as the Strict + flag if the FunctionDeclaration + is contained in strict code or if its FunctionBody + is strict code.
+
+ The
+ production
FunctionExpression : function
+ ( FormalParameterListopt) {
+ FunctionBody }
+
is evaluated as follows:
+ Return + the result of creating a new Function object as specified in 13.2 + with parameters specified by FormalParameterListopt + and body specified by FunctionBody. + Pass in the LexicalEnvironment of the running execution context as + the Scope. + Pass in true + as the Strict + flag if the FunctionExpression + is contained in strict code or if its FunctionBody + is strict code.
+
+ The
+ production
FunctionExpression
+ : function
+ Identifier (
+ FormalParameterListopt) {
+ FunctionBody }
is
+ evaluated as follows:
+ Let + funcEnv be + the result of calling NewDeclarativeEnvironment passing the running + execution context’s Lexical Environment as the argument
++ Let + envRec be + funcEnv’s environment record.
++ Call + the CreateImmutableBinding(N) concrete method of envRec passing the String + value of Identifier + as the argument.
++ Let + closure be + the result of creating a new Function object as specified in 13.2 + with parameters specified by FormalParameterListopt + and body specified by FunctionBody. + Pass in funcEnv as + the Scope. + Pass in true + as the Strict + flag if the FunctionExpression + is contained in strict code or if its FunctionBody + is strict code.
++ Call + the InitializeImmutableBinding(N,V) + concrete method of envRec passing the String + value of Identifier and closure as the arguments.
++ Return + closure.
+NOTE The + Identifier in a FunctionExpression + can be referenced from inside the FunctionExpression's + FunctionBody to + allow the function to call itself recursively. However, unlike in a + FunctionDeclaration, + the Identifier in + a FunctionExpression + cannot be referenced from and does not affect the scope enclosing + the FunctionExpression.
++ The + production FunctionBody :SourceElementsopt is evaluated as follows:
++ The + code of this FunctionBody is strict mode code + if it is part of a FunctionDeclaration + or FunctionExpression + that is contained in strict mode code or if the Directive Prologue + (14.1) of its SourceElements + contains a Use Strict Directive or if any of the conditions in + 10.1.1 apply. If the code of this FunctionBody is strict mode code, + SourceElements + is evaluated in the following steps as strict mode code. Otherwise, + SourceElements + is evaluated in the following steps as non-strict mode code.
++ If + SourceElements + is present return the result of evaluating SourceElements.
++ Else + return (normal, + undefined, + empty).
++ It is + a SyntaxError if any Identifier + value occurs more than once within a FormalParameterList + of a strict mode FunctionDeclaration + or FunctionExpression.
+
+ It is
+ a SyntaxError if the Identifier
+ "eval"
+ or the Identifier "arguments"
+ occurs within a FormalParameterList
+ of a strict mode FunctionDeclaration
+ or FunctionExpression.
+ It is
+ a SyntaxError if the Identifier
+ "eval"
+ or the Identifier "arguments"
+ occurs as the Identifier
+ of a strict mode FunctionDeclaration
+ or FunctionExpression.
+ Given + an optional parameter list specified by FormalParameterList, + a body specified by FunctionBody, + a Lexical Environment specified by Scope, + and a Boolean flag Strict, + a Function object is constructed as follows:
++ Create + a new native ECMAScript object and let F + be that object.
++ Set + all the internal methods, except for [[Get]], of F + as described in 8.12.
+
+ Set
+ the [[Class]] internal property of F
+ to "Function".
+ Set + the [[Prototype]] internal property of F + to the standard built-in Function prototype object as specified in + 15.3.3.1.
++ Set + the [[Get]] internal property of F + as described in 15.3.5.4.
++ Set + the [[Call]] internal property of F + as described in 13.2.1.
++ Set + the [[Construct]] internal property of F + as described in 13.2.2.
++ Set + the [[HasInstance]] internal property of F + as described in 15.3.5.3.
++ Set + the [[Scope]] internal property of F + to the value of Scope.
++ Let + names be + a List containing, in left to right textual order, the Strings + corresponding to the identifiers of FormalParameterList.
++ Set + the [[FormalParameters]] internal property of F to names.
++ Set + the [[Code]] internal property of F to FunctionBody.
++ Set + the [[Extensible]] internal property of F to true.
++ Let + len + be the number of formal parameters specified in + FormalParameterList. + If no parameters are specified, let len + be 0.
+
+ Call
+ the [[DefineOwnProperty]] internal method of F
+ with arguments "length",
+ Property Descriptor {[[Value]]: len,
+ [[Writable]]: false,
+ [[Enumerable]]: false,
+ [[Configurable]]: false},
+ and false.
+
+
+ Let
+ proto
+ be the result of creating a new object as would be constructed by
+ the expression new
+ Object()where Object
+ is the standard built-in constructor with that name.
+ Call
+ the [[DefineOwnProperty]] internal method of proto
+ with arguments "constructor",
+ Property Descriptor {[[Value]]: F,
+ { [[Writable]]: true,
+ [[Enumerable]]: false,
+ [[Configurable]]: true},
+ and false.
+ Call
+ the [[DefineOwnProperty]] internal method of F
+ with arguments "prototype",
+ Property Descriptor {[[Value]]: proto,
+ { [[Writable]]: true,
+ [[Enumerable]]: false,
+ [[Configurable]]: false},
+ and false.
+ If + Strict + is true, + then
++ Let + thrower + be the [[ThrowTypeError]] function Object (13.2.3).
+
+ Call
+ the [[DefineOwnProperty]] internal method of F
+ with arguments "caller",
+ PropertyDescriptor {[[Get]]: thrower,
+ [[Set]]: thrower,
+ [[Enumerable]]: false,
+ [[Configurable]]: false},
+ and false.
+ Call
+ the [[DefineOwnProperty]] internal method of F
+ with arguments "arguments",
+ PropertyDescriptor {[[Get]]: thrower,
+ [[Set]]: thrower,
+ [[Enumerable]]: false,
+ [[Configurable]]: false},
+ and false.
+ Return + F.
+NOTE A
+ prototype
+ property is automatically created for every function, to allow for
+ the possibility that the function will be used as a constructor.
+ When + the [[Call]] internal method for a Function object F + is called with a this value and a list of arguments, the following + steps are taken:
++ Let + funcCtx be the result of establishing a new execution + context for function code using the value of F's + [[FormalParameters]] internal property, the passed arguments List + args, and the this value as described in 10.4.3.
++ Let + result be the result of evaluating the FunctionBody + that is the value of F's [[Code]] internal property. If F + does not have a [[Code]] internal property or if its value is an + empty FunctionBody, then result is (normal, + undefined, empty).
++ Exit + the execution context funcCtx, restoring the previous + execution context.
++ If + result.type is throw + then throw result.value.
++ If + result.type is return + then return result.value.
++ Otherwise + result.type must be normal. + Return undefined.
++ When + the [[Construct]] internal method for a Function object F + is called with a possibly empty list of arguments, the following + steps are taken:
++ Let + obj be + a newly created native ECMAScript object.
++ Set + all the internal methods of obj + as specified in 8.12.
+
+ Set
+ the [[Class]] internal property of obj to "Object".
+ Set + the [[Extensible]] internal property of obj to true.
+
+ Let
+ proto be
+ the value of calling the [[Get]] internal property of F
+ with argument "prototype".
+ If + Type(proto) is Object, set the + [[Prototype]] internal property of obj to proto.
++ If + Type(proto) is not Object, set + the [[Prototype]] internal property of obj to the standard + built-in Object prototype object as described in 15.2.4.
++ Let + result be + the result of calling the [[Call]] internal property of F, + providing obj as + the this + value and providing the argument list passed into [[Construct]] as + args.
++ If + Type(result) + is Object then return result.
++ Return + obj.
++ The + [[ThrowTypeError]] object is a unique function object that is + defined once as follows:
++ Create + a new native ECMAScript object and let F + be that object.
++ Set + all the internal methods of F + as described in 8.12.
+
+ Set
+ the [[Class]] internal property of F
+ to "Function".
+ Set + the [[Prototype]] internal property of F + to the standard built-in Function prototype object as specified in + 15.3.3.1.
++ Set + the [[Call]] internal property of F + as described in 13.2.1.
++ Set + the [[Scope]] internal property of F + to the Global Environment.
++ Set + the [[FormalParameters]] internal property of F to an empty List.
++ Set + the [[Code]] internal property of F to be a FunctionBody + that unconditionally throws a TypeError + exception and performs no other action.
+
+ Call
+ the [[DefineOwnProperty]] internal method of F
+ with arguments "length",
+ Property Descriptor {[[Value]]: 0,
+ [[Writable]]: false,
+ [[Enumerable]]: false,
+ [[Configurable]]: false},
+ and false.
+
+
+ Set + the [[Extensible]] internal property of F to false.
++ Let + [[ThrowTypeError]] be F.
+‟Ex igne vita”
+ ++ Syntax
++ Program :
++ SourceElementsopt
++ SourceElements :
+
+ SourceElement
SourceElements
+ SourceElement
+ SourceElement :
+
+ Statement
FunctionDeclaration
+ Semantics
+
+ The
+ production Program :SourceElementsopt
+ is evaluated as follows:
+ The + code of this Program is strict mode code if the Directive + Prologue (14.1) of its SourceElements contains a Use Strict + Directive or if any of the conditions of 10.1.1 apply. If the code + of this Program is strict mode code, SourceElements + is evaluated in the following steps as strict mode code. Otherwise + SourceElements is evaluated in the following steps as + non-strict mode code.
++ If + SourceElements is not present, return (normal, + empty, empty).
++ Let + progCxt be a new execution context for global code as + described in 10.4.1. +
++ Let + result be the result of evaluating SourceElements.
++ Exit + the execution context progCxt.
++ Return + result.
+NOTE The + processes for initiating the evaluation of a Program + and for dealing with the result of such an evaluation are defined by + an ECMAScript implementation and not by this specification.
++ The + production SourceElements + : SourceElements + SourceElement is + evaluated as follows:
++ Let + headResult be the result of evaluating SourceElements.
++ If + headResult is an abrupt completion, return headResult
++ Let + tailResult be result of evaluating SourceElement.
++ If + tailResult.value is empty, + let V = headResult.value, otherwise let V = + tailResult.value.
++ Return + (tailResult.type, V, tailResult.target) +
++ The + production SourceElement :Statement is evaluated as follows:
++ Return + the result of evaluating Statement.
++ The + production SourceElement :FunctionDeclaration is evaluated as follows:
++ Return + (normal, empty, + empty).
++ A + Directive Prologue is the longest sequence of ExpressionStatement productions occurring as the initial SourceElement + productions of a Program + or FunctionBody + and where each ExpressionStatement in the sequence + consists entirely of a StringLiteral + token followed a semicolon. + The semicolon may appear explicitly or may be inserted by +automatic semicolon insertion. A Directive Prologue may be an empty sequence.
+
+ A Use
+ Strict Directive is an ExpressionStatement
+ in a Directive Prologue whose StringLiteral
+ is either the exact character sequences "use strict"
+ or 'use strict'.
+ A Use Strict Directive may not contain an EscapeSequence
+ or LineContinuation.
+ A + Directive Prologue may contain more than one Use Strict Directive. + However, an implementation may issue a warning if this occurs.
+NOTE The + ExpressionStatement + productions of a Directive Prologue are evaluated normally during + evaluation of the containing SourceElements + production. Implementations may define implementation specific + meanings for ExpressionStatement + productions which are not a Use Strict Directive and which occur in + a Directive Prologue. If an appropriate notification mechanism + exists, an implementation should issue a warning if it encounters in + a Directive Prologue an ExpressionStatement + that is not a Use Strict Directive or which does not have a meaning + defined by the implementation.
+ \ No newline at end of file diff --git a/x15.html b/x15.html new file mode 100644 index 0000000..c5a8a85 --- /dev/null +++ b/x15.html @@ -0,0 +1,15238 @@ + +‟Ex igne vita”
+ ++ There + are certain built-in objects available whenever an ECMAScript + program begins execution. One, the global object, is part of the + lexical environment of the executing program. Others are accessible + as initial properties of the global object.
+
+ Unless
+ specified otherwise, the [[Class]] internal property of a built-in
+ object is "Function"
+ if that built-in object has a [[Call]] internal property, or
+ "Object"
+ if that built-in object does not have a [[Call]] internal property.
+ Unless specified otherwise, the [[Extensible]] internal property of
+ a built-in object initially has the value true.
+ Many
+ built-in objects are functions: they can be invoked with arguments.
+ Some of them furthermore are constructors: they are functions
+ intended for use with the new
+ operator. For each built-in function, this specification describes
+ the arguments required by that function and properties of the
+ Function object. For each built-in constructor, this specification
+ furthermore describes properties of the prototype object of that
+ constructor and properties of specific object instances returned by
+ a new expression
+ that invokes that constructor.
+ Unless + otherwise specified in the description of a particular function, if + a function or constructor described in this clause is given fewer + arguments than the function is specified to require, the function or + constructor shall behave exactly as if it had been given sufficient + additional arguments, each such argument being the undefined + value.
++ Unless + otherwise specified in the description of a particular function, if + a function or constructor described in this clause is given more + arguments than the function is specified to allow, the extra + arguments are evaluated by the call and then ignored by the + function. However, an implementation may define implementation + specific behaviour relating to such arguments as long as the + behaviour is not the throwing of a TypeError exception that + is predicated simply on the presence of an extra argument.
+NOTE Implementations + that add additional capabilities to the set of built-in functions + are encouraged to do so by adding new functions rather than adding + new parameters to existing functions.
+
+ Every
+ built-in function and every built-in constructor has the
+ Function prototype object, which is the initial value of the expression
+ Function.prototype
+ (15.3.4), as the value of its [[Prototype]] internal property.
+ Unless
+ otherwise specified every built-in prototype object has the
+ Object prototype object, which is the initial value of the expression
+ Object.prototype
+ (15.2.4), as the value of its [[Prototype]] internal property,
+ except the Object prototype object itself.
+ None
+ of the built-in functions described in this clause that are not
+ constructors shall implement the [[Construct]] internal method
+ unless otherwise specified in the description of a particular
+ function. None of the built-in functions described in this clause
+ shall have a prototype
+ property unless otherwise specified in the description of a
+ particular function.
+ This + clause generally describes distinct behaviours for when a + constructor is “called as a function” and for when it is “called + as part of a new expression”. The “called as a function” + behaviour corresponds to the invocation of the constructor’s + [[Call]] internal method and the “called as part of a new + expression” behaviour corresponds to the invocation of the + constructor’s [[Construct]] internal method. +
+
+ Every
+ built-in Function object described in this clause—whether as a
+ constructor, an ordinary function, or both—has a length
+ property whose value is an integer. Unless otherwise specified, this
+ value is equal to the largest number of named arguments shown in the
+ subclause headings for the function description, including optional
+ parameters.
NOTE For
+ example, the Function object that is the initial value of the slice
+ property of the String prototype object is described under the
+ subclause heading “String.prototype.slice (start, end)” which
+ shows the two named arguments start and end; therefore the value of
+ the length property of
+ that Function object is 2.
+ In
+ every case, the length
+ property of a built-in Function object described in this clause has
+ the attributes { [[Writable]]: false, [[Enumerable]]:
+ false, [[Configurable]]: false }. Every other property
+ described in this clause has the attributes { [[Writable]]: true,
+ [[Enumerable]]: false, [[Configurable]]: true } unless
+ otherwise specified.
+ The + unique global object is created before control enters any + execution context. +
++ Unless + otherwise specified, the standard built-in properties of the global + object have attributes {[[Writable]]: true, [[Enumerable]]: + false, [[Configurable]]: true}.
+
+ The
+ global object does not have a [[Construct]] internal property; it is
+ not possible to use the global object as a constructor with the new
+ operator.
+ The + global object does not have a [[Call]] internal property; it is not + possible to invoke the global object as a function.
++ The + values of the [[Prototype]] and [[Class]] internal properties of the + global object are implementation-dependent.
+
+ In
+ addition to the properties defined in this specification the global
+ object may have additional host defined properties. This may include
+ a property whose value is the global object itself; for example, in
+ the HTML document object model the window
+ property of the global object is the global object itself.
+ The
+ value of NaN is
+ NaN (see 8.5). This property has the attributes {
+ [[Writable]]: false, [[Enumerable]]: false,
+ [[Configurable]]: false }.
+ The
+ value of Infinity
+ is +∞ (see 8.5).
+ This property has the attributes { [[Writable]]: false,
+ [[Enumerable]]: false, [[Configurable]]: false }.
+ The
+ value of undefined
+ is undefined (see 8.1). This property has the attributes {
+ [[Writable]]: false, [[Enumerable]]: false,
+ [[Configurable]]: false }.
+ When
+ the eval function
+ is called with one argument x,
+ the following steps are taken:
+ If + Type(x) + is not String, return x.
++ Let + prog be + the ECMAScript code that is the result of parsing x as a Program. + If the parse fails, throw a SyntaxError + exception (but see also clause 16).
++ Let + evalCtx be + the result of establishing a new execution context (10.4.2) for the + eval code prog.
++ Let + result be + the result of evaluating the program prog.
++ Exit + the running execution context evalCtx, restoring the previous + execution context.
++ If + result.type + is normal and its + completion value is a value V, + then return the value V.
++ If + result.type + is normal and its + completion value is empty, + then return the value undefined.
++ Otherwise, + result.type + must be throw. Throw + result.value + as an exception.
++ A + direct call to the eval function is one that is expressed as a + CallExpression + that meets the following two conditions:
+
+ The
+ Reference that is the result of evaluating the MemberExpression
+ in the CallExpression
+ has an environment record as its base value and its reference name
+ is "eval".
+ The + result of calling the abstract operation GetValue with that + Reference as the argument is the standard built-in function defined + in 15.1.2.1.
+
+ The
+ parseInt function
+ produces an integer value dictated by interpretation of the contents
+ of the string
+ argument according to the specified radix.
+ Leading white space in string
+ is ignored. If radix
+ is undefined or 0, it is assumed to be 10
+ except when the number begins with the character pairs 0x
+ or 0X, in which
+ case a radix of 16 is assumed. If radix
+ is 16, number may also
+ optionally begin with the character pairs 0x
+ or 0X.
+ When
+ the parseInt
+ function is called, the following steps are taken:
+ Let + inputString be ToString(string).
++ Let + S be a newly created substring of inputString + consisting of the first character that is not a StrWhiteSpaceChar + and all characters following that character. (In other words, + remove leading white space.) +If inputString does not contain any such characters, let S be the +empty string.
++ Let + sign be 1.
+
+ If
+ S is not empty and the first character of S is a
+ minus sign -, let
+ sign be −1.
+ If
+ S is not empty and the first character of S is a plus
+ sign + or a minus
+ sign -, then
+ remove the first character from S.
+ Let + R = ToInt32(radix).
++ Let + stripPrefix be true.
++ If + R ≠ 0, then
++ If + R < 2 or R > 36, then return NaN.
++ If + R ≠ 16, let stripPrefix + be false.
++ Else, + R = 0
++ Let + R = 10.
++ If + stripPrefix is true, then
+
+ If
+ the length of S is at least 2 and the first two characters
+ of S are either “0x”
+ or “0X”,
+ then remove the first two characters from S and let R
+ = 16.
+ If + S contains any character that is not a radix-R digit, + then let Z be the substring of S consisting of all + characters before the first such character; otherwise, let Z + be S.
++ If + Z is empty, return NaN.
+
+ Let
+ mathInt be the mathematical integer value that is
+ represented by Z in radix-R notation, using the
+ letters A-Z
+ and a-z
+ for digits with values 10 through 35. (However, if R is 10
+ and Z contains more than 20 significant digits, every
+ significant digit after the 20th may be replaced by a 0
+ digit, at the option of the implementation; and if R
+ is not 2, 4, 8, 10, 16, or 32, then mathInt may be an
+ implementation-dependent approximation to the mathematical integer
+ value that is represented by Z in radix-R notation.)
+ Let + number be the Number value for mathInt.
++ Return + sign × number.
+NOTE parseInt
+ may interpret only a leading portion of string
+ as an integer value; it ignores any characters that cannot be
+ interpreted as part of the notation of an integer, and no indication
+ is given that any such characters were ignored.
+ The
+ parseFloat
+ function produces a Number value dictated by interpretation of the
+ contents of the string
+ argument as a decimal literal.
+ When
+ the parseFloat
+ function is called, the following steps are taken:
+ Let + inputString be ToString(string).
++ Let + trimmedString be a substring of inputString + consisting of the leftmost character that is not a + StrWhiteSpaceChar and all characters to the right of that + character. (In other words, remove leading white space.) +If inputString does not contain any such characters, let +trimmedString be the empty string.
++ If + neither trimmedString nor any prefix of trimmedString + satisfies the syntax of a StrDecimalLiteral (see 9.3.1), + return NaN.
++ Let + numberString be the longest prefix of trimmedString, + which might be trimmedString itself, that satisfies the + syntax of a StrDecimalLiteral.
++ Return + the Number value for the MV of numberString.
+NOTE parseFloat
+ may interpret only a leading portion of string
+ as a Number value; it ignores any characters that cannot be
+ interpreted as part of the notation of an decimal literal, and no
+ indication is given that any such characters were ignored.
+ Returns + true if the argument coerces to NaN, and otherwise + returns false.
++ If + ToNumber(number) is NaN, return true.
++ Otherwise, + return false.
+NOTE A
+ reliable way for ECMAScript code to test if a value X
+ is a NaN is an expression of the form X
+ !== X. The result will be true if and only if X
+ is a NaN.
+ Returns + false if the argument coerces to NaN, +∞, + or −∞, and otherwise + returns true.
++ If + ToNumber(number) is NaN, +∞, + or −∞, return false.
++ Otherwise, + return true.
++ Uniform + Resource Identifiers, or URIs, are Strings that identify resources + (e.g. web pages or files) and transport protocols by which to access + them (e.g. HTTP or FTP) on the Internet. The ECMAScript language + itself does not provide any support for using URIs except for + functions that encode and decode URIs as described in 15.1.3.1, + 15.1.3.2, 15.1.3.3 and 15.1.3.4.
+NOTE Many + implementations of ECMAScript provide additional functions and + methods that manipulate web pages; these functions are beyond the + scope of this standard.
++ A URI + is composed of a sequence of components separated by component + separators. The general form is:
+
+ Scheme
+ :
+ First
+ /
+ Second
+ ;
+ Third
+ ?
+ Fourth
+ where
+ the italicised names represent components and the “:”,
+ “/”, “;”
+ and “?” are
+ reserved characters used as separators. The encodeURI
+ and decodeURI
+ functions are intended to work with complete URIs; they assume that
+ any reserved characters in the URI are intended to have special
+ meaning and so are not encoded. The encodeURIComponent
+ and decodeURIComponent
+ functions are intended to work with the individual
+ component parts of a URI; they assume that any reserved characters
+ represent text and so must be encoded so that they are not
+ interpreted as reserved characters when the component is part of a
+ complete URI.
+ The + following lexical grammar specifies the form of encoded URIs.
++ uri :::
++ uriCharactersopt
++ uriCharacters :::
++ uriCharacter + uriCharactersopt
++ uriCharacter :::
+
+ uriReserved
uriUnescaped
uriEscaped
+ uriReserved ::: one + of
+
+ ;
+ / ? : @ & = + $ ,
+ uriUnescaped :::
+
+ uriAlpha
DecimalDigit
uriMark
+ uriEscaped :::
+
+ % HexDigit HexDigit
+ uriAlpha ::: one + of
+
+ a
+ b c d e f g h i j k l m n o p q r s t u v w x
+ y z
A B C D E F G H I J K L M N O P Q R S T
+ U V W X Y Z
+ uriMark ::: one + of
+
+ -
+ _ . ! ~ * ' ( )
NOTE The above syntax is based upon RFC 2396 + and does not reflect changes introduced by the more recent RFC 3986.
+ +
+ When
+ a character to be included in a URI is not listed above or is not
+ intended to have the special meaning sometimes given to the reserved
+ characters, that character must be encoded. The character is
+ transformed into its UTF-8 encoding, with surrogate pairs first
+ converted from UTF-16 to the corresponding code point value. (Note
+ that for code units in the range [0,127] this results in a single
+ octet with the same value.) The resulting sequence of octets is then
+ transformed into a String with each octet represented by an escape
+ sequence of the form “%xx”.
+ The + encoding and escaping process is described by the abstract operation + Encode taking two String arguments string + and unescapedSet.
++ Let + strLen be the number of characters in string.
++ Let + R be the empty String.
++ Let + k be 0.
++ Repeat
++ If + k equals strLen, return R.
++ Let + C be the character at position k within string.
++ If + C is in unescapedSet, then
++ Let + S be a String containing only the character C.
++ Let + R be a new String value computed by concatenating the + previous value of R and S.
++ Else, + C is not in unescapedSet
++ If + the code unit value of C is not less than 0xDC00 and not + greater than 0xDFFF, throw a URIError exception.
++ If + the code unit value of C is less than 0xD800 or greater + than 0xDBFF, then
++ Let + V be the code unit value of C.
++ Else, + +
++ Increase + k by 1.
++ If + k equals strLen, throw a URIError + exception.
++ Let + kChar be the code unit value of the character at position + k within string.
++ If + kChar is less than 0xDC00 or greater than 0xDFFF, throw a + URIError exception.
++ Let + V be (((the code unit value of C) – 0xD800) * + 0x400 + (kChar – 0xDC00) + 0x10000).
++ Let + Octets be the array of octets resulting by applying the + UTF-8 transformation to V, and let L be the array + size.
++ Let + j be 0.
++ Repeat, + while j < L
++ Let + jOctet be the value at position j within Octets.
+
+ Let
+ S be a String containing three characters “%XY”
+ where XY are two uppercase hexadecimal digits encoding
+ the value of jOctet.
+ Let + R be a new String value computed by concatenating the + previous value of R and S.
++ Increase + j by 1.
++ Increase + k by 1.
++ The + unescaping and decoding process is described by the abstract + operation Decode taking two String arguments string + and reservedSet.
++ Let + strLen be the number of characters in string.
++ Let + R be the empty String.
++ Let + k be 0.
++ Repeat
++ If + k equals strLen, return R.
++ Let + C be the character at position k within string.
+
+ If
+ C is not ‘%’,
+ then
+ Let + S be the String containing only the character C.
+
+ Else,
+ C is ‘%’
+ Let + start be k.
++ If + k + 2 is greater than or equal to strLen, throw a + URIError exception.
++ If + the characters at position (k+1) and (k + 2) within + string do not represent hexadecimal digits, throw a + URIError exception.
++ Let + B be the 8-bit value represented by the two hexadecimal + digits at position (k + 1) and (k + 2).
++ Increment + k by 2.
++ If + the most significant bit in B is 0, then
++ Let + C be the character with code unit value B.
++ If + C is not in reservedSet, then
++ Let + S be the String containing only the character C.
++ Else, + C is in reservedSet
++ Let + S be the substring of string from position start + to position k included.
++ Else, + the most significant bit in B is 1
++ Let + n be the smallest non-negative number such that (B + << n) & 0x80 is equal to 0.
++ If + n equals 1 or n is greater than 4, throw a + URIError exception.
++ Let + Octets be an array of 8-bit integers of size n.
++ Put + B into Octets at position 0.
++ If + k + (3 * (n – 1)) is greater than or equal to + strLen, throw a URIError exception.
++ Let + j be 1.
++ Repeat, + while j < n
++ Increment + k by 1.
++ If + the character at position k is not ‘%’, throw a + URIError exception.
++ If + the characters at position (k +1) and (k + 2) + within string do not represent hexadecimal digits, throw + a URIError exception.
++ Let + B be the 8-bit value represented by the two hexadecimal + digits at position (k + 1) and (k + 2).
++ If + the two most significant bits in B are not 10, throw a + URIError exception.
++ Increment + k by 2.
++ Put + B into Octets at position j.
++ Increment + j by 1.
++ Let + V be the value obtained by applying the UTF-8 + transformation to Octets, that is, from an array of + octets into a 32-bit value. If Octets does not contain a + valid UTF-8 encoding of a Unicode code point throw a URIError + exception.
++ If + V is less than 0x10000, then
++ Let + C be the character with code unit value V.
++ If + C is not in reservedSet, then
++ Let + S be the String containing only the character C.
++ Else, + C is in reservedSet
++ Let + S be the substring of string from position start + to position k included.
++ Else, + V is ≥ 0x10000
++ Let + L be (((V – 0x10000) & 0x3FF) + 0xDC00).
++ Let + H be ((((V – 0x10000) >> 10) & 0x3FF) + + 0xD800).
++ Let + S be the String containing the two characters with code + unit values H and L.
++ Let + R be a new String value computed by concatenating the + previous value of R and S.
++ Increase + k by 1.
+NOTE The + syntax of Uniform Resource Identifiers is given in RFC 2396 and + does not reflect the more recent RFC 3986 which replaces RFC 2396. A + formal description and implementation of UTF-8 is given in RFC 3629.
+ ++ In + UTF-8, characters are encoded using sequences of 1 to 6 octets. The + only octet of a "sequence" of one has the higher-order bit + set to 0, the remaining 7 bits being used to encode the character + value. In a sequence of n octets, n>1, the initial octet has the + n higher-order bits set to 1, followed by a bit set to 0. The + remaining bits of that octet contain bits from the value of the + character to be encoded. The following octets all have the + higher-order bit set to 1 and the following bit set to 0, leaving 6 + bits in each to contain bits from the character to be encoded. The + possible UTF-8 encodings of ECMAScript characters are specified in + Table 21.
+|
+ + Code + Unit Value + |
+
+ + Representation + |
+
+ + 1st + Octet + |
+
+ + 2nd + Octet + |
+
+ + 3rd + Octet + |
+
+ + 4th + Octet + |
+
|
+
+ |
+
+
+ |
+
+
+ |
+ + | ++ | ++ | +
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+ + | ++ | +
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+ + | +
|
+
+ + followed + by +
+ |
+
+
+ + followed + by +
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ + not + followed by +
+ |
+
+
+ |
+ + | ++ | ++ | ++ | +
|
+
+ |
+
+
+ |
+ + | ++ | ++ | ++ | +
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+ + | +
+ Where
+
+ uuuuu
+ =
+ vvvv +
+ 1
+ to + account for the addition of 0x10000 as in Surrogates, section 3.7, + of the Unicode Standard.
++ The + range of code unit values 0xD800-0xDFFF is used to encode surrogate + pairs; the above transformation combines a UTF-16 surrogate pair + into a UTF-32 representation and encodes the resulting 21-bit value + in UTF-8. Decoding reconstructs the surrogate pair.
++ RFC + 3629 prohibits the decoding of invalid UTF-8 octet sequences. For + example, the invalid sequence C0 80 must not decode into the + character U+0000. Implementations of the Decode algorithm are + required to throw a URIError + when encountering such invalid sequences.
+
+ The
+ decodeURI function
+ computes a new version of a URI in which each escape sequence and
+ UTF-8 encoding of the sort that might be introduced by the encodeURI
+ function is replaced with the character that it represents. Escape
+ sequences that could not have been introduced by encodeURI
+ are not replaced.
+ When
+ the decodeURI
+ function is called with one argument encodedURI,
+ the following steps are taken:
+ Let + uriString be ToString(encodedURI).
+
+ Let
+ reservedURISet be a String containing one instance of each
+ character valid in uriReserved plus “#”.
+ Return + the result of calling Decode(uriString, reservedURISet)
+NOTE The
+ character “#”
+ is not decoded from escape sequences even though it is not a
+ reserved URI character.
+ The
+ decodeURIComponent
+ function computes a new version of a URI in which each escape
+ sequence and UTF-8 encoding of the sort that might be introduced by
+ the encodeURIComponent
+ function is replaced with the character that it represents.
+ When
+ the decodeURIComponent
+ function is called with one argument encodedURIComponent,
+ the following steps are taken:
+ Let + componentString be ToString(encodedURIComponent).
++ Let + reservedURIComponentSet be the empty String.
++ Return + the result of calling Decode(componentString, + reservedURIComponentSet)
+
+ The
+ encodeURI function
+ computes a new version of a URI in which each instance of certain
+ characters is replaced by one, two or three escape sequences
+ representing the UTF-8 encoding of the character.
+ When
+ the encodeURI
+ function is called with one argument uri,
+ the following steps are taken:
+ Let + uriString be ToString(uri).
+
+ Let
+ unescapedURISet be a String containing one instance of each
+ character valid in uriReserved and uriUnescaped plus
+ “#”.
+ Return + the result of calling Encode(uriString, unescapedURISet)
+NOTE The
+ character “#”
+ is not encoded to an escape sequence even though it is not a
+ reserved or unescaped URI character.
+ The
+ encodeURIComponent
+ function computes a new version of a URI in which each instance of
+ certain characters is replaced by one, two or three escape sequences
+ representing the UTF-8 encoding of the character.
+ When
+ the encodeURIComponent
+ function is called with one argument uriComponent,
+ the following steps are taken:
+ Let + componentString be ToString(uriComponent).
++ Let + unescapedURIComponentSet be a String containing one instance + of each character valid in uriUnescaped.
++ Return + the result of calling Encode(componentString, + unescapedURIComponentSet)
++ See + 15.9.2.
++ See + 15.11.6.1.
++ See + 15.11.6.2.
++ See + 15.11.6.3.
++ See + 15.11.6.4.
++ See + 15.11.6.5.
++ See + 15.11.6.6.
++ See + 15.8.
++ See + 15.12.
+
+ When
+ Object is called
+ as a function rather than as a constructor, it performs a type
+ conversion.
+ When
+ the Object
+ function is called with no arguments or with one argument value,
+ the following steps are taken:
+ If + value is null, undefined or not supplied, + create and return a new Object object exactly as if the standard + built-in Object constructor had been called with the same arguments + (15.2.2.1).
++ Return + ToObject(value).
+
+ When
+ Object is called
+ as part of a new
+ expression, it is a constructor that may create an object.
+ When
+ the Object
+ constructor is called with no arguments or with one argument value,
+ the following steps are taken:
+ If + value is supplied, then
++ If + Type(value) is Object, then
++ If + the value is a native ECMAScript object, do not create a + new object but simply return value.
++ If + the value is a host object, then actions are taken and a + result is returned in an implementation-dependent manner that may + depend on the host object.
++ Asset: + The argument value was not supplied or its type was Null or + Undefined. +
++ Let + obj be a newly created native ECMAScript object.
++ Set + the [[Prototype]] internal property of obj t to the standard + built-in Object prototype object (15.2.4).
+
+ Set
+ the [[Class]] internal property of obj to "Object".
+ Set + the [[Extensible]] internal property of obj to true.
++ Set + the all the internal methods of obj as specified in 8.12
++ Return + obj.
++ The + value of the [[Prototype]] internal property of the Object + constructor is the standard built-in Function prototype object.
+
+ Besides
+ the internal properties and the length
+ property (whose value is 1), the Object constructor has the
+ following properties:
+ The
+ initial value of Object.prototype
+ is the standard built-in Object prototype object (15.2.4).
+ This + property has the attributes {[[Writable]]: false, [[Enumerable]]: + false, [[Configurable]]: false }.
+
+ When
+ the getPrototypeOf
+ function is called with argument O,
+ the following steps are taken:
+ If + Type(O) is not Object throw a TypeError exception.
++ Return + the value of the [[Prototype]] internal property of O.
++ When + the getOwnPropertyDescriptor function is called, the + following steps are taken:
++ If + Type(O) is not Object throw a TypeError exception.
++ Let + name be ToString(P).
++ Let + desc be the result of calling the [[GetOwnProperty]] + internal method of O with argument name.
++ Return + the result of calling FromPropertyDescriptor(desc) (8.10.4). +
++ When + the getOwnPropertyNames function is called, the following + steps are taken:
++ If + Type(O) is not Object throw a TypeError exception.
+
+ Let
+ array be the result of creating a new object as if by the
+ expression new Array ()
+ where Array is
+ the standard built-in constructor with that name.
+ Let + n be 0.
++ For + each named own property P of O
++ Let + name be the String value that is the name of P.
++ Call + the [[DefineOwnProperty]] internal method of array with + arguments ToString(n), the PropertyDescriptor {[[Value]]: + name, [[Writable]]: true, [[Enumerable]]: true, + [[Configurable]]: true}, and false.
++ Increment + n by 1.
++ Return + array.
+NOTE If + O is a String + instance, the set of own properties processed in step 4 includes the + implicit properties defined in 15.5.5.2 that correspond to character + positions within the object’s [[PrimitiveValue]] String.
++ The + create function creates a new object with a specified + prototype. When the create function is called, the following + steps are taken:
++ If + Type(O) is not Object or Null throw a TypeError + exception.
++ Let + obj be the result of creating a new object as if by the + expression new Object() where Object is the standard built-in + constructor with that name
++ Set + the [[Prototype]] internal property of obj to O.
+
+ If
+ the argument Properties is present and not undefined,
+ add own properties to obj as if by calling the standard
+ built-in function Object.defineProperties
+with arguments obj and Properties.
+ Return + obj.
++ The + defineProperty function is used to add an own property and/or + update the attributes of an existing own property of an object. When + the defineProperty function is called, the following steps + are taken:
++ If + Type(O) is not Object throw a TypeError exception.
++ Let + name be ToString(P).
++ Let + desc be the result of calling ToPropertyDescriptor with + Attributes as the argument.
++ Call + the [[DefineOwnProperty]] internal method of O with + arguments name, desc, and true.
++ Return + O.
++ The + defineProperties function is used to add own properties + and/or update the attributes of existing own properties of an + object. When the defineProperties function is called, the + following steps are taken:
++ Let + props be ToObject(Properties).
++ Let + names be an internal list containing the names of each + enumerable own property of props.
++ Let + descriptors be an empty internal List.
++ For + each element P of names in list order,
++ Let + descObj be the result of calling the [[Get]] internal + method of props with P as the argument.
++ Let + desc be the result of calling ToPropertyDescriptor with + descObj as the argument.
++ Append + desc to the end of descriptors.
+For + each element desc of descriptors in list order,
+Call the [[DefineOwnProperty]] internal method of O with + arguments P, desc, and true.
Return O
++ If an + implementation defines a specific order of enumeration for the + for-in statement, that same enumeration order must be used to order + the list elements in step 3 of this algorithm.
++ When + the seal function is called, the following steps are taken:
++ If + Type(O) is not Object throw a TypeError exception.
++ For + each named own property name P of O,
++ Let + desc be the result of calling the [[GetOwnProperty]] + internal method of O with P.
++ If + desc.[[Configurable]] is true, set + desc.[[Configurable]] to false.
++ Call + the [[DefineOwnProperty]] internal method of O with P, + desc, and true as arguments.
++ Set + the [[Extensible]] internal property of O to false.
++ Return + O.
++ When + the freeze function is called, the following steps are taken:
++ If + Type(O) is not Object throw a TypeError exception.
++ For + each named own property name P of O,
++ Let + desc be the result of calling the [[GetOwnProperty]] + internal method of O with P.
++ If + IsDataDescriptor(desc) is true, then
++ If + desc.[[Writable]] is true, set desc.[[Writable]] + to false.
++ If + desc.[[Configurable]] is true, set + desc.[[Configurable]] to false.
++ Call + the [[DefineOwnProperty]] internal method of O with P, + desc, and true as arguments.
++ Set + the [[Extensible]] internal property of O to false.
++ Return + O.
++ When + the preventExtensions function is called, the following steps + are taken:
++ If + Type(O) is not Object throw a TypeError exception.
++ Set + the [[Extensible]] internal property of O to false.
++ Return + O.
++ When + the isSealed function is called with argument O, + the following steps are taken:
++ If + Type(O) is not Object throw a TypeError exception.
++ For + each named own property name P of O,
++ Let + desc be the result of calling the [[GetOwnProperty]] + internal method of O with P.
++ If + desc.[[Configurable]] is true, then return false.
++ If + the [[Extensible]] internal property of O is false, + then return true.
++ Otherwise, + return false.
++ When + the isFrozen function is called with argument O, + the following steps are taken:
++ If + Type(O) is not Object throw a TypeError exception.
++ For + each named own property name P of O,
++ Let + desc be the result of calling the [[GetOwnProperty]] + internal method of O with P.
++ If + IsDataDescriptor(desc) is true then
++ If + desc.[[Writable]] is true, return false.
++ If + desc.[[Configurable]] is true, then return false.
++ If + the [[Extensible]] internal property of O is false, + then return true.
++ Otherwise, + return false.
++ When + the isExtensible function is called with argument O, + the following steps are taken:
++ If + Type(O) is not Object throw a TypeError exception.
++ Return + the Boolean value of the [[Extensible]] internal property of O.
++ When + the keys function is called with argument O, + the following steps are taken:
++ If + the Type(O) is not Object, throw a TypeError + exception.
++ Let + n be the number of own enumerable properties of O
+
+ Let
+ array be the result of creating a new Object as if by the
+ expression new Array(n)
+ where Array
+ is the standard built-in constructor with that name.
+ Let + index be 0.
++ For + each own enumerable property of O whose name String is P + +
++ Call + the [[DefineOwnProperty]] internal method of array with + arguments ToString(index), the PropertyDescriptor + {[[Value]]: P, [[Writable]]: true, [[Enumerable]]: + true, [[Configurable]]: true}, and false.
++ Increment + index by 1.
++ Return + array.
++ If an + implementation defines a specific order of enumeration for the + for-in statement, that same enumeration order must be used in step 5 + of this algorithm.
+
+ The
+ value of the [[Prototype]] internal property of the Object prototype
+ object is null, the value of the [[Class]] internal property
+ is "Object",
+ and the initial value of the [[Extensible]] internal property is
+ true.
+ The
+ initial value of Object.prototype.constructor
+ is the standard built-in Object
+ constructor.
+ When
+ the toString
+ method is called, the following steps are taken:
If + the this + value is undefined, + return "[object Undefined]".
If + the this + value is null, + return "[object Null]".
Let + O be the result of calling ToObject passing the this value + as the argument.
Let + class be the value of the [[Class]] internal property of O.
Return + the String value that is the result of concatenating the three + Strings "[object ", + class, and "]".
+ When + the toLocaleString method is called, the following steps are + taken:
++ Let + O be the result of calling ToObject passing the this + value as the argument.
++ Let + toString be the result of calling the [[Get]] internal + method of O passing "toString" as the + argument.
++ If + IsCallable(toString) is false, throw a TypeError + exception.
++ Return + the result of calling the [[Call]] internal method of toString + passing O as the this value and no arguments.
+NOTE 1 This function is provided to give all Objects a generic
+ toLocaleString
+ interface, even though not all may use it. Currently, Array,
+ Number, and Date
+ provide their own locale-sensitive toLocaleString
+ methods.
NOTE 2 The first parameter to this function is likely to be used in a + future version of this standard; it is recommended that + implementations do not use this parameter position for anything + else.
++ When + the valueOf method is called, the following steps are taken: +
++ Let + O be the result of calling ToObject passing the this + value as the argument.
++ If + O is the result of calling the Object constructor with a + host object (15.2.2.1), then
++ Return + either O or another value such as the host object + originally passed to the constructor. The specific result that is + returned is implementation-defined.
++ Return + O.
+
+ When
+ the hasOwnProperty
+ method is called with argument V,
+ the following steps are taken:
+ Let + P be ToString(V).
++ Let + O be the result of calling ToObject passing the this + value as the argument.
++ Let + desc be the result of calling the [[GetOwnProperty]] + internal method of O passing P as the argument.
++ If + desc is undefined, return false.
++ Return + true.
+NOTE 1 Unlike [[HasProperty]] (8.12.6), this method does not consider + objects in the prototype chain.
+NOTE 2 The ordering of steps 1 and 2 is chosen to ensure that any + exception that would have been thrown by step 1 in previous editions + of this specification will continue to be thrown even if the this + value is undefined or null.
+
+ When
+ the isPrototypeOf
+ method is called with argument V,
+ the following steps are taken:
+ If + V is not an object, return false.
++ Let + O be the result of calling ToObject passing the this + value as the argument.
++ Repeat
++ Let + V be the value of the [[Prototype]] internal property of V.
++ if + V is null, return false
++ If + O and V refer to the same object, return true.
+NOTE The + ordering of steps 1 and 2 is chosen to preserve the behaviour + specified by previous editions of this specification for the case + where V is not an object and the this value is undefined or null.
+
+ When
+ the propertyIsEnumerable
+ method is called with argument V,
+ the following steps are taken:
+ Let + P be ToString(V).
++ Let + O be the result of calling ToObject passing the this + value as the argument.
++ Let + desc be the result of calling the [[GetOwnProperty]] + internal method of O passing P as the argument.
++ If + desc is undefined, return false.
++ Return + the value of desc.[[Enumerable]].
+NOTE 1 This method does not consider objects in the prototype chain.
+NOTE 2 The ordering of steps 1 and 2 is chosen to ensure that any + exception that would have been thrown by step 1 in previous editions + of this specification will continue to be thrown even if the this + value is undefined or null.
++ Object + instances have no special properties beyond those inherited from the + Object prototype object.
+
+ When
+ Function is called
+ as a function rather than as a constructor, it creates and
+ initialises a new Function object. Thus the function call
+ Function(…)
+ is equivalent to the object creation expression new
+ Function(…)
+ with the same arguments.
+ When
+ the Function
+ function is called with some arguments p1,
+ p2, … , pn,
+ body (where n
+ might be 0, that is,
+ there are no “p”
+ arguments, and where body
+ might also not be provided), the following steps are taken:
+ Create + and return a new Function object as if the standard built-in + constructor Function was used in a new expression with the + same arguments (15.3.2.1).
+
+ When
+ Function is called
+ as part of a new
+ expression, it is a constructor: it initialises the newly created
+ object.
+ The + last argument specifies the body (executable code) of a function; + any preceding arguments specify formal parameters.
+
+ When
+ the Function
+ constructor is called with some arguments p1,
+ p2, … , pn,
+ body (where n
+ might be 0, that is,
+ there are no “p”
+ arguments, and where body
+ might also not be provided), the following steps are taken:
+ Let + argCount be the total number of arguments passed to this + function invocation.
++ Let + P be the empty String.
++ If + argCount = 0, let body be the empty String.
++ Else + if argCount = 1, let body be that argument.
++ Else, + argCount > 1
++ Let + firstArg be the first argument.
++ Let + P be ToString(firstArg).
++ Let + k be 2.
++ Repeat, + while k < argCount
++ Let + nextArg be the k’th argument.
+
+ Let
+ P be the result of concatenating the previous value of P,
+ the String ","
+ (a comma), and ToString(nextArg).
+ Increase + k by 1.
++ Let + body be the k’th argument.
++ Let + body be ToString(body).
++ If + P is not parsable as a FormalParameterListopt + then throw a SyntaxError exception.
++ If + body is not parsable as FunctionBody then throw a + SyntaxError exception.
++ Ifbody is strict mode code (see 10.1.1) then let strict be + true, else let strict be false.
++ If + strict is true, throw any exceptions specified in + 13.1 that apply. +
++ Return + a new Function object created as specified in 13.2 passing P + as the FormalParameterList and body as the + FunctionBody. Pass in the Global Environment as the Scope + parameter and strict as the Strict flag.
+
+ A
+ prototype property
+ is automatically created for every function, to provide for the
+ possibility that the function will be used as a constructor.
+
NOTE It + is permissible but not necessary to have one argument for each + formal parameter to be specified. For example, all three of the + following expressions produce the same result:
+
+ new
+ Function("a", "b", "c", "return
+ a+b+c")
+ new
+ Function("a, b, c", "return a+b+c")
+ new
+ Function("a,b", "c", "return a+b+c")
+ The
+ Function constructor is itself a Function object and its [[Class]]
+ is "Function".
+ The value of the [[Prototype]] internal property of the Function
+ constructor is the standard built-in Function prototype object
+ (15.3.4).
+ The + value of the [[Extensible]] internal property of the Function + constructor is true.
++ The + Function constructor has the following properties:
+
+ The
+ initial value of Function.prototype
+ is the standard built-in Function prototype object (15.3.4).
+ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
++ This + is a data property with a value of 1. This property has the + attributes { [[Writable]]: false, [[Enumerable]]: false, + [[Configurable]]: false }.
+
+ The
+ Function prototype object is itself a Function object (its [[Class]]
+ is "Function")
+ that, when invoked, accepts any arguments and returns undefined.
+ The + value of the [[Prototype]] internal property of the Function + prototype object is the standard built-in Object prototype object + (15.2.4). The initial value of the [[Extensible]] internal property + of the Function prototype object is true.
+
+ The
+ Function prototype object does not have a valueOf
+ property of its own; however, it inherits the valueOf
+ property from the Object prototype Object.
+ The
+ length property of
+ the Function prototype object is 0.
+ The
+ initial value of Function.prototype.constructor
+ is the built-in Function
+ constructor.
+ An + implementation-dependent representation of the function is returned. + This representation has the syntax of a FunctionDeclaration. + Note in particular that the use and placement of white space, line + terminators, and semicolons within the representation String is + implementation-dependent.
+
+ The
+ toString function
+ is not generic; it throws a TypeError exception if its this
+ value is not a Function object. Therefore, it cannot be transferred
+ to other kinds of objects for use as a method.
+ When
+ the apply method
+ is called on an object func
+ with arguments thisArg
+ and argArray, the
+ following steps are taken:
+
+ If + IsCallable(func) is false, then throw a TypeError + exception.
++ If + argArray is null or undefined, then
++ Return + the result of calling the [[Call]] internal method of func, + providing thisArg as the this value and an empty + list of arguments.
++ If + Type(argArray) is not Object, then throw a TypeError + exception.
+
+ Let
+ len be the result of calling the [[Get]] internal method of
+ argArray with argument "length".
+ Let + n be ToUint32(len).
++ Let + argList be an empty List.
++ Let + index be 0.
++ Repeat + while index < n
++ Let + indexName be ToString(index).
++ Let + nextArg be the result of calling the [[Get]] internal + method of argArray with indexName as the argument.
++ Append + nextArg as the last element of argList.
++ Set + index to index + 1.
++ Return + the result of calling the [[Call]] internal method of func, + providing thisArg as the this value and argList + as the list of arguments.
+
+ The
+ length property of
+ the apply method
+ is 2.
NOTE The + thisArg value is passed without modification as the this + value. This is a change from Edition 3, where a undefined or + null thisArg is replaced with the global object and ToObject + is applied to all other values and that result is passed as the this + value.
+
+ When
+ the call method is
+ called on an object func
+ with argument thisArg
+ and optional arguments arg1,
+ arg2 etc, the
+ following steps are taken:
+ If + IsCallable(func) is false, then throw a TypeError + exception.
++ Let + argList be an empty List.
++ If + this method was called with more than one argument then in left to + right order starting with arg1 append each argument as the + last element of argList
++ Return + the result of calling the [[Call]] internal method of func, + providing thisArg as the this value and argList + as the list of arguments.
+
+ The
+ length property of
+ the call method is
+ 1.
NOTE The + thisArg value is passed without modification as the this + value. This is a change from Edition 3, where a undefined or + null thisArg is replaced with the global object and ToObject + is applied to all other values and that result is passed as the this + value.
++ The + bind method takes one or more arguments, thisArg + and (optionally) arg1, + arg2, etc, and + returns a new function object by performing the following steps:
++ Let + Target be the this value.
++ If + IsCallable(Target) is false, throw a TypeError + exception.
++ Let + A be a new (possibly empty) internal list of all of the + argument values provided after thisArg (arg1, arg2 + etc), in order.
++ Let + F be a new native ECMAScript object .
++ Set + all the internal methods, except for [[Get]], of F as + specified in 8.12.
++ Set + the [[Get]] internal property of F as specified in 15.3.5.4.
++ Set + the [[TargetFunction]] internal property of F to Target.
++ Set + the [[BoundThis]] internal property of F to the value of + thisArg.
++ Set + the [[BoundArgs]] internal property of F to A.
++ Set + the [[Class]] internal property of F to "Function".
++ Set + the [[Prototype]] internal property of F to the standard + built-in Function prototype object as specified in 15.3.3.1.
++ Set + the [[Call]] internal property of F as described in + 15.3.4.5.1.
++ Set + the [[Construct]] internal property of F as described in + 15.3.4.5.2.
++ Set + the [[HasInstance]] internal property of F as described in + 15.3.4.5.3.
++ If + the [[Class]] internal property of Target is "Function", + then
++ Let + L be the length property of Target minus the + length of A.
++ Set + the length own property of F to either 0 or + L, whichever is larger. +
++ Else + set the length own property of F to 0.
++ Set + the attributes of the length own property of F to + the values specified in 15.3.5.1.
++ Set + the [[Extensible]] internal property of F to true.
++ Let + thrower be the [[ThrowTypeError]] function Object (13.2.3).
+
+ Call
+ the [[DefineOwnProperty]] internal method of F with
+ arguments "caller",
+ PropertyDescriptor {[[Get]]: thrower, [[Set]]: thrower,
+ [[Enumerable]]: false, [[Configurable]]: false}, and
+ false.
+ Call
+ the [[DefineOwnProperty]] internal method of F with
+ arguments "arguments",
+ PropertyDescriptor {[[Get]]: thrower, [[Set]]: thrower,
+ [[Enumerable]]: false, [[Configurable]]: false}, and
+ false.
+ Return + F.
+
+ The
+ length property of
+ the bind method is
+ 1.
NOTE Function
+ objects created using Function.prototype.bind
+ do not have a prototype
+ property or the [[Code]], [[FormalParameters]], and [[Scope]]
+ internal properties.
+ When + the [[Call]] internal method of a function object, F, + which was created using the bind function is called with a this + value and a list of arguments ExtraArgs, + the following steps are taken:
++ Let + boundArgs be the value of F’s [[BoundArgs]] + internal property.
++ Let + boundThis be the value of F’s [[BoundThis]] + internal property.
++ Let + target be the value of F’s [[TargetFunction]] + internal property.
++ Let + args be a new list containing the same values as the list + boundArgs in the same order followed by the same values as + the list ExtraArgs in the same order.
++ Return + the result of calling the [[Call]] internal method of target + providing boundThis as the this value and providing + args as the arguments.
++ When + the [[Construct]] internal method of a function object, F + that was created using the bind function is called with a list of + arguments ExtraArgs, + the following steps are taken:
++ Let + target be the value of F’s [[TargetFunction]] + internal property.
++ If + target has no [[Construct]] internal method, a TypeError + exception is thrown.
++ Let + boundArgs be the value of F’s [[BoundArgs]] + internal property.
++ Let + args be a new list containing the same values as the list + boundArgs in the same order followed by the same values as + the list ExtraArgs in the same order.
++ Return + the result of calling the [[Construct]] internal method oftarget providing args as the arguments.
++ When + the [[HasInstance]] internal method of a function object F, + that was created using the bind function is called with argument V, + the following steps are taken:
++ Let + target be the value of F’s [[TargetFunction]] + internal property.
++ If + target has no [[HasInstance]] internal method, a TypeError + exception is thrown.
++ Return + the result of calling the [[HasInstance]] internal method oftarget providing V as the argument.
++ In + addition to the required internal properties, every function + instance has a [[Call]] internal property and in most cases use a + different version of the [[Get]] internal property. Depending on how + they are created (see 8.6.2 ,13.2, 15, and 15.3.4.5), function + instances may have a [[HasInstance]] internal property, a [[Scope]] + internal property, a [[Construct]] internal property, a + [[FormalParameters]] internal property, a [[Code]] internal + property, a [[TargetFunction]] internal property, a [[BoundThis]] + internal property, and a [[BoundArgs]] internal property.
++ The + value of the [[Class]] internal property is "Function".
++ Function + instances that correspond to strict mode functions (13.2) and + function instances created using the Function.prototype.bind + method (15.3.4.5) have properties named “caller” and + “arguments” that throw a TypeError exception. An + ECMAScript implementation must not associate any implementation + specific behaviour with accesses of these properties from strict + mode function code. +
+
+ The
+ value of the length
+ property is an integer that indicates the “typical” number of
+ arguments expected by the function. However, the language permits
+ the function to be invoked with some other number of arguments. The
+ behaviour of a function when invoked on a number of arguments other
+ than the number specified by its length
+ property depends on the function. This property has the attributes
+ { [[Writable]]: false,
+ [[Enumerable]]: false,
+ [[Configurable]]: false }.
+ The
+ value of the prototype
+ property is used to initialise the [[Prototype]] internal property
+ of a newly created object before the Function object is invoked as a
+ constructor for that newly created object. This property has the
+ attribute { [[Writable]]: true,
+ [[Enumerable]]: false,
+ [[Configurable]]: false
+ }.
NOTE Function
+ objects created using Function.prototype.bind
+ do not have a prototype
+ property.
+ Assume + F is a Function + object.
++ When + the [[HasInstance]] internal method of F + is called with value V, + the following steps are taken:
++ If + V is not an object, return false.
+
+ Let
+ O be the result of calling the [[Get]] internal method of F
+ with property name "prototype".
+ Repeat
++ Let + V be the value of the [[Prototype]] internal property of V.
+
+ If
+ V is null,
+ return false.
+ If + O and V refer to the same object, return true.
++
NOTE Function
+ objects created using Function.prototype.bind
+ have a different implementation of [[HasInstance]] defined in
+ 15.3.4.5.3.
+ Function + objects use a variation of the [[Get]] internal method used for + other native ECMAScript objects (8.12.3).
++ Assume + F is a Function + object. When the [[Get]] internal method of F + is called with property name P, + the following steps are taken:
++ Let + v be the result of calling the default [[Get]] internal + method (8.12.3) on F passing P as the property name + argument.
+
+ If
+ P is "caller"
+ and v is a strict mode Function object, throw a
+ TypeError exception.
+
+ Return + v.
+NOTE Function
+ objects created using Function.prototype.bind
+ use the default [[Get]] internal method.
+ Array
+ objects give special treatment to a certain class of property names.
+ A property name P
+ (in the form of a String value) is an array index if and only
+ if ToString(ToUint32(P))
+ is equal to P and
+ ToUint32(P)
+ is not equal to 232−1.
+ A property whose property name is an array index is also called an
+ element. Every Array object has a length
+ property whose value is always a nonnegative integer less than 232.
+ The value of the length
+ property is numerically greater than the name of every property
+ whose name is an array index; whenever a property of an Array object
+ is created or changed, other properties are adjusted as necessary to
+ maintain this invariant. Specifically, whenever a property is added
+ whose name is an array index, the length
+ property is changed, if necessary, to be one more than the numeric
+ value of that array index; and whenever the length
+ property is changed, every property whose name is an array index
+ whose value is not smaller than the new length is automatically
+ deleted. This constraint applies only to own properties of an Array
+ object and is unaffected by length
+ or array index properties that may be inherited from its prototypes.
+ An + object, O, is + said to be sparse if the following algorithm returns true:
++ Let + len + be the result of calling the [[Get]] internal method of O + with argument "length".
++ For + each integer i + in the range 0≤i<ToUint32(len)
++ Let + elem + be the result of calling the [[GetOwnProperty]] internal method of + O + with argument ToString(i).
++ If + elem + is undefined, + return true.
++ Return + false.
+
+ When
+ Array is called as
+ a function rather than as a constructor, it creates and initialises
+ a new Array object. Thus the function call Array(…)
+ is equivalent to the object creation expression new Array(…)
+ with the same arguments.
+ When
+ the Array function
+ is called the following steps are taken:
+ Create
+ and return a new Array object exactly as if the standard built-in
+ constructor Array
+ was used in a new
+ expression with the same arguments (15.4.2).
+ When
+ Array is called as
+ part of a new
+ expression, it is a constructor: it initialises the newly created
+ object.
+ This + description applies if and only if the Array constructor is given no + arguments or at least two arguments.
+
+ The
+ [[Prototype]] internal property of the newly constructed object is
+ set to the original Array prototype object, the one that is the
+ initial value of Array.prototype
+ (15.4.3.1).
+ The
+ [[Class]] internal property of the newly constructed object is set
+ to "Array".
+ The + [[Extensible]] internal property of the newly constructed object is + set to true.
+
+ The
+ length property of
+ the newly constructed object is set to the number of arguments.
+ The 0
+ property of the newly constructed object is set to item0
+ (if supplied); the 1
+ property of the newly constructed object is set to item1
+ (if supplied); and, in general, for as many arguments as there are,
+ the k property of
+ the newly constructed object is set to argument k,
+ where the first argument is considered to be argument number 0.
+ These properties all have the attributes {[[Writable]]: true,
+ [[Enumerable]]: true, [[Configurable]]: true}.
+ The
+ [[Prototype]] internal property of the newly constructed object is
+ set to the original Array prototype object, the one that is the
+ initial value of Array.prototype
+ (15.4.3.1). The [[Class]] internal property of the newly constructed
+ object is set to "Array".
+ The [[Extensible]] internal property of the newly constructed object
+ is set to true.
+ If
+ the argument len
+ is a Number and ToUint32(len)
+ is equal to len,
+ then the length
+ property of the newly constructed object is set to ToUint32(len).
+ If the argument len
+ is a Number and ToUint32(len)
+ is not equal to len,
+ a RangeError exception is thrown.
+ If
+ the argument len
+ is not a Number, then the length
+ property of the newly constructed object is set to 1
+ and the 0 property
+ of the newly constructed object is set to len
+ with attributes {[[Writable]]: true, [[Enumerable]]: true,
+ [[Configurable]]: true}..
+ The + value of the [[Prototype]] internal property of the Array + constructor is the Function prototype object (15.3.4).
+
+ Besides
+ the internal properties and the length
+ property (whose value is 1), the Array constructor has the
+ following properties:
+ The
+ initial value of Array.prototype
+ is the Array prototype object (15.4.4).
+ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+
+ The
+ isArray function takes one argument arg,
+ and returns the Boolean value true if the argument is an
+ object whose class internal property is "Array";
+ otherwise it returns false. The following steps are taken:
+ If + Type(arg) is not Object, return false.
+
+ If
+ the value of the [[Class]] internal property of arg is
+ "Array",
+ then return true.
+ Return + false.
++ The + value of the [[Prototype]] internal property of the Array prototype + object is the standard built-in Object prototype object (15.2.4).
+
+ The
+ Array prototype object is itself an array; its [[Class]] is "Array",
+ and it has a length
+ property (whose initial value is +0) and the special
+ [[DefineOwnProperty]] internal method described in 15.4.5.1.
+ In
+ following descriptions of functions that are properties of the Array
+ prototype object, the phrase “this object” refers to the object
+ that is the this value for the invocation of the function. It
+ is permitted for the this to be an object for which the value
+ of the [[Class]] internal property is not "Array".
NOTE The
+ Array prototype object does not have a valueOf
+ property of its own; however, it inherits the valueOf
+ property from the standard built-in Object prototype Object.
+ The
+ initial value of Array.prototype.constructor
+ is the standard built-in Array
+ constructor.
+ When
+ the toString
+ method is called, the following steps are taken:
+ Let + array be the result of calling ToObject on the this + value.
+
+ Let
+ func be the result of calling the [[Get]] internal method of
+ array with argument "join".
+ If + IsCallable(func) is false, then let func be + the standard built-in method Object.prototype.toString (15.2.4.2).
++ Return + the result of calling the [[Call]] internal method of func + providing array as the this value and an empty + arguments list.
++
NOTE The toString
+ function is intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the toString
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ The
+ elements of the array are converted to Strings using their
+ toLocaleString
+ methods, and these Strings are then concatenated, separated by
+ occurrences of a separator String that has been derived in an
+ implementation-defined locale-specific way. The result of calling
+ this function is intended to be analogous to the result of toString,
+ except that the result of this function is intended to be
+ locale-specific.
+ The + result is calculated as follows:
++ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ arrayLen be the result of calling the [[Get]] internal
+ method of array with argument "length".
+ Let + len be ToUint32(arrayLen).
++ Let + separator be the String value for the list-separator String + appropriate for the host environment’s current locale (this is + derived in an implementation-defined way).
++ If + len is zero, return the empty String.
+
+ Let
+ firstElement be the result of calling the [[Get]] internal
+ method of array with argument "0".
+ If + firstElement is undefined or null, then
++ Let + R be the empty String.
++ Else + +
++ Let + elementObj be ToObject(firstElement).
+
+ Let
+ func be the result of calling the [[Get]] internal method
+ of elementObj with argument "toLocaleString".
+ If + IsCallable(func) is false, throw a TypeError + exception.
++ Let + R be the result of calling the [[Call]] internal method of + func providing elementObj as the this value + and an empty arguments list. +
+
+ Let
+ k be 1.
+ Repeat, + while k < len
++ Let + S be a String value produced by concatenating R and + separator.
++ Let + nextElement be the result of calling the [[Get]] internal + method of array with argument ToString(k).
++ If + nextElement is undefined or null, then
++ Let + R be the empty String.
++ Else + +
++ Let + elementObj be ToObject(nextElement).
+
+ Let
+ func be the result of calling the [[Get]] internal method
+ of elementObj with argument "toLocaleString".
+ If + IsCallable(func) is false, throw a TypeError + exception.
++ Let + R be the result of calling the [[Call]] internal method of + func providing elementObj as the this value + and an empty arguments list. +
++ Let + R be a String value produced by concatenating S and + R.
++ Increase + k by 1.
++ Return + R.
+NOTE 1 The first parameter to this function is likely to be used in a + future version of this standard; it is recommended that + implementations do not use this parameter position for anything + else.
+NOTE 2 The toLocaleString
+ function is intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the toLocaleString
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ When
+ the concat method
+ is called with zero or more arguments item1,
+ item2, etc., it
+ returns an array containing the array elements of the object
+ followed by the array elements of each argument in order.
+ The + following steps are taken:
++ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ A be a new array created as if by the expression new
+ Array() where Array
+ is the standard built-in constructor with that name.
+ Let + n be 0.
++ Let + items be an internal List whose first element is O + and whose subsequent elements are, in left to right order, the + arguments that were passed to this function invocation.
++ Repeat, + while items is not empty
++ Remove + the first element from items and let E be the value + of the element.
+
+ If
+ the value of the [[Class]] internal property of E is
+ "Array",
+ then
+ Let + k be 0.
+
+ Let
+ len be the result of calling the [[Get]] internal method
+ of E with argument "length".
+ Repeat, + while k < len
++ Let + P be ToString(k).
++ Let + exists be the result of calling the [[HasProperty]] + internal method of E with P.
++ If + exists is true, then
++ Let + subElement be the result of calling the [[Get]] internal + method of E with argument P.
++ Call + the [[DefineOwnProperty]] internal method of A with + arguments ToString(n), Property Descriptor {[[Value]]: + subElement, [[Writable]]: true, [[Enumerable]]: + true, [[Configurable]]: true}, and false.
++ Increase + n by 1.
++ Increase + k by 1.
++ Else, + E is not an Array
++ Call + the [[DefineOwnProperty]] internal method of A with + arguments ToString(n), Property Descriptor {[[Value]]: E, + [[Writable]]: true, [[Enumerable]]: true, + [[Configurable]]: true}, and false.
++ Increase + n by 1.
++ Return + A.
+
+ The
+ length property of
+ the concat method
+ is 1.
NOTE The
+ concat function is
+ intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the concat
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ The + elements of the array are converted to Strings, and these Strings + are then concatenated, separated by occurrences of the separator. + If no separator is provided, a single comma is used as the + separator.
+
+ The
+ join method takes
+ one argument, separator,
+ and performs the following steps:
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenVal be the result of calling the [[Get]] internal method
+ of O with argument "length".
+ Let + len be ToUint32(lenVal).
+
+ If
+ separator is undefined, let separator be the
+ single-character String ",".
+ Let + sep be ToString(separator).
++ If + len is zero, return the empty String.
+
+ Let
+ element0 be the result of calling the [[Get]] internal
+ method of O with argument "0".
+ If + element0 is undefined or null, let R be + the empty String; otherwise, Let R be ToString(element0).
+
+ Let
+ k be 1.
+ Repeat, + while k < len
++ Let + S be the String value produced by concatenating R + and sep.
++ Let + element be the result of calling the [[Get]] internal + method of O with argument ToString(k).
++ If + element is undefined or null, Let next + be the empty String; otherwise, let next be + ToString(element).
++ Let + R be a String value produced by concatenating S and + next.
++ Increase + k by 1.
++ Return + R.
+
+ The
+ length property of
+ the join method is
+ 1.
NOTE The
+ join function is
+ intentionally generic; it does not require that its this
+ value be an Array object. Therefore, it can be transferred to other
+ kinds of objects for use as a method. Whether the join
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ The + last element of the array is removed from the array and returned.
++ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenVal be the result of calling the [[Get]] internal method
+ of O with argument "length".
+ Let + len be ToUint32(lenVal).
++ If + len is zero, +
+
+ Call
+ the [[Put]] internal method of O with arguments "length",
+ 0, and true.
+ Return + undefined.
++ Else, + len > 0
++ Let + indx be ToString(len–1).
++ Let + element be the result of calling the [[Get]] internal + method of O with argument indx.
++ Call + the [[Delete]] internal method of O with arguments indx + and true.
+
+ Call
+ the [[Put]] internal method of O with arguments "length",
+ indx, and true.
+ Return + element.
+NOTE The
+ pop function is
+ intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the pop
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ The + arguments are appended to the end of the array, in the order in + which they appear. The new length of the array is returned as the + result of the call.
+
+ When
+ the push method is
+ called with zero or more arguments item1,item2, etc., the following steps are taken:
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenVal be the result of calling the [[Get]] internal method
+ of O with argument "length".
+ Let + n be ToUint32(lenVal).
++ Let + items be an internal List whose elements are, in left to + right order, the arguments that were passed to this function + invocation.
++ Repeat, + while items is not empty
++ Remove + the first element from items and let E be the value + of the element.
++ Call + the [[Put]] internal method of O with arguments + ToString(n), E, and true.
++ Increase + n by 1.
+
+ Call
+ the [[Put]] internal method of O with arguments "length",
+ n, and true.
+ Return + n.
+
+ The
+ length property of
+ the push method is
+ 1.
NOTE The
+ push function is
+ intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the push
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ The + elements of the array are rearranged so as to reverse their order. + The object is returned as the result of the call.
++ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenVal be the result of calling the [[Get]] internal method
+ of O with argument "length".
+ Let + len be ToUint32(lenVal).
++ Let + middle be floor(len/2).
++ Letlower be 0.
++ Repeat, + while lower ≠ middle
++ Let + upper be len−lower −1.
++ Let + upperP be ToString(upper).
++ Let + lowerP be ToString(lower).
++ Let + lowerValue be the result of calling the [[Get]] internal + method of O with argument lowerP.
++ Let + upperValue be the result of calling the [[Get]] internal + method of O with argument upperP .
++ Let + lowerExists be the result of calling the [[HasProperty]] + internal method of O with argument lowerP.
++ Let + upperExists be the result of calling the [[HasProperty]] + internal method of O with argument upperP.
++ If + lowerExists is true and upperExists is true, + then
++ Call + the [[Put]] internal method of O with arguments lowerP, + upperValue, and true .
++ Call + the [[Put]] internal method of O with arguments upperP, + lowerValue, and true .
++ Else + if lowerExists is false and upperExists is + true, then
++ Call + the [[Put]] internal method of O with arguments lowerP, + upperValue, and true .
++ Call + the [[Delete]] internal method of O, with arguments upperP + and true.
++ Else + if lowerExists is true and upperExists is + false, then
++ Call + the [[Delete]] internal method of O, with arguments lowerP + and true .
++ Call + the [[Put]] internal method of O with arguments upperP, + lowerValue, and true .
++ Else, + both lowerExists and upperExists are false
++ No + action is required.
++ Increase + lower by 1.
++ Return + O .
+NOTE The
+ reverse function
+ is intentionally generic; it does not require that its this
+ value be an Array object. Therefore, it can be transferred to other
+ kinds of objects for use as a method. Whether the reverse
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ The + first element of the array is removed from the array and returned.
++ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenVal be the result of calling the [[Get]] internal method
+ of O with argument "length".
+ Let + len be ToUint32(lenVal).
++ If + len is zero, then
+
+ Call
+ the [[Put]] internal method of O with arguments "length",
+ 0, and true.
+ Return + undefined.
+
+ Let
+ first be the result of calling the [[Get]] internal method
+ of O with argument "0".
+ Let + k be 1.
++ Repeat, + while k < len
++ Let + from be ToString(k).
++ Let + to be ToString(k–1).
++ Let + fromPresent be the result of calling the [[HasProperty]] + internal method of O with argument from.
++ If + fromPresent is true, then
++ Let + fromVal be the result of calling the [[Get]] internal + method of O with argument from.
++ Call + the [[Put]] internal method of O with arguments to, + fromVal, and true.
++ Else, + fromPresent is false
++ Call + the [[Delete]] internal method of O with arguments to + and true.
++ Increase + k by 1.
++ Call + the [[Delete]] internal method of O with arguments + ToString(len–1) and true.
+
+ Call
+ the [[Put]] internal method of O with arguments "length",
+ (len–1) , and true.
+ Return + first.
+NOTE The
+ shift function is
+ intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the shift
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ The
+ slice method takes
+ two arguments, start
+ and end, and
+ returns an array containing the elements of the array from element
+ start up to, but
+ not including, element end
+ (or through the end of the array if end
+ is undefined). If start
+ is negative, it is treated as length+start
+ where length is
+ the length of the array. If end
+ is negative, it is treated as length+end
+ where length
+ is the length of the array. The following steps are taken:
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ A be a new array created as if by the expression new
+ Array() where Array
+ is the standard built-in constructor with that name.
+ Let
+ lenVal be the result of calling the [[Get]] internal method
+ of O with argument "length".
+ Let + len be ToUint32(lenVal).
++ Let + relativeStart be ToInteger(start).
++ If + relativeStart is negative, let k be max((len +relativeStart),0); else let k be min(relativeStart,len).
++ If + end is undefined, let relativeEnd be len; + else let relativeEnd be ToInteger(end).
++ If + relativeEnd is negative, let final be max((len + + relativeEnd),0); else let final be min(relativeEnd,len).
++ Let + n be 0.
++ Repeat, + while k < final
++ Let + Pk be ToString(k).
++ Let + kPresent be the result of calling the [[HasProperty]] + internal method of O with argument Pk.
++ If + kPresent is true, then
++ Let + kValue be the result of calling the [[Get]] internal + method of O with argument Pk.
++ Call + the [[DefineOwnProperty]] internal method of A with + arguments ToString(n), Property Descriptor {[[Value]]: + kValue, [[Writable]]: true, [[Enumerable]]: true, + [[Configurable]]: true}, and false.
++ Increase + k by 1.
++ Increase + n by 1.
++ Return + A.
+
+ The
+ length property of
+ the slice method
+ is 2.
NOTE The
+ slice function is
+ intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the slice
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ The + elements of this array are sorted. The sort is not necessarily + stable (that is, elements that compare equal do not necessarily + remain in their original order). If comparefn + is not undefined, it should be a function that accepts two + arguments x and y + and returns a negative value if x + < y, + zero if x = + y, or a positive + value if x > + y.
++ Let + obj be the result + of calling ToObject passing the this value as the argument.
+
+ Let
+ len be the result
+ of applying Uint32 to the result of calling the [[Get]] internal
+ method of obj with
+ argument "length".
+ If
+ comparefn is not
+ undefined and is not a consistent comparison function for the
+ elements of this array (see below), the behaviour of sort
+ is implementation-defined.
+ Let
+ proto be the value
+ of the [[Prototype]] internal property of obj.
+ If proto is not
+ null and there exists an integer j
+ such that all of the conditions below are satisfied then the
+ behaviour of sort
+ is implementation-defined:
+ 0 ≤ + j < len
++ The + result of calling the [[HasProperty]] internal method of proto + with argument ToString(j) + is true.
+
+ The
+ behaviour of sort
+ is also implementation defined if obj is sparse and any of the following conditions are true:
+ The + [[Extensible]] internal property of obj + is false.
++ Any + array index property of obj + whose name is a nonnegative integer less than len is a data property whose [[Configurable]] attribute is + false.
+
+ The
+ behaviour of sort
+ is also implementation defined if any array index property of obj
+ whose name is a nonnegative integer less than len
+ is an accessor property or is a data property whose [[Writable]]
+ attribute is false.
+ Otherwise, + the following steps are taken.
++ Perform + an implementation-dependent sequence of calls to the [[Get]] , + [[Put]], and [[Delete]] internal methods of obj and to + SortCompare (described below), where the first argument for each + call to [[Get]], [[Put]], or [[Delete]] is a nonnegative integer + less than len and where the arguments for calls to + SortCompare are results of previous calls to the [[Get]] internal + method. The throw argument to the [[Put]] and [[Delete]] internal + methods will be the value true. If obj is not sparse + then [[Delete]] must not be called.
++ Return + obj.
++ The + returned object must have the following two properties.
+
+ There
+ must be some mathematical permutation π
+ of the nonnegative integers less than len,
+ such that for every nonnegative integer j
+ less than len, if
+ property old[j]
+ existed, then new[π(j)]
+ is exactly the same value as old[j],.
+ But if property old[j]
+ did not exist, then new[π(j)]
+ does not exist.
+ Then
+ for all nonnegative integers j
+ and k, each less
+ than len, if
+ SortCompare(j,k)
+ < 0 (see
+ SortCompare below), then π(j)
+ < π(k).
+ Here + the notation old[j] + is used to refer to the hypothetical result of calling the [[Get]] + internal method of obj + with argument j + before this function is executed, and the notation new[j] + to refer to the hypothetical result of calling the [[Get]] internal + method of obj with + argument j after + this function has been executed.
++ A + function comparefn + is a consistent comparison function for a set of values S + if all of the requirements below are met for all values a, + b, and c + (possibly the same value) in the set S: + The notation a <CF b + means comparefn(a,b) < 0; + a =CF b + means comparefn(a,b) = 0 + (of either sign); and a >CF b + means comparefn(a,b) > 0.
++ Calling + comparefn(a,b) + always returns the same value v + when given a specific pair of values a + and b + as its two arguments. Furthermore, Type(v) + is Number, and v + is not NaN. Note that this implies that exactly one of a <CF b, + a =CF b, + and a >CF b + will be true for a given pair of a + and b.
++ Calling + comparefn(a,b) + does not modify the this + object.
++ a =CF a + (reflexivity)
++ If + a =CF b, + then b =CF a + (symmetry)
++ If + a =CF b + and b =CF c, + then a =CF c + (transitivity of =CF)
++ If + a <CF b + and b <CF c, + then a <CF c + (transitivity of <CF)
++ If + a >CF b + and b >CF c, + then a >CF c + (transitivity of >CF)
+NOTE The + above conditions are necessary and sufficient to ensure that + comparefn divides + the set S into + equivalence classes and that these equivalence classes are totally + ordered.
++ When + the SortCompare abstract operation is called with two arguments j + and k, the + following steps are taken:
++ Let + jString be ToString(j).
++ Let + kString be ToString(k).
++ Let + hasj be the result of calling the [[HasProperty]] internal + method of obj with argument jString.
++ Let + hask be the result of calling the [[HasProperty]] internal + method of obj with argument kString.
++ If + hasj and hask are both false, then + return +0.
++ If + hasj is false, then return 1.
++ If + hask is false, then return –1.
++ Let + x be the result of calling the [[Get]] internal method of + obj with argument jString.
++ Let + y be the result of calling the [[Get]] internal method of + obj with argument kString.
++ If + x and y are both undefined, return +0.
++ If + x is undefined, return 1.
++ If + y is undefined, return −1.
++ If + the argument comparefn is not undefined, then
++ If + IsCallable(comparefn) is false, throw a TypeError + exception.
++ Return + the result of calling the [[Call]] internal method of comparefn + passing undefined as the this value and with + arguments x and y.
++ Let + xString be ToString(x).
++ Let + yString be ToString(y).
++ If + xString < yString, return −1.
++ If + xString > yString, return 1.
++ Return + +0.
+NOTE 1 Because non-existent property values always compare greater than + undefined property values, and undefined always + compares greater than any other value, undefined property values + always sort to the end of the result, followed by non-existent + property values.
+NOTE 2 The sort
+ function is intentionally generic; it does not require that its this
+ value be an Array object. Therefore, it can be transferred to other
+ kinds of objects for use as a method. Whether the sort
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ When
+ the splice method
+ is called with two or more arguments start,
+ deleteCount and
+ (optionally) item1,
+ item2, etc., the
+ deleteCount
+ elements of the array starting at array index start
+ are replaced by the arguments item1,
+ item2, etc. An
+ Array object containing the deleted elements (if any) is returned.
+ The following steps are taken:
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ A be a new array created as if by the expression new
+ Array()where Array
+ is the standard built-in constructor with that name.
+ Let
+ lenVal be the result of calling the [[Get]] internal method
+ of O with argument "length".
+ Let + len be ToUint32(lenVal).
++ Let + relativeStart be ToInteger(start).
++ If + relativeStart is negative, let actualStart be + max((len + relativeStart),0); else let actualStart + be min(relativeStart, len).
++ Let + actualDeleteCount be min(max(ToInteger(deleteCount),0),len – actualStart).
++ Let + k be 0.
++ Repeat, + while k < actualDeleteCount
++ Let + from be ToString(actualStart+k).
++ Let + fromPresent be the result of calling the [[HasProperty]] + internal method of O with argument from.
++ If + fromPresent is true, then
++ Let + fromValue be the result of calling the [[Get]] internal + method of O with argument from.
++ Call + the [[DefineOwnProperty]] internal method of A with + arguments ToString(k), Property Descriptor {[[Value]]: + fromValue, [[Writable]]: true, [[Enumerable]]: + true, [[Configurable]]: true}, and false.
++ Increment + k by 1.
++ Let + items be an internal List whose elements are, in left to + right order, the portion of the actual argument list starting with + item1. The list will be empty if no such items are present.
++ Let + itemCount be the number of elements in items.
++ If + itemCount < actualDeleteCount, then
++ Let + k be actualStart.
++ Repeat, + while k < (len – actualDeleteCount)
++ Let + from be ToString(k+actualDeleteCount).
++ Let + to be ToString(k+itemCount).
++ Let + fromPresent be the result of calling the [[HasProperty]] + internal method of O with argument from.
++ If + fromPresent is true, then
++ Let + fromValue be the result of calling the [[Get]] internal + method of O with argument from.
++ Call + the [[Put]] internal method of O with arguments to, + fromValue, and true.
++ Else, + fromPresent is false
++ Call + the [[Delete]] internal method of O with arguments to + and true.
++ Increase + k by 1.
++ Let + k be len.
++ Repeat, + while k > (len – actualDeleteCount +itemCount) +
++ Call + the [[Delete]] internal method of O with arguments + ToString(k–1) and true.
++ Decrease + k by 1.
++ Else + if itemCount > actualDeleteCount, then
++ Let + k be (len – actualDeleteCount).
++ Repeat, + while k > actualStart
++ Let + from be ToString(k + actualDeleteCount – + 1).
++ Let + to be ToString(k + itemCount – 1)
++ Let + fromPresent be the result of calling the [[HasProperty]] + internal method of O with argument from.
++ If + fromPresent is true, then
++ Let + fromValue be the result of calling the [[Get]] internal + method of O with argument from.
++ Call + the [[Put]] internal method of O with arguments to, + fromValue, and true.
++ Else, + fromPresent is false
++ Call + the [[Delete]] internal method of O with argument to + and true.
++ Decrease + k by 1.
++ Let + k be actualStart.
++ Repeat, + while items is not empty
++ Remove + the first element from items and let E be the value + of that element.
++ Call + the [[Put]] internal method of O with arguments + ToString(k), E, and true.
++ Increase + k by 1.
+
+ Call
+ the [[Put]] internal method of O with arguments "length",
+ (len – actualDeleteCount + itemCount), and
+ true.
+ Return + A.
+
+ The
+ length property of
+ the splice method
+ is 2.
NOTE The
+ splice function is
+ intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the splice
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ The + arguments are prepended to the start of the array, such that their + order within the array is the same as the order in which they appear + in the argument list.
+
+ When
+ the unshift method
+ is called with zero or more arguments item1,item2, etc., the following steps are taken:
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenVal be the result of calling the [[Get]] internal method
+ of O with argument "length".
+ Let + len be ToUint32(lenVal).
++ Let + argCount be the number of actual arguments.
++ Let + k be len.
++ Repeat, + while k > 0, +
++ Let + from be ToString(k–1).
++ Let + to be ToString(k+argCount –1).
++ Let + fromPresent be the result of calling the [[HasProperty]] + internal method of O with argument from.
++ If + fromPresent is true, then
++ Let + fromValue be the result of calling the [[Get]] internal + method of O with argument from.
++ Call + the [[Put]] internal method of O with arguments to, + fromValue, and true.
++ Else, + fromPresent is false
++ Call + the [[Delete]] internal method of O with arguments to, + and true.
++ Decrease + k by 1.
++ Let + j be 0.
++ Let + items be an internal List whose elements are, in left to + right order, the arguments that were passed to this function + invocation.
++ Repeat, + while items is not empty
++ Remove + the first element from items and let E be the value + of that element.
++ Call + the [[Put]] internal method of O with arguments + ToString(j), E, and true.
++ Increase + j by 1.
+
+ Call
+ the [[Put]] internal method of O with arguments "length",
+ len+argCount, and true.
+ Return + len+argCount.
+
+ The
+ length property of
+ the unshift method
+ is 1.
NOTE The
+ unshift function
+ is intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the unshift
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ indexOf
+ compares searchElement
+ to the elements of the array, in ascending order, using the internal
+ Strict Equality Comparison Algorithm (11.9.6), and if found at one
+ or more positions, returns the index of the first such position;
+ otherwise, -1 is returned.
+ The + optional second argument fromIndex + defaults to 0 (i.e. the whole array is searched). If it is greater + than or equal to the length of the array, -1 is returned, i.e. the + array will not be searched. If it is negative, it is used as the + offset from the end of the array to compute fromIndex. + If the computed index is less than 0, the whole array will be + searched.
+
+ When
+ the indexOf method
+ is called with one or two arguments, the following steps are taken:
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenValue be the result of calling the [[Get]] internal
+ method of O with the argument "length".
+ Let + len be ToUint32(lenValue).
++ If + len is 0, return -1.
++ If + argument fromIndex was passed let n be + ToInteger(fromIndex); else let n be 0.
++ If + n ≥ len, return -1.
++ If + n ≥ 0, then +
++ Let + k be n.
++ Else, + n<0
++ Let + k be len - abs(n).
++ If + k is less than 0, then let k be 0.
++ Repeat, + while k<len
++ Let + kPresent be the result of calling the [[HasProperty]] + internal method of O with argument ToString(k).
++ If + kPresent is true, then
++ Let + elementK be the result of calling the [[Get]] internal + method of O with the argument ToString(k).
++ Let + same be the result of applying the Strict Equality + Comparison Algorithm to searchElement and elementK.
++ If + same is true, return k.
++ Increase + k by 1.
++ Return + -1.
+
+ The
+ length property of
+ the indexOf method
+ is 1.
NOTE The
+ indexOf function
+ is intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the indexOf
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ lastIndexOf
+ compares searchElement
+ to the elements of the array in descending order using the internal
+ Strict Equality Comparison Algorithm (11.9.6), and if found at one
+ or more positions, returns the index of the last such position;
+ otherwise, -1 is returned.
+ The + optional second argument fromIndex + defaults to the array's length minus one (i.e. the whole array is searched). + If it is greater than or equal to the length of the array, the whole + array will be searched. If it is negative, it is used as the offset + from the end of the array to compute fromIndex. + If the computed index is less than 0, -1 is returned.
+
+ When
+ the lastIndexOf
+ method is called with one or two arguments, the following steps are
+ taken:
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenValue be the result of calling the [[Get]] internal
+ method of O with the argument "length".
+ Let + len be ToUint32(lenValue).
++ If + len is 0, return -1.
++ If + argument fromIndex was passed let n be + ToInteger(fromIndex); else let n be len.
++ If + n ≥ 0, then let k be min(n, len + – 1).
++ Else, + n < 0
++ Let + k be len - abs(n).
++ Repeat, + while k≥ 0
++ Let + kPresent be the result of calling the [[HasProperty]] + internal method of O with argument ToString(k).
++ If + kPresent is true, then
++ Let + elementK be the result of calling the [[Get]] internal + method of O with the argument ToString(k).
++ Let + same be the result of applying the Strict Equality + Comparision Algorithm to searchElement and elementK.
++ If + same is true, return k.
++ Decrease + k by 1.
++ Return + -1.
+
+ The
+ length property of
+ the lastIndexOf
+ method is 1.
NOTE The
+ lastIndexOf
+ function is intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the lastIndexOf
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ callbackfn should be a function that accepts three arguments and
+ returns a value that is coercible to the Boolean value true
+ or false. every
+ calls callbackfn
+ once for each element present in the array, in ascending order,
+ until it finds one where callbackfn
+ returns false. If such an element is found, every
+ immediately returns false. Otherwise, if callbackfn
+ returned true for all elements, every
+ will return true. callbackfn
+ is called only for elements of the array which actually exist; it is
+ not called for missing elements of the array.
+ If a + thisArg parameter + is provided, it will be used as the this value for each + invocation of callbackfn. + If it is not provided, undefined is used instead.
++ callbackfn + is called with three arguments: the value of the element, the index + of the element, and the object being traversed.
+
+ every
+ does not directly mutate the object on which it is called but the
+ object may be mutated by the calls to callbackfn.
+
+
+ The
+ range of elements processed by every
+ is set before the first call to callbackfn.
+ Elements which are appended to the array after the call to every
+ begins will not be visited by callbackfn.
+ If existing elements of the array are changed, their value as passed
+ to callbackfn will
+ be the value at the time every
+ visits them; elements that are deleted after the call to every
+ begins and before being visited are not visited. every
+ acts like the "for all" quantifier in mathematics. In
+ particular, for an empty array, it returns true.
+ When
+ the every method
+ is called with one or two arguments, the following steps are taken:
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenValue be the result of calling the [[Get]] internal
+ method of O with the argument "length".
+ Let + len be ToUint32(lenValue).
++ If + IsCallable(callbackfn) is false, throw a TypeError + exception.
++ If + thisArg was supplied, let T be thisArg; else + let T be undefined.
++ Let + k be 0.
++ Repeat, + while k < len
++ Let + Pk be ToString(k).
++ Let + kPresent be the result of calling the [[HasProperty]] + internal method of O with argument Pk.
++ If + kPresent is true, then
++ Let + kValue be the result of calling the [[Get]] internal + method of O with argument Pk.
++ Let + testResult be the result of calling the [[Call]] internal + method of callbackfn with T as the this + value and argument list containing kValue, k, and + O.
++ If + ToBoolean(testResult) is false, return false.
++ Increase + k by 1.
++ Return + true.
+
+ The
+ length property of
+ the every method
+ is 1.
NOTE The
+ every function is
+ intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the every
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ callbackfn should be a function that accepts three arguments and
+ returns a value that is coercible to the Boolean value true
+ or false. some
+ calls callbackfn
+ once for each element present in the array, in ascending order,
+ until it finds one where callbackfn
+ returns true. If such an element is found, some
+ immediately returns true. Otherwise, some
+ returns false. callbackfn
+ is called only for elements of the array which actually exist; it is
+ not called for missing elements of the array.
+ If a + thisArg parameter + is provided, it will be used as the this value for each + invocation of callbackfn. + If it is not provided, undefined is used instead.
++ callbackfn + is called with three arguments: the value of the element, the index + of the element, and the object being traversed.
+
+ some
+ does not directly mutate the object on which it is called but the
+ object may be mutated by the calls to callbackfn.
+ The
+ range of elements processed by some
+ is set before the first call to callbackfn.
+ Elements that are appended to the array after the call to some
+ begins will not be visited by callbackfn.
+ If existing elements of the array are changed, their value as passed
+ to callbackfn will
+ be the value at the time that some
+ visits them; elements that are deleted after the call to some
+ begins and before being visited are not visited.
+ some acts like the "exists" quantifier in
+ mathematics. In particular, for an empty array, it returns false.
+ When
+ the some method is
+ called with one or two arguments, the following steps are taken:
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenValue be the result of calling the [[Get]] internal
+ method of O with the argument "length".
+ Let + len be ToUint32(lenValue).
++ If + IsCallable(callbackfn) is false, throw a TypeError + exception.
++ If + thisArg was supplied, let T be thisArg; else + let T be undefined.
++ Let + k be 0.
++ Repeat, + while k < len
++ Let + Pk be ToString(k).
++ Let + kPresent be the result of calling the [[HasProperty]] + internal method of O with argument Pk.
++ If + kPresent is true, then
++ Let + kValue be the result of calling the [[Get]] internal + method of O with argument Pk.
++ Let + testResult be the result of calling the [[Call]] internal + method of callbackfn with T as the this + value and argument list containing kValue, k, and + O.
++ If + ToBoolean(testResult) is true, return true.
++ Increase + k by 1.
++ Return + false.
+
+ The
+ length property of
+ the some method is
+ 1.
NOTE The
+ some function
+ is intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the some
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ callbackfn should be a function that accepts three arguments.
+ forEach calls
+ callbackfn once
+ for each element present in the array, in ascending order.
+ callbackfn is
+ called only for elements of the array which actually exist; it is
+ not called for missing elements of the array.
+ If a + thisArg parameter + is provided, it will be used as the this value for each + invocation of callbackfn. + If it is not provided, undefined is used instead.
++ callbackfn + is called with three arguments: the value of the element, the index + of the element, and the object being traversed. +
+
+ forEach
+ does not directly mutate the object on which it is called but the
+ object may be mutated by the calls to callbackfn.
+
+
+ The
+ range of elements processed by forEach
+ is set before the first call to callbackfn.
+ Elements which are appended to the array after the call to forEach
+ begins will not be visited by callbackfn.
+ If existing elements of the array are changed, their value as passed
+ to callback will be the value at the time forEach
+ visits them; elements that are deleted after the call to forEach
+ begins and before being visited are not visited.
+ When
+ the forEach method
+ is called with one or two arguments, the following steps are taken:
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenValue be the result of calling the [[Get]] internal
+ method of O with the argument "length".
+ Let + len be ToUint32(lenValue).
++ If + IsCallable(callbackfn) is false, throw a TypeError + exception.
++ If + thisArg was supplied, let T be thisArg; else + let T be undefined.
++ Let + k be 0.
++ Repeat, + while k < len
++ Let + Pk be ToString(k).
++ Let + kPresent be the result of calling the [[HasProperty]] + internal method of O with argument Pk.
++ If + kPresent is true, then
++ Let + kValue be the result of calling the [[Get]] internal + method of O with argument Pk.
++ Call + the [[Call]] internal method of callbackfn with T + as the this value and argument list containing kValue, + k, and O.
++ Increase + k by 1.
++ Return undefined.
+
+ The
+ length property of
+ the forEach method
+ is 1.
NOTE The
+ forEach
+ function is intentionally generic; it does not require that its
+ this value be an Array object. Therefore it can be
+ transferred to other kinds of objects for use as a method. Whether
+ the forEach
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ callbackfn should be a function that accepts three arguments. map
+ calls callbackfn
+ once for each element in the array, in ascending order, and
+ constructs a new Array from the results. callbackfn
+ is called only for elements of the array which actually exist; it is
+ not called for missing elements of the array.
+ If a + thisArg parameter + is provided, it will be used as the this value for + each invocation of callbackfn. + If it is not provided, undefined is used instead.
++ callbackfn + is called with three arguments: the value of the element, the index + of the element, and the object being traversed.
+
+ map
+ does not directly mutate the object on which it is called but the
+ object may be mutated by the calls to callbackfn.
+ The
+ range of elements processed by map
+ is set before the first call to callbackfn.
+ Elements which are appended to the array after the call to map
+ begins will not be visited by callbackfn.
+ If existing elements of the array are changed, their value as passed
+ to callbackfn will
+ be the value at the time map
+ visits them; elements that are deleted after the call to map
+ begins and before being visited are not visited.
+ When
+ the map method is
+ called with one or two arguments, the following steps are taken:
+
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenValue be the result of calling the [[Get]] internal
+ method of O with the argument "length".
+ Let + len be ToUint32(lenValue).
++ If + IsCallable(callbackfn) is false, throw a TypeError + exception.
++ If + thisArg was supplied, let T be thisArg; else + let T be undefined.
+
+ Let
+ A be a new array created as if by the expression new
+ Array( len)
+ where Array is
+ the standard built-in constructor with that name and len is
+ the value of len.
+ Let + k be 0.
++ Repeat, + while k < len
++ Let + Pk be ToString(k).
++ Let + kPresent be the result of calling the [[HasProperty]] + internal method of O with argument Pk.
++ If + kPresent is true, then
++ Let + kValue be the result of calling the [[Get]] internal + method of O with argument Pk.
++ Let + mappedValue be the result of calling the [[Call]] internal + method of callbackfn with T as the this + value and argument list containing kValue, k, and + O.
++ Call + the [[DefineOwnProperty]] internal method of A with + arguments Pk, Property Descriptor {[[Value]]: mappedValue, + [[Writable]]: true, [[Enumerable]]: true, + [[Configurable]]: true}, and false.
++ Increase + k by 1.
++ Return + A.
+
+ The
+ length property of
+ the map method is
+ 1.
NOTE The
+ map function
+ is intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the map
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ callbackfn should be a function that accepts three arguments and
+ returns a value that is coercible to the Boolean value true
+ or false. filter
+ calls callbackfn
+ once for each element in the array, in ascending order, and
+ constructs a new array of all the values for which callbackfn
+ returns true. callbackfn
+ is called only for elements of the array which actually exist; it is
+ not called for missing elements of the array.
+ If a + thisArg parameter + is provided, it will be used as the this value for each + invocation of callbackfn. + If it is not provided, undefined is used instead.
++ callbackfn + is called with three arguments: the value of the element, the index + of the element, and the object being traversed.
+
+ filter
+ does not directly mutate the object on which it is called but the
+ object may be mutated by the calls to callbackfn.
+ The
+ range of elements processed by filter
+ is set before the first call to callbackfn.
+ Elements which are appended to the array after the call to filter
+ begins will not be visited by callbackfn.
+ If existing elements of the array are changed their value as passed
+ to callbackfn will
+ be the value at the time filter
+ visits them; elements that are deleted after the call to filter
+ begins and before being visited are not visited.
+ When
+ the filter method
+ is called with one or two arguments, the following steps are taken:
+
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenValue be the result of calling the [[Get]] internal
+ method of O with the argument "length".
+ Let + len be ToUint32(lenValue).
++ If + IsCallable(callbackfn) is false, throw a TypeError + exception.
++ If + thisArg was supplied, let T be thisArg; else + let T be undefined.
+
+ Let
+ A be a new array created as if by the expression new
+ Array() where Array
+ is the standard built-in constructor with that name.
+ Let + k be 0.
++ Let + to be 0.
++ Repeat, + while k < len
++ Let + Pk be ToString(k).
++ Let + kPresent be the result of calling the [[HasProperty]] + internal method of O with argument Pk.
++ If + kPresent is true, then
++ Let + kValue be the result of calling the [[Get]] internal + method of O with argument Pk.
++ Let + selected be the result of calling the [[Call]] internal + method of callbackfn with T as the this + value and argument list containing kValue, k, and + O.
++ If + ToBoolean(selected) is true, then
++ Call + the [[DefineOwnProperty]] internal method of A with + arguments ToString(to), Property Descriptor {[[Value]]: + kValue, [[Writable]]: true, [[Enumerable]]: true, + [[Configurable]]: true}, and false.
++ Increase + to by 1.
++ Increase + k by 1.
++ Return + A.
+
+ The
+ length property of
+ the filter method
+ is 1.
NOTE The
+ filter function
+ is intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the filter
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ callbackfn should be a function that takes four arguments. reduce
+ calls the callback, as a function, once for each element present in
+ the array, in ascending order.
+ callbackfn is called with four arguments: the previousValue
+ (or value from the previous call to callbackfn),
+ the currentValue (value of the current element), the
+ currentIndex, and the object being traversed. The first time
+ that callback is called, the previousValue and currentValue
+ can be one of two values. If an initialValue was provided in the call to reduce,
+ then previousValue will be equal to initialValue and currentValue will be equal to the first value
+ in the array. If no initialValue was provided, then previousValue will be equal to
+ the first value in the array and currentValue will be equal
+ to the second. It is a TypeError if the array contains no
+ elements and initialValue
+ is not provided.
+ reduce
+ does not directly mutate the object on which it is called but the
+ object may be mutated by the calls to callbackfn.
+ The
+ range of elements processed by reduce
+ is set before the first call to callbackfn.
+ Elements that are appended to the array after the call to reduce
+ begins will not be visited by callbackfn.
+ If existing elements of the array are changed, their value as passed
+ to callbackfn will
+ be the value at the time reduce
+ visits them; elements that are deleted after the call to reduce
+ begins and before being visited are not visited.
+ When
+ the reduce method
+ is called with one or two arguments, the following steps are taken:
+
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenValue be the result of calling the [[Get]] internal
+ method of O with the argument "length".
+ Let + len be ToUint32(lenValue ).
++ If + IsCallable(callbackfn) is false, throw a TypeError + exception.
++ If + len is 0 and initialValue is not present, throw a TypeError + exception.
++ Let + k be 0.
++ If + initialValue is present, then
++ Set + accumulator to initialValue.
++ Else, + initialValue is not present
++ Let + kPresent be false.
++ Repeat, + while kPresent is false and k < len
++ Let + Pk be ToString(k).
++ Let + kPresent be the result of calling the [[HasProperty]] + internal method of O with argument Pk.
++ If + kPresent is true, then
++ Let + accumulator be the result of calling the [[Get]] internal + method of O with argument Pk.
++ Increase + k by 1.
++ If + kPresent is false, throw a TypeError + exception.
++ Repeat, + while k < len
++ Let + Pk be ToString(k).
++ Let + kPresent be the result of calling the [[HasProperty]] + internal method of O with argument Pk.
++ If + kPresent is true, then
++ Let + kValue be the result of calling the [[Get]] internal + method of O with argument Pk.
++ Let + accumulator be the result of calling the [[Call]] internal + method of callbackfn with undefined as the this + value and argument list containing accumulator, kValue, + k, and O.
++ Increase + k by 1.
++ Return + accumulator.
+
+ The
+ length property of
+ the reduce method
+ is 1.
NOTE The
+ reduce function
+ is intentionally generic; it does not require that its this
+ value be an Array object. Therefore it can be transferred to other
+ kinds of objects for use as a method. Whether the reduce
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ callbackfn should be a function that takes four arguments.
+ reduceRight calls
+ the callback, as a function, once for each element present in the array, in descending order.
+ callbackfn is called with four arguments: the previousValue (or
+ value from the previous call to callbackfn),
+ the currentValue (value of the current element), the currentIndex,
+ and the object being traversed. The first time the function is
+ called, the previousValue and currentValue can be one of two values.
+ If an initialValue was
+ provided in the call to reduceRight,
+ then previousValue will be equal to initialValue
+ and currentValue will be equal to the last value in the array. If no
+ initialValue was
+ provided, then previousValue will be equal to the last value in the
+ array and currentValue will be equal to the second-to-last value. It
+ is a TypeError if the array contains no
+ elements and
+ initialValue is
+ not provided.
+ reduceRight
+ does not directly mutate the object on which it is called
+ but the object may be mutated by the calls to callbackfn.
+ The
+ range of elements processed by reduceRight is set before the first call to callbackfn.
+ Elements that are appended to the array after the call to
+ reduceRight begins
+ will not be visited by callbackfn.
+ If existing elements of the array are changed by callbackfn,
+ their value as passed to callbackfn will be the value at the time reduceRight
+ visits them; elements that are deleted after the call to
+ reduceRight begins and
+ before being visited are not visited.
+ When
+ the reduceRight method
+ is called with one or two arguments, the following steps are taken:
+
+ Let + O be the result of calling ToObject passing the this + value as the argument.
+
+ Let
+ lenValue be the result of calling the [[Get]] internal
+ method of O with the argument "length".
+ Let + len be ToUint32(lenValue ).
++ If + IsCallable(callbackfn) is false, throw a TypeError + exception.
++ If + len is 0 and initialValue is not present, throw a TypeError + exception.
++ Let + k be len-1.
++ If + initialValue is present, then
++ Set + accumulator to initialValue.
++ Else, + initialValue is not present
++ Let + kPresent be false.
++ Repeat, + while kPresent is false and k ≥ 0
++ Let + Pk be ToString(k).
++ Let + kPresent be the result of calling the [[HasProperty]] + internal method of O with argument Pk.
++ If + kPresent is true, then
++ Let + accumulator be the result of calling the [[Get]] internal + method of O with argument Pk.
++ Decrease + k by 1.
++ If + kPresent is false, throw a TypeError + exception.
++ Repeat, + while k ≥ 0
++ Let + Pk be ToString(k).
++ Let + kPresent be the result of calling the [[HasProperty]] + internal method of O with argument Pk.
++ If + kPresent is true, then
++ Let + kValue be the result of calling the [[Get]] internal + method of O with argument Pk.
++ Let + accumulator be the result of calling the [[Call]] internal + method of callbackfn with undefined as the this + value and argument list containing accumulator, kValue, + k, and O.
++ Decrease + k by 1.
++ Return + accumulator.
+
+ The
+ length property of
+ the reduceRight
+ method is 1.
NOTE The
+ reduceRight function
+ is intentionally generic; it does not require that its this value be
+ an Array object. Therefore it can be transferred to other kinds of
+ objects for use as a method. Whether the reduceRight
+ function can be applied successfully to a host object is
+ implementation-dependent.
+ Array
+ instances inherit properties from the Array prototype object and
+ their [[Class]] internal property value is "Array".
+ Array instances also have the following properties.
+ Array + objects use a variation of the [[DefineOwnProperty]] internal method + used for other native ECMAScript objects (8.12.9).
++ Assume + A is an Array + object, Desc is a + Property Descriptor, and Throw is a Boolean flag.
++ In + the following algorithm, the term “Reject” + means “If Throw is true, + then throw a TypeError + exception, otherwise return false.”
++ When + the [[DefineOwnProperty]] internal method of A + is called with property P, + Property Descriptor Desc, + and Boolean flag Throw, + the following steps are taken:
+
+ Let
+ oldLenDesc be the result of calling the [[GetOwnProperty]]
+ internal method of A passing "length"
+ as the argument. The result will never be undefined or an
+ accessor descriptor because Array objects are created with a length
+ data property that cannot be deleted or reconfigured.
+ Let + oldLen be oldLenDesc.[[Value]].
+
+ If
+ P is "length",
+ then
+ If + the [[Value]] field of Desc is absent, then
+
+ Return
+ the result of calling the default [[DefineOwnProperty]] internal
+ method (8.12.9) on A passing "length",
+ Desc, and Throw as arguments.
+ Let + newLenDesc be a copy of Desc.
++ Let + newLen be ToUint32(Desc.[[Value]]).
++ If + newLen is not equal to ToNumber( Desc.[[Value]]), + throw a RangeError exception.
++ Set + newLenDesc.[[Value] to newLen.
++ If + newLen ≥oldLen, then
+
+ Return
+ the result of calling the default [[DefineOwnProperty]] internal
+ method (8.12.9) on A passing "length",
+ newLenDesc, and Throw as arguments.
+ Reject + if oldLenDesc.[[Writable]] is false.
++ If + newLenDesc.[[Writable]] is absent or has the value true, + let newWritable be true.
++ Else,
++ Need + to defer setting the [[Writable]] attribute to false in + case any elements cannot be deleted.
++ Let + newWritable be false.
++ Set + newLenDesc.[[Writable] to true.
+
+ Let
+ succeeded be the result of calling the default
+ [[DefineOwnProperty]] internal method (8.12.9) on A passing
+ "length",
+ newLenDesc, and Throw as arguments.
+ If + succeeded is false, return false..
++ While + newLen < oldLen repeat,
++ Set + oldLen to oldLen – 1.
++ Let + deleteSucceeded + be the result of calling the [[Delete]] + internal method of A passing ToString(oldLen) and + false as arguments.
++ If + deleteSucceeded + is false, then
++ If + newWritable is false, then
+
+ Call
+ the default [[DefineOwnProperty]] internal method (8.12.9) on A
+ passing "length",
+ Property Descriptor{[[Writable]]: false}, and false
+ as arguments. This call will always return true.
+ Return + true.
++ Else + if P is an array index (15.4), then
++ Let + index be ToUint32(P).
++ Reject + if index ≥ oldLen and oldLenDesc.[[Writable]] + is false.
++ Let + succeeded be the result of calling the default + [[DefineOwnProperty]] internal method (8.12.9) on A passing + P, Desc, and false as arguments.
++ Reject + if succeeded is false.
++ If + index ≥ oldLen
++ Set + oldLenDesc.[[Value]] to index + 1.
+
+ Call
+ the default [[DefineOwnProperty]] internal method (8.12.9) on A
+ passing "length",
+ oldLenDesc, and false as arguments. This call will
+ always return true.
+ Return + true.
++ Return + the result of calling the default [[DefineOwnProperty]] internal + method (8.12.9) on A passing P, Desc, and + Throw as arguments.
+
+ The
+ length property of
+ this Array object is a data property whose value is always
+ numerically greater than the name of every deletable property whose
+ name is an array index.
+ The
+ length property
+ initially has the attributes {
+ [[Writable]]: true,
+ [[Enumerable]]: false,
+ [[Configurable]]: false
+ }.
NOTE Attempting + to set the length property of an Array object to a value that is + numerically less than or equal to the largest numeric property name + of an existing array indexed non-deletable property of the array + will result in the length being set to a numeric value that is one + greater than that largest numeric property name. See 15.4.5.1.
+
+ When
+ String is called
+ as a function rather than as a constructor, it performs a type
+ conversion.
+ Returns
+ a String value (not a String object) computed by ToString(value).
+ If value is not
+ supplied, the empty String ""
+ is returned.
+ When
+ String is called
+ as part of a new
+ expression, it is a constructor: it initialises the newly created
+ object.
+ The
+ [[Prototype]] internal
+ property of the newly constructed object is set to the standard
+ built-in String prototype object that is the initial value of
+ String.prototype
+ (15.5.3.1).
+ The
+ [[Class]] internal
+ property of the newly constructed object is set to "String".
+ The + [[Extensible]] internal + property of the newly constructed object is set to true.
++ The + [[PrimitiveValue]] internal + property of the newly constructed object is set to ToString(value), + or to the empty String if value + is not supplied.
++ The + value of the [[Prototype]] internal property of the String + constructor is the standard built-in Function prototype object + (15.3.4).
+
+ Besides
+ the internal properties and the length
+ property (whose value is 1), the String constructor has the
+ following properties:
+ The
+ initial value of String.prototype
+ is the standard built-in String prototype object (15.5.4).
+ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
++ Returns + a String value containing as many characters as the number of + arguments. Each argument specifies one character of the resulting + String, with the first argument specifying the first character, and + so on, from left to right. An argument is converted to a character + by applying the operation ToUint16 (9.7) and regarding the resulting + 16-bit integer as the code unit value of a character. If no + arguments are supplied, the result is the empty String.
+
+ The
+ length property of
+ the fromCharCode
+ function is 1.
+ The
+ String prototype object is itself a String object (its [[Class]] is
+ "String")
+ whose value is an empty String.
+ The + value of the [[Prototype]] internal property of the String prototype + object is the standard built-in Object prototype object (15.2.4).
+
+ The
+ initial value of String.prototype.constructor
+ is the built-in String
+ constructor.
+ Returns
+ this String value. (Note that, for a String object, the toString
+ method happens to return the same thing as the valueOf
+ method.)
+ The
+ toString function
+ is not generic; it throws a TypeError exception if its this
+ value is not a String or a String object. Therefore, it cannot be
+ transferred to other kinds of objects for use as a method.
+ Returns + this String value.
+
+ The
+ valueOf function
+ is not generic; it throws a TypeError exception if its this
+ value is not a String or String object. Therefore, it cannot be
+ transferred to other kinds of objects for use as a method.
+ Returns + a String containing the character at position pos + in the String resulting from converting this object to a String. If + there is no character at that position, the result is the empty + String. The result is a String value, not a String object.
+
+ If
+ pos is a value of
+ Number type that is an integer, then the result of x.charAt( pos)
+ is equal to the result of x.substring( pos,
+ pos+1).
+ When
+ the charAt method
+ is called with one argument pos,
+ the following steps are taken:
+ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + S be the result of calling ToString, giving it the this + value as its argument.
++ Let + position be ToInteger(pos).
++ Let + size be the number of characters in S.
++ If + position < 0 or position ≥ size, return + the empty String.
++ Return + a String of length 1, containing one character from S, + namely the character at position position, where the first + (leftmost) character in S is considered to be at position 0, + the next one at position 1, and so on.
+NOTE The
+ charAt function is
+ intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ Returns + a Number (a nonnegative integer less than 216) + representing the code unit value of the character at position pos + in the String resulting from converting this object to a String. If + there is no character at that position, the result is NaN.
+
+ When
+ the charCodeAt
+ method is called with one argument pos,
+ the following steps are taken:
+ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + S be the result of calling ToString, giving it the this + value as its argument.
++ Let + position be ToInteger(pos).
++ Let + size be the number of characters in S.
++ If + position < 0 or position ≥ size, return + NaN.
++ Return + a value of Number type, whose value is the code unit value of the + character at position position in the String S, where + the first (leftmost) character in S is considered to be at + position 0, the next one at position 1, and so on.
+NOTE The
+ charCodeAt
+ function is intentionally generic; it does not require that its this
+ value be a String object. Therefore it can be transferred to other
+ kinds of objects for use as a method.
+ When
+ the concat method
+ is called with zero or more arguments string1,
+ string2, etc., it
+ returns a String consisting of the characters of this object
+ (converted to a String) followed by the characters of each of
+ string1, string2,
+ etc. (where each argument is converted to a String). The result is a
+ String value, not a String object. The following steps are taken:
+ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + S be the result of calling ToString, giving it the this + value as its argument.
++ Let + args be an internal list that is a copy of the argument list + passed to this function.
++ Let + R be S.
++ Repeat, + while args is not empty
++ Remove + the first element from args and let next be the + value of that element.
++ Let + R be the String value consisting of the characters in the + previous value of R followed by the characters of + ToString(next).
++ Return + R.
+
+ The
+ length property of
+ the concat method
+ is 1.
NOTE The
+ concat function is
+ intentionally generic; it does not require that its this
+ value be a String object. Therefore it can be transferred to other
+ kinds of objects for use as a method.
+ If
+ searchString
+ appears as a substring of the result of converting this object to a
+ String, at one or more positions that are greater than or equal to
+ position, then the
+ index of the smallest such position is returned; otherwise, -1
+ is returned. If position
+ is undefined, 0 is assumed, so as to search all of the
+ String.
+ The
+ indexOf method
+ takes two arguments, searchString and position,
+ and performs the following steps:
+ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + S be the result of calling ToString, giving it the this + value as its argument.
++ Let + searchStr be ToString(searchString).
+
+ Let
+ pos be ToInteger(position). (If position is
+ undefined, this step produces the value 0).
+ Let + len be the number of characters in S.
++ Let + start be min(max(pos, 0), len).
++ Let + searchLen be the number of characters in searchStr.
+
+ Return
+ the smallest possible integer k not smaller than start
+ such that k+ searchLen is not greater than len,
+ and for all nonnegative integers j less than searchLen,
+ the character at position k+j of S is the same
+ as the character at position j of searchStr); but if
+ there is no such integer k, then return the value -1.
+ The
+ length property of
+ the indexOf method
+ is 1.
NOTE The
+ indexOf function
+ is intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ If
+ searchString
+ appears as a substring of the result of converting this object to a
+ String at one or more positions that are smaller than or equal to
+ position, then the
+ index of the greatest such position is returned; otherwise, -1
+ is returned. If position
+ is undefined, the length of the String value is assumed, so
+ as to search all of the String.
+ The
+ lastIndexOf method
+ takes two arguments, searchString and position,
+ and performs the following steps:
+ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + S be the result of calling ToString, giving it the this + value as its argument.
++ Let + searchStr be ToString(searchString).
++ Let + numPos be ToNumber(position). (If position is + undefined, this step produces the value NaN).
++ If + numPos is NaN, let pos be +∞; + otherwise, let pos be ToInteger(numPos).
++ Let + len be the number of characters in S.
++ Let + start min(max(pos, 0), len).
++ Let + searchLen be the number of characters in searchStr.
+
+ Return
+ the largest possible nonnegative integer k not larger than
+ start such that k+ searchLen is not greater
+ than len, and for all nonnegative integers j less
+ than searchLen, the character at position k+j
+ of S is the same as the character at position j of
+ searchStr; but if there is no such integer k, then
+ return the value -1.
+ The
+ length property of
+ the lastIndexOf
+ method is 1.
NOTE The
+ lastIndexOf
+ function is intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ When
+ the localeCompare
+ method is called with one argument that,
+ it returns a Number other than NaN that represents the result
+ of a locale-sensitive String comparison of the this value (converted
+ to a String) with that
+ (converted to a String). The two Strings are S
+ and That. The two
+ Strings are compared in an implementation-defined fashion. The
+ result is intended to order String values in the sort order
+ specified by the system default locale, and will be negative, zero,
+ or positive, depending on whether S
+ comes before That
+ in the sort order, the Strings are equal, or S
+ comes after That
+ in the sort order, respectively.
+ Before + perform the comparisons the following steps are performed to prepare + the Strings:
++ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + S be the result of calling ToString, giving it the this + value as its argument.
++ Let + That be ToString(that).
+
+ The
+ localeCompare
+ method, if considered as a function of two arguments this and
+ that, is a
+ consistent comparison function (as defined in 15.4.4.11) on the set
+ of all Strings.
+ The
+ actual return values are implementation-defined to permit
+ implementers to encode additional information in the value, but the
+ function is required to define a total ordering on all Strings and
+ to return 0 when
+ comparing Strings that are considered canonically equivalent by the
+ Unicode standard.
+ If no + language-sensitive comparison at all is available from the host + environment, this function may perform a bitwise comparison.
+NOTE 1 The localeCompare
+ method itself is not directly suitable as an argument to
+ Array.prototype.sort
+ because the latter requires a function of two arguments.
NOTE 2 This function is intended to rely on whatever language-sensitive + comparison functionality is available to the ECMAScript environment + from the host environment, and to compare according to the rules of + the host environment’s current locale. It is strongly recommended + that this function treat Strings that are canonically equivalent + according to the Unicode standard as identical (in other words, + compare the Strings as if they had both been converted to Normalised + Form C or D first). It is also recommended that this function not + honour Unicode compatibility equivalences or decompositions.
+NOTE 3 The second parameter to this function is likely to be used in a + future version of this standard; it is recommended that + implementations do not use this parameter position for anything + else.
+NOTE 4 The localeCompare
+ function is intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ When
+ the match method
+ is called with argument regexp,
+ the following steps are taken:
+ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + S be the result of calling ToString, giving it the this + value as its argument.
+
+ If
+ Type(regexp) is Object and the value of the [[Class]]
+ internal property of regexp is "RegExp",
+ then let rx be regexp;
+ Else,
+ let rx be a new RegExp object created as if by the
+ expression new
+ RegExp( regexp)
+ where RegExp is
+ the standard built-in constructor with that name.
+ Let
+ global be the result of calling the [[Get]] internal method
+ of rx with argument "global".
+ Let
+ exec be the standard built-in function RegExp.prototype.exec
+ (see 15.10.6.2)
+ If + global is not true, then
++ Return + the result of calling the [[Call]] internal method of exec + with rx as the this value and argument list + containing S.
++ Else, + global is true
+
+ Call
+ the [[Put]] internal method of rx with arguments
+ "lastIndex"
+ and 0.
+ Let
+ A be a new array created as if by the expression new
+ Array() where Array
+ is the standard built-in constructor with that name.
+ Let + previousLastIndex be 0.
++ Let + n be 0.
++ Let + lastMatch be true.
++ Repeat, + while lastMatch is true
++ Let + result be the result of calling the [[Call]] internal + method of exec with rx as the this value and + argument list containing S.
++ If + result is null, then set lastMatch to false.
++ Else, + result is not null
+
+ Let
+ thisIndex be the result of calling the [[Get]] internal
+ method of rx with argument "lastIndex".
+ If + thisIndex = previousLastIndex then
+
+ Call
+ the [[Put]] internal method of rx with arguments
+ "lastIndex"
+ and thisIndex+1.
+ Set + previousLastIndex to thisIndex+1.
++ Else, + set previousLastIndex to thisIndex.
+
+ Let
+ matchStr be the result of calling the [[Get]] internal
+ method of result with argument "0".
+ Call + the [[DefineOwnProperty]] internal method of A with + arguments ToString(n), the Property Descriptor + {[[Value]]: matchStr, [[Writable]]: true, + [[Enumerable]]: true, [[configurable]]: true}, and + false.
++ Increment + n.
++ If + n = 0, then return null.
++ Return + A.
+NOTE The
+ match function is
+ intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ First + set string according to the following steps:
++ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + string be the result of calling ToString, giving it the this + value as its argument.
+
+ If
+ searchValue is a
+ regular expression (an object whose [[Class]] internal property is
+ "RegExp"),
+ do the following: If searchValue.global
+ is false, then search string
+ for the first match of the regular expression searchValue.
+ If searchValue.global
+ is true, then search string
+ for all matches of the regular expression searchValue.
+ Do the search in the same manner as in String.prototype.match,
+ including the update of searchValue.lastIndex.
+ Let m be the
+ number of left capturing parentheses in searchValue
+ (using NcapturingParens
+ as specified in 15.10.2.1).
+ If + searchValue is not + a regular expression, let searchString + be ToString(searchValue) + and search string + for the first occurrence of searchString. + Let m be 0.
++ If + replaceValue is a + function, then for each matched substring, call the function with + the following m + + 3 arguments. Argument 1 is the substring that matched. If + searchValue is a + regular expression, the next m + arguments are all of the captures in the MatchResult (see + 15.10.2.1). Argument m + + 2 is the offset within string + where the match occurred, and argument m + + 3 is string. The + result is a String value derived from the original input by + replacing each matched substring with the corresponding return value + of the function call, converted to a String if need be.
+
+ Otherwise,
+ let newstring
+ denote the result of converting replaceValue
+ to a String. The result is a String value derived from the original
+ input String by replacing each matched substring with a String
+ derived from newstring
+ by replacing characters in newstring
+ by replacement text as specified in Table 22. These $
+ replacements are done left-to-right, and, once such a replacement is
+ performed, the new replacement text is not subject to further
+ replacements. For example, "$1,$2".replace(/(\$(\d))/g,
+ "$$1-$1$2") returns "$1-$11,$1-$22".
+ A $ in newstring
+ that does not match any of the forms below is left as is.
|
+ + Characters + |
+
+ + Replacement + text + |
+
|
+
+ |
+
+
+ |
+
|
+
+ |
+
+ + The + matched substring. + |
+
|
+
+ |
+
+ + The + portion of string + that precedes the matched substring. + |
+
|
+
+ |
+
+ + The + portion of string + that follows the matched substring. + |
+
|
+
+ |
+
+
+ The
+ nth
+ capture, where n
+ is a single digit in the range 1
+ to 9 and |
+
|
+
+ |
+
+ + The + nnth + capture, where nn + is a two-digit decimal number in the range 01 + to 99. If nn≤m + and the nnth + capture is undefined, use the empty String instead. If + nn>m, + the result is implementation-defined. + |
+
NOTE The
+ replace function
+ is intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ When + the search method is called with argument regexp, + the following steps are taken:
++ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + string be the result of calling ToString, giving it the this + value as its argument.
+
+ If
+ Type(regexp) is Object and the value of the [[Class]]
+ internal property of regexp is "RegExp",
+ then let rx be regexp;
+ Else,
+ let rx be a new RegExp object created as if by the
+ expression new
+ RegExp( regexp)
+ where RegExp is
+ the standard built-in constructor with that name.
+ Search
+ the value string from its beginning for an occurrence of the
+ regular expression pattern rx. Let result be a Number
+ indicating the offset within string where the pattern
+ matched, or –1 if there was no match. The lastIndex
+ and global
+ properties of regexp are ignored when performing the search. The
+ lastIndex
+ property of regexp is left unchanged.
+ Return + result.
+NOTE The
+ search function is
+ intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ The
+ slice method takes
+ two arguments, start
+ and end, and
+ returns a substring of the result of converting this object to a
+ String, starting from character position start
+ and running to, but not including, character position end
+ (or through the end of the String if end
+ is undefined). If start
+ is negative, it is treated as sourceLength+start where sourceLength
+ is the length of the String. If end
+ is negative, it is treated as sourceLength+end
+ where sourceLength
+ is the length of the String. The result is a String value, not a
+ String object. The following steps are taken:
+ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + S be the result of calling ToString, giving it the this + value as its argument.
++ Let + len be the number of characters in S.
++ Let + intStart be ToInteger(start).
++ If + end is undefined, let intEnd be len; + else let intEnd be ToInteger(end).
++ If + intStart is negative, let from be max(len + intStart,0); else let from be min(intStart,len).
++ If + intEnd is negative, let to be max(len +intEnd,0); else let to be min(intEnd, len).
++ Let + span be max(to – from,0).
++ Return + a String containing span consecutive characters from S + beginning with the character at position from.
+
+ The
+ length property of
+ the slice method
+ is 2.
NOTE The
+ slice function is
+ intentionally generic; it does not require that its this
+ value be a String object. Therefore it can be transferred to other
+ kinds of objects for use as a method.
+ Returns
+ an Array object into which substrings of the result of converting
+ this object to a String have been stored. The substrings are
+ determined by searching from left to right for occurrences of
+ separator; these
+ occurrences are not part of any substring in the returned array, but
+ serve to divide up the String value. The value of separator
+ may be a String of any length or it may be a RegExp object (i.e., an
+ object whose [[Class]] internal property is "RegExp";
+ see 15.10).
+ The
+ value of separator
+ may be an empty String, an empty regular expression, or a regular
+ expression that can match an empty String. In this case, separator
+ does not match the empty substring at the beginning or end of the
+ input String, nor does it match the empty substring at the end of
+ the previous separator match. (For example, if separator
+ is the empty String, the String is split up into individual
+ characters; the length of the result array equals the length of the
+ String, and each substring contains one character.) If separator
+ is a regular expression, only the first match at a given position of
+ the this String is considered, even if backtracking could
+ yield a non-empty-substring match at that position. (For example,
+ "ab".split(/a*?/)
+ evaluates to the array ["a","b"],
+ while "ab".split(/a*/)
+ evaluates to the array["","b"].)
+ If + the this object is (or converts to) the empty String, the + result depends on whether separator + can match the empty String. If it can, the result array contains no + elements. Otherwise, the result array contains one element, which is + the empty String.
+If + separator is a + regular expression that contains capturing parentheses, then each + time separator is + matched the results (including any undefined results) of the + capturing parentheses are spliced into the output array. + For example,
+
+ "A<B>bold</B>and<CODE>coded</CODE>".split(/<(\/)?([^<>]+)>/)
evaluates + to the array
+
+ ["A",
+ undefined, "B", "bold", "/", "B",
+ "and", undefined,
"CODE", "coded",
+ "/", "CODE", ""]
+ If + separator is + undefined, then the result array contains just one String, + which is the this value (converted to a String). If limit + is not undefined, then the output array is truncated so that + it contains no more than limit + elements.
+
+ When
+ the split method
+ is called, the following steps are taken:
+ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + S be the result of calling ToString, giving it the this + value as its argument.
+
+ Let
+ A be a new array created as if by the expression new
+ Array()where Array
+ is the standard built-in constructor with that name.
+ Let + lengthA be 0.
++ If + limit is undefined, let lim = 232–1; + else let lim = ToUint32(limit).
++ Let + s be the number of characters in S.
++ Let + p = 0.
+
+ If
+ separator is a RegExp object (its [[Class]] is "RegExp"),
+ let R = separator; otherwise let R =
+ ToString(separator).
+ If + lim = 0, return A.
++ If + separator is undefined, then
+
+ Call
+ the [[DefineOwnProperty]] internal method of A with
+ arguments "0",
+ Property Descriptor {[[Value]]: S, [[Writable]]: true,
+ [[Enumerable]]: true, [[Configurable]]: true}, and
+ false.
+ Return + A.
++ If + s = 0, then
++ Call + SplitMatch(S, 0, R) and let z be its + MatchResult result.
++ If + z is not failure, return A.
+
+ Call
+ the [[DefineOwnProperty]] internal method of A with
+ arguments "0",
+ Property Descriptor {[[Value]]: S, [[Writable]]: true,
+ [[Enumerable]]: true, [[Configurable]]: true}, and
+ false.
+ Return + A.
++ Let + q = p.
++ Repeat, + while q ≠ s
++ Call + SplitMatch(S, q, R) and let z + be its MatchResult result.
++ If + z is failure, then let q = q+1.
++ Else, + z is not failure
++ z + must be a State. Let e be z's endIndex and + let cap be z's captures array.
++ If + e = p, then let q = q+1.
++ Else, + e ≠ p
++ Let + T be a String value equal to the substring of S + consisting of the characters at positions p (inclusive) + through q (exclusive).
++ Call + the [[DefineOwnProperty]] internal method of A with + arguments ToString(lengthA), Property Descriptor + {[[Value]]: T, [[Writable]]: true, [[Enumerable]]: + true, [[Configurable]]: true}, and false.
++ Increment + lengthA by 1.
++ If + lengthA = lim, return A.
++ Let + p = e.
++ Let + i = 0.
++ Repeat, + while i is not equal to the number of elements in cap.
++ Let + i = i+1.
++ Call + the [[DefineOwnProperty]] internal method of A with + arguments ToString(lengthA), Property Descriptor + {[[Value]]: cap[i], [[Writable]]: true, + [[Enumerable]]: true, [[Configurable]]: true}, + and false.
++ Increment + lengthA by 1.
++ If + lengthA + = lim, return A.
++ Let + q = p.
++ Let + T be a String value equal to the substring of S + consisting of the characters at positions p (inclusive) + through s (exclusive).
++ Call + the [[DefineOwnProperty]] internal method of A with + arguments ToString(lengthA), Property Descriptor {[[Value]]: + T, [[Writable]]: true, [[Enumerable]]: true, + [[Configurable]]: true}, and false.
++ Return + A.
++ The + abstract operation SplitMatch + takes three parameters, a String S, + an integer q, and + a String or RegExp R, + and performs the following in order to return a MatchResult (see + 15.10.2.1):
+
+ If
+ R is a RegExp object (its [[Class]] is "RegExp"),
+ then
+ Call + the [[Match]] internal method of R giving it the arguments + S and q, and return the MatchResult result.
++ Type(R) + must be String. Let r be the number of characters in R.
++ Let + s be the number of characters in S.
++ If + q+r > s then return the MatchResult + failure.
++ If + there exists an integer i between 0 (inclusive) and r + (exclusive) such that the character at position q+i + of S is different from the character at position i of + R, then return failure.
+
+ The
+ length property of
+ the split method
+ is 2.
NOTE 1 The split method
+ ignores the value of separator.global
+ for separators that are RegExp objects.
NOTE 2 The split
+ function is intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ The + substring method takes two arguments, start + and end, and + returns a substring of the result of converting this object to a + String, starting from character position start + and running to, but not including, character position end + of the String (or through the end of the String is end + is undefined). The result is a String value, not a String + object.
++ If + either argument is NaN or negative, it is replaced with zero; + if either argument is larger than the length of the String, it is + replaced with the length of the String.
++ If + start is larger + than end, they are + swapped.
++ The + following steps are taken:
++ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + S be the result of calling ToString, giving it the this + value as its argument.
++ Let + len be the number of characters in S.
++ Let + intStart be ToInteger(start).
++ If + end is undefined, let intEnd be len; + else let intEnd be ToInteger(end).
++ Let + finalStart be min(max(intStart, 0), len).
++ Let + finalEnd be min(max(intEnd, 0), len).
++ Let + from be min(finalStart, finalEnd).
++ Let + to be max(finalStart, finalEnd).
++ Return + a String whose length is to - from, containing + characters from S, namely the characters with indices from + through to −1, in + ascending order.
+
+ The
+ length property of
+ the substring
+ method is 2.
NOTE The
+ substring function
+ is intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ The + following steps are taken:
++ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + S be the result of calling ToString, giving it the this + value as its argument.
++ Let + L be a String where each character of L is either the + Unicode lowercase equivalent of the corresponding character of S + or the actual corresponding character of S if no Unicode + lowercase equivalent exists.
++ Return + L.
++ For + the purposes of this operation, the 16-bit code units of the Strings + are treated as code points in the Unicode Basic Multilingual Plane. + Surrogate code points are directly transferred from S + to L without any + mapping.
+The + result must be derived according to the case mappings in the Unicode + character database (this explicitly includes not only the + UnicodeData.txt file, but also the SpecialCasings.txt file that + accompanies it in Unicode 2.1.8 and later).
+NOTE 1 The case mapping of some characters may produce multiple
+ characters. In this case the result String may not be the same
+ length as the source String. Because both toUpperCase
+ and toLowerCase
+ have context-sensitive behaviour, the functions are not symmetrical.
+ In other words, s.toUpperCase().toLowerCase()
+ is not necessarily equal to s.toLowerCase().
NOTE 2 The toLowerCase
+ function is intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ This
+ function works exactly the same as toLowerCase
+ except that its result is intended to yield the correct result for
+ the host environment’s current locale, rather than a
+ locale-independent result. There will only be a difference in the
+ few cases (such as Turkish) where the rules for that language
+ conflict with the regular Unicode case mappings.
NOTE 1 The first parameter to this function is likely to be used in a + future version of this standard; it is recommended that + implementations do not use this parameter position for anything + else.
+NOTE 2 The toLocaleLowerCase
+ function is intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ This
+ function behaves in exactly the same way as
+ String.prototype.toLowerCase,
+ except that characters are mapped to their uppercase
+ equivalents as specified in the Unicode Character Database.
NOTE The
+ toUpperCase
+ function is intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ This
+ function works exactly the same as toUpperCase
+ except that its result is intended to yield the correct result for
+ the host environment’s current locale, rather than a
+ locale-independent result. There will only be a difference in the
+ few cases (such as Turkish) where the rules for that language
+ conflict with the regular Unicode case mappings.
NOTE 1 The first parameter to this function is likely to be used in a + future version of this standard; it is recommended that + implementations do not use this parameter position for anything + else.
+NOTE 2 The toLocaleUpperCase
+ function is intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ The + following steps are taken:
++ Call + CheckObjectCoercible passing the this value as its argument.
++ Let + S be the result of calling ToString, giving it the this + value as its argument.
++ Let + T be a String value that is a copy of S with both + leading and trailing white space removed. The definition of white + space is the union of WhiteSpace and LineTerminator.
++ Return + T.
+NOTE The
+ trim function is
+ intentionally generic; it does not require that its this
+ value be a String object. Therefore, it can be transferred to other
+ kinds of objects for use as a method.
+ String
+ instances inherit properties from the String prototype object and
+ their [[Class]] internal property value is "String".
+ String instances also have a [[PrimitiveValue]] internal property, a
+ length property,
+ and a set of enumerable properties with array index names.
+ The + [[PrimitiveValue]] internal property is the String value represented + by this String object. The array index named properties correspond + to the individual characters of the String value. A special + [[GetOwnProperty]] internal method is used to specify the number, + values, and attributes of the array index named properties. +
++ The + number of characters in the String value represented by this String + object.
++ Once + a String object is created, this property is unchanging. It has the + attributes { [[Writable]]: false, [[Enumerable]]: false, + [[Configurable]]: false }.
++ String + objects use a variation of the [[GetOwnProperty]] internal method + used for other native ECMAScript objects (8.12.1). + + This special internal method is used to add access for named properties + corresponding to individual characters of String objects.
++ Assume + S is a String + object and P is a + String.
++ When + the [[GetOwnProperty]] internal method of S is called with property name P, + the following steps are taken:
++ Let + desc be the result of calling the default [[GetOwnProperty]] + internal method (8.12.1) on S with argument P.
++ If + desc is not undefined return desc. +
++ If + ToString(abs(ToInteger(P))) + is not + the same value as P, + return undefined.
++ Let + str be the String value of the [[PrimitiveValue]] internal + property of S.
++ Let + index be + ToInteger(P).
+ Let + len be the number of characters in str.
++ If + len ≤ index, return undefined.
++ Let + resultStr be a String of length 1, containing one character + from str, specifically the character at position index, + where the first (leftmost) character in str is considered to + be at position 0, the next one at position 1, and so on.
++ Return + a Property Descriptor { [[Value]]: resultStr, + [[Enumerable]]: true, [[Writable]]: false, + [[Configurable]]: false }
+
+ When
+ Boolean is called
+ as a function rather than as a constructor, it performs a type
+ conversion.
+ Returns + a Boolean value (not a Boolean object) computed by ToBoolean(value).
+
+ When
+ Boolean is called
+ as part of a new
+ expression it is a constructor: it initialises the newly created
+ object.
+ The
+ [[Prototype]] internal property of the newly constructed object is
+ set to the original Boolean prototype object, the one that is the
+ initial value of Boolean.prototype
+ (15.6.3.1).
+ The
+ [[Class]] internal property of the newly constructed Boolean object
+ is set to "Boolean".
+ The + [[PrimitiveValue]] internal property of the newly constructed + Boolean object is set to ToBoolean(value).
++ The + [[Extensible]] internal property of the newly constructed object is + set to true.
++ The + value of the [[Prototype]] internal property of the Boolean + constructor is the Function prototype object (15.3.4).
+
+ Besides
+ the internal properties and the length
+ property (whose value is 1), the Boolean constructor has the
+ following property:
+ The
+ initial value of Boolean.prototype
+ is the Boolean prototype object (15.6.4).
+ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+
+ The
+ Boolean prototype object is itself a Boolean object (its [[Class]]
+ is "Boolean")
+ whose value is false.
+ The + value of the [[Prototype]] internal property of the Boolean + prototype object is the standard built-in Object prototype object + (15.2.4).
+
+ The
+ initial value of Boolean.prototype.constructor
+ is the built-in Boolean
+ constructor.
+ The + following steps are taken:
++ Let + B be the this value.
++ If + Type(B) is Boolean, then let b be B.
+
+ Else
+ if Type(B) is Object and the value of the [[Class]] internal
+ property of B is "Boolean",
+ then let b be the value of the [[PrimitiveValue]] internal
+ property of B.
+ Else + throw a TypeError exception.
+
+ If
+ b is true, then return "true";
+ else return "false".
+ The + following steps are taken:
++ Let + B be the this value.
++ If + Type(B) is Boolean, then let b be B.
+
+ Else
+ if Type(B) is Object and the value of the [[Class]] internal
+ property of B is "Boolean",
+ then let b be the value of the [[PrimitiveValue]] internal
+ property of B.
+ Else + throw a TypeError exception.
++ Return + b.
+
+ Boolean
+ instances inherit properties from the Boolean prototype object and
+ their [[Class]] internal property value is "Boolean".
+ Boolean instances also have a [[PrimitiveValue]] internal property.
+ The + [[PrimitiveValue]] internal property is the Boolean value + represented by this Boolean object.
+
+ When
+ Number is called
+ as a function rather than as a constructor, it performs a type
+ conversion.
+ Returns + a Number value (not a Number object) computed by ToNumber(value) + if value was + supplied, else returns +0.
+
+ When
+ Number is called
+ as part of a new
+ expression it is a constructor: it initialises the newly created
+ object.
+ The
+ [[Prototype]] internal property of the newly constructed object is
+ set to the original Number prototype object, the one that is the
+ initial value of Number.prototype
+ (15.7.3.1).
+ The
+ [[Class]] internal property of the newly constructed object is set
+ to "Number".
+ The + [[PrimitiveValue]] internal property of the newly constructed object + is set to ToNumber(value) + if value was + supplied, else to +0.
++ The + [[Extensible]] internal property of the newly constructed object is + set to true.
++ The + value of the [[Prototype]] internal property of the Number + constructor is the Function prototype object (15.3.4).
+
+ Besides
+ the internal properties and the length
+ property (whose value is 1), the Number constructor has the
+ following property:
+ The
+ initial value of Number.prototype
+ is the Number prototype object (15.7.4).
+ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+
+ The
+ value of Number.MAX_VALUE
+ is the largest positive finite value of the Number type, which is
+ approximately 1.7976931348623157 × 10308.
+ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+
+ The
+ value of Number.MIN_VALUE
+ is the smallest positive value of the Number type, which is
+ approximately 5 × 10 324.
+ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+
+ The
+ value of Number.NaN
+ is NaN.
+ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
++ The + value of Number.NEGATIVE_INFINITY is −∞.
++ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
++ The + value of Number.POSITIVE_INFINITY is +∞.
++ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+
+ The
+ Number prototype object is itself a Number object (its [[Class]] is
+ "Number")
+ whose value is +0.
+ The + value of the [[Prototype]] internal property of the Number prototype + object is the standard built-in Object prototype object (15.2.4).
+
+ Unless
+ explicitly stated otherwise, the methods of the Number prototype
+ object defined below are not generic and the this value passed to
+ them must be either a Number value or an Object for which the value
+ of the [[Class]] internal property is "Number".
+ In
+ the following descriptions of functions that are properties of the
+ Number prototype object, the phrase “this Number object” refers
+ to either the object that is the this value for the
+ invocation of the function or, if Type(this value) is Number,
+ an object that is created as if by the expression new
+ Number(this value)
+ where Number is
+ the standard built-in constructor with that name. Also, the phrase
+ “this Number value” refers to either the Number value
+ represented by this Number object, that is, the value of the
+ [[PrimitiveValue]] internal property of this Number object or the
+ this value if its type is Number. A TypeError
+ exception is thrown if the this value is neither an object
+ for which the value of the [[Class]] internal property is "Number"
+ or a value whose type is Number.
+ The
+ initial value of Number.prototype.constructor
+ is the built-in Number
+ constructor.
+ The + optional radix + should be an integer value in the inclusive range 2 + to 36. If radix + not present or is undefined the Number 10 + is used as the value of radix. + If ToInteger(radix) + is the Number 10 then + this Number value is given as an argument to the ToString abstract + operation; the resulting String value is returned.
+
+ If
+ ToInteger(radix)
+ is not an integer between 2 and 36 inclusive throw a RangeError
+ exception. If ToInteger(radix)
+ is an integer from 2 to 36, but not 10, the result is a String
+ representation of this Number value using the specified radix.
+ Letters a-z
+ are used for digits with values 10 through 35. The precise algorithm
+ is implementation-dependent if the radix is not 10, however the
+ algorithm should be a generalization of that specified in 9.8.1.
+ The
+ toString function
+ is not generic; it throws a TypeError exception if its this
+ value is not a Number or a Number object. Therefore, it cannot be
+ transferred to other kinds of objects for use as a method.
+ Produces
+ a String value that represents this Number value formatted according
+ to the conventions of the host environment’s current locale. This
+ function is implementation-dependent, and it is permissible, but not
+ encouraged, for it to return the same thing as toString.
NOTE The + first parameter to this function is likely to be used in a future + version of this standard; it is recommended that implementations do + not use this parameter position for anything else.
++ Returns + this Number value.
+
+ The
+ valueOf function
+ is not generic; it throws a TypeError exception if its this
+ value is not a Number or a Number object. Therefore, it cannot be
+ transferred to other kinds of objects for use as a method.
+ Return + a String containing this Number value represented in decimal + fixed-point notation with fractionDigits + digits after the decimal point. If fractionDigits + is undefined, 0 is assumed. Specifically, perform the + following steps:
+
+ Let
+ f be ToInteger(fractionDigits). (If fractionDigits
+ is undefined, this step produces the value 0).
+ If + f < 0 or f > 20, throw a RangeError + exception.
++ Let + x be this Number value.
+
+ If
+ x is NaN, return the String "NaN".
+ Let + s be the empty String.
++ If + x < 0, then
+
+ Let
+ s be "-".
+ Let + x = –x.
++ If + x ≥ 1021, + then
++ Let + m = ToString(x).
++ Else, + x < 1021
++ Let + n be an integer for which the exact mathematical value of n + ÷ 10f – x + is as close to zero as possible. If there are two such n, + pick the larger n.
+
+ If
+ n = 0, let m be the String "0".
+ Otherwise, let m be the String consisting of the digits of
+ the decimal representation of n (in order, with no leading
+ zeroes).
+ If + f ≠ 0, then
++ Let + k be the number of characters in m.
++ If + k ≤ f, then
+
+ Let
+ z be the String consisting of f+1–k
+ occurrences of the character ‘0’.
+ Let + m be the concatenation of Strings z and m.
++ Let + k = f + 1.
++ Let + a be the first k–f characters of m, and + let b be the remaining f characters of m.
+
+ Let
+ m be the concatenation of the three Strings a, ".",
+ and b.
+ Return + the concatenation of the Strings s and m.
+
+ The
+ length property of
+ the toFixed method
+ is 1.
+ If
+ the toFixed method
+ is called with more than one argument, then the behaviour is
+ undefined (see clause 15).
+ An
+ implementation is permitted to extend the behaviour of toFixed
+ for values of fractionDigits
+ less than 0 or greater than 20. In this case toFixed
+ would not necessarily throw RangeError for such values.
NOTE The
+ output of toFixed
+ may be more precise than toString
+ for some values because toString only prints enough significant
+ digits to distinguish the number from adjacent number values. For
+ example,
+
(1000000000000000128).toString()
+ returns "1000000000000000100",
while
+ (1000000000000000128).toFixed(0)
+ returns "1000000000000000128".
+ Return + a String containing this Number value represented in decmal + exponential notation with one digit before the significand's decimal + point and fractionDigits + digits after the significand's decimal point. If fractionDigits + is undefined, include as many significand digits as necessary + to uniquely specify the Number (just like in ToString except that in + this case the Number is always output in exponential notation). + Specifically, perform the following steps:
++ Let + x be this Number value.
++ Let + f be ToInteger(fractionDigits).
+
+ If
+ x is NaN, return the String "NaN".
+ Let + s be the empty String.
++ If + x < 0, then
+
+ Let
+ s be "-".
+ Let + x = –x.
++ If + x = +∞, then
+
+ Return
+ the concatenation of the Strings s and "Infinity".
+
+
+ If + fractionDigits is not undefined and (f < 0 + or f > 20), throw a RangeError exception.
++ If + x = 0, then
++ Let + f = 0.
+
+ Let
+ m be the String consisting of f+1 occurrences of the
+ character ‘0’.
+ Let + e = 0.
++ Else, + x ≠ 0
++ If + fractionDigits is not undefined, then
++ Let + e and n be integers such that 10f≤ n < 10f+1 + and for which the exact mathematical value of n × + 10e–f – x + is as close to zero as possible. If there are two such sets of e + and n, pick the e and n for which n × + 10e–f is larger.
++ Else, + fractionDigits is undefined +
++ Let + e, n, and f be integers such that f ≥ + 0, 10f≤ n + < 10f+1, the number value for n × + 10e–f is x, + and f is as small as possible. Note that the decimal + representation of n has f+1 digits, n is not + divisible by 10, and the least significant digit of n is + not necessarily uniquely determined by these criteria.
++ Let + m be the String consisting of the digits of the decimal + representation of n (in order, with no leading zeroes).
++ If + f ≠ 0, then
++ Let + a be the first character of m, and let b be + the remaining f characters of m.
+
+ Let
+ m be the concatenation of the three Strings a, ".",
+ and b.
+ If + e = 0, then +
+
+ Let
+ c = "+".
+ Let
+ d = "0".
+ Else
+
+ If
+ e > 0, then let c = "+".
+ Else, + e ≤ 0
+
+ Let
+ c = "-".
+ Let + e = –e.
++ Let + d be the String consisting of the digits of the decimal + representation of e (in order, with no leading zeroes).
+
+ Let
+ m be the concatenation of the four Strings m, "e",
+ c, and d.
+ Return + the concatenation of the Strings s and m.
+
+ The
+ length property of
+ the toExponential
+ method is 1.
+ If
+ the toExponential
+ method is called with more than one argument, then the behaviour is
+ undefined (see clause 15).
+ An
+ implementation is permitted to extend the behaviour of toExponential
+ for values of fractionDigits
+ less than 0 or greater than 20. In this case toExponential
+ would not necessarily throw RangeError for such values.
NOTE For + implementations that provide more accurate conversions than required + by the rules above, it is recommended that the following alternative + version of step 9.b.i be used as a guideline:
++ Let + e, + n, + and f be + integers such that f + ≥ + 0, 10f≤ + n < 10f+1, + the number value for n × + 10e–f + is x, and f + is as small as possible. If there are multiple possibilities for + n, + choose the value of n + for which n + × + 10e–f + is closest in value to x. + If there are two such possible values of n, + choose the one that is even.
++ Return + a String containing this Number value represented either in decimal + exponential notation with one digit before the significand's decimal + point and precision–1 + digits after the significand's decimal point or in decimal fixed + notation with precision + significant digits. If precision + is undefined, call ToString (9.8.1) instead. Specifically, + perform the following steps:
++ Let + x be this Number value.
++ If + precision is undefined, return ToString(x).
++ Let + p be ToInteger(precision).
+
+ If
+ x is NaN, return the String "NaN".
+ Let + s be the empty String.
++ If + x < 0, then
+
+ Let
+ s be "-".
+ Let + x = –x.
++ If + x = +∞, then
+
+ Return
+ the concatenation of the Strings s and "Infinity".
+ If + p < 1 or p > 21, throw a RangeError + exception.
++ If + x = 0, then
+
+ Let
+ m be the String consisting of p occurrences of the
+ character ‘0’.
+ Let + e = 0.
++ Else + x ≠ 0,
++ Let + e and n be integers such that 10p–1≤ n < 10p + and for which the exact mathematical value of n × + 10e–p+1 + – x is as close to zero as possible. If there are two + such sets of e and n, pick the e and n + for which n × 10e–p+1 + is larger.
++ Let + m be the String consisting of the digits of the decimal + representation of n (in order, with no leading zeroes).
++ If + e < –6 or e ≥ + p, then
++ Let + a be the first character of m, and let b be + the remaining p–1 characters of m.
+
+ Let
+ m be the concatenation of the three Strings a, ".",
+ and b.
+ If + e = 0, then
+
+ Let
+ c = "+"
+ and d = "0".
+ Else + e ≠ 0,
++ If + e > 0, then +
+
+ Let
+ c = "+".
+ Else + e < 0,
+
+ Let
+ c = "-".
+ Let + e = –e.
++ Let + d be the String consisting of the digits of the decimal + representation of e (in order, with no leading zeroes).
+
+ Let
+ m be the concatenation of the five Strings s, m,
+ "e",
+ c, and d.
+ If + e = p–1, then return the concatenation of the + Strings s and m.
++ If + e ≥ 0, then
+
+ Let
+ m be the concatenation of the first e+1 characters
+ of m, the character ‘.’,
+ and the remaining p– (e+1) characters of m.
+ Else + e < 0,
+
+ Let
+ m be the concatenation of the String "0.",
+ –(e+1) occurrences of the character ‘0’,
+ and the String m.
+ Return + the concatenation of the Strings s and m.
+
+ The
+ length property of
+ the toPrecision
+ method is 1.
+ If
+ the toPrecision
+ method is called with more than one argument, then the behaviour is
+ undefined (see clause 15).
+ An
+ implementation is permitted to extend the behaviour of toPrecision
+ for values of precision
+ less than 1 or greater than 21. In this case toPrecision
+ would not necessarily throw RangeError for such values.
+ Number
+ instances inherit properties from the Number prototype object and
+ their [[Class]] internal property value is "Number".
+ Number instances also have a [[PrimitiveValue]] internal property.
+ The + [[PrimitiveValue]] internal property is the Number value represented + by this Number object.
++ The + Math object is a single object that has some named properties, some + of which are functions.
+
+ The
+ value of the [[Prototype]] internal property of the Math object is
+ the standard built-in Object prototype object (15.2.4). The value of
+ the [[Class]] internal property of the Math object is "Math".
+ The
+ Math object does not have a [[Construct]] internal property; it is
+ not possible to use the Math object as a constructor with the new
+ operator.
+ The + Math object does not have a [[Call]] internal property; it is not + possible to invoke the Math object as a function.
+NOTE In + this specification, the phrase “the Number value for x” + has a technical meaning defined in 8.5.
++ The + Number value for e, + the base of the natural logarithms, which is approximately + 2.7182818284590452354.
++ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
++ The + Number value for the natural logarithm of 10, which is approximately + 2.302585092994046.
++ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
++ The + Number value for the natural logarithm of 2, which is approximately + 0.6931471805599453.
++ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
++ The + Number value for the base-2 + logarithm of e, + the base of the natural logarithms; this value is approximately + 1.4426950408889634.
++ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+NOTE The
+ value of Math.LOG2E
+ is approximately the reciprocal of the value of Math.LN2.
+ The + Number value for the base-10 + logarithm of e, + the base of the natural logarithms; this value is approximately + 0.4342944819032518.
++ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+NOTE The
+ value of Math.LOG10E
+ is approximately the reciprocal of the value of Math.LN10.
+ The + Number value for π, the ratio of + the circumference of a circle to its diameter, which is + approximately 3.1415926535897932.
++ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
++ The + Number value for the square root of ½, + which is approximately 0.7071067811865476.
++ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+NOTE The
+ value of Math.SQRT1_2
+ is approximately the reciprocal of the value of Math.SQRT2.
+ The + Number value for the square root of 2, + which is approximately 1.4142135623730951.
++ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+
+ Each
+ of the following Math object functions applies the ToNumber abstract operator to each of
+ its arguments (in left-to-right order if there is more than one) and
+ then performs a computation on the resulting Number value(s).
+ In + the function descriptions below, the symbols NaN, −0, + +0, −∞ and +∞ + refer to the Number values described in 8.5.
+NOTE The
+ behaviour of the functions acos,
+ asin, atan,
+ atan2, cos,
+ exp, log,
+ pow, sin,
+ and sqrt is not
+ precisely specified here except to require specific results for
+ certain argument values that represent boundary cases of interest.
+ For other argument values, these functions are intended to compute
+ approximations to the results of familiar mathematical functions,
+ but some latitude is allowed in the choice of approximation
+ algorithms. The general intent is that an implementer should be able
+ to use the same mathematical library for ECMAScript on a given
+ hardware platform that is available to C programmers on that
+ platform.
+ Although
+ the choice of algorithms is left to the implementation, it is
+ recommended (but not specified by this standard) that
+ implementations use the approximation algorithms for IEEE 754
+ arithmetic contained in fdlibm,
+ the freely distributable mathematical library from Sun Microsystems
+ (http://www.netlib.org/fdlibm).
+
+
+ Returns + the absolute value of x; + the result has the same magnitude as x + but has positive sign.
++ If + x + is NaN, the result is NaN.
++ If + x + is −0, + the result is +0.
++ If + x + is −∞, + the result is +∞.
++ Returns + an implementation-dependent approximation to the arc cosine of x. + The result is expressed in radians and ranges from +0 + to +π.
++ If + x + is NaN, the result is NaN.
++ If + x + is greater than 1, the result is NaN.
++ If + x + is less than −1, + the result is NaN.
++ If + x + is exactly 1, the result is +0.
++ Returns + an implementation-dependent approximation to the arc sine of x. + The result is expressed in radians and ranges from −π/2 + to +π/2.
++ If + x + is NaN, the result is NaN.
++ If + x + is greater than 1, the result is NaN.
++ If + x + is less than –1, the result is NaN.
++ If + x + is +0, the result is +0.
++ If + x + is −0, + the result is −0.
++ Returns + an implementation-dependent approximation to the arc tangent of x. + The result is expressed in radians and ranges from −π/2 + to +π/2.
++ If + x + is NaN, the result is NaN.
++ If + x + is +0, the result is +0.
++ If + x + is −0, + the result is −0.
++ If + x + is +∞, + the result is an implementation-dependent approximation to +π/2.
++ If + x + is −∞, + the result is an implementation-dependent approximation to −π/2.
++ Returns + an implementation-dependent approximation to the arc tangent of the + quotient y/x + of the arguments y + and x, where the + signs of y and x + are used to determine the quadrant of the result. Note that it is + intentional and traditional for the two-argument arc tangent + function that the argument named y + be first and the argument named x + be second. The result is expressed in radians and ranges from −π + to +π.
++ If + either x + or y + is NaN, the result is NaN.
++ If + y>0 + and x + is +0, the result is an implementation-dependent approximation to + +π/2.
++ If + y>0 + and x + is −0, + the result is an implementation-dependent approximation to +π/2.
++ If + y + is +0 and x>0, + the result is +0.
++ If + y + is +0 and x + is +0, the result is +0.
++ If + y + is +0 and x + is −0, + the result is an implementation-dependent approximation to +π.
++ If + y + is +0 and x<0, + the result is an implementation-dependent approximation to +π.
++ If + y + is −0 + and x>0, + the result is −0.
++ If + y + is −0 + and x + is +0, the result is −0.
++ If + y + is −0 + and x + is −0, + the result is an implementation-dependent approximation to −π.
++ If + y + is −0 + and x<0, + the result is an implementation-dependent approximation to −π.
++ If + y<0 + and x + is +0, the result is an implementation-dependent approximation to + −π/2.
++ If + y<0 + and x + is −0, + the result is an implementation-dependent approximation to −π/2.
++ If + y>0 + and y + is finite and x + is +∞, + the result is +0.
++ If + y>0 + and y + is finite and x + is −∞, + the result if an implementation-dependent approximation to +π.
++ If + y<0 + and y + is finite and x + is +∞, + the result is −0.
++ If + y<0 + and y + is finite and x + is −∞, + the result is an implementation-dependent approximation to −π.
++ If + y + is +∞ + and x + is finite, the result is an implementation-dependent approximation + to +π/2.
++ If + y + is −∞ + and x + is finite, the result is an implementation-dependent approximation + to −π/2.
++ If + y + is +∞ + and x + is +∞, + the result is an implementation-dependent approximation to +π/4.
++ If + y + is +∞ + and x + is −∞, + the result is an implementation-dependent approximation to +3π/4.
++ If + y + is −∞ + and x + is +∞, + the result is an implementation-dependent approximation to −π/4.
++ If + y + is −∞ + and x + is −∞, + the result is an implementation-dependent approximation to −3π/4.
++ Returns + the smallest (closest to −∞) + Number value that is not less than x + and is equal to a mathematical integer. If x + is already an integer, the result is x.
++ If + x + is NaN, the result is NaN.
++ If + x + is +0, the result is +0.
++ If + x + is −0, + the result is −0.
++ If + x + is +∞, + the result is +∞.
++ If + x + is −∞, + the result is −∞.
++ If + x + is less than 0 but greater than -1, the result is −0.
+
+ The
+ value of Math.ceil(x)
+ is the same as the value of -Math.floor(-x).
+ Returns + an implementation-dependent approximation to the cosine of x. + The argument is expressed in radians.
++ If + x + is NaN, the result is NaN.
++ If + x + is +0, the result is 1.
++ If + x + is −0, + the result is 1.
++ If + x + is +∞, + the result is NaN.
++ If + x + is −∞, + the result is NaN.
++ Returns + an implementation-dependent approximation to the exponential + function of x (e + raised to the power of x, + where e is the + base of the natural logarithms).
++ If + x + is NaN, the result is NaN.
++ If + x + is +0, the result is 1.
++ If + x + is −0, + the result is 1.
++ If + x + is +∞, + the result is +∞.
++ If + x + is −∞, + the result is +0.
++ Returns + the greatest (closest to +∞) + Number value that is not greater than x + and is equal to a mathematical integer. If x + is already an integer, the result is x.
++ If + x + is NaN, the result is NaN.
++ If + x + is +0, the result is +0.
++ If + x + is −0, + the result is −0.
++ If + x + is +∞, + the result is +∞.
++ If + x + is −∞, + the result is −∞.
++ If + x + is greater than 0 but less than 1, the result is +0.
+NOTE The
+ value of Math.floor(x)
+ is the same as the value of -Math.ceil(-x).
+ Returns + an implementation-dependent approximation to the natural logarithm + of x.
++ If + x + is NaN, the result is NaN.
++ If + x + is less than 0, the result is NaN.
++ If + x + is +0 or −0, + the result is −∞.
++ If + x + is 1, the result is +0.
++ If + x + is +∞, + the result is +∞.
++ Given + zero or more arguments, calls ToNumber on each of the arguments and + returns the largest of the resulting values.
++ If + no arguments are given, the result is −∞.
++ If + any value is NaN, the result is NaN.
++ The + comparison of values to determine the largest value is done as in + 11.8.5 except that +0 is considered to be larger than −0.
+
+ The
+ length property of
+ the max method is
+ 2.
+ Given + zero or more arguments, calls ToNumber on each of the arguments and + returns the smallest of the resulting values.
++ If + no arguments are given, the result is +∞.
++ If + any value is NaN, the result is NaN.
++ The + comparison of values to determine the smallest value is done as in + 11.8.5 except that +0 is considered to be larger than −0.
+
+ The
+ length property of
+ the min method is
+ 2.
+ Returns + an implementation-dependent approximation to the result of raising x + to the power y.
++ If + y + is NaN, the result is NaN.
++ If + y + is +0, the result is 1, even if x + is NaN.
++ If + y + is −0, + the result is 1, even if x + is NaN.
++ If + x + is NaN and y + is nonzero, the result is NaN.
++ If + abs(x)>1 + and y + is +∞, + the result is +∞.
++ If + abs(x)>1 + and y + is −∞, + the result is +0.
++ If + abs(x)==1 + and y + is +∞, + the result is NaN.
++ If + abs(x)==1 + and y + is −∞, + the result is NaN.
++ If + abs(x)<1 + and y + is +∞, + the result is +0.
++ If + abs(x)<1 + and y + is −∞, + the result is +∞.
++ If + x + is +∞ + and y>0, + the result is +∞.
++ If + x + is +∞ + and y<0, + the result is +0.
++ If + x + is −∞ + and y>0 + and y + is an odd integer, the result is −∞.
++ If + x + is −∞ + and y>0 + and y + is not an odd integer, the result is +∞.
++ If + x + is −∞ + and y<0 + and y + is an odd integer, the result is −0.
++ If + x + is −∞ + and y<0 + and y + is not an odd integer, the result is +0.
++ If + x + is +0 and y>0, + the result is +0.
++ If + x + is +0 and y<0, + the result is +∞.
++ If + x + is −0 + and y>0 + and y + is an odd integer, the result is −0.
++ If + x + is −0 + and y>0 + and y + is not an odd integer, the result is +0.
++ If + x + is −0 + and y<0 + and y + is an odd integer, the result is −∞.
++ If + x + is −0 + and y<0 + and y + is not an odd integer, the result is +∞.
++ If + x<0 + and x + is finite and y + is finite and y + is not an integer, the result is NaN.
++ Returns + a Number value with positive sign, greater than or equal to 0 but + less than 1, chosen randomly or pseudo randomly with approximately + uniform distribution over that range, using an + implementation-dependent algorithm or strategy. This function takes + no arguments.
++ Returns + the Number value that is closest to x + and is equal to a mathematical integer. If two integer Number values + are equally close to x, + then the result is the Number value that is closer to +∞. + If x is already an + integer, the result is x.
++ If + x + is NaN, the result is NaN.
++ If + x + is +0, the result is +0.
++ If + x + is −0, + the result is −0.
++ If + x + is +∞, + the result is +∞.
++ If + x + is −∞, + the result is −∞.
++ If + x + is greater than 0 but less than 0.5, the result is +0.
++ If + x + is less than 0 but greater than or equal to -0.5, the result is −0.
+NOTE 1 Math.round(3.5)
+ returns 4, but
+ Math.round(–3.5)
+ returns –3.
NOTE 2 The value of Math.round(x)
+ is the same as the value of Math.floor(x+0.5),
+ except when x is
+ −0
+ or is less than 0
+ but greater than or equal to -0.5;
+ for these cases Math.round(x)
+ returns −0,
+ but Math.floor(x+0.5)
+ returns +0.
+ Returns + an implementation-dependent approximation to the sine of x. + The argument is expressed in radians.
++ If + x + is NaN, the result is NaN.
++ If + x + is +0, the result is +0.
++ If + x + is −0, + the result is −0.
++ If + x + is +∞ + or −∞, + the result is NaN.
++ Returns + an implementation-dependent approximation to the square root of x.
++ If + x + is NaN, the result is NaN.
++ If + x + is less than 0, the result is NaN.
++ If + x + is +0, the result is +0.
++ If + x + is −0, + the result is −0.
++ If + x + is +∞, + the result is +∞.
++ Returns + an implementation-dependent approximation to the tangent of x. + The argument is expressed in radians.
++ If + x + is NaN, the result is NaN.
++ If + x + is +0, the result is +0.
++ If + x + is −0, + the result is −0.
++ If + x + is +∞ + or −∞, + the result is NaN.
++ The + following functions are abstract operations that operate on time + values (defined in 15.9.1.1). Note that, in every case, if any + argument to one of these functions is NaN, the result will be + NaN.
++ A + Date object contains a Number indicating a particular instant in + time to within a millisecond. Such a Number is called a time + value. A time value may also be NaN, indicating that the + Date object does not represent a specific instant of time.
++ Time + is measured in ECMAScript in milliseconds since 01 January, 1970 + UTC. In time values leap seconds are ignored. It is assumed that + there are exactly 86,400,000 milliseconds per day. ECMAScript Number + values can represent all integers from –9,007,199,254,740,991 to + 9,007,199,254,740,991; this range suffices to measure times to + millisecond precision for any instant that is within approximately + 285,616 years, either forward or backward, from 01 January, 1970 + UTC.
++ The + actual range of times supported by ECMAScript Date objects is + slightly smaller: exactly –100,000,000 days to 100,000,000 days + measured relative to midnight at the beginning of 01 January, 1970 + UTC. This gives a range of 8,640,000,000,000,000 milliseconds to + either side of 01 January, 1970 UTC.
++ The + exact moment of midnight at the beginning of 01 January, 1970 UTC is + represented by the value +0.
++ A + given time value t belongs to day number
++ Day(t) + = floor(t / msPerDay)
++ where + the number of milliseconds per day is
++ msPerDay + = 86400000
++ The + remainder is called the time within the day:
++ TimeWithinDay(t) + = t modulo msPerDay
++ ECMAScript + uses an extrapolated Gregorian system to map a day number to a year + number and to determine the month and date within that year. In this + system, leap years are precisely those which are (divisible by 4) + and ((not divisible by 100) + or (divisible by 400)). + The number of days in year number y + is therefore defined by
+
+ DaysInYear(y)
+ = 365 if (y modulo 4) ≠
+ 0
= 366 if (y modulo 4) = 0 and (y modulo 100) ≠
+ 0
= 365 if (y modulo 100) = 0 and (y modulo 400) ≠
+ 0
= 366 if (y modulo 400) = 0
+ All + non-leap years have 365 + days with the usual number of days per month and leap years have an + extra day in February. The day number of the first day of year y + is given by:
++ DayFromYear(y) = + 365 × (y−1970) + + floor((y−1969)/4) − + floor((y−1901)/100) + + floor((y−1601)/400)
++ The + time value of the start of a year is:
++ TimeFromYear(y) = + msPerDay × DayFromYear(y)
++ A + time value determines a year by:
++ YearFromTime(t) = + the largest integer y (closest to positive infinity) such + that TimeFromYear(y) ≤ t
++ The + leap-year function is 1 for a time within a leap year and otherwise + is zero:
+
+ InLeapYear(t) =
+ 0 if DaysInYear(YearFromTime(t)) = 365
= 1 if
+ DaysInYear(YearFromTime(t)) = 366
+ Months + are identified by an integer in the range 0 + to 11, inclusive. The + mapping MonthFromTime(t) from a time value t to a + month number is defined by:
+
+ MonthFromTime(t) =
+ 0 if 0 ≤ DayWithinYear(t)
+ < 31
= 1 if 31 ≤
+ DayWithinYear (t) < 59+InLeapYear(t)
=
+ 2 if 59+InLeapYear(t) ≤
+ DayWithinYear (t) < 90+InLeapYear(t)
=
+ 3 if 90+InLeapYear(t) ≤
+ DayWithinYear (t) < 120+InLeapYear(t)
=
+ 4 if 120+InLeapYear(t) ≤
+ DayWithinYear (t) < 151+InLeapYear(t)
=
+ 5 if 151+InLeapYear(t) ≤
+ DayWithinYear (t) < 181+InLeapYear(t)
=
+ 6 if 181+InLeapYear(t) ≤
+ DayWithinYear (t) < 212+InLeapYear(t)
=
+ 7 if 212+InLeapYear(t) ≤
+ DayWithinYear (t) < 243+InLeapYear(t)
=
+ 8 if 243+InLeapYear(t) ≤
+ DayWithinYear (t) < 273+InLeapYear(t)
=
+ 9 if 273+InLeapYear(t) ≤
+ DayWithinYear (t) < 304+InLeapYear(t)
=
+ 10 if 304+InLeapYear(t) ≤
+ DayWithinYear (t) < 334+InLeapYear(t)
=
+ 11 if 334+InLeapYear(t) ≤
+ DayWithinYear (t) < 365+InLeapYear(t)
where
++ DayWithinYear(t) = + Day(t)−DayFromYear(YearFromTime(t))
++ A + month value of 0 + specifies January; 1 + specifies February; 2 + specifies March; 3 + specifies April; 4 specifies + May; 5 specifies June; 6 + specifies July; 7 + specifies August; 8 + specifies September; 9 + specifies October; 10 + specifies November; and 11 + specifies December. Note that MonthFromTime(0) + = 0, corresponding to Thursday, 01 January, 1970.
++ A + date number is identified by an integer in the range 1 + through 31, inclusive. + The mapping DateFromTime(t) from a time value t to a + month number is defined by:
+
+ DateFromTime(t) =
+ DayWithinYear(t)+1 if MonthFromTime(t)=0
=
+ DayWithinYear(t)−30 if
+ MonthFromTime(t)=1
= DayWithinYear(t)−58−InLeapYear(t) if
+ MonthFromTime(t)=2
= DayWithinYear(t)−89−InLeapYear(t) if
+ MonthFromTime(t)=3
=
+ DayWithinYear(t)−119−InLeapYear(t) if
+ MonthFromTime(t)=4
=
+ DayWithinYear(t)−150−InLeapYear(t) if
+ MonthFromTime(t)=5
=
+ DayWithinYear(t)−180−InLeapYear(t) if
+ MonthFromTime(t)=6
=
+ DayWithinYear(t)−211−InLeapYear(t) if
+ MonthFromTime(t)=7
=
+ DayWithinYear(t)−242−InLeapYear(t) if
+ MonthFromTime(t)=8
=
+ DayWithinYear(t)−272−InLeapYear(t) if
+ MonthFromTime(t)=9
=
+ DayWithinYear(t)−303−InLeapYear(t) if
+ MonthFromTime(t)=10
=
+ DayWithinYear(t)−333−InLeapYear(t) if
+ MonthFromTime(t)=11
+ The + weekday for a particular time value t + is defined as
++ WeekDay(t) + = (Day(t) + 4) modulo 7
++ A + weekday value of 0 + specifies Sunday; 1 + specifies Monday; 2 + specifies Tuesday; 3 + specifies Wednesday; 4 specifies + Thursday; 5 specifies + Friday; and 6 specifies + Saturday. Note that WeekDay(0) = + 4, corresponding to Thursday, 01 January, 1970.
++ An + implementation of ECMAScript is expected to determine the local time + zone adjustment. The local time zone adjustment is a value LocalTZA + measured in milliseconds which when added to UTC represents the + local standard time. Daylight saving time is not + reflected by LocalTZA. The value LocalTZA does not vary with time + but depends only on the geographic location.
++ An + implementation of ECMAScript is expected to determine the daylight + saving time algorithm. The algorithm to determine the daylight + saving time adjustment DaylightSavingTA(t), measured in + milliseconds, must depend only on four things:
++ (1) + the time since the beginning of the year
++ t + – TimeFromYear(YearFromTime(t))
++ (2) + whether t is in a + leap year
++ InLeapYear(t)
++ (3) + the week day of the beginning of the year
++ WeekDay(TimeFromYear(YearFromTime(t))
++ and + (4) the geographic location.
++ The + implementation of ECMAScript should not try to determine whether the + exact time was subject to daylight saving time, but just whether + daylight saving time would have been in effect if the current + daylight saving time algorithm had been used at the time. This + avoids complications such as taking into account the years that the + locale observed daylight saving time year round.
++ If + the host environment provides functionality for determining daylight + saving time, the implementation of ECMAScript is free to map the + year in question to an equivalent year (same leap-year-ness and same + starting week day for the year) for which the host environment + provides daylight saving time information. The only restriction is + that all equivalent years should produce the same result.
++ Conversion + from UTC to local time is defined by
++ LocalTime(t) + = t + LocalTZA + DaylightSavingTA(t)
++ Conversion + from local time to UTC is defined by
++ UTC(t) + = t – + LocalTZA – DaylightSavingTA(t + – LocalTZA)
++ Note + that UTC(LocalTime(t)) + is not necessarily always equal to t.
++ The + following functions are useful in decomposing time values:
++ HourFromTime(t) = + floor(t / msPerHour) modulo HoursPerDay
++ MinFromTime(t) = + floor(t / msPerMinute) modulo MinutesPerHour
++ SecFromTime(t) = + floor(t / msPerSecond) modulo SecondsPerMinute
++ msFromTime(t) = + t modulo msPerSecond
++ where
++ HoursPerDay = + 24
++ MinutesPerHour = + 60
++ SecondsPerMinute = + 60
++ msPerSecond = + 1000
++ msPerMinute = + 60000 = msPerSecond × + SecondsPerMinute
++ msPerHour = + 3600000 = msPerMinute × + MinutesPerHour
++ The + operator MakeTime calculates a number of milliseconds from its four + arguments, which must be ECMAScript Number values. This operator + functions as follows:
++ If + hour is not finite or min is not finite or sec + is not finite or ms is not finite, return NaN.
++ Let + h be ToInteger(hour).
++ Let + m be ToInteger(min).
++ Let + s be ToInteger(sec).
++ Let + milli be ToInteger(ms).
+
+ Let
+ t be h *
+ msPerHour + m
+ * msPerMinute +
+ s *
+ msPerSecond +
+ milli, performing the arithmetic according to IEEE 754 rules
+ (that is, as if using the ECMAScript operators *
+ and +).
+ Return + t.
++ The + operator MakeDay calculates a number of days from its three + arguments, which must be ECMAScript Number values. This operator + functions as follows:
++ If + year is not finite or month is not finite or date + is not finite, return NaN.
++ Let + y be ToInteger(year).
++ Let + m be ToInteger(month).
++ Let + dt be ToInteger(date).
++ Let + ym be y + floor(m /12).
++ Let + mn be m modulo 12.
+
+ Find
+ a value t such that YearFromTime(t) ==
+ ym and MonthFromTime(t) ==
+ mn) and DateFromTime(t) ==
+ 1; but if this is not possible (because some argument is out of
+ range), return NaN.
+ Return + Day(t) + dt − 1.
++ The + operator MakeDate calculates a number of milliseconds from its two + arguments, which must be ECMAScript Number values. This operator + functions as follows:
++ If + day is not finite or time is not finite, return NaN.
++ Return + day × msPerDay + time.
++ The + operator TimeClip calculates a number of milliseconds from its + argument, which must be an ECMAScript Number value. This operator + functions as follows:
++ If + time is not finite, return NaN.
++ If + abs(time) > 8.64 x 1015, + return NaN.
++ Return + an implementation-dependent choice of either ToInteger(time) + or ToInteger(time) + (+0). (Adding a positive zero + converts −0 to + +0.)
++
NOTE The point of + step 3 is that an implementation is permitted a choice of internal + representations of time values, for example as a 64-bit signed + integer or as a 64-bit floating-point value. Depending on the + implementation, this internal representation may or may not + distinguish −0 and + +0.
+
+ ECMAScript
+ defines a string interchange format for date-times based upon a
+ simplification of the ISO 8601 Extended Format. The format is as
+ follows: YYYY-MM-DDTHH:mm:ss.sssZ
+ Where + the fields are as follows:
+YYYY | is the decimal digits of the year in the Gregorian calendar. |
- | “:” (hyphen) appears literally twice in the string. |
MM | is the month of the year from 01 (January) to 12 (December). |
DD | is the day of the month from 01 to 31. |
T | “T” appears literally in the string, to indicate the beginning of the time element. |
HH | is the number of complete hours that have passed since midnight as two decimal digits. |
: | “:” (colon) appears literally twice in the string. |
mm | is the number of complete minutes since the start of the hour as two decimal digits. |
ss | is the number of complete seconds since the start of the minute as two decimal digits. |
. | “.” (dot) appears literally in the string. |
sss | is the number of complete milliseconds since the start of the second as three decimal digits. |
Z | is the time zone offset specified as “Z” (for UTC) or either
+ “+” or “-” followed by a time expression hh:mm |
This + format includes date-only forms:
+YYYY
YYYY-MM
YYYY-MM-DD
It also includes “date-time” forms that consist of one of the above
+date-only forms immediately followed by “T”
+and one of the following time forms with an optional time zone offset
+appended:
+ THH:mm
THH:mm:ss
THH:mm:ss.sss
All
+ numbers must be base 10.
+If the MM or DD fields are absent
+“01” is used as the value. If the mm or
+ss fields are absent “00” is used as the value
+and the value of an absent sss file is “000”. The
+value of an absent time zone offset is “Z”.
+ Illegal + values (out-of-bounds as well as syntax errors) in a format string + means that the format string is not a valid instance of this format.
+NOTE 1 As every day both starts and ends with
+ midnight, the two notations 00:00
+ and 24:00
+ are available to distinguish the two midnights that can be
+ associated with one date. This means that the following two
+ notations refer to exactly the same point in time: 1995-02-04T24:00
+ and 1995-02-05T00:00
NOTE 2 There exists no international standard that + specifies abbreviations for civil time zones like CET, EST, etc. and + sometimes the same abbreviation is even used for two very different + time zones. For this reason, ISO 8601 and this format specifies + numeric representations of date and time.
++ ECMAScript + requires the ability to specify 6 + digit years (extended years); approximately 285,616 + years, either forward or backward, from 01 January, 1970 UTC. To + represent years before 0 + or after 9999, ISO 8601 + permits the expansion of the year representation, but only by prior + agreement between the sender and the receiver. In the simplified + ECMAScript format such an expanded year representation shall have 2 + extra year digits and is always prefixed with a + or – sign. The + year 0 is considered + positive and hence prefixed with a + sign.
+
+ When
+ Date is called as
+ a function rather than as a constructor, it returns a String
+ representing the current time (UTC).
NOTE The
+ function call Date(…)
+ is not equivalent to the object creation expression new Date(…)
+ with the same arguments.
+ All
+ of the arguments are optional; any arguments supplied are accepted
+ but are completely ignored. A String is created and returned as if
+ by the expression (new
+ Date()).toString() where Date
+ is the standard built-in constructor with that name and toString
+ is the standard built-in method Date.prototype.toString.
+ When
+ Date is called as
+ part of a new
+ expression, it is a constructor: it initialises the newly created
+ object.
+ When + Date is called with two to seven arguments, it computes the + date from year, month, and (optionally) date, + hours, minutes, seconds and ms.
+
+ The
+ [[Prototype]] internal property of the newly constructed object is
+ set to the original Date prototype object, the one that is the
+ initial value of Date.prototype
+ (15.9.4.1).
+ The
+ [[Class]] internal property of the newly constructed object is set
+ to "Date".
+ The + [[Extensible]] internal property of the newly constructed object is + set to true.
++ The + [[PrimitiveValue]] internal property of the newly constructed object + is set as follows:
++ Let + y be ToNumber(year).
++ Let + m be ToNumber(month).
++ If + date is supplied then let dt be ToNumber(date); + else let dt be 1.
++ If + hours is supplied then let h be ToNumber(hours); + else let h be 0.
++ If + minutes is supplied then let min be + ToNumber(minutes); else let min be 0.
++ If + seconds is supplied then let s be ToNumber(seconds); + else let s be 0.
++ If + ms is supplied then let milli be ToNumber(ms); + else let milli be 0.
++ If y is not NaN and 0 ≤ ToInteger(y) ≤ 99, then + let yr be 1900+ToInteger(y); otherwise, let yr + be y.
++ Let + finalDate be MakeDate(MakeDay(yr, m, dt), + MakeTime(h, min, s, milli)).
++ Set + the [[PrimitiveValue]] internal property of the newly constructed + object to TimeClip(UTC(finalDate)).
+
+ The
+ [[Prototype]] internal property of the newly constructed object is
+ set to the original Date prototype object, the one that is the
+ initial value of Date.prototype
+ (15.9.4.1).
+ The
+ [[Class]] internal property of the newly constructed object is set
+ to "Date".
+ The + [[Extensible]] internal property of the newly constructed object is + set to true.
++ The + [[PrimitiveValue]] internal property of the newly constructed object + is set as follows:
++ Let + v be ToPrimitive(value).
++ If + Type(v) is String, then +
+
+ Parse
+ v as a date, in exactly the same manner as for the parse
+ method (15.9.4.2); let V be the time value for this date.
+ Else, + let V be ToNumber(v).
++ Set + the [[PrimitiveValue]] internal property of the newly constructed + object to TimeClip(V) and return.
+
+ The
+ [[Prototype]] internal property of the newly constructed object is
+ set to the original Date prototype object, the one that is the
+ initial value of Date.prototype
+ (15.9.4.1).
+ The
+ [[Class]] internal property of the newly constructed object is set
+ to "Date".
+ The + [[Extensible]] internal property of the newly constructed object is + set to true.
++ The + [[PrimitiveValue]] internal property of the newly constructed object + is set to the time value (UTC) identifying the current time.
++ The + value of the [[Prototype]] internal property of the Date constructor + is the Function prototype object (15.3.4).
+
+ Besides
+ the internal properties and the length
+ property (whose value is 7),
+ the Date constructor has the following properties:
+ The
+ initial value of Date.prototype
+ is the built-in Date prototype object (15.9.5).
+ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+
+ The
+ parse function
+ applies the ToString operator to its argument and interprets the
+ resulting String as a date and time; it returns a Number, the UTC
+ time value corresponding to the date and time. The String may be
+ interpreted as a local time, a UTC time, or a time in some other
+ time zone, depending on the contents of the String. The function
+ first attempts to parse the format of the String according to the
+ rules called out in Date Time String Format (15.9.1.15). If the
+ String does not conform to that format the function may fall back to
+ any implementation-specific heuristics or implementation-specific
+ date formats. Unrecognizable Strings or dates containing illegal
+ element values in the format String shall cause Date.parse
+ to return NaN.
If + x is any Date + object whose milliseconds amount is zero within a particular + implementation of ECMAScript, then all of the following expressions + should produce the same numeric value in that implementation, if all + the properties referenced have their initial values:
+
+ x.valueOf()
+ Date.parse(x.toString())
+ Date.parse(x.toUTCString())
+ Date.parse(x.toISOString())
However, + the expression
+
+ Date.parse( x.toLocaleString())
+ is
+ not required to produce the same Number value as the preceding three
+ expressions and, in general, the value produced by Date.parse
+ is implementation-dependent when given any String value that does
+ not conform to the Date Time String Format (15.9.1.15) and that
+ could not be produced in that implementation by the toString
+ or toUTCString
+ method.
+ When
+ the UTC function
+ is called with fewer than two arguments, the behaviour is
+ implementation-dependent. When the UTC
+ function is called with two to seven arguments, it computes the date
+ from year, month
+ and (optionally) date,
+ hours, minutes,
+ seconds and ms.
+ The following steps are taken:
+ Let + y be ToNumber(year).
++ Let + m be ToNumber(month).
++ If + date is supplied then let dt be ToNumber(date); + else let dt be 1.
++ If + hours is supplied then let h be ToNumber(hours); + else let h be 0.
++ If + minutes is supplied then let min be + ToNumber(minutes); else let min be 0.
++ If + seconds is supplied then let s be ToNumber(seconds); + else let s be 0.
++ If + ms is supplied then let milli be ToNumber(ms); + else let milli be 0.
++ If y is not NaN and 0 ≤ ToInteger(y) ≤ 99, then + let yr be 1900+ToInteger(y); otherwise, let yr + be y.
++ Return + TimeClip(MakeDate(MakeDay(yr, m, dt), + MakeTime(h, min, s, milli))).
+
+ The
+ length property of
+ the UTC function
+ is 7.
NOTE The
+ UTC function differs from
+ the Date constructor in
+ two ways: it returns a time value as a Number, rather than creating
+ a Date object, and it interprets the arguments in UTC rather than as
+ local time.
+ The
+ now function
+ return a Number value that is the time value designating the UTC
+ date and time of the occurrence of the call to now.
+ The
+ Date prototype object is itself a Date object (its [[Class]] is
+ "Date")
+ whose [[PrimitiveValue]] is NaN.
+ The + value of the [[Prototype]] internal property of the Date prototype + object is the standard built-in Object prototype object (15.2.4).
+
+ In
+ following descriptions of functions that are properties of the Date
+ prototype object, the phrase “this Date object” refers to the
+ object that is the this value for the invocation of the
+ function. Unless explicitly noted otherwise, none of these functions
+ are generic; a TypeError exception is thrown if the this
+ value is not an object for which the value of the [[Class]] internal
+ property is "Date".
+ Also, the phrase “this time value” refers to the Number value
+ for the time represented by this Date object, that is, the value of
+ the [[PrimitiveValue]] internal property of this Date object.
+ The
+ initial value of Date.prototype.constructor
+ is the built-in Date
+ constructor.
+ This + function returns a String value. The contents of the String are + implementation-dependent, but are intended to represent the Date in + the current time zone in a convenient, human-readable form.
+NOTE For
+ any Date value d
+ whose milliseconds amount is zero, the result of
+ Date.parse(d.toString())
+ is equal to d.valueOf().
+ See 15.9.4.2.
+ This + function returns a String value. The contents of the String are + implementation-dependent, but are intended to represent the “date” + portion of the Date in the current time zone in a convenient, + human-readable form.
++ This + function returns a String value. The contents of the String are + implementation-dependent, but are intended to represent the “time” + portion of the Date in the current time zone in a convenient, + human-readable form.
++ This + function returns a String value. The contents of the String are + implementation-dependent, but are intended to represent the Date in + the current time zone in a convenient, human-readable form that + corresponds to the conventions of the host environment’s current + locale.
+NOTE The + first parameter to this function is likely to be used in a future + version of this standard; it is recommended that implementations do + not use this parameter position for anything else.
++ This + function returns a String value. The contents of the String are + implementation-dependent, but are intended to represent the “date” + portion of the Date in the current time zone in a convenient, + human-readable form that corresponds to the conventions of the host + environment’s current locale.
+NOTE The + first parameter to this function is likely to be used in a future + version of this standard; it is recommended that implementations do + not use this parameter position for anything else.
++ This + function returns a String value. The contents of the String are + implementation-dependent, but are intended to represent the “time” + portion of the Date in the current time zone in a convenient, + human-readable form that corresponds to the conventions of the host + environment’s current locale.
+NOTE The + first parameter to this function is likely to be used in a future + version of this standard; it is recommended that implementations do + not use this parameter position for anything else.
+
+ The
+ valueOf function
+ returns a Number, which is this time value.
+ Return + this time value.
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + YearFromTime(LocalTime(t)).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + YearFromTime(t).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + MonthFromTime(LocalTime(t)).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + MonthFromTime(t).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + DateFromTime(LocalTime(t)).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + DateFromTime(t).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + WeekDay(t).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + HourFromTime(LocalTime(t)).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + HourFromTime(t).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + MinFromTime(LocalTime(t)).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + MinFromTime(t).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + SecFromTime(LocalTime(t)).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + SecFromTime(t).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + msFromTime(LocalTime(t)).
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + msFromTime(t).
++ Returns + the difference between local time and UTC time in minutes.
++ Let + t be this time value.
++ If + t is NaN, return NaN.
++ Return + (t − LocalTime(t)) + / msPerMinute.
++ Set + the [[PrimitiveValue]] internal property of this Date object to v.
++ Return + v.
++ Let + t be the result of LocalTime(this time value).
++ Let + time be MakeTime(HourFromTime(t), MinFromTime(t), + SecFromTime(t), ToNumber(ms)).
++ Set + the [[PrimitiveValue]] internal property of this Date object to u.
++ Return + u.
++ Let + t be this time value.
++ Let + time be MakeTime(HourFromTime(t), MinFromTime(t), + SecFromTime(t), ToNumber(ms)).
++ Set + the [[PrimitiveValue]] internal property of this Date object to v.
++ Return + v.
+
+ If ms
+ is not specified, this behaves as if ms
+ were specified with the value getMilliseconds().
+ Let + t be the result of LocalTime(this time value).
++ Let + s be ToNumber(sec).
++ If + ms is not specified, then let milli be msFromTime(t); + otherwise, let milli be ToNumber(ms).
++ Let + date be MakeDate(Day(t), MakeTime(HourFromTime(t), + MinFromTime(t), s, milli)).
++ Set + the [[PrimitiveValue]] internal property of this Date object to u.
++ Return + u.
+
+ The
+ length property of
+ the setSeconds
+ method is 2.
+ If ms
+ is not specified, this behaves as if ms
+ were specified with the value getUTCMilliseconds().
+ Let + t be this time value.
++ Let + s be ToNumber(sec).
++ If + ms is not specified, then let milli be msFromTime(t); + otherwise, let milli be ToNumber(ms).
++ Let + date be MakeDate(Day(t), MakeTime(HourFromTime(t), + MinFromTime(t), s, milli)).
++ Let + v be TimeClip(date).
++ Set + the [[PrimitiveValue]] internal property of this Date object to v.
++ Return + v.
+
+ The
+ length property of
+ the setUTCSeconds
+ method is 2.
+ If
+ sec is not
+ specified, this behaves as if sec
+ were specified with the value getSeconds().
+ If ms
+ is not specified, this behaves as if ms
+ were specified with the value getMilliseconds().
+ Let + t be the result of LocalTime(this time value).
++ Let + m be ToNumber(min).
++ If + sec is not specified, then let s be SecFromTime(t); + otherwise, let s be ToNumber(sec).
++ If + ms is not specified, then let milli be msFromTime(t); + otherwise, let milli be ToNumber(ms).
++ Let + date be MakeDate(Day(t), MakeTime(HourFromTime(t), + m, s, milli)).
++ Set + the [[PrimitiveValue]] internal property of this Date object to u.
++ Return + u.
+
+ The
+ length property of
+ the setMinutes
+ method is 3.
+ If
+ sec is not
+ specified, this behaves as if sec
+ were specified with the value getUTCSeconds().
+ If ms
+ is not specified, this function behaves as if ms
+ were specified with the value return by getUTCMilliseconds().
+ Let + t be this time value.
++ Let + m be ToNumber(min).
++ If + sec is not specified, then let s be SecFromTime(t); + otherwise, let s be ToNumber(sec).
++ If + ms is not specified, then let milli be msFromTime(t); + otherwise, let milli be ToNumber(ms).
++ Let + date be MakeDate(Day(t), MakeTime(HourFromTime(t), + m, s, milli)).
++ Let + v be TimeClip(date).
++ Set + the [[PrimitiveValue]] internal property of this Date object to v.
++ Return + v.
+
+ The
+ length property of
+ the setUTCMinutes
+ method is 3.
+ If
+ min is not
+ specified, this behaves as if min
+ were specified with the value getMinutes().
+ If
+ sec is not
+ specified, this behaves as if sec
+ were specified with the value getSeconds().
+ If ms
+ is not specified, this behaves as if ms
+ were specified with the value getMilliseconds().
+ Let + t be the result of LocalTime(this time value).
++ Let + h be ToNumber(hour).
++ If + min is not specified, then let m be MinFromTime(t); + otherwise, let m be ToNumber(min).
++ If + If sec is not specified, then let s be + SecFromTime(t); otherwise, let s be ToNumber(sec).
++ If + ms is not specified, then let milli be msFromTime(t); + otherwise, let milli be ToNumber(ms).
++ Let + date be MakeDate(Day(t), MakeTime(h, m, + s, milli)).
++ Set + the [[PrimitiveValue]] internal property of this Date object to u.
++ Return + u.
+
+ The
+ length property of
+ the setHours
+ method is 4.
+ If
+ min is not
+ specified, this behaves as if min
+ were specified with the value getUTCMinutes().
+ If
+ sec is not
+ specified, this behaves as if sec
+ were specified with the value getUTCSeconds().
+ If ms
+ is not specified, this behaves as if ms
+ were specified with the value getUTCMilliseconds().
+ Let + t be this time value.
++ Let + h be ToNumber(hour).
++ If + min is not specified, then let m be MinFromTime(t); + otherwise, let m be ToNumber(min).
++ If + sec is not specified, then let s be SecFromTime(t); + otherwise, let s be ToNumber(sec).
++ If + ms is not specified, then let milli be msFromTime(t); + otherwise, let milli be ToNumber(ms).
++ Let + newDate be MakeDate(Day(t), MakeTime(h, m, + s, milli)).
++ Let + v be TimeClip(newDate).
++ Set + the [[PrimitiveValue]] internal property of this Date object to v.
++ Return + v.
+
+ The
+ length property of
+ the setUTCHours
+ method is 4.
+ Let + t be the result of LocalTime(this time value).
++ Let + dt be ToNumber(date).
++ Let + newDate be MakeDate(MakeDay(YearFromTime(t), + MonthFromTime(t), dt), TimeWithinDay(t)).
++ Set + the [[PrimitiveValue]] internal property of this Date object to u.
++ Return + u.
++ Let + t be this time value.
++ Let + dt be ToNumber(date).
++ Let + newDate be MakeDate(MakeDay(YearFromTime(t), + MonthFromTime(t), dt), TimeWithinDay(t)).
++ Let + v be TimeClip(newDate).
++ Set + the [[PrimitiveValue]] internal property of this Date object to v.
++ Return + v.
+
+ If
+ date is not
+ specified, this behaves as if date
+ were specified with the value getDate().
+ Let + t be the result of LocalTime(this time value).
++ Let + m be ToNumber(month).
++ If + date is not specified, then let dt be + DateFromTime(t); otherwise, let dt be ToNumber(date).
++ Let + newDate be MakeDate(MakeDay(YearFromTime(t), m, + dt), TimeWithinDay(t)).
++ Set + the [[PrimitiveValue]] internal property of this Date object to u.
++ Return + u.
+
+ The
+ length property of
+ the setMonth
+ method is 2.
+ If
+ date is not
+ specified, this behaves as if date
+ were specified with the value getUTCDate().
+ Let + t be this time value.
++ Let + m be ToNumber(month).
++ If + date is not specified, then let dt be + DateFromTime(t); otherwise, let dt be ToNumber(date).
++ Let + newDate be MakeDate(MakeDay(YearFromTime(t), m, + dt), TimeWithinDay(t)).
++ Let + v be TimeClip(newDate).
++ Set + the [[PrimitiveValue]] internal property of this Date object to v.
++ Return + v.
+
+ The
+ length property of
+ the setUTCMonth
+ method is 2.
+ If
+ month is not
+ specified, this behaves as if month
+ were specified with the value getMonth().
+ If
+ date is not
+ specified, this behaves as if date
+ were specified with the value getDate().
+ Let + t be the result of LocalTime(this time value); but if this time value is NaN, let t be +0.
++ Let + y be ToNumber(year).
++ If + month is not specified, then let m be + MonthFromTime(t); otherwise, let m be + ToNumber(month).
++ If + date is not specified, then let dt be + DateFromTime(t); otherwise, let dt be ToNumber(date).
++ Let + newDate be MakeDate(MakeDay(y, m, dt), + TimeWithinDay(t)).
++ Set + the [[PrimitiveValue]] internal property of this Date object to u.
++ Return + u.
+
+ The
+ length property of
+ the setFullYear
+ method is 3.
+ If
+ month is not
+ specified, this behaves as if month
+ were specified with the value getUTCMonth().
+ If
+ date is not
+ specified, this behaves as if date
+ were specified with the value getUTCDate().
+ Let + t be this time value; but if this time value is NaN, + let t be +0.
++ Let + y be ToNumber(year).
++ If + month is not specified, then let m be + MonthFromTime(t); otherwise, let m be + ToNumber(month).
++ If + date is not specified, then let dt be + DateFromTime(t); otherwise, let dt be ToNumber(date).
++ Let + newDate be MakeDate(MakeDay(y, m, dt), + TimeWithinDay(t)).
++ Let + v be TimeClip(newDate).
++ Set + the [[PrimitiveValue]] internal property of this Date object to v.
++ Return + v.
+
+ The
+ length property of
+ the setUTCFullYear
+ method is 3.
+ This + function returns a String value. The contents of the String are + implementation-dependent, but are intended to represent the Date in + a convenient, human-readable form in UTC.
+NOTE The
+ intent is to produce a String representation of a date that is more
+ readable than the format specified in 15.9.1.15. It is not essential
+ that the chosen format be unambiguous or easily machine parsable. If
+ an implementation does not have a preferred human-readable format it
+ is recommended to use the format defined in 15.9.1.15 but with a
+ space rather than a “T”
+ used to separate the date and time elements.
+ This + function returns a String value represent the instance in time + represented by this Date object. The format of the String is the + Date Time string format defined in 15.9.1.15. All fields are present + in the String. The time zone is always UTC, denoted by the suffix Z. + If the time value of this object is not a finite Number a RangeError + exception is thrown.
+
+ This
+ function provides a String representation of a Date object for use
+ by JSON.stringify
+ (15.12.3).
+ When
+ the toJSON method
+ is called with argument key,
+ the following steps are taken:
+ Let + O be the result of calling ToObject, giving it the this + value as its argument.
++ Let + tv be ToPrimitive(O, hint Number).
++ If + tv is a Number and is not finite, return null.
+
+ Let
+ toISO be the result of calling the [[Get]] internal method
+ of O with argument "toISOString".
+ If + IsCallable(toISO) is false, throw a TypeError + exception.
++ Return + the result of calling the [[Call]] internal method of toISO + with O as the this value and an empty argument list.
+NOTE 1 The argument is ignored.
+NOTE 2 The toJSON
+ function is intentionally generic; it does not require that its this
+ value be a Date object. Therefore, it can be transferred to other
+ kinds of objects for use as a method. However, it does require that
+ any such object have a toISOString
+ method. An object is free to use the argument key
+ to filter its stringification.
+
+ Date
+ instances inherit properties from the Date prototype object and
+ their [[Class]] internal property value is "Date".
+ Date instances also have a [[PrimitiveValue]] internal property.
+ The + [[PrimitiveValue]] internal property is time value represented by + this Date object.
++ A + RegExp object contains a regular expression and the associated + flags.
+NOTE The + form and functionality of regular expressions is modelled after the + regular expression facility in the Perl 5 programming language.
+
+ The
+ RegExp constructor
+ applies the following grammar to the input pattern String. An error
+ occurs if the grammar cannot interpret the String as an expansion of
+ Pattern.
+ Syntax
++ Pattern ::
++ Disjunction
++ Disjunction ::
+
+ Alternative
+ Alternative | Disjunction
+ Alternative ::
+
+ [empty]
Alternative
+ Term
+ Term ::
+
+ Assertion
Atom
Atom
+ Quantifier
+ Assertion ::
+
+ ^ $ \
+ b \
+ B
+
(?
+ =
+ Disjunction ) (
+ ?
+ !
+ Disjunction )
+ Quantifier ::
+
+ QuantifierPrefix
QuantifierPrefix
+ ?
+ QuantifierPrefix ::
+
+ *
+? { DecimalDigits } { DecimalDigits
+ ,
+ } { DecimalDigits
+ , DecimalDigits }
+ Atom ::
+
+ PatternCharacter.\
+ AtomEscape
CharacterClass
() (
+ ?
+ :
+ Disjunction )
+ PatternCharacter ::SourceCharacter but + not any + of:
+
+ ^ $
+ \ . * + ? ( ) [ ] { } |
+ AtomEscape ::
+
+ DecimalEscape
CharacterEscape
CharacterClassEscape
+ CharacterEscape ::
+
+ ControlEscapec
+ ControlLetter
HexEscapeSequence
UnicodeEscapeSequence
IdentityEscape
+ ControlEscape :: + one + of
+
+ f
+ n r t v
+ ControlLetter :: + one + of
+
+ a
+ b c d e f g h i j k l m n o p q r s t u v w x
+ y z
A B C D E F G H I J K L M N O P Q R S T
+ U V W X Y Z
+ IdentityEscape ::
+
+ SourceCharacter but
+ not
+ IdentifierPart
<ZWJ>
<ZWNJ>
+ DecimalEscape ::
++ DecimalIntegerLiteral [lookahead + ∉ + DecimalDigit]
++ CharacterClassEscape :: + one + of
+
+ d
+ D s S w W
+ CharacterClass ::
+
+ [
+ [lookahead
+ ∉
+ {^}]
+ ClassRanges
+ ] [
+ ^ ClassRanges
+ ]
+ ClassRanges ::
+
+ [empty]
NonemptyClassRanges
+ NonemptyClassRanges ::
+
+ ClassAtom
ClassAtom
+ NonemptyClassRangesNoDash
ClassAtom
+ - ClassAtom ClassRanges
+ NonemptyClassRangesNoDash ::
+
+ ClassAtom
ClassAtomNoDash
+ NonemptyClassRangesNoDash
ClassAtomNoDash
+ - ClassAtom ClassRanges
+ ClassAtom ::
+
+ -
ClassAtomNoDash
+ ClassAtomNoDash ::
+
+ SourceCharacter but
+ not one
+ of \ or ] or - \
+ ClassEscape
+ ClassEscape ::
+
+ DecimalEscapeb
CharacterEscape
+ A + regular expression pattern is converted into an internal procedure + using the process described below. An implementation is encouraged + to use more efficient algorithms than the ones listed below, as long + as the results are the same. The internal procedure is used as the + value of a RegExp object’s [[Match]] internal property.
++ The + descriptions below use the following variables:
++ Input + is the String being matched by the regular expression pattern. The + notation input[n] + means the nth + character of input, + where n can range + between 0 (inclusive) and InputLength + (exclusive).
++ InputLength + is the number of characters in the Input + String.
+
+ NcapturingParens
+ is the total number of left capturing parentheses (i.e. the total
+ number of times the Atom
+ :: (
+ Disjunction )
+ production is expanded) in the pattern. A left capturing
+ parenthesis is any (
+ pattern character that is matched by the (
+ terminal of the Atom
+ :: (
+ Disjunction )
+ production.
+ IgnoreCase
+ is the setting of the RegExp object's ignoreCase
+ property.
+ Multiline
+ is the setting of the RegExp object’s multiline
+ property.
+ Furthermore, + the descriptions below use the following internal data structures:
++ A + CharSet is a + mathematical set of characters.
++ A + State is an + ordered pair (endIndex, + captures) + where endIndex is + an integer and captures + is an internal array of NcapturingParens + values. States + are used to represent partial match states in the regular + expression matching algorithms. The endIndex + is one plus the index of the last input character matched so far by + the pattern, while captures + holds the results of capturing parentheses. The nth + element of captures + is either a String that represents the value obtained by the nth + set of capturing parentheses or undefined if the nth + set of capturing parentheses hasn’t been reached yet. Due to + backtracking, many States + may be in use at any time during the matching process.
++ A + MatchResult is + either a State or + the special token failure that indicates that the match + failed.
++ A + Continuation + procedure is an internal closure (i.e. an internal procedure with + some arguments already bound to values) that takes one State + argument and returns a MatchResult + result. If an internal closure references variables bound in the + function that creates the closure, the closure uses the values that + these variables had at the time the closure was created. The + Continuation + attempts to match the remaining portion (specified by the closure's + already-bound arguments) of the pattern against the input String, + starting at the intermediate state given by its State + argument. If the match succeeds, the Continuation + returns the final State + that it reached; if the match fails, the Continuation + returns failure.
++ A + Matcher procedure + is an internal closure that takes two arguments -- a State + and a Continuation + -- and returns a MatchResult + result. A Matcher + attempts to match a middle subpattern (specified by the closure's + already-bound arguments) of the pattern against the input String, + starting at the intermediate state given by its State + argument. The Continuation + argument should be a closure that matches the rest of the pattern. + After matching the subpattern of a pattern to obtain a new State, + the Matcher then + calls Continuation + on that new State + to test if the rest of the pattern can match as well. If it can, + the matcher returns the State + returned by Continuation; + if not, the Matcher + may try different choices at its choice points, repeatedly calling + Continuation + until it either succeeds or all possibilities have been exhausted.
++ An + AssertionTester + procedure is an internal closure that takes a State + argument and returns a Boolean result. The assertion tester tests a + specific condition (specified by the closure's already-bound + arguments) against the current place in the input String and + returns true if the condition matched or false if + not.
++ An + EscapeValue is + either a character or an integer. An EscapeValue + is used to denote the interpretation of a DecimalEscape + escape sequence: a character ch + means that the escape sequence is interpreted as the character ch, + while an integer n + means that the escape sequence is interpreted as a backreference to + the nth + set of capturing parentheses.
++ The + production Pattern + :: Disjunction + evaluates as follows:
++ Evaluate + Disjunction to obtain a Matcher m.
++ Return + an internal closure that takes two arguments, a String str + and an integer index, and performs the following:
++ Let + Input be the given String str. This variable will be + used throughout the algorithms in 15.10.2.
++ Let + InputLength be the length of Input. This variable + will be used throughout the algorithms in 15.10.2.
++ Let + c be a Continuation that always returns its State argument + as a successful MatchResult.
++ Let + cap be an internal array of NcapturingParens + undefined values, indexed 1 through NcapturingParens.
++ Let + x be the State (index, cap).
++ Call + m(x, c) and return its result.
+NOTE A
+ Pattern evaluates ("compiles") to an internal procedure
+ value. RegExp.prototype.exec
+ can then apply this procedure to a String and an offset within the
+ String to determine whether the pattern would match starting at
+ exactly that offset within the String, and, if it does match, what
+ the values of the capturing parentheses would be. The algorithms in
+ 15.10.2 are designed so that compiling a pattern may throw a
+ SyntaxError exception; on the other hand, once the pattern is
+ successfully compiled, applying its result internal procedure to
+ find a match in a String cannot throw an exception (except for any
+ host-defined exceptions that can occur anywhere such as
+ out-of-memory).
+ The + production Disjunction + :: Alternative + evaluates by evaluating Alternative + to obtain a Matcher + and returning that Matcher.
+
+ The
+ production Disjunction
+ :: Alternative
+ | Disjunction
+ evaluates as follows:
+ Evaluate + Alternative to obtain a Matcher m1.
++ Evaluate + Disjunction to obtain a Matcher m2.
++ Return + an internal Matcher closure that takes two arguments, a State x + and a Continuation c, and performs the following:
++ Call + m1(x, c) and let r be its result.
++ If + r isn't failure, return r.
++ Call + m2(x, c) and return its result.
++
NOTE The
+ | regular
+ expression operator separates two alternatives. The pattern first
+ tries to match the left Alternative
+ (followed by the sequel of the regular expression); if it fails, it
+ tries to match the right Disjunction
+ (followed by the sequel of the regular expression). If the left
+ Alternative, the
+ right Disjunction,
+ and the sequel all have choice points, all choices in the sequel are
+ tried before moving on to the next choice in the left Alternative.
+ If choices in the left Alternative
+ are exhausted, the right Disjunction
+ is tried instead of the left Alternative.
+ Any capturing parentheses inside a portion of the pattern skipped by
+ | produce
+ undefined values instead of Strings. Thus, for example,
+ /a|ab/.exec("abc")
returns
+ the result "a"
+ and not "ab".
+ Moreover,
+ /((a)|(ab))((c)|(bc))/.exec("abc")
returns + the array
+
+ ["abc",
+ "a", "a", undefined, "bc", undefined,
+ "bc"]
and + not
+
+ ["abc",
+ "ab", undefined, "ab", "c", "c",
+ undefined]
+ The + production Alternative + :: [empty] + evaluates by returning a Matcher that takes two arguments, a State x + and a Continuation c, + and returns the result of calling c(x).
++ The + production Alternative + :: Alternative + Term evaluates as + follows:
++ Evaluate + Alternative to obtain a Matcher m1.
++ Evaluate + Term to obtain a Matcher m2.
++ Return + an internal Matcher closure that takes two arguments, a State x + and a Continuation c, and performs the following:
++ Create + a Continuation d that takes a State argument y and + returns the result of calling m2(y, c).
++ Call + m1(x, d) and return its result.
+NOTE Consecutive + Terms try to + simultaneously match consecutive portions of the input String. If + the left Alternative, + the right Term, + and the sequel of the regular expression all have choice points, all + choices in the sequel are tried before moving on to the next choice + in the right Term, + and all choices in the right Term + are tried before moving on to the next choice in the left + Alternative.
++ The + production Term :: + Assertion + evaluates by returning an internal Matcher closure that takes two + arguments, a State x + and a Continuation c, + and performs the following:
++ Evaluate + Assertion to obtain an AssertionTester t.
++ Call + t(x) and let r be the resulting Boolean value.
++ If + r is false, return failure.
++ Call + c(x) and return its result.
++ The + production Term :: + Atom evaluates + by evaluating Atom + to obtain a Matcher and returning that Matcher.
++ The + production Term :: + Atom + Quantifier + evaluates as follows:
++ Evaluate + Atom to obtain a Matcher m.
++ Evaluate + Quantifier to obtain the three results: an integer min, + an integer (or ∞) max, + and Boolean greedy.
++ If + max is finite and less than min, then throw a + SyntaxError exception.
+
+ Let
+ parenIndex be the number of left capturing parentheses in
+ the entire regular expression that occur to the left of this
+ production expansion's Term. This is the total number of
+ times the Atom :: (
+ Disjunction )
+ production is expanded prior to this production's Term plus
+ the total number of Atom :: (
+ Disjunction )
+ productions enclosing this Term.
+ Let
+ parenCount be the number of left capturing parentheses in
+ the expansion of this production's Atom. This is the total
+ number of Atom :: (
+ Disjunction )
+ productions enclosed by this production's Atom.
+ Return + an internal Matcher closure that takes two arguments, a State x + and a Continuation c, and performs the following:
++ Call + RepeatMatcher(m, min, max, greedy, + x, c, parenIndex, parenCount) and + return its result.
++ The + abstract operation RepeatMatcher takes eight parameters, a + Matcher m, an + integer min, an + integer (or ∞) max, + a Boolean greedy, + a State x, a + Continuation c, an + integer parenIndex, + and an integer parenCount, + and performs the following:
++ If + max is zero, then call c(x) and return its + result.
++ Create + an internal Continuation closure d that takes one State argument y and performs the following:
++ If + min is zero and y's endIndex is equal to + x's endIndex, then return failure.
++ If + min is zero then let min2 be zero; otherwise let + min2 be min–1.
++ If + max is ∞, then let + max2 be ∞; otherwise + let max2 be max–1.
++ Call + RepeatMatcher(m, min2, max2, greedy, + y, c, parenIndex, parenCount) and + return its result.
++ Let + cap be a fresh copy of x's captures internal + array.
++ For + every integer k that satisfies parenIndex < k + and k ≤ + parenIndex+parenCount, set cap[k] to + undefined.
++ Let + e be x's endIndex.
++ Let + xr be the State (e, cap).
++ If + min is not zero, then call m(xr, d) and + return its result.
++ If + greedy is false, then
++ Call + c(x) and let z be its result.
++ If + z is not failure, return z.
++ Call + m(xr, d) and return its result.
++ Call + m(xr, d) and let z be its result.
++ If + z is not failure, return z.
++ Call + c(x) and return its result.
+NOTE An + Atom followed by a + Quantifier is + repeated the number of times specified by the Quantifier. + A Quantifier can + be non-greedy, in which case the Atom + pattern is repeated as few times as possible while still matching + the sequel, or it can be greedy, in which case the Atom + pattern is repeated as many times as possible while still matching + the sequel. The Atom + pattern is repeated rather than the input String that it matches, so + different repetitions of the Atom + can match different input substrings.
+NOTE 2 If the Atom and + the sequel of the regular expression all have choice points, the + Atom is first + matched as many (or as few, if non-greedy) times as possible. All + choices in the sequel are tried before moving on to the next choice + in the last repetition of Atom. + All choices in the last (nth) repetition of Atom + are tried before moving on to the next choice in the next-to-last + (n–1)st repetition of Atom; + at which point it may turn out that more or fewer repetitions of + Atom are now + possible; these are exhausted (again, starting with either as few or + as many as possible) before moving on to the next choice in the + (n-1)st repetition of Atom + and so on.
+Compare
+
+ /a[a-z]{2,4}/.exec("abcdefghi")
which
+ returns "abcde"
+ with
+ /a[a-z]{2,4}?/.exec("abcdefghi")
which
+ returns "abc".
Consider + also
+
+ /(aa|aabaac|ba|b|c)*/.exec("aabaac")
which, + by the choice point ordering above, returns the array
+
+ ["aaba",
+ "ba"]
and + not any of:
+
+ ["aabaac",
+ "aabaac"]
+ ["aabaac",
+ "c"]
The + above ordering of choice points can be used to write a regular + expression that calculates the greatest common divisor of two + numbers (represented in unary notation). The following example + calculates the gcd of 10 and 15:
+
+ "aaaaaaaaaa,aaaaaaaaaaaaaaa".replace(/^(a+)\1*,\1+$/,"$1")
+ which
+ returns the gcd in unary notation "aaaaa".
NOTE 3 Step 4 of the RepeatMatcher clears Atom's + captures each time Atom + is repeated. We can see its behaviour in the regular expression
+
+ /(z)((a+)?(b+)?(c))*/.exec("zaacbbbcac")
which + returns the array
+
+ ["zaacbbbcac",
+ "z", "ac", "a", undefined, "c"]
and + not
+
+ ["zaacbbbcac",
+ "z", "ac", "a", "bbb", "c"]
+ because
+ each iteration of the outermost *
+ clears all captured Strings contained in the quantified Atom,
+ which in this case includes capture Strings numbered 2, 3, and 4.
NOTE 4 Step 1 of the RepeatMatcher's d + closure states that, once the minimum number of repetitions has been + satisfied, any more expansions of Atom + that match the empty String are not considered for further + repetitions. This prevents the regular expression engine from + falling into an infinite loop on patterns such as:
+
+ /(a*)*/.exec("b")
or + the slightly more complicated:
+
+ /(a*)b\1+/.exec("baaaac")
which + returns the array
+
+ ["b",
+ ""]
+ The
+ production Assertion
+ :: ^
+ evaluates by returning an internal AssertionTester closure that
+ takes a State argument x
+ and performs the following:
+ Let + e be x's endIndex.
++ If + e is zero, return true.
++ If + Multiline is false, return false.
++ If + the character Input[e–1] is one of LineTerminator, + return true.
++ Return + false.
+
+ The
+ production Assertion
+ :: $
+ evaluates by returning an internal AssertionTester closure that
+ takes a State argument x
+ and performs the following:
+ Let + e be x's endIndex.
++ If + e is equal to InputLength, return true.
++ If + multiline is false, return false.
++ If + the character Input[e] is one of LineTerminator, + return true.
++ Return + false.
+
+ The
+ production Assertion
+ :: \ b
+ evaluates by returning an internal AssertionTester closure that
+ takes a State argument x
+ and performs the following:
+ Let + e be x's endIndex.
++ Call + IsWordChar(e–1) and let a be the Boolean + result.
++ Call + IsWordChar(e) and let b be the Boolean result.
++ If + a is true and b is false, return true.
++ If + a is false and b is true, return true.
++ Return + false.
+
+ The
+ production Assertion
+ :: \ B
+ evaluates by returning an internal AssertionTester closure that
+ takes a State argument x
+ and performs the following:
+ Let + e be x's endIndex.
++ Call + IsWordChar(e–1) and let a be the Boolean + result.
++ Call + IsWordChar(e) and let b be the Boolean result.
++ If + a is true and b is false, return false.
++ If + a is false and b is true, return false.
++ Return + true.
+
+ The
+ production Assertion
+ :: ( ? = Disjunction
+ ) evaluates as follows:
+ Evaluate + Disjunction to obtain a Matcher m.
++ Return + an internal Matcher closure that takes two arguments, a State x + and a Continuation c, and performs the following steps:
++ Let + d be a Continuation that always returns its State argument as a successful MatchResult.
++ Call + m(x, d) and let r be its result.
++ If + r is failure, return failure.
++ Let + y be r's State.
++ Let + cap be y's captures internal array.
++ Let + xe be x's endIndex.
++ Let + z be the State (xe, cap).
++ Call + c(z) and return its result.
+
+ The
+ production Assertion ::
+ ( ? ! Disjunction
+ ) evaluates as follows:
+ Evaluate + Disjunction to obtain a Matcher m.
++ Return + an internal Matcher closure that takes two arguments, a State x + and a Continuation c, and performs the following steps:
++ Let + d be a Continuation that always returns its State argument as a successful MatchResult.
++ Call + m(x, d) and let r be its result.
++ If + r isn't failure, return failure.
++ Call + c(x) and return its result.
++ The + abstract operation IsWordChar + takes an integer parameter e + and performs the following:
++ If + e == –1 or e == InputLength, return false.
++ Let + c be the character Input[e].
++ If + c is one of the sixty-three characters below, return true.
+|
+
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+
+
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+
+
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+
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+
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+
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+
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+
+
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+
+
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+ + | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | +
+ Return + false.
++ The + production Quantifier + :: QuantifierPrefix + evaluates as follows:
++ Evaluate + QuantifierPrefix to obtain the two results: an integer min + and an integer (or ∞) max.
++ Return + the three results min , max, and true.
+
+ The
+ production Quantifier
+ :: QuantifierPrefix
+ ? evaluates as follows:
+ Evaluate + QuantifierPrefix to obtain the two results: an integer min + and an integer (or ∞) max.
++ Return + the three results min , max, and false.
+
+ The
+ production QuantifierPrefix
+ :: *
+ evaluates by returning the two results 0 and ∞.
+ The
+ production QuantifierPrefix
+ :: +
+ evaluates by returning the two results 1 and ∞.
+ The
+ production QuantifierPrefix
+ :: ?
+ evaluates by returning the two results 0 and 1.
+ The
+ production QuantifierPrefix
+ :: { DecimalDigits
+ } evaluates as follows:
+ The
+ production QuantifierPrefix
+ :: { DecimalDigits
+ , } evaluates as follows:
+ Let + i be the MV of DecimalDigits.
++ Return + the two results i and ∞.
+
+ The
+ production QuantifierPrefix
+ :: { DecimalDigits
+ , DecimalDigits
+ } evaluates as follows:
+ Let + i be the MV of the first DecimalDigits.
++ Let + j be the MV of the second DecimalDigits.
++ Return + the two results i and j.
++ The + production Atom :: + PatternCharacter + evaluates as follows:
++ Let + ch be the character represented by PatternCharacter.
++ Let + A be a one-element CharSet containing the character ch.
++ Call + CharacterSetMatcher(A, false) and return its + Matcher result.
+
+ The
+ production Atom ::
+ . evaluates as
+ follows:
+ Let + A be the set of all characters except LineTerminator.
++ Call + CharacterSetMatcher(A, false) and return its + Matcher result.
+
+ The
+ production Atom ::
+ \ AtomEscape
+ evaluates by evaluating AtomEscape
+ to obtain a Matcher and returning that Matcher.
+ The + production Atom :: + CharacterClass + evaluates as follows:
++ Evaluate + CharacterClass to obtain a CharSet A and a Boolean + invert.
++ Call + CharacterSetMatcher(A, invert) and return its + Matcher result.
+
+ The
+ production Atom ::
+ ( Disjunction
+ ) evaluates as follows:
+ Evaluate + Disjunction to obtain a Matcher m.
+
+ Let
+ parenIndex be the number of left capturing parentheses in
+ the entire regular expression that occur to the left of this
+ production expansion's initial left parenthesis. This is the total
+ number of times the Atom :: ( Disjunction )
+ production is expanded prior to this production's Atom plus
+ the total number of Atom :: ( Disjunction )
+ productions enclosing this Atom.
+ Return + an internal Matcher closure that takes two arguments, a State x + and a Continuation c, and performs the following steps:
++ Create + an internal Continuation closure d that takes one State argument y and performs the following steps:
++ Let + cap be a fresh copy of y's captures + internal array.
++ Let + xe be x's endIndex.
++ Let + ye be y's endIndex.
++ Let + s be a fresh String whose characters are the + characters of Input at positions xe (inclusive) + through ye (exclusive).
++ Set + cap[parenIndex+1] to s.
++ Let + z be the State (ye, cap).
++ Call + c(z) and return its result.
++ Call + m(x, d) and return its result.
+
+ The
+ production Atom ::
+ ( ? : Disjunction
+ ) evaluates by evaluating Disjunction
+ to obtain a Matcher and returning that Matcher.
+ The + abstract operation CharacterSetMatcher takes two arguments, a CharSet A + and a Boolean flag invert, + and performs the following:
++ Return + an internal Matcher closure that takes two arguments, a State x + and a Continuation c, and performs the following steps:
++ Let + e be x's endIndex.
++ If + e == InputLength, return failure.
++ Let + ch be the character Input[e].
++ Let + cc be the result of Canonicalize(ch).
++ If + invert is false, then
++ If + there does not exist a member a of set A such + that Canonicalize(a) == cc, return + failure.
++ Else + invert is true,
++ If + there exists a member a of set A such that + Canonicalize(a) == cc, return failure.
++ Let + cap be x's captures internal array.
++ Let + y be the State (e+1, cap).
++ Call + c(y) and return its result.
++ The + abstract operation Canonicalize takes a character parameter ch + and performs the following steps:
++ If + IgnoreCase is false, return ch.
+
+ Let
+ u be ch converted to upper case as if by calling the
+ standard built-in method String.prototype.toUpperCase
+ on the one-character String ch.
+ If + u does not consist of a single character, return ch.
++ Let + cu be u's character.
++ If + ch's code unit value is greater than or equal to decimal 128 + and cu's code unit value is less than decimal 128, then + return ch.
++ Return + cu.
+NOTE 1 Parentheses of the form (
+ Disjunction
+ ) serve both to group the components of the Disjunction
+ pattern together and to save the result of the match. The result can
+ be used either in a backreference (\
+ followed by a nonzero decimal number), referenced in a replace
+ String, or returned as part of an array from the regular expression
+ matching internal procedure. To inhibit the capturing behaviour of
+ parentheses, use the form (?:
+ Disjunction
+ ) instead.
NOTE 2 The form (?= Disjunction
+ ) specifies a zero-width positive lookahead. In order for
+ it to succeed, the pattern inside Disjunction
+ must match at the current position, but the current position is not
+ advanced before matching the sequel. If Disjunction
+ can match at the current position in several ways, only the first
+ one is tried. Unlike other regular expression operators, there is no
+ backtracking into a (?=
+ form (this unusual behaviour is inherited from Perl). This only
+ matters when the Disjunction
+ contains capturing parentheses and the sequel of the pattern
+ contains backreferences to those captures.
For + example,
+
+ /(?=(a+))/.exec("baaabac")
matches
+ the empty String immediately after the first b
+ and therefore returns the array:
+ ["",
+ "aaa"]
To + illustrate the lack of backtracking into the lookahead, consider:
+
+ /(?=(a+))a*b\1/.exec("baaabac")
This + expression returns
+
+ ["aba",
+ "a"]
and + not:
+
+ ["aaaba",
+ "a"]
NOTE 3 The form (?! Disjunction
+ ) specifies a zero-width negative lookahead. In order for
+ it to succeed, the pattern inside Disjunction
+ must fail to match at the current position. The current position is
+ not advanced before matching the sequel. Disjunction
+ can contain capturing parentheses, but backreferences to them only
+ make sense from within Disjunction
+ itself. Backreferences to these capturing parentheses from elsewhere
+ in the pattern always return undefined because the negative
+ lookahead must fail for the pattern to succeed. For example,
+ /(.*?)a(?!(a+)b\2c)\2(.*)/.exec("baaabaac")
looks
+ for an a not
+ immediately followed by some positive number n of a's,
+ a b, another n a's
+ (specified by the first \2)
+ and a c. The
+ second \2 is
+ outside the negative lookahead, so it matches against undefined
+ and therefore always succeeds. The whole expression returns the
+ array:
+ ["baaabaac",
+ "ba", undefined, "abaac"]
+ In
+ case-insignificant matches all characters are implicitly converted
+ to upper case immediately before they are compared. However, if
+ converting a character to upper case would expand that character
+ into more than one character (such as converting "ß"
+ (\u00DF)
+ into "SS"),
+ then the character is left as-is instead. The character is also left
+ as-is if it is not an ASCII character but converting it to upper
+ case would make it into an ASCII character. This prevents Unicode
+ characters such as \u0131
+ and \u017F
+ from matching regular expressions such as /[a z]/i,
+ which are only intended to match ASCII letters. Furthermore, if
+ these conversions were allowed, then /[^\W]/i
+ would match each of a,
+ b,
+ …, h,
+ but not i
+ or s.
+ The + production AtomEscape + :: DecimalEscape + evaluates as follows:
++ Evaluate + DecimalEscape to obtain an EscapeValue E.
++ If + E is a character, then
++ Let + ch be E's character.
++ Let + A be a one-element CharSet containing the character ch.
++ Call + CharacterSetMatcher(A, false) and return its + Matcher result.
++ E + must be an integer. Let n be that integer.
++ If + n=0 or n>NCapturingParens then throw a + SyntaxError exception.
++ Return + an internal Matcher closure that takes two arguments, a State x + and a Continuation c, and performs the following:
++ Let + cap be x's captures internal array.
++ Let + s be cap[n].
++ If + s is undefined, then call c(x) and + return its result.
++ Let + e be x's endIndex.
++ Let + len be s's length.
++ Let + f be e+len.
++ If + f>InputLength, return failure.
++ If + there exists an integer i between 0 (inclusive) and len + (exclusive) such that Canonicalize(s[i]) is + not the same character as Canonicalize(Input + [e+i]), then return failure.
++ Let + y be the State (f, cap).
++ Call + c(y) and return its result.
++ The + production AtomEscape + :: CharacterEscape + evaluates as follows:
++ Evaluate + CharacterEscape to obtain a character ch.
++ Let + A be a one-element CharSet containing the character ch.
++ Call + CharacterSetMatcher(A, false) and return its + Matcher result.
++ The + production AtomEscape + :: CharacterClassEscape + evaluates as follows:
++ Evaluate + CharacterClassEscape to obtain a CharSet A.
++ Call + CharacterSetMatcher(A, false) and return its + Matcher result.
+NOTE An
+ escape sequence of the form \
+ followed by a nonzero decimal number n
+ matches the result of the nth
+ set of capturing parentheses (see 15.10.2.11). It is an error if the
+ regular expression has fewer than n
+ capturing parentheses. If the regular expression has n
+ or more capturing parentheses but the nth
+ one is undefined because it has not captured anything, then
+ the backreference always succeeds.
+ The + production CharacterEscape + :: ControlEscape + evaluates by returning the character according to Table 23 +
+|
+ + ControlEscape + + + |
+
+ + Code + Unit + |
+
+ + Name + |
+
+ + Symbol + |
+
|
+
+ |
+
+
+ |
+
+ + horizontal + tab + |
+
+ + <HT> + |
+
|
+
+ |
+
+
+ |
+
+ + line + feed (new line) + |
+
+ + <LF> + |
+
|
+
+ |
+
+
+ |
+
+ + vertical + tab + |
+
+ + <VT> + |
+
|
+
+ |
+
+
+ |
+
+ + form + feed + |
+
+ + <FF> + |
+
|
+
+ |
+
+
+ |
+
+ + carriage + return + |
+
+ + <CR> + |
+
+ The
+ production CharacterEscape
+ :: c ControlLetter
+ evaluates as follows:
+ Let + ch be the character represented by ControlLetter.
++ Let + i be ch's code unit value.
++ Let + j be the remainder of dividing i by 32.
++ Return + the code unit numbered j.
++ The + production CharacterEscape + :: HexEscapeSequence + evaluates by evaluating the CV of the HexEscapeSequence + (see 7.8.4) and returning its character result.
++ The + production CharacterEscape + :: UnicodeEscapeSequence + evaluates by evaluating the CV of the UnicodeEscapeSequence + (see 7.8.4) and returning its character result.
++ The + production CharacterEscape + :: IdentityEscape + evaluates by returning the character represented by IdentityEscape.
++ The + production DecimalEscape + :: DecimalIntegerLiteral + [lookahead ∉ + DecimalDigit] + evaluates as follows.
++ Let + i be the MV of DecimalIntegerLiteral.
++ If + i is zero, return the EscapeValue consisting of a <NUL> + character (Unicode value 0000).
++ Return + the EscapeValue consisting of the integer i.
++ The + definition of “the MV of DecimalIntegerLiteral” + is in 7.8.3.
+NOTE If
+ \ is followed by a
+ decimal number n
+ whose first digit is not 0,
+ then the escape sequence is considered to be a backreference. It is
+ an error if n is
+ greater than the total number of left capturing parentheses in the
+ entire regular expression. \0
+ represents the <NUL> character and cannot be followed by a
+ decimal digit.
+ The
+ production CharacterClassEscape
+ :: d
+ evaluates by returning the ten-element set of characters containing
+ the characters 0
+ through 9
+ inclusive.
+ The
+ production CharacterClassEscape
+ :: D
+ evaluates by returning the set of all characters not included in the
+ set returned by CharacterClassEscape
+ :: d.
+ The
+ production CharacterClassEscape
+ :: s
+ evaluates by returning the set of characters containing the
+ characters that are on the right-hand side of the WhiteSpace
+ (7.2) or LineTerminator
+ (7.3) productions.
+ The
+ production CharacterClassEscape
+ :: S
+ evaluates by returning the set of all characters not included in the
+ set returned by CharacterClassEscape
+ :: s.
+ The
+ production CharacterClassEscape
+ :: w
+ evaluates by returning the set of characters containing the
+ sixty-three characters:
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+ + | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | ++ | +
+ The
+ production CharacterClassEscape
+ :: W
+ evaluates by returning the set of all characters not included in the
+ set returned by CharacterClassEscape
+ :: w.
+ The
+ production CharacterClass
+ :: [ [lookahead
+ ∉
+ {^}]
+ ClassRanges
+ ] evaluates by evaluating ClassRanges
+ to obtain a CharSet and returning that CharSet and the Boolean
+ false.
+ The
+ production CharacterClass
+ :: [ ^ ClassRanges
+ ] evaluates by evaluating ClassRanges
+ to obtain a CharSet and returning that CharSet and the Boolean true.
+ The
+ production ClassRanges
+ :: [empty]
+ evaluates by returning the empty CharSet.
+ The
+ production ClassRanges
+ :: NonemptyClassRanges
+ evaluates by evaluating NonemptyClassRanges
+ to obtain a CharSet and returning that CharSet.
+ The + production NonemptyClassRanges + :: ClassAtom + evaluates by evaluating ClassAtom + to obtain a CharSet and returning that CharSet.
++ The + production NonemptyClassRanges :: ClassAtom + NonemptyClassRangesNoDash evaluates as follows:
++ Evaluate + ClassAtom to obtain a CharSet A.
++ Evaluate + NonemptyClassRangesNoDash to obtain a CharSet B.
++ Return + the union of CharSets A and B.
+
+ The
+ production NonemptyClassRanges :: ClassAtom
+ - ClassAtom ClassRanges evaluates as follows:
+ Evaluate + the first ClassAtom to obtain a CharSet A.
++ Evaluate + the second ClassAtom to obtain a CharSet B.
++ Evaluate + ClassRanges to obtain a CharSet C.
++ Call + CharacterRange(A, B) and let D be the + resulting CharSet.
++ Return + the union of CharSets D and C.
++ The + abstract operation CharacterRange + takes two CharSet parameters A + and B and performs + the following:
++ If + A does not contain exactly one character or B does + not contain exactly one character then throw a SyntaxError + exception.
++ Let + a be the one character in CharSet A.
++ Let + b be the one character in CharSet B.
++ Let + i be the code unit value of character a.
++ Let + j be the code unit value of character b.
++ If + i > j then throw a SyntaxError exception.
++ Return + the set containing all characters numbered i through j, + inclusive.
++ The + production NonemptyClassRangesNoDash + :: ClassAtom + evaluates by evaluating ClassAtom + to obtain a CharSet and returning that CharSet.
++ The + production NonemptyClassRangesNoDash + :: ClassAtomNoDash + NonemptyClassRangesNoDash + evaluates as follows:
++ Evaluate + ClassAtomNoDash to obtain a CharSet A.
++ Evaluate + NonemptyClassRangesNoDash to obtain a CharSet B.
++ Return + the union of CharSets A and B.
+
+ The
+ production NonemptyClassRangesNoDash
+ :: ClassAtomNoDash
+ - ClassAtom
+ ClassRanges
+ evaluates as follows:
+ Evaluate + ClassAtomNoDash to obtain a CharSet A.
++ Evaluate + ClassAtom to obtain a CharSet B.
++ Evaluate + ClassRanges to obtain a CharSet C.
++ Call + CharacterRange(A, B) and let D be the + resulting CharSet.
++ Return + the union of CharSets D and C.
+NOTE 1 ClassRanges can
+ expand into single ClassAtoms
+ and/or ranges of two ClassAtoms
+ separated by dashes. In the latter case the ClassRanges
+ includes all characters between the first ClassAtom
+ and the second ClassAtom,
+ inclusive; an error occurs if either ClassAtom
+ does not represent a single character (for example, if one is \w)
+ or if the first ClassAtom's
+ code unit value is greater than the second ClassAtom's
+ code unit value.
NOTE 2 Even if the pattern ignores case, the case of the two ends of a
+ range is significant in determining which characters belong to the
+ range. Thus, for example, the pattern /[E-F]/i
+ matches only the letters E,
+ F, e,
+ and f, while the
+ pattern /[E-f]/i
+ matches all upper and lower-case ASCII letters as well as the
+ symbols [, \,
+ ], ^,
+ _, and `.
NOTE 3 A -
+ character can be treated literally or it can denote a range. It is
+ treated literally if it is the first or last character of
+ ClassRanges,
+ the beginning or end limit of a range specification, or immediately
+ follows a range specification.
+ The
+ production ClassAtom
+ :: -
+ evaluates by returning the CharSet containing the one character -.
+ The + production ClassAtom + :: ClassAtomNoDash + evaluates by evaluating ClassAtomNoDash + to obtain a CharSet and returning that CharSet.
+
+ The
+ production ClassAtomNoDash
+ :: SourceCharacter
+ but not one of \
+ or ] or -
+ evaluates by returning a one-element CharSet containing
+ the character represented by SourceCharacter.
+ The
+ production ClassAtomNoDash
+ :: \ ClassEscape
+ evaluates by evaluating ClassEscape
+ to obtain a CharSet and returning that CharSet.
+ The + production ClassEscape + :: DecimalEscape + evaluates as follows:
++ Evaluate + DecimalEscape to obtain an EscapeValue E.
++ If + E is not a character then throw a SyntaxError + exception.
++ Let + ch be E's character.
++ Return + the one-element CharSet containing the character ch.
+
+ The
+ production ClassEscape
+ :: b
+ evaluates by returning the CharSet containing the one character <BS>
+ (Unicode value 0008).
+ The + production ClassEscape + :: CharacterEscape + evaluates by evaluating CharacterEscape + to obtain a character and returning a one-element CharSet containing + that character.
++ The + production ClassEscape + :: CharacterClassEscape + evaluates by evaluating CharacterClassEscape + to obtain a CharSet and returning that CharSet.
+NOTE A
+ ClassAtom can use
+ any of the escape sequences that are allowed in the rest of the
+ regular expression except for \b,
+ \B, and
+ backreferences. Inside a CharacterClass,
+ \b means the
+ backspace character, while \B
+ and backreferences raise errors. Using a backreference inside a
+ ClassAtom causes
+ an error.
+ If
+ pattern is an
+ object R whose
+ [[Class]] internal property is "RegExp"
+ and flags is
+ undefined, then return R
+ unchanged. Otherwise call the standard built-in RegExp
+ constructor (15.10.4.1) as if by the expression new
+ RegExp( pattern,
+ flags)
+ and return the object constructed by that constructor.
+ When
+ RegExp is called
+ as part of a new
+ expression, it is a constructor: it initialises the newly created
+ object.
+ If
+ pattern is an
+ object R whose
+ [[Class]] internal property is "RegExp"
+ and flags is
+ undefined, then let P
+ be the pattern
+ used to construct R
+ and let F be the
+ flags used to construct R.
+ If pattern is an
+ object R whose
+ [[Class]] internal property is "RegExp"
+ and flags is not
+ undefined, then throw a TypeError exception.
+ Otherwise, let P
+ be the empty String if pattern
+ is undefined and ToString(pattern)
+ otherwise, and let F
+ be the empty String if flags
+ is undefined and ToString(flags)
+ otherwise.
+ If + the characters of P + do not have the syntactic form Pattern, + then throw a SyntaxError + exception. Otherwise let the newly constructed object have a + [[Match]] internal property obtained by + evaluating ("compiling") the characters of P + as a Pattern + as described in 15.10.2. +
+
+ If
+ F
+ contains any character other than "g",
+ "i",
+ or "m",
+ or if it contains the same character more than once, then throw a
+ SyntaxError
+ exception.
+
+ If + a SyntaxError + exception is not thrown, then: +
++ Let + S + be a String in the form of a Pattern + equivalent to P, + in which certain characters are escaped as described below. S + may or may not be identical to P + or pattern; + however, the internal procedure that would result from evaluating S + as a Pattern + must behave identically to the internal procedure given by the + constructed object's [[Match]] internal property. + +
+
+ The
+ characters /
+ or backslash
+ \
+ occurring in the pattern shall be escaped in S
+ as necessary to ensure that the String value formed by concatenating
+ the Strings "/",
+ S,
+ "/",
+ and F
+ can be parsed (in an appropriate lexical context) as a
+ RegularExpressionLiteral
+ that behaves identically to the constructed regular expression. For
+ example, if P
+ is "/",
+ then S
+ could be "\/"
+ or "\u002F",
+ among other possibilities, but not "/",
+ because ///
+ followed by F
+ would be parsed as a SingleLineComment
+ rather than a RegularExpressionLiteral.
+ If P
+ is the empty String, this specification can be met by letting S
+ be "(?:)".
+
+
+ The + following properties of the newly constructed object are data + properties with the attributes that are specified in 15.10.7. The + [[Value]] of each property is set as follows:
+
+ The
+ source property of
+ the newly constructed object is set to S.
+ The
+ global property of
+ the newly constructed object is set to a Boolean value that is true
+ if F contains the
+ character "g"
+ and false otherwise.
+ The
+ ignoreCase
+ property of the newly constructed object is set to a Boolean value
+ that is true if F
+ contains the character "i"
+ and false otherwise.
+ The
+ multiline property
+ of the newly constructed object is set to a Boolean value that is
+ true if F
+ contains the character "m"
+ and false otherwise.
+ The
+ lastIndex property
+ of the newly constructed object is set to 0.
+ The + [[Prototype]] internal property of the newly constructed object is + set to the standard built-in RegExp prototype object as specified in + 15.10.6.
+
+ The
+ [[Class]] internal property of the newly constructed object is set
+ to "RegExp".
NOTE If
+ pattern is a StringLiteral,
+ the usual escape sequence substitutions are performed before the
+ String is processed by RegExp. If pattern must contain an escape
+ sequence to be recognised by RegExp, any
+ backslash \
+ characters must be escaped within the StringLiteral
+ to prevent them being removed when the contents of the StringLiteral
+ are formed.
+
+ The + value of the [[Prototype]] internal property of the RegExp + constructor is the standard built-in Function prototype object + (15.3.4).
+
+ Besides
+ the internal properties and the length
+ property (whose value is 2), the RegExp constructor has the
+ following properties:
+ The
+ initial value of RegExp.prototype
+ is the RegExp prototype object (15.10.6).
+ This + property shall have the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+
+ The
+ value of the [[Prototype]] internal property of the RegExp prototype
+ object is the standard built-in Object prototype object (15.2.4).
+ The RegExp prototype object is itself a regular expression object;
+ its [[Class]] is "RegExp".
+ The initial values of the RegExp prototype object’s data
+ properties (15.10.7) are set as if the object was created by the
+ expression new RegExp()
+ where RegExp is
+ that standard built-in constructor with that name.
+ The
+ RegExp prototype object does not have a valueOf
+ property of its own; however, it inherits the valueOf
+ property from the Object prototype object.
+ In
+ the following descriptions of functions that are properties of the
+ RegExp prototype object, the phrase “this RegExp object” refers
+ to the object that is the this value for the invocation of
+ the function; a TypeError exception is thrown if the this
+ value is not an object or an object for which the value of the
+ [[Class]] internal property is not "RegExp".
+ The
+ initial value of RegExp.prototype.constructor
+ is the standard built-in RegExp
+ constructor.
+ Performs + a regular expression match of string + against the regular expression and returns an Array object + containing the results of the match, or null if string + did not match.
++ The + String ToString(string) + is searched for an occurrence of the regular expression pattern as + follows:
++ Let + R be this RegExp object.
++ Let + S be the value of ToString(string).
++ Let + length be the length of S.
+
+ Let
+ lastIndex be the result of calling the [[Get]] internal
+ method of R with argument "lastIndex"..
+ Let + i be the value of ToInteger(lastIndex).
+
+ Let
+ global be the result of calling the [[Get]] internal method
+ of R with argument "global".
+ If + global is false, then let i = 0.
++ Let + matchSucceeded be false.
++ Repeat, + while matchSucceeded is false
++ If + i < 0 or i > length, then
+
+ Call
+ the [[Put]] internal method of R with arguments
+ "lastIndex",
+ 0, and true.
+ Return
+ null.
+ Call + the [[Match]] internal method of R with arguments S + and i.
++ If + [[Match]] returned failure, then +
++ Let + i = i+1.
++ else + +
++ Let + r be the State result of the call to [[Match]].
++ Set + matchSucceeded to true.
++ Let + e be r's endIndex value.
++ If + global is true,
+
+ Call
+ the [[Put]] internal method of R with arguments
+ "lastIndex",
+ e, and true.
+ Let + n be the length of r's captures array. (This + is the same value as 15.10.2.1's NCapturingParens.)
+
+ Let
+ A be a new array created as if by the expression new
+ Array() where Array
+ is the standard built-in constructor with that name.
+ Let + matchIndex be the position of the matched substring within + the complete String S.
+
+ Call
+ the [[DefineOwnProperty]] internal method of A with
+ arguments "index",
+ Property Descriptor {[[Value]]: matchIndex, [[Writable]:
+ true, [[Enumerable]]: true, [[Configurable]]: true},
+ and true.
+ Call
+ the [[DefineOwnProperty]] internal method of A with
+ arguments "input",
+ Property Descriptor {[[Value]]: S, [[Writable]: true,
+ [[Enumerable]]: true, [[Configurable]]: true}, and
+ true.
+ Call
+ the [[DefineOwnProperty]] internal method of A with
+ arguments "length",
+ Property Descriptor {[[Value]]: n + 1}, and true.
+ Let + matchedSubstr be the matched substring (i.e. the portion of + S between offset i inclusive and offset e + exclusive).
+
+ Call
+ the [[DefineOwnProperty]] internal method of A with
+ arguments "0",
+ Property Descriptor {[[Value]]: matchedSubstr, [[Writable]:
+ true, [[Enumerable]]: true, [[Configurable]]: true},
+ and true.
+ For + each integer i such that I > 0 and I ≤ + n
++ Let + captureI be ith element of r's + captures array.
++ Call + the [[DefineOwnProperty]] internal method of A with + arguments ToString(i), Property Descriptor {[[Value]]: + captureI, [[Writable]: true, [[Enumerable]]: true, + [[Configurable]]: true}, and true.
++ Return + A.
++ The + following steps are taken:
+
+ Let
+ match be the result of evaluating the RegExp.prototype.exec
+ (15.10.6.2) algorithm upon this RegExp object using string
+ as the argument.
+ If + match is not null, then return true; else return + false.
+
+ Return
+ the String value formed by concatenating the Strings "/",
+ the String value of the source property of this RegExp
+ object, and "/";
+ plus "g"
+ if the global
+ property is true, "i"
+ if the ignoreCase
+ property is true, and "m"
+ if the multiline
+ property is true.
NOTE The + returned String has the form of a + RegularExpressionLiteral + that evaluates to another RegExp object with the same + behaviour as this object. +
+
+ RegExp
+ instances inherit properties from the RegExp prototype object and
+ their [[Class]] internal property value is "RegExp".
+ RegExp instances also have a [[Match]] internal property and a
+ length property.
+ The + value of the [[Match]] internal property is an implementation + dependent representation of the Pattern + of the RegExp object.
++ RegExp + instances also have the following properties.
+
+ The
+ value of the source
+ property is a String in the form of a Pattern
+ representing the current regular expression. This property shall
+ have the attributes { [[Writable]]: false,
+ [[Enumerable]]: false, [[Configurable]]: false }.
+ The
+ value of the global
+ property is a Boolean value indicating whether the flags contained
+ the character “g”.
+ This property shall have the attributes { [[Writable]]: false,
+ [[Enumerable]]: false, [[Configurable]]: false }.
+ The
+ value of the ignoreCase
+ property is a Boolean value indicating whether the flags contained
+ the character “i”.
+ This property shall have the attributes { [[Writable]]: false,
+ [[Enumerable]]: false, [[Configurable]]: false }.
+ The
+ value of the multiline
+ property is a Boolean value indicating whether the flags contained
+ the character “m”.
+ This property shall have the attributes { [[Writable]]: false,
+ [[Enumerable]]: false, [[Configurable]]: false }.
+ The
+ value of the lastIndex
+ property specifies the String position at which to start the next
+ match. It is coerced to an integer when used (see
+ 15.10.6.2). This property shall have the attributes
+ { [[Writable]]: true, [[Enumerable]]: false,
+ [[Configurable]]: false }.
NOTE Unlike
+ the other standard built-in properties of RegExp instances,
+ lastIndex is
+ writable.
+ Instances + of Error objects are thrown as exceptions when runtime errors occur. + The Error objects may also serve as base objects for user-defined + exception classes.
+
+ When
+ Error is
+ called as a function rather than as a constructor, it creates and
+ initialises a new Error object. Thus the function call Error(…)
+ is equivalent to the object creation expression new
+ Error(…)
+ with the same arguments.
+ The
+ [[Prototype]] internal property of the newly constructed object is
+ set to the original Error prototype object, the one that is the
+ initial value of Error.prototype
+ (15.11.3.1).
+ The
+ [[Class]] internal property of the newly constructed object is set
+ to "Error".
+ The + [[Extensible]] internal property of the newly constructed object is + set to true.
+
+ If
+ the argument message
+ is not undefined, the message
+ own property of the newly constructed object is set to
+ ToString(message).
+ When
+ Error is called as
+ part of a new
+ expression, it is a constructor: it initialises the newly created
+ object.
+ The
+ [[Prototype]] internal property of the newly constructed object is
+ set to the original Error prototype object, the one that is the
+ initial value of Error.prototype
+ (15.11.3.1).
+ The
+ [[Class]] internal property of the newly constructed Error object is
+ set to "Error".
+ The + [[Extensible]] internal property of the newly constructed object is + set to true.
+
+ If
+ the argument message
+ is not undefined, the message
+ own property of the newly constructed object is set to
+ ToString(message).
+ The + value of the [[Prototype]] internal property of the Error + constructor is the Function prototype object (15.3.4).
+
+ Besides
+ the internal properties and the length
+ property (whose value is 1), the Error constructor has the
+ following property:
+ The
+ initial value of Error.prototype
+ is the Error prototype object (15.11.4).
+ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+
+ The
+ Error prototype object is itself an Error object (its [[Class]] is
+ "Error").
+ The + value of the [[Prototype]] internal property of the Error prototype + object is the standard built-in Object prototype object (15.2.4).
+
+ The
+ initial value of Error.prototype.constructor
+ is the built-in Error
+ constructor.
+ The
+ initial value of Error.prototype.name
+ is "Error".
+ The
+ initial value of Error.prototype.message
+ is the empty String.
+ The + following steps are taken:
++ Let + O be the this value.
+
+ Let
+ name be the result of calling the [[Get]] internal method of
+ O with argument "name".
+ If
+ name is undefined, then let name be "Error";
+ else let name be ToString(name).
+ Let
+ msg be the result of calling the [[Get]] internal method of
+ O with argument "message".
If + msg is undefined, then let + msg + be + the empty String; else let msg be ToString(msg).
If name and msg are both the empty String, return "Error".
If name is the empty String, return msg.
If msg is the empty String, return name.
Return the result of concatenating name, ":", a single space
+ character, and msg.
+ Error
+ instances inherit properties from the Error prototype object and
+ their [[Class]] internal property value is "Error".
+ Error instances have no special properties.
+ One + of the NativeError objects below is thrown when a runtime + error is detected. All of these objects share the same structure, as + described in 15.11.7.
++ This + exception is not currently used within this specification. This + object remains for compatibility with previous editions of this + specification.
++ Indicates + a numeric value has exceeded the allowable range. See 15.4.2.2, + 15.4.5.1, 15.7.4.2, 15.7.4.5, 15.7.4.6, and 15.7.4.7, 15.9.5.43.
++ Indicate + that an invalid reference value has been detected. See 8.7.1, 8.7.2, + 10.2.1, 10.2.1.1.4, 10.2.1.2.4, and 11.13.1.
++ Indicates + that a parsing error has occurred. See 11.1.5, 11.3.1, 11.3.2, + 11.4.1, 11.4.4, 11.4.5, 11.13.1, 11.13.2, 12.2.1, 12.10.1, 12.14.1, + 13.1, 15.1.2.1, 15.3.2.1, 15.10.2.2, 15.10.2.5, 15.10.2.9, + 15.10.2.15, 15.10.2.19, 15.10.4.1, and 15.12.2.
++ Indicates + the actual type of an operand is different than the expected type. + See 8.6.2, 8.7.2, 8.10.5, 8.12.5, 8.12.7, 8.12.8, 8.12.9, 9.9, 9.10, + 10.2.1, 10.2.1.1.3, 10.6, 11.2.2, 11.2.3, 11.4.1, 11.8.6, 11.8.7, + 11.3.1, 13.2, 13.2.3, 15, 15.2.3.2, 15.2.3.3, 15.2.3.4, 15.2.3.5, + 15.2.3.6, 15.2.3.7, 15.2.3.8, 15.2.3.9, 15.2.3.10, 15.2.3.11, + 15.2.3.12, 15.2.3.13, 15.2.3.14, 15.2.4.3, 15.3.4.2, 15.3.4.3, + 15.3.4.4, 15.3.4.5, 15.3.4.5.2, 15.3.4.5.3, 15.3.5, 15.3.5.3, + 15.3.5.4, 15.4.4.3, 15.4.4.11, 15.4.4.16, 15.4.4.17, 15.4.4.18, + 15.4.4.19, 15.4.4.20, 15.4.4.21, 15.4.4.22, 15.4.5.1, 15.5.4.2, + 15.5.4.3, 15.6.4.2, 15.6.4.3, 15.7.4, 15.7.4.2, 15.7.4.4, 15.7.4.8 [?], + 15.9.5, 15.9.5.44, 15.10.4.1, 15.10.6, 15.11.4.4 and 15.12.3.
++ Indicates + that one of the global URI handling functions was used in a way that + is incompatible with its definition. See 15.1.3.
+
+ When
+ an ECMAScript implementation detects a runtime error, it throws an
+ instance of one of the NativeError objects defined in
+ 15.11.6. Each of these objects has the structure described below,
+ differing only in the name used as the constructor name instead of
+ NativeError, in the name property of the prototype
+ object, and in the implementation-defined message
+ property of the prototype object.
+ For + each error object, references to NativeError in the + definition should be replaced with the appropriate error object name + from 15.11.6.
++ When + a NativeError constructor is called as a function rather than + as a constructor, it creates and initialises a new object. A call + of the object as a function is equivalent to calling it as a + constructor with the same arguments.
+
+ The
+ [[Prototype]] internal property of the newly constructed object is
+ set to the prototype object for this error constructor. The
+ [[Class]] internal property of the newly constructed object is set
+ to "Error".
+ The [[Extensible]] internal property of the newly constructed object
+ is set to true.
+ If
+ the argument message
+ is not undefined, the message
+ own property of the newly constructed object is set to
+ ToString(message).
+ When
+ a NativeError constructor is called as part of a new
+ expression, it is a constructor: it initialises the newly created
+ object.
+ The
+ [[Prototype]] internal property of the newly constructed object is
+ set to the prototype object for this NativeError constructor.
+ The [[Class]] internal property of the newly constructed object is
+ set to "Error".
+ The [[Extensible]] internal property of the newly constructed object
+ is set to true.
+ If
+ the argument message
+ is not undefined, the message
+ property of the newly constructed object is set to
+ ToString(message).
+ The + value of the [[Prototype]] internal property of a NativeError + constructor is the Function prototype object (15.3.4).
+
+ Besides
+ the internal properties and the length
+ property (whose value is 1), each NativeError
+ constructor has the following property:
+ The
+ initial value of NativeError.prototype
+ is a NativeError prototype object (15.11.7.7). Each
+ NativeError constructor has a separate prototype object.
+ This + property has the attributes { [[Writable]]: false, + [[Enumerable]]: false, [[Configurable]]: false }.
+
+ Each
+ NativeError prototype object is an Error object (its
+ [[Class]] is "Error").
+ The + value of the [[Prototype]] internal property of each NativeError + prototype object is the standard built-in Error prototype object + (15.11.4).
+
+ The
+ initial value of the constructor
+ property of the prototype for a given NativeError constructor
+ is the NativeError constructor function itself (15.11.7).
+ The
+ initial value of the name
+ property of the prototype for a given NativeError constructor
+ is the name of the constructor (the name used instead of
+ NativeError).
+ The
+ initial value of the message
+ property of the prototype for a given NativeError constructor
+ is the empty String.
NOTE The
+ prototypes for the NativeError constructors do not themselves
+ provide a toString function,
+ but instances of errors will inherit it from the Error prototype
+ object.
+ NativeError
+ instances inherit properties from their NativeError prototype
+ object and their [[Class]] internal property value is "Error".
+ NativeError instances have no special properties.
+ The + JSON object is a single object that contains two functions, + parse and stringify, that are used to parse and + construct JSON texts. The JSON Data Interchange Format is described + in RFC 4627 <http://www.ietf.org/rfc/rfc4627.txt>. The JSON + interchange format used in this specification is exactly that + described by RFC 4627 with two exceptions:
++ The + top level JSONText + production of the ECMAScript JSON grammar may consist of any + JSONValue rather + than being restricted to being a JSONObject + or a JSONArray as + specified by RFC 4627. +
++ Conforming + implementations of JSON.parse and JSON.stringify must + support the exact interchange format described in this + specification without any deletions or extensions to the format. + This differs from RFC 4627 which permits a JSON parser to accept + non-JSON forms and extensions.
+
+ The
+ value of the [[Prototype]] internal property of the JSON object is
+ the standard built-in Object prototype object (15.2.4). The value of
+ the [[Class]] internal property of the JSON object is "JSON".
+ The value of the [[Extensible]] internal property of the JSON object
+ is set to true.
+ The
+ JSON object does not have a [[Construct]] internal property; it is
+ not possible to use the JSON object as a constructor with the new
+ operator.
+ The + JSON object does not have a [[Call]] internal property; it is not + possible to invoke the JSON object as a function.
++ JSON.stringify + produces a String that conforms to the following JSON grammar. + JSON.parse accepts a String that conforms to the JSON grammar.
++ JSON + is similar to ECMAScript source text in that it consists of a + sequence of characters conforming to the rules of SourceCharacter. + The JSON Lexical Grammar defines the tokens that make up a JSON text + similar to the manner that the ECMAScript lexical grammar defines + the tokens of an ECMAScript source test. The JSON Lexical grammar + only recognizes the white space character specified by the + production JSONWhiteSpace. + The JSON lexical grammar shares some productions with the + ECMAScript lexical grammar. All nonterminal symbols of the grammar + that do not begin with the characters “JSON” are defined by + productions of the ECMAScript lexical grammar.
++ Syntax
++ JSONWhiteSpace ::
+
+ <TAB>
<CR>
<LF>
<SP>
+ JSONString ::
+
+ " JSONStringCharactersopt"
+ JSONStringCharacters ::
++ JSONStringCharacter + JSONStringCharactersopt
++ JSONStringCharacter ::
+
+ SourceCharacter but
+ not double-quote " orbackslash \
+ orU+0000 thru U+001F
+ \ JSONEscapeSequence
+ JSONEscapeSequence ::
++ JSONEscapeCharacter
++ UnicodeEscapeSequence +
++ JSONEscapeCharacter :: one + of
+
+ "
+ / \ b f n r t
+ JSONNumber ::
+
+ -optDecimalIntegerLiteral JSONFractionoptExponentPartopt
+ JSONFraction ::
+
+ . DecimalDigits
+ JSONNullLiteral ::
++ NullLiteral
++ JSONBooleanLiteral ::
++ BooleanLiteral
++ The + JSON Syntactic Grammar defines a valid JSON text in terms of tokens + defined by the JSON lexical grammar. The goal symbol of the grammar + is JSONText. +
++ Syntax
++ JSONText : +
++ JSONValue
++ JSONValue : +
+
+ JSONNullLiteral
JSONBooleanLiteral
JSONObject
JSONArray
JSONString
JSONNumber
+ JSONObject :
+
+ {
+ } { JSONMemberList }
+ JSONMember :
+
+ JSONString : JSONValue
+ JSONMemberList :
+
+ JSONMember
+
JSONMemberList ,
+ JSONMember
+
+ JSONArray :
+
+ [
+ ] [ JSONElementList
+ ]
+ JSONElementList :
+
+ JSONValue
JSONElementList
+ , JSONValue
+ The
+ parse function
+ parses a JSON text (a JSON-formatted String) and produces an
+ ECMAScript value. The JSON format is a restricted form of ECMAScript
+ literal. JSON objects are realized as ECMAScript objects. JSON
+ arrays are realized as ECMAScript arrays. JSON strings, numbers,
+ booleans, and null are realized as ECMAScript Strings, Numbers,
+ Booleans, and null. JSON uses a more limited set of white
+ space characters than WhiteSpace
+ and allows Unicode code points U+2028 and U+2029 to directly appear
+ in JSONString
+ literals without using an escape sequence. The process of parsing is
+ similar to 11.1.4 and 11.1.5 as constrained by the JSON grammar.
+ The + optional reviver parameter is a function that takes two + parameters, (key and value). It can filter and + transform the results. It is called with each of the key/value + pairs produced by the parse, and its return value is used instead of + the original value. If it returns what it received, the structure is + not modified. If it returns undefined then the property is + deleted from the result.
++ Let + JText be ToString(text).
++ Parse + JText using the grammars in 15.12.1. Throw a SyntaxError + exception if JText did not conform to the JSON grammar for + the goal symbol JSONText. +
++ Let + unfiltered be the result of parsing and evaluating JText + as if it was the source text of an ECMAScript Program but + using JSONString in place of StringLiteral. + Note that since JText conforms to the JSON grammar this + result will be either a primitive value or an object that is + defined by either an ArrayLiteral or an ObjectLiteral.
++ If + IsCallable(reviver) is true, then
+
+ Let
+ root be a new object created as if by the expression new
+ Object(), where Object
+ is the standard built-in constructor with that name.
+ Call + the [[DefineOwnProperty]] internal method of root with the + empty String, the PropertyDescriptor {[[Value]]: unfiltered, + [[Writable]]: true, [[Enumerable]]: true, + [[Configurable]]: true}, and false as arguments.
++ Return + the result of calling the abstract operation Walk, passing root + and the empty String. The abstract operation Walk is described + below.
++ Else
++ Return + unfiltered.
++ The + abstract operation Walk is a recursive abstract operation that takes + two parameters: a holder + object and the String name + of a property in that object. Walk uses the value of reviver + that was originally passed to the above parse function.
++ Let + val be the result of calling the [[Get]] internal method of + holder with argument name.
++ If + val is an object, then
+
+ If
+ the [[Class]] internal property of val is "Array"
+ Set + I to 0.
+
+ Let
+ len be the result of calling the [[Get]] internal method
+ of val with argument "length".
+ Repeat + while I < len, +
++ Let + newElement be the result of calling the abstract + operation Walk, passing val and ToString(I).
++ If + newElement is undefined, then
++ Call + the [[Delete]] internal method of val with ToString(I) + and false as arguments. +
++ Else
++ Call + the [[DefineOwnProperty]] internal method of val with + arguments ToString(I), the Property Descriptor + {[[Value]]: newElement, [[Writable]]: true, + [[Enumerable]]: true, [[Configurable]]: true}, and false.
++ Add + 1 to I.
++ Else
++ Let + keys be an internal List of String values consisting of + the names of all the own properties of val whose + [[Enumerable]] attribute is true. The ordering of the + Strings should be the same as that used by the + Object.keys + standard built-in function.
++ For + each String P in keys do, +
++ Let + newElement be the result of calling the abstract + operation Walk, passing val and P. +
++ If + newElement is undefined, then
++ Call + the [[Delete]] internal method of val with P and + false as arguments. +
++ Else
++ Call + the [[DefineOwnProperty]] internal method of val with + arguments P, the Property Descriptor {[[Value]]: + newElement, [[Writable]]: true, [[Enumerable]]: + true, [[Configurable]]: true}, and false.
++ Return + the result of calling the [[Call]] internal method of reviver + passing holder as the this value and with an argument + list consisting of name and val.
+
+ It is
+ not permitted for a conforming implementation of JSON.parse
+ to extend the JSON grammars. If an implementation wishes to support
+ a modified or extended JSON interchange format it must do so by
+ defining a different parse function.
+
NOTE In + the case where there are duplicate name Strings within an object, + lexically preceding values for the same key shall be overwritten.
+
+ The
+ stringify function
+ returns a String in JSON format representing an ECMAScript value. It
+ can take three parameters. The first parameter is required. The
+ value parameter is
+ an ECMAScript value, which is usually an object or array, although
+ it can also be a String, Boolean, Number or null. The
+ optional replacer
+ parameter is either a function that alters the way objects and
+ arrays are stringified, or an array of Strings and Numbers that acts
+ as a white list for selecting the object properties that will be
+ stringified. The optional space
+ parameter is a String or Number that allows the result to have white
+ space injected into it to improve human readability.
+ These + are the steps in stringifying an object:
++ Let + stack be an empty List.
++ Let + indent be the empty String.
++ Let + PropertyList and ReplacerFunction be undefined.
++ If + Type(replacer) is Object, then
++ If + IsCallable(replacer) is true, then
++ Let + ReplacerFunction be replacer.
+
+ Else
+ if the [[Class]] internal property of replacer is "Array",
+ then
+ Let + PropertyList be an empty internal List
++ For + each value v of a property of replacer that has an + array index property name. The properties are enumerated in the + ascending array index order of their names.
++ Let + item be undefined.
++ If + Type(v) is String then let item be v.
++ Else + if Type(v) is Object then,
+
+ If
+ the [[Class]] internal property of v is "String"
+ or "Number"
+ then let item be ToString(v).
+ If + item is not undefined and item is not currently an + element of PropertyList then,
++ Append + item to the end of PropertyList.
++ If + Type(space) is Object then,
++ If + Type(space) is Number
++ Let + space be min(10, ToInteger(space)).
++ Set + gap to a String containing space space characters. + This will be the empty String if space is less than 1.
++ Else + if Type(space) is String
++ If + the number of characters in space is 10 or less, set gap + to space otherwise set gap to a String consisting of + the first 10 characters of space.
++ Else
++ Set + gap to the empty String.
+
+ Let
+ wrapper be a new object created as if by the expression new
+ Object(), where Object
+ is the standard built-in constructor with that name.
+ Call + the [[DefineOwnProperty]] internal method of wrapper with + arguments the empty String, the Property Descriptor {[[Value]]: + value, [[Writable]]: true, [[Enumerable]]: true, + [[Configurable]]: true}, and false.
++ Return + the result of calling the abstract operation Str with the + empty String and wrapper.
+
+ The
+ abstract operation Str(key,
+ holder)
+ has access to ReplacerFunction from the invocation of the stringify
+ method. Its algorithm is as follows:
+ Let + value be the result of calling the [[Get]] internal method + of holder with argument key.
++ If + Type(value) is Object, then
+
+ Let
+ toJSON be the result of calling the [[Get]] internal method
+ of value with argument "toJSON".
+ If + IsCallable(toJSON) is true
++ Let + value be the result of calling the [[Call]] internal + method of toJSON passing value as the this + value and with an argument list consisting of key.
++ If + ReplacerFunction is not undefined, then
++ Let + value be the result of calling the [[Call]] internal method + of ReplacerFunction passing holder as the this + value and with an argument list consisting of key and + value.
++ If + Type(value) is Object then,
+
+ If
+ the [[Class]] internal property of value is "Number"
+ then,
+ Let + value be ToNumber(value).
+
+ Else
+ if the [[Class]] internal property of value is "String"
+ then,
+ Let + value be ToString(value).
+
+ Else
+ if the [[Class]] internal property of value is "Boolean"
+ then,
+ Let + value be the value of the [[PrimitiveValue]] internal + property of value.
+
+ If
+ value is null then return "null".
+ If
+ value is true then return "true".
+ If
+ value is false then return "false".
+ If + Type(value) is String, then return the result of calling the + abstract operation Quote with argument value.
++ If + Type(value) is Number
++ If + value is finite then return ToString(value).
+
+ Else,
+ return "null".
+ If + Type(value) is Object, and IsCallable(value) is false
++ Return + undefined.
++ The + abstract operation Quote(value) + wraps a String value in double quotes and escapes characters within + it. +
++ Let + product be the double quote character.
++ For + each character C in value
++ If + C is the double quote character or the backslash character
++ Let + product be the concatenation of product and the + backslash character.
++ Let + product be the concatenation of product and C.
++ Else + if C is backspace, formfeed, newline, carriage return, or + tab
++ Let + product be the concatenation of product and the + backslash character.
++ Let + abbrev be the character corresponding to the value of C + as follows:
+backspace "b"
formfeed "f"
newline "n"
carriage return "r"
tab "t"
+ Let + product be the concatenation of product and abbrev.
++ Else + if C is a control character having a code unit value less + than the space character
++ Let + product be the concatenation of product and the + backslash character.
+
+ Let
+ product be the concatenation of product and "u".
+ Let + hex be the result of converting the numeric code unit + value of C to a String of four hexadecimal digits.
++ Let + product be the concatenation of product and hex.
++ Else
++ Let + product be the concatenation of product and C.
++ Let + product be the concatenation of product and the + double quote character.
++ Return + product.
++ The + abstract operation JO(value) + serializes an object. It has access to the stack, + indent, gap, + PropertyList, + ReplacerFunction, + and space of the + invocation of the stringify method.
++ If + stack contains value then throw a TypeError + exception because the structure is cyclical.
++ Append + value to stack.
++ Let + stepback be indent.
++ Let + indent be the concatenation of indent and gap.
++ If + PropertyList is not undefined, then
++ Let + K be PropertyList.
++ Else
++ Let + K be an internal List of Strings consisting of the names of + all the own properties of value whose [[Enumerable]] + attribute is true. The ordering of the Strings should be + the same as that used by the Object.keys standard built-in + function.
++ Let + partial be an empty List.
++ For + each element P of K.
++ Let + strP be the result of calling the abstract operation Str + with arguments P and value.
++ If + strP is not undefined
++ Let + member be the result of calling the abstract operation + Quote with argument P.
++ Let + member be the concatenation of member and the colon + character.
++ If + gap is not the empty String
++ Let + member be the concatenation of member and the + space character.
++ Let + member be the concatenation of member and strP.
++ Append + member to partial.
++ If + partial is empty, then
+
+ Let
+ final be "{}".
+ Else
++ If + gap is the empty String
++ Let + properties be a String formed by concatenating all the + element Strings of partial with each adjacent pair of + Strings separated with the comma character. A comma is not + inserted either before the first String or after the last String. + +
+
+ Let
+ final be the result of concatenating "{",
+ properties, and "}".
+ Else + gap is not the empty String
++ Let + separator be the result of concatenating the comma + character, the line feed character, and indent.
++ Let + properties be a String formed by concatenating all the + element Strings of partial with each adjacent pair of + Strings separated with separator. The separator + String is not inserted either before the first String or after + the last String.
+
+ Let
+ final be the result of concatenating "{",
+ the line feed character, indent, properties, the
+ line feed character, stepback, and "}".
+ Remove + the last element of stack.
++ Let + indent be stepback.
++ Return + final.
+
+ The
+ abstract operation JA(value)
+ serializes an array. It has access to the stack,
+ indent, gap,
+ and space of the
+ invocation of the stringify method. The representation of arrays
+ includes only the elements between zero and array.length
+ – 1 inclusive. Named
+ properties are excluded from the stringification. An array is
+ stringified as an open left bracket, elements separated by comma,
+ and a closing right bracket.
+ If + stack contains value then throw a TypeError + exception because the structure is cyclical.
++ Append + value to stack.
++ Let + stepback be indent.
++ Let + indent be the concatenation of indent and gap.
++ Let + partial be an empty List.
+
+ Let
+ len be the result of calling the [[Get]] internal method of
+ value with argument "length".
+ Let + index be 0.
++ Repeat + while index < len
++ Let + strP be the result of calling the abstract operation Str + with arguments ToString(index) and value. +
++ If + strP is undefined
+
+ Append
+ "null"
+ to partial.
+ Else
++ Append + strP to partial.
++ Increment + index by 1.
++ If + partial is empty ,then
+
+ Let
+ final be "[]".
+ Else
++ If + gap is the empty String
++ Let + properties be a String formed by concatenating all the + element Strings of partial with each adjacent pair of + Strings separated with the comma character. A comma is not + inserted either before the first String or after the last String. + +
+
+ Let
+ final be the result of concatenating "[",
+ properties, and "]".
+ Else
++ Let + separator be the result of concatenating the comma + character, the line feed character, and indent.
++ Let + properties be a String formed by concatenating all the + element Strings of partial with each adjacent pair of + Strings separated with separator. The separator + String is not inserted either before the first String or after + the last String.
+
+ Let
+ final be the result of concatenating "[",
+ the line feed character, indent, properties, the
+ line feed character, stepback, and "]".
+ Remove + the last element of stack.
++ Let + indent be stepback.
++ Return + final.
+NOTE 1 JSON structures are allowed to be nested to any depth, but they + must be acyclic. If value + is or contains a cyclic structure, then the stringify function must + throw a TypeError exception. This is an example of a value + that cannot be stringified:
+a = [];
a[0] = a;
my_text = JSON.stringify(a); // This must throw an TypeError.
NOTE 2 Symbolic primitive values are rendered as follows:
+The
+ null value is rendered in JSON text as the String null.
The + undefined value is not rendered.
+The
+ true value is rendered in JSON text as the String true.
The
+ false value is rendered in JSON text as the String false.
NOTE 3 String values are wrapped in double quotes. The characters "
+ and \ are escaped
+ with \ prefixes.
+ Control characters are replaced with escape sequences \uHHHH,
+ or with the shorter forms, \b
+ (backspace), \f
+ (formfeed), \n
+ (newline), \r
+ (carriage return), \t
+ (tab).
NOTE 4 Finite numbers are stringified as if by calling ToString(number).
+ NaN and Infinity regardless of sign are represented as the
+ String null.
NOTE 5 Values that do not have a JSON representation (such as undefined
+ and functions) do not produce a String. Instead they produce the
+ undefined value. In arrays these values are represented as the
+ String null.
+ In objects an unrepresentable value causes the property to be
+ excluded from stringification.
NOTE 6 An object is rendered as an opening left brace followed by zero or + more properties, separated with commas, closed with a right brace. A + property is a quoted String representing the key or property name, a + colon, and then the stringified property value. An array is rendered + as an opening left bracket followed by zero or more values, + separated with commas, closed with a right bracket.
+ \ No newline at end of file diff --git a/x16.html b/x16.html new file mode 100644 index 0000000..7b9e7b4 --- /dev/null +++ b/x16.html @@ -0,0 +1,128 @@ + +‟Ex igne vita”
+ +
+ An
+ implementation must report most errors at the time the relevant
+ ECMAScript language construct is evaluated. An early error is
+ an error that can be detected and reported prior to the evaluation
+ of any construct in the Program
+ containing the error. An implementation must report early errors in
+ a Program prior to
+ the first evaluation of that Program.
+ Early errors in eval code are reported at the time eval
+ is called but prior to evaluation of any construct within the eval
+ code. All errors that are not early errors are runtime errors.
+ An + implementation must treat any instance of the following kinds of + errors as an early error:
++ Any + syntax error.
++ Attempts + to define an ObjectLiteral that has multiple get property assignments with + the same name or multiple set property assignments with the + same name.
++ Attempts + to define an ObjectLiteral + that has both a data property assignment and a get or + set property assignment with the same name.
++ Errors + in regular expression literals that are not implementation-defined + syntax extensions.
++ Attempts + in strict mode code to define an ObjectLiteral + that has multiple data property assignments with the same name.
++ The + occurrence of a WithStatement + in strict mode code.
++ The + occurrence of an Identifier + value appearing more than once within a FormalParameterList + of an individual strict mode FunctionDeclaration + or FunctionExpression.
+
+ Improper
+ uses of return,
+ break, and
+ continue.
+ Attempts
+ to call PutValue on any value for which an early determination can
+ be made that the value is not a Reference (for example, executing
+ the assignment statement 3=4).
+ An + implementation shall not treat other kinds of errors as early errors + even if the compiler can prove that a construct cannot execute + without error under any circumstances. An implementation may issue + an early warning in such a case, but it should not report the error + until the relevant construct is actually executed. +
++ An + implementation shall report all errors as specified, except for the + following:
+
+ An
+ implementation may extend program syntax and regular expression
+ pattern or flag syntax. To permit this, all operations (such as
+ calling eval,
+ using a regular expression literal, or using the Function
+ or RegExp
+ constructor) that are allowed to throw SyntaxError
+ are permitted to exhibit implementation-defined behaviour instead
+ of throwing SyntaxError
+ when they encounter an implementation-defined extension to the
+ program syntax or regular expression pattern or flag syntax.
+ An + implementation may provide additional types, values, objects, + properties, and functions beyond those described in this + specification. This may cause constructs (such as looking up a + variable in the global scope) to have implementation-defined + behaviour instead of throwing an error (such as ReferenceError).
+
+ An
+ implementation may define behaviour other than throwing RangeError
+ for toFixed,
+ toExponential,
+ and toPrecision
+ when the fractionDigits
+ or precision
+ argument is outside the specified range.
+
+ \ No newline at end of file diff --git a/x2.html b/x2.html new file mode 100644 index 0000000..9b6cc2c --- /dev/null +++ b/x2.html @@ -0,0 +1,49 @@ + +‟Ex igne vita”
+ ++ A + conforming implementation of ECMAScript must provide and support all + the types, values, objects, properties, functions, and program + syntax and semantics described in this specification.
++ A + conforming implementation of this International standard shall + interpret characters in conformance with the Unicode Standard, + Version 3.0 or later and ISO/IEC 10646-1 with either UCS-2 or UTF-16 + as the adopted encoding form, implementation level 3. If the adopted + ISO/IEC 10646-1 subset is not otherwise specified, it is presumed to + be the BMP subset, collection 300. If the adopted encoding form is + not otherwise specified, it presumed to be the UTF-16 encoding form.
++ A + conforming implementation of ECMAScript is permitted to provide + additional types, values, objects, properties, and functions beyond + those described in this specification. In particular, a conforming + implementation of ECMAScript is permitted to provide properties not + described in this specification, and values for those properties, + for objects that are described in this specification.
++ A + conforming implementation of ECMAScript is permitted to support + program and regular expression syntax not described in this + specification. In particular, a conforming implementation of + ECMAScript is permitted to support program syntax that makes use of + the “future reserved words” listed in 7.6.1.2 of this + specification.
+ \ No newline at end of file diff --git a/x3.html b/x3.html new file mode 100644 index 0000000..4bbc64e --- /dev/null +++ b/x3.html @@ -0,0 +1,33 @@ + +‟Ex igne vita”
+ ++ The + following referenced documents are indispensable for the application + of this document. For dated references, only the edition cited + applies. For undated references, the latest edition of the + referenced document (including any amendments) applies.
++ ISO/IEC 9899:1996, + Programming Languages – C, including amendment 1 and technical + corrigenda 1 and 2
++ ISO/IEC 10646-1:1993, + Information Technology – Universal Multiple-Octet Coded Character + Set (UCS) plus its amendments and corrigenda
+ \ No newline at end of file diff --git a/x4.html b/x4.html new file mode 100644 index 0000000..d23c020 --- /dev/null +++ b/x4.html @@ -0,0 +1,510 @@ + +‟Ex igne vita”
+ ++ This + section contains a non-normative overview of the ECMAScript + language.
++ ECMAScript + is an object-oriented programming language for performing + computations and manipulating computational objects within a host + environment. ECMAScript as defined here is not intended to be + computationally self-sufficient; indeed, there are no provisions in + this specification for input of external data or output of computed + results. Instead, it is expected that the computational environment + of an ECMAScript program will provide not only the objects and other + facilities described in this specification but also certain + environment-specific host objects, whose description and + behaviour are beyond the scope of this specification except to + indicate that they may provide certain properties that can be + accessed and certain functions that can be called from an ECMAScript + program.
++ A + scripting language is a programming language that is + used to manipulate, customise, and automate the facilities of an + existing system. In such systems, useful functionality is already + available through a user interface, and the scripting language is a + mechanism for exposing that functionality to program control. In + this way, the existing system is said to provide a host environment + of objects and facilities, which completes the capabilities of the + scripting language. A scripting language is intended for use by both + professional and non-professional programmers.
++ ECMAScript + was originally designed to be a Web scripting language, + providing a mechanism to enliven Web pages in browsers and to + perform server computation as part of a Web-based client-server + architecture. ECMAScript can provide core scripting capabilities for + a variety of host environments, and therefore the core scripting + language is specified in this document apart from any particular + host environment.
++ Some + of the facilities of ECMAScript are similar to those used in other + programming languages; in particular Java™, + Self, and Scheme as described in:
++ Gosling, + James, Bill Joy and Guy Steele. The Java™ + Language Specification. Addison Wesley Publishing Co., 1996.
++ Ungar, + David, and Smith, Randall B. Self: The Power of Simplicity. OOPSLA + '87 Conference Proceedings, pp. 227–241, Orlando, FL, October + 1987.
++ IEEE + Standard for the Scheme Programming Language. IEEE Std 1178-1990.
++ A web + browser provides an ECMAScript host environment for client-side + computation including, for instance, objects that represent windows, + menus, pop-ups, dialog boxes, text areas, anchors, frames, history, + cookies, and input/output. Further, the host environment provides a + means to attach scripting code to events such as change of focus, + page and image loading, unloading, error and abort, selection, form + submission, and mouse actions. Scripting code appears within the + HTML and the displayed page is a combination of user interface + elements and fixed and computed text and images. The scripting code + is reactive to user interaction and there is no need for a main + program.
++ A web + server provides a different host environment for server-side + computation including objects representing requests, clients, and + files; and mechanisms to lock and share data. By using browser-side + and server-side scripting together, it is possible to distribute + computation between the client and server while providing a + customised user interface for a Web-based application.
++ Each + Web browser and server that supports ECMAScript supplies its own + host environment, completing the ECMAScript execution environment.
++ The + following is an informal overview of ECMAScript—not all parts of + the language are described. This overview is not part of the + standard proper.
++ ECMAScript + is object-based: basic language and host facilities are provided by + objects, and an ECMAScript program is a cluster of communicating + objects. An ECMAScript object is a collection of + properties each with zero or more attributes + that determine how each property can be used—for example, when the + Writable attribute for a property is set to false, any + attempt by executed ECMAScript code to change the value of the + property fails. Properties are containers that hold other objects, + primitive values, or functions. A + primitive value is a member of one of the following built-in types: +Undefined, +Null, +Boolean, +Number, +and +String; +an object is a member of the remaining built-in type +Object; and a function is a + callable object. A function that + is associated with an object via a property is a method.
++ ECMAScript + defines a collection of built-in objects that round + out the definition of ECMAScript entities. These built-in objects + include the global object, the Object object, the Function object, the Array object, the String object, the + Boolean object, the Number object, the Math object, the Date object, the RegExp object, the JSON object, and the Error objects Error, EvalError, RangeError, + ReferenceError, SyntaxError, TypeError and URIError.
++ ECMAScript + also defines a set of built-in operators. ECMAScript + operators include various +unary operations, +multiplicative operators, +additive operators, +bitwise shift operators, +relational operators, +equality operators, +binary bitwise operators, +binary logical operators, +assignment operators, and +the comma operator.
++ ECMAScript + syntax intentionally resembles Java syntax. ECMAScript syntax + is relaxed to enable it to serve as an easy-to-use scripting + language. For example, a variable is not required to have its type + declared nor are types associated with properties, and defined + functions are not required to have their declarations appear + textually before calls to them.
+
+ ECMAScript
+ does not use classes such as those in C++, Smalltalk, or Java.
+ Instead objects may be created in various ways including via a
+ literal notation or via constructors which create
+ objects and then execute code that initialises all or part of them
+ by assigning initial values to their properties. Each constructor is
+ a function that has a property named “prototype”
+ that is used to implement prototype-based inheritance
+ and shared properties. Objects are created by using
+ constructors in new expressions; for example, new
+ Date(2009,11) creates a new Date object. Invoking
+ a constructor without using new has consequences that depend
+ on the constructor. For example, Date()
+ produces a string representation of the current date and time rather
+ than an object.
+ Every
+ object created by a constructor has an implicit reference (called
+ the object’s prototype) to the value of its constructor’s
+ “prototype”
+ property. Furthermore, a prototype may have a non-null implicit
+ reference to its prototype, and so on; this is called the prototype
+ chain. When a reference is made to a property in an object, that
+ reference is to the property of that name in the first object in the
+ prototype chain that contains a property of that name. In other
+ words, first the object mentioned directly is examined for such a
+ property; if that object contains the named property, that is the
+ property to which the reference refers; if that object does not
+ contain the named property, the prototype for that object is
+ examined next; and so on.
Figure 1 — Object/Prototype Relationships
++ In a + class-based object-oriented language, in general, state is carried + by instances, methods are carried by classes, and inheritance is + only of structure and behaviour. In ECMAScript, the state and + methods are carried by objects, and structure, behaviour, and state + are all inherited.
++ All + objects that do not directly contain a particular property that + their prototype contains share that property and its value. Figure 1 + illustrates this:
+
+ CF
+ is a constructor (and also an object). Five objects have been
+ created by using new
+ expressions: cf1, cf2,
+ cf3, cf4, and cf5.
+ Each of these objects contains properties named q1
+ and q2. The dashed lines
+ represent the implicit prototype relationship; so, for example,
+ cf3’s prototype is CFp.
+ The constructor, CF, has two properties itself, named P1
+ and P2, which are not
+ visible to CFp, cf1,
+ cf2, cf3, cf4,
+ or cf5. The property named CFP1
+ in CFp is shared by cf1,
+ cf2, cf3, cf4,
+ and cf5 (but not by CF), as are any
+ properties found in CFp’s implicit
+ prototype chain that are not named q1,
+ q2, or CFP1.
+ Notice that there is no implicit prototype link between CF
+ and CFp.
+ Unlike + class-based object languages, properties can be added to objects + dynamically by assigning values to them. That is, constructors are + not required to name or assign values to all or any of the + constructed object’s properties. In the above diagram, one could + add a new shared property for cf1, cf2, + cf3, cf4, and cf5 + by assigning a new value to the property in CFp.
++ The + ECMAScript Language recognizes the possibility that some users of + the language may wish to restrict their usage of some features + available in the language. They might do so in the interests of + security, to avoid what they consider to be error-prone features, to + get enhanced error checking, or for other reasons of their choosing. + In support of this possibility, ECMAScript defines a strict variant + of the language. The strict variant of the language excludes some + specific syntactic and semantic features of the regular ECMAScript + language and modifies the detailed semantics of some features. The + strict variant also specifies additional error conditions that must + be reported by throwing error exceptions in situations that are not + specified as errors by the non-strict form of the language.
++ The + strict variant of ECMAScript is commonly referred to as the strict + mode of the language. Strict mode selection and use of the + strict mode syntax and semantics of ECMAScript is explicitly made at + the level of individual ECMAScript code units. Because strict mode + is selected at the level of a syntactic code unit, strict mode only + imposes restrictions that have local effect within such a code unit. + Strict mode does not restrict or modify any aspect of the ECMAScript + semantics that must operate consistently across multiple code units. + A complete ECMAScript program may be composed for both strict mode + and non-strict mode ECMAScript code units. In this case, strict mode + only applies when actually executing code that is defined within a + strict mode code unit. +
++ In + order to conform to this specification, an ECMAScript implementation + must implement both the full unrestricted ECMAScript language and + the strict mode variant of the ECMAScript language as defined by + this specification. In addition, an implementation must support the + combination of unrestricted and strict mode code units into a single + composite program.
++ For + the purposes of this document, the following terms and definitions + apply.
++ set + of data values as defined in Clause 8 of this specification.
++ member + of one of the types Undefined, Null, Boolean, Number, or String as + defined in Clause 8.
+NOTE A + primitive value is a datum that is represented directly at the + lowest level of the language implementation.
++ member + of the type Object.
+NOTE An + object is a collection of properties and has a single prototype + object. The prototype may be the null value.
++ Function + object that creates and initialises objects.
+NOTE The
+ value of a constructor’s “prototype”
+ property is a prototype object that is used to implement inheritance
+ and shared properties.
+ object + that provides shared properties for other objects.
+NOTE When
+ a constructor creates an object, that object implicitly references
+ the constructor’s “prototype”
+ property for the purpose of resolving property references. The
+ constructor’s “prototype”
+ property can be referenced by the program expression
+ constructor.prototype,
+ and properties added to an object’s prototype are shared, through
+ inheritance, by all objects sharing the prototype. Alternatively, a
+ new object may be created with an explicitly specified prototype by
+ using the Object.create
+ built-in function.
+ object + in an ECMAScript implementation whose semantics are fully defined by + this specification rather than by the host environment.
+NOTE Standard + native objects are defined in this specification. Some native + objects are built-in; others may be constructed during the course of + execution of an ECMAScript program.
++ object + supplied by an ECMAScript implementation, independent of the host + environment, that is present at the start of the execution of an + ECMAScript program.
+NOTE Standard + built-in objects are defined in this specification, and an + ECMAScript implementation may specify and define others. Every + built-in object is a native object. A built-in constructor + is a built-in object that is also a constructor.
++ object + supplied by the host environment to complete the execution + environment of ECMAScript.
+NOTE Any + object that is not native is a host object.
++ primitive value used when a variable has not been assigned a value.
++ type + whose sole value is the undefined value. +
++ primitive value that represents the intentional absence of any object value.
++ type + whose sole value is the null value.
++ member + of the Boolean type.
+NOTE There + are only two Boolean values, true and false.
++ type + consisting of the primitive values true and false.
+
+ member
+ of the Object type that is an instance of the standard built-in
+ Boolean
+ constructor.
NOTE A
+ Boolean object is created by using the Boolean
+ constructor in a new
+ expression, supplying a Boolean value as an argument. The resulting
+ object has an internal property whose value is the Boolean value. A
+ Boolean object can be coerced to a Boolean value.
+ primitive value that is a finite ordered sequence of zero or more 16-bit + unsigned integer. +
+NOTE A + String value is a member of the String type. Each integer value in + the sequence usually represents a single 16-bit unit of UTF-16 text. + However, ECMAScript does not place any restrictions or requirements + on the values except that they must be 16-bit unsigned integers.
++ set + of all possible String values.
+
+ member
+ of the Object type that is an instance of the standard built-in
+ String
+ constructor.
NOTE A
+ String object is created by using the String
+ constructor in a new
+ expression, supplying a String value as an argument. The resulting
+ object has an internal property whose value is the String value. A
+ String object can be coerced to a String value by calling the String
+ constructor as a function (15.5.1).
+ primitive value corresponding to a double-precision 64-bit binary format IEEE + 754 value.
+NOTE A + Number value is a member of the Number type and is a direct + representation of a number.
++ set + of all possible Number values including the special “Not-a-Number” + (NaN) values, positive infinity, and negative infinity.
+
+ member
+ of the Object type that is an instance of the standard built-in
+ Number
+ constructor.
NOTE A
+ Number object is created by using the Number
+ constructor in a new
+ expression, supplying a Number value as an argument. The resulting
+ object has an internal property whose value is the Number value. A
+ Number object can be coerced to a Number value by calling the Number
+ constructor as a function (15.7.1).
+ Number + value that is the + positive infinite Number value.
++ Number + value that is a IEEE 754 “Not-a-Number” value.
+
+ member
+ of the Object type that is an instance of the standard built-in
+ Function
+ constructor and that may be invoked as a subroutine.
NOTE In + addition to its named properties, a function contains executable + code and state that determine how it behaves when invoked. A + function’s code may or may not be written in ECMAScript.
++ built-in + object that is a function.
+NOTE Examples
+ of built-in functions include parseInt
+ and Math.exp. An
+ implementation may provide implementation-dependent built-in
+ functions that are not described in this specification.
+
+
+ association + between a name and a value that is a part of an object.
+NOTE Depending + upon the form of the property the value may be represented either + directly as a data value (a primitive value, an object, or a + function object) or indirectly by a pair of accessor functions.
++ function + that is the value of a property.
+NOTE When + a function is called as a method of an object, the object is passed + to the function as its this value.
++ method + that is a built-in function.
+NOTE Standard + built-in methods are defined in this specification, and an + ECMAScript implementation may specify and provide other additional + built-in methods. +
++ internal + value that defines some characteristic of a property.
++ property + that is directly contained by its object.
++ property + of an object that is not an own property but is a property (either + own or inherited) of the object’s prototype.
+ \ No newline at end of file diff --git a/x5.html b/x5.html new file mode 100644 index 0000000..795e051 --- /dev/null +++ b/x5.html @@ -0,0 +1,562 @@ + +‟Ex igne vita”
+ ++ A + context-free grammar consists of a number of productions. + Each production has an abstract symbol called a nonterminal + as its left-hand side, and a sequence of zero or more + nonterminal and terminal symbols as its right-hand side. + For each grammar, the terminal symbols are drawn from a specified + alphabet.
++ Starting + from a sentence consisting of a single distinguished nonterminal, + called the goal symbol, a given context-free grammar + specifies a language, namely, the (perhaps infinite) set of + possible sequences of terminal symbols that can result from + repeatedly replacing any nonterminal in the sequence with a + right-hand side of a production for which the nonterminal is the + left-hand side.
++ A + lexical grammar for ECMAScript is given in clause 7. This + grammar has as its terminal symbols characters (Unicode code units) + that conform to the rules for SourceCharacter + defined in Clause 6. It defines a set of productions, starting from + the goal symbol InputElementDiv + or InputElementRegExp, + that describe how sequences of such characters are translated into a + sequence of input elements.
+
+ Input
+ elements other than white space and comments form the terminal
+ symbols for the syntactic grammar for ECMAScript and are called
+ ECMAScript tokens. These tokens are the reserved words,
+ identifiers, literals, and punctuators of the ECMAScript language.
+ Moreover, line terminators, although not considered to be tokens,
+ also become part of the stream of input elements and guide the
+ process of automatic semicolon insertion (7.9). Simple white space
+ and single-line comments are discarded and do not appear in the
+ stream of input elements for the syntactic grammar. A
+ MultiLineComment
+ (that is, a comment of the form “/*…*/”
+ regardless of whether it spans more than one line) is likewise
+ simply discarded if it contains no line terminator; but if a
+ MultiLineComment
+ contains one or more line terminators, then it is replaced by a
+ single line terminator, which becomes part of the stream of input
+ elements for the syntactic grammar.
+ A + RegExp grammar for ECMAScript is given in 15.10. This grammar + also has as its terminal symbols the characters as defined by + SourceCharacter. + It defines a set of productions, starting from the goal symbol + Pattern, that + describe how sequences of characters are translated into regular + expression patterns.
++ Productions + of the lexical and RegExp grammars are distinguished by having two + colons “::” as separating punctuation. The lexical and + RegExp grammars share some productions.
++ Another + grammar is used for translating Strings into numeric values. This + grammar is similar to the part of the lexical grammar having to do + with numeric literals and has as its terminal symbols + SourceCharacter. + This grammar appears in 9.3.1.
++ Productions + of the numeric string grammar are distinguished by having three + colons “:::” as punctuation.
++ The + syntactic grammar for ECMAScript is given in clauses 11, 12, + 13 and 14. This grammar has ECMAScript tokens defined by the lexical + grammar as its terminal symbols (5.1.2). It defines a set of + productions, starting from the goal symbol Program, + that describe how sequences of tokens can form syntactically correct + ECMAScript programs.
++ When + a stream of characters is to be parsed as an ECMAScript program, it + is first converted to a stream of input elements by repeated + application of the lexical grammar; this stream of input elements is + then parsed by a single application of the syntactic grammar. The + program is syntactically in error if the tokens in the stream of + input elements cannot be parsed as a single instance of the goal + nonterminal Program, + with no tokens left over.
++ Productions + of the syntactic grammar are distinguished by having just one colon + “:” as punctuation.
++ The + syntactic grammar as presented in clauses 11, 12, 13 and 14 is + actually not a complete account of which token sequences are + accepted as correct ECMAScript programs. Certain additional token + sequences are also accepted, namely, those that would be described + by the grammar if only semicolons were added to the sequence in + certain places (such as before line terminator characters). + Furthermore, certain token sequences that are described by the + grammar are not considered acceptable if a terminator character + appears in certain “awkward” places.
++ The + JSON grammar is used to translate a String describing a set of + ECMAScript objects into actual objects. The JSON grammar is given in + 15.12.1.
++ The + JSON grammar consists of the JSON lexical grammar and the JSON + syntactic grammar. The JSON lexical grammar is used to translate + character sequences into tokens and is similar to parts of the + ECMAScript lexical grammar. The JSON syntactic grammar describes how + sequences of tokens from the JSON lexical grammar can form + syntactically correct JSON object descriptions.
++ Productions + of the JSON lexical grammar are distinguished by having two colons + “::” as separating punctuation. The JSON lexical grammar + uses some productions from the ECMAScript lexical grammar. The JSON + syntactic grammar is similar to parts of the ECMAScript syntactic + grammar. Productions of the JSON syntactic grammar are distinguished + by using one colon “:” as separating punctuation.
+
+ Terminal
+ symbols of the lexical and string grammars, and some of the terminal
+ symbols of the syntactic grammar, are shown in fixed
+ width font, both in the productions of the grammars and
+ throughout this specification whenever the text directly refers to
+ such a terminal symbol. These are to appear in a program exactly as
+ written. All terminal symbol characters specified in this way are to
+ be understood as the appropriate Unicode character from the ASCII
+ range, as opposed to any similar-looking characters from other
+ Unicode ranges.
+ Nonterminal + symbols are shown in italic + type. The definition of a nonterminal is introduced by the name of + the nonterminal being defined followed by one or more colons. (The + number of colons indicates to which grammar the production belongs.) + One or more alternative right-hand sides for the nonterminal then + follow on succeeding lines. For example, the syntactic definition:
++ WhileStatement :
+
+ while
+ (
+ Expression )
+ Statement
+ states
+ that the nonterminal WhileStatement
+ represents the token while,
+ followed by a left parenthesis token, followed by an Expression,
+ followed by a right parenthesis token, followed by a Statement.
+ The occurrences of Expression
+ and Statement are
+ themselves nonterminals. As another example, the syntactic
+ definition:
+ ArgumentList + :
+
+ AssignmentExpression
ArgumentList
+ , AssignmentExpression
+ states + that an ArgumentList + may represent either a single AssignmentExpression + or an ArgumentList, + followed by a comma, followed by an AssignmentExpression. + This definition of ArgumentList + is recursive, that is, it is defined in terms of itself. The result + is that an ArgumentList + may contain any positive number of arguments, separated by commas, + where each argument expression is an AssignmentExpression. + Such recursive definitions of nonterminals are common.
++ The + subscripted suffix “opt”, which may appear after a + terminal or nonterminal, indicates an optional symbol. The + alternative containing the optional symbol actually specifies two + right-hand sides, one that omits the optional element and one that + includes it. This means that:
++ VariableDeclaration + :
++ Identifier + Initialiseropt
++ is a + convenient abbreviation for:
++ VariableDeclaration + :
+
+ Identifier
Identifier
+ Initialiser
+ and + that:
++ IterationStatement + :
+
+ for
+ ( ExpressionNoInopt
+ ; Expressionopt
+ ; Expressionopt
+ ) Statement
+ is a + convenient abbreviation for:
++ IterationStatement + :
+
+ for
+ ( ; Expressionopt
+ ; Expressionopt
+ ) Statement
for
+ (
+ ; Expressionopt
+ ; Expressionopt
+ ) Statement
+ which + in turn is an abbreviation for:
++ IterationStatement + :
+
+ for
+ ( ; ; Expressionopt
+ ) Statement
for
+ ( ;
+ ; Expressionopt)
+ Statement
for
+ (
+ ; ; Expressionopt)
+ Statement
for
+ (
+ ; Expression
+ ; Expressionopt)
+ Statement
+ which + in turn is an abbreviation for:
++ IterationStatement + :
+
+ for
+ ( ; ; ) Statementfor
+ ( ; ; Expression
+ ) Statement
for
+ ( ;
+ ; ) Statement
for
+ ( ;
+ ; Expression
+ ) Statement
for
+ (;
+ ; ) Statement
for
+ (;
+ ; Expression
+ ) Statement
for
+ (;
+ Expression
+ ; ) Statement
for
+ (;
+ Expression
+ ; Expression
+ ) Statement
+ so + the nonterminal IterationStatement + actually has eight alternative right-hand sides.
++ If + the phrase “[empty]” + appears as the right-hand side of a production, it indicates that + the production's right-hand side contains no terminals or + nonterminals.
++ If + the phrase + “[lookahead ∉ set]” + appears in the right-hand side of a production, it indicates that + the production may not be used if the immediately following input + token is a member of the given set. + The set can be + written as a list of terminals enclosed in curly braces. For + convenience, the set can also be written as a nonterminal, in which + case it represents the set of all terminals to which that + nonterminal could expand. For example, given the definitions
++ DecimalDigit :: + one + of
+
+ 0
+ 1 2 3 4 5 6 7 8 9
+ DecimalDigits + ::
+
+ DecimalDigit
DecimalDigits
+ DecimalDigit
+ the + definition
++ LookaheadExample + ::
+
+ n
+ [lookahead
+ ∉
+ {1 , 3 , 5 , 7 , 9}]DecimalDigits
DecimalDigit [lookahead
+ ∉
+ DecimalDigit ]
+ matches
+ either the letter n
+ followed by one or more decimal digits the first of which is even,
+ or a decimal digit not followed by another decimal digit.
+ If the phrase “[no LineTerminator here]” appears in the right-hand side of a production of + the syntactic grammar, it indicates that the production is a restricted production: it may not be used if a LineTerminator + occurs in the input stream at the indicated position. For example, + the production:
++ ReturnStatement + :
+
+ return
+ [no LineTerminator here]
+ Expressionopt;
+ indicates
+ that the production may not be used if a LineTerminator
+ occurs in the program between the return
+ token and the Expression.
+ Unless + the presence of a LineTerminator + is forbidden by a restricted production, any number of occurrences + of LineTerminator + may appear between any two consecutive tokens in the stream of input + elements without affecting the syntactic acceptability of the + program.
++ When + the words “one of” follow the colon(s) in a grammar + definition, they signify that each of the terminal symbols on the + following line or lines is an alternative definition. For example, + the lexical grammar for ECMAScript contains the production:
++ NonZeroDigit :: + one + of
+
+ 1
+ 2 3 4 5 6 7 8 9
+ which + is merely a convenient abbreviation for:
++ NonZeroDigit ::
+
+ 1
2
3
4
5
6
7
8
9
+ When + an alternative in a production of the lexical grammar or the numeric + string grammar appears to be a multi-character token, it represents + the sequence of characters that would make up such a token.
++ The + right-hand side of a production may specify that certain expansions + are not permitted by using the phrase “but not” and then + indicating the expansions to be excluded. For example, the + production:
++ Identifier + ::
++ IdentifierName but + not ReservedWord
++ means + that the nonterminal Identifier + may be replaced by any sequence of characters that could replace + IdentifierName + provided that the same sequence of characters could not replace + ReservedWord.
++ Finally, + a few nonterminal symbols are described by a descriptive phrase in + sans-serif type in cases where it would be impractical to list all + the alternatives:
++ SourceCharacter + ::
++ any + Unicode code unit
++ The + specification often uses a numbered list to specify steps in an + algorithm. These algorithms are used to precisely specify the + required semantics of ECMAScript language constructs. The algorithms + are not intended to imply the use of any specific implementation + technique. In practice, there may be more efficient algorithms + available to implement a given feature.
++ In + order to facilitate their use in multiple parts of this + specification, some algorithms, called abstract operations, + are named and written in parameterized functional form so that they + may be referenced by name from within other algorithms.
++ When + an algorithm is to produce a value as a result, the directive + “return x” + is used to indicate that the result of the algorithm is the value of + x and that the + algorithm should terminate. The notation Result(n) + is used as shorthand for “the result + of step n”. + +
++ For + clarity of expression, algorithm steps may be subdivided into + sequential substeps. Substeps are indented and may themselves be + further divided into indented substeps. Outline numbering + conventions are used to identify substeps with the first level of + substeps labelled with lower case alphabetic characters and the + second level of substeps labelled with lower case roman numerals. + If more than three levels are required these rules repeat with the + fourth level using numeric labels. For example:
++ Top-level + step
++ Substep.
++ Substep + +
++ Subsubstep.
++ Subsubstep.
++ Subsubsubstep
++ Subsubsubsubstep
++ A + step or substep may be written as an “if” predicate that + conditions its substeps. In this case, the substeps are only + applied if the predicate is true. If a step or substep begins with + the word “else”, it is a predicate that is the negation of the + preceding “if” predicate step at the same level.
++ A + step may specify the iterative application of its substeps.
++ Mathematical + operations such as addition, subtraction, negation, multiplication, + division, and the mathematical functions defined later in this + clause should always be understood as computing exact mathematical + results on mathematical real numbers, which do not include + infinities and do not include a negative zero that is distinguished + from positive zero. Algorithms in this standard that model + floating-point arithmetic include explicit steps, where necessary, + to handle infinities and signed zero and to perform rounding. If a + mathematical operation or function is applied to a floating-point + number, it should be understood as being applied to the exact + mathematical value represented by that floating-point number; such a + floating-point number must be finite, and if it is +0 + or −0 + then the corresponding mathematical value is simply 0.
++ The + mathematical function abs(x) + yields the absolute value of x, + which is −x + if x is negative + (less than zero) and otherwise is x + itself.
++ The + mathematical function sign(x) + yields 1 if x + is positive and −1 + if x is negative. + The sign function is not used in this standard for cases when x + is zero.
++ The + notation “x modulo y” (y + must be finite and nonzero) computes a value k + of the same sign as y + (or zero) such that abs(k) + < abs(y) + and x−k = q + × + y for some + integer q.
++ The + mathematical function floor(x) + yields the largest integer (closest to positive infinity) that is + not larger than x.
+NOTE floor(x) + = x−(x + modulo 1).
++ If an + algorithm is defined to “throw an exception”, execution of the + algorithm is terminated and no result is returned. The calling + algorithms are also terminated, until an algorithm step is reached + that explicitly deals with the exception, using terminology such as + “If an exception was thrown…”. Once such an algorithm step has + been encountered the exception is no longer considered to have + occurred.
+ \ No newline at end of file diff --git a/x6.html b/x6.html new file mode 100644 index 0000000..bc921a6 --- /dev/null +++ b/x6.html @@ -0,0 +1,91 @@ + +‟Ex igne vita”
+ ++ ECMAScript + source text is represented as a sequence of characters in the + Unicode character encoding, version 3.0 or later. The text is + expected to have been normalised to Unicode Normalised Form C + (canonical composition), as described in Unicode Technical Report + #15. Conforming ECMAScript implementations are not required to + perform any normalisation of text, or behave as though they were + performing normalisation of text, themselves. ECMAScript source + text is assumed to be a sequence of 16-bit code units for the + purposes of this specification. Such a source text may include + sequences of 16-bit code units that are not valid UTF-16 character + encodings. If an actual source text is encoded in a form other than + 16-bit code units it must be processed as if it was first convert to + UTF-16.
++ SourceCharacter ::
++ any + Unicode code unit
++ Throughout + the rest of this document, the phrase “code unit” and the word + “character” will be used to refer to a 16-bit unsigned value + used to represent a single 16-bit unit of text. The phrase “Unicode + character” will be used to refer to the abstract linguistic or + typographical unit represented by a single Unicode scalar value + (which may be longer than 16 bits and thus may be represented by + more than one code unit). The phrase “code point” refers to such + a Unicode scalar value. “Unicode character” only refers to + entities represented by single Unicode scalar values: the components + of a combining character sequence are still individual “Unicode + characters,” even though a user might think of the whole sequence + as a single character.
+
+ In
+ string literals, regular expression literals, and identifiers, any
+ character (code unit) may also be expressed as a Unicode escape
+ sequence consisting of six characters, namely \u
+ plus four hexadecimal digits. Within a comment, such an escape
+ sequence is effectively ignored as part of the comment. Within a
+ string literal or regular expression literal, the Unicode escape
+ sequence contributes one character to the value of the literal.
+ Within an identifier, the escape sequence contributes one character
+ to the identifier.
NOTE Although + this document sometimes refers to a “transformation” between a + “character” within a “string” and the 16-bit unsigned + integer that is the code unit of that character, there is actually + no transformation because a “character” within a “string” is + actually represented using that 16-bit unsigned value.
+
+ ECMAScript
+ differs from the Java programming language in the behaviour of
+ Unicode escape sequences. In a Java program, if the Unicode escape
+ sequence \u000A,
+ for example, occurs within a single-line comment, it is interpreted
+ as a line terminator (Unicode character 000A
+ is line feed) and therefore the next character is not part of the
+ comment. Similarly, if the Unicode escape sequence \u000A
+ occurs within a string literal in a Java program, it is likewise
+ interpreted as a line terminator, which is not allowed within a
+ string literal—one must write \n
+ instead of \u000A
+ to cause a line feed to be part of the string value of a string
+ literal. In an ECMAScript program, a Unicode escape sequence
+ occurring within a comment is never interpreted and therefore cannot
+ contribute to termination of the comment. Similarly, a Unicode
+ escape sequence occurring within a string literal in an ECMAScript
+ program always contributes a character to the String value of the
+ literal and is never interpreted as a line terminator or as a quote
+ mark that might terminate the string literal.
‟Ex igne vita”
+ ++ The + source text of an ECMAScript program is first converted into a + sequence of input elements, which are tokens, line terminators, + comments, or white space. The source text is scanned from left to + right, repeatedly taking the longest possible sequence of characters + as the next input element.
+
+ There
+ are two goal symbols for the lexical grammar. The InputElementDiv
+ symbol is used in those syntactic grammar contexts where a leading
+ division (/) or
+ division-assignment (/=)
+ operator is permitted. The InputElementRegExp
+ symbol is used in other syntactic grammar contexts.
NOTE There + are no syntactic grammar contexts where both a leading division or + division-assignment, and a leading RegularExpressionLiteral + are permitted. This is not affected by semicolon insertion (see + 7.9); in examples such as the following:
+
+ a
+ = b
/hi/g.exec(c).map(d);
+ where
+ the first non-whitespace, non-comment
+ character after a LineTerminator
+ is slash
+ (/)
+ and the syntactic context allows division
+ or division-assignment, no semicolon is inserted at the
+ LineTerminator.
+ That is, the above example is interpreted in the same way as:
+ a
+ = b / hi / g.exec(c).map(d);
+ Syntax
++ InputElementDiv ::
+
+ WhiteSpace
LineTerminator
Comment
Token
DivPunctuator
+
+ InputElementRegExp ::
+
+ WhiteSpace
LineTerminator
Comment
Token
RegularExpressionLiteral
+ The + Unicode format-control characters (i.e., the characters in category + “Cf” in the Unicode Character Database such as left-to-right + mark or right-to-left + mark) are control codes used to control the formatting of a + range of text in the absence of higher-level protocols for this + (such as mark-up languages).
++ It is + useful to allow format-control characters in source text to + facilitate editing and display. All format control characters may be + used within comments, and within string literals and regular + expression literals.
++ <ZWNJ> + and <ZWJ> are + format-control characters that are used to make necessary + distinctions when forming words or phrases in certain languages. In + ECMAScript source text, <ZWNJ> + and <ZWJ> + may also be used in an identifier after the first character. +
++ <BOM> + is a format-control character used primarily at the start of a text + to mark it as Unicode and to allow detection of the text's encoding + and byte order. <BOM> + characters intended for this purpose can sometimes also appear after + the start of a text, for example as a result of concatenating files. + <BOM> characters are treated as white space characters (see + 7.2). +
++ The + special treatment of certain format-control characters outside of + comments, string literals, and regular expression literals is + summarized in Table 1.
+|
+ + Code + Unit Value + |
+
+ + Name + |
+
+ + Formal + Name + |
+
+ + Usage + |
+
|
+
+ |
+
+ + Zero + width non-joiner + |
+
+ + <ZWNJ> + |
+
+ + IdentifierPart + |
+
|
+
+ |
+
+ + Zero + width joiner + |
+
+ + <ZWJ> + |
+
+ + IdentifierPart + |
+
|
+
+ |
+
+ + Byte + Order Mark + |
+
+ + <BOM> + |
+
+ + Whitespace + |
+
+ White + space characters are used to improve source text readability and to + separate tokens (indivisible lexical units) from each other, but are + otherwise insignificant. White space characters may occur between + any two tokens and at the start or end of input. White space + characters may also occur within a StringLiteral + or a RegularExpressionLiteral + (where they are considered significant characters forming part of + the literal value) or within a Comment, + but cannot appear within any other kind of token.
++ The + ECMAScript white space characters are listed in Table 2.
+|
+ + Code + Unit Value + |
+
+ + Name + |
+
+ + Formal + Name + |
+
|
+
+ |
+
+ + Tab + |
+
+ + <TAB> + |
+
|
+
+ |
+
+ + Vertical + Tab + |
+
+ + <VT> + |
+
|
+
+ |
+
+ + Form + Feed + |
+
+ + <FF> + |
+
|
+
+ |
+
+ + Space + |
+
+ + <SP> + |
+
|
+
+ |
+
+ + No-break + space + |
+
+ + <#x0a> + |
+
|
+
+ + Other + category “Zs” + |
+
+ + Byte + Order Mark ++ Any + other Unicode “space separator” + |
+
+ + <BOM> ++ <USP> + |
+
+ ECMAScript + implementations must recognize all of the white space characters + defined in Unicode 3.0. Later editions of the Unicode Standard may + define other white space characters. ECMAScript implementations may + recognize white space characters from later editions of the Unicode + Standard.
++ Syntax
++ WhiteSpace + ::
+
+ <TAB>
<VT>
<FF>
<SP>
<#x0a>
<BOM>
<USP>
+ Like + white space characters, line terminator characters are used to + improve source text readability and to separate tokens (indivisible + lexical units) from each other. However, unlike white space + characters, line terminators have some influence over the behaviour + of the syntactic grammar. In general, line terminators may occur + between any two tokens, but there are a few places where they are + forbidden by the syntactic grammar. Line terminators also affect the + process of automatic semicolon insertion (7.9). A line terminator + cannot occur within any token except a StringLiteral. + Line terminators may only occur within a StringLiteral + token as part of a LineContinuation. + +
++ A + line terminator can occur within a MultiLineComment + (7.4) but cannot occur within a SingleLineComment. + +
+
+ Line
+ terminators are included in the set of white space characters that
+ are matched by the \s
+ class in regular expressions.
+ The + ECMAScript line terminator characters are listed in Table 3.
+|
+ + Code + Unit Value + |
+
+ + Name + |
+
+ + Formal + Name + |
+
|
+
+ |
+
+ + Line + Feed + |
+
+ + <LF> + |
+
|
+
+ |
+
+ + Carriage + Return + + |
+
+ + <CR> + |
+
|
+
+ |
+
+ + Line + separator + |
+
+ + <LS> + |
+
|
+
+ |
+
+ + Paragraph + separator + |
+
+ + <PS> + |
+
+ Only + the characters in Table 3 are treated as line terminators. Other new + line or line breaking characters are treated as white space but not + as line terminators. The character sequence <CR><LF> is + commonly used as a line terminator. It should be considered a single + character for the purpose of reporting line numbers.
++ Syntax
++ LineTerminator ::
+
+ <LF>
<CR>
<LS>
<PS>
+ LineTerminatorSequence ::
+
+ <LF>
<CR>
+ [lookahead
+ ∉
+ <LF>
+ ]
<LS>
<PS>
<CR>
+ <LF>
+ Comments + can be either single or multi-line. Multi-line comments cannot nest.
+
+ Because
+ a single-line comment can contain any character except a
+ LineTerminator
+ character, and because of the general rule that a token is always as
+ long as possible, a single-line comment always consists of all
+ characters from the //
+ marker to the end of the line. However, the LineTerminator
+ at the end of the line is not considered to be part of the
+ single-line comment; it is recognised separately by the lexical
+ grammar and becomes part of the stream of input elements for the
+ syntactic grammar. This point is very important, because it implies
+ that the presence or absence of single-line comments does not affect
+ the process of automatic semicolon insertion (see 7.9).
+ Comments + behave like white space and are discarded except that, if a + MultiLineComment + contains a line terminator character, then the entire comment is + considered to be a LineTerminator + for purposes of parsing by the syntactic grammar.
++ Syntax
++ Comment ::
+
+ MultiLineComment
SingleLineComment
+ MultiLineComment ::
+
+ /* MultiLineCommentCharsopt*/
+ MultiLineCommentChars ::
+
+ MultiLineNotAsteriskChar
+ MultiLineCommentCharsopt* PostAsteriskCommentCharsopt
+ PostAsteriskCommentChars ::
+
+ MultiLineNotForwardSlashOrAsteriskChar
+ MultiLineCommentCharsopt* PostAsteriskCommentCharsopt
+ MultiLineNotAsteriskChar + ::
+
+ SourceCharacter but
+ not asterisk *
+ MultiLineNotForwardSlashOrAsteriskChar ::
+
+ SourceCharacter
+ but
+ not forward-slash /
+ orasterisk *
+ SingleLineComment ::
+
+ // SingleLineCommentCharsopt
+ SingleLineCommentChars ::
++ SingleLineCommentChar + SingleLineCommentCharsopt
++ SingleLineCommentChar ::
++ SourceCharacter + but + not LineTerminator
++ Syntax
++ Token ::
+
+ IdentifierName
Punctuator
NumericLiteral
StringLiteral
+
NOTE The + DivPunctuator and + RegularExpressionLiteral + productions define tokens, but are not included in the Token + production.
++ Identifier + Names are tokens that are interpreted according to the grammar given + in the “Identifiers” section of chapter 5 of the Unicode + standard, with some small modifications. An Identifier + is an IdentifierName + that is not a ReservedWord + (see 7.6.1). The Unicode identifier grammar is based on both + normative and informative character categories specified by the + Unicode Standard. The characters in the specified categories in + version 3.0 of the Unicode standard must be treated as in those + categories by all conforming ECMAScript implementations.
+
+ This
+ standard specifies specific character additions: The dollar sign ($)
+ and the underscore (_)
+ are permitted anywhere in an IdentifierName.
+ Unicode
+ escape sequences are also permitted in an IdentifierName,
+ where they contribute a single character to the IdentifierName,
+ as computed by the CV of the UnicodeEscapeSequence
+ (see 7.8.4). The \
+ preceding the UnicodeEscapeSequence
+ does not contribute a character to the IdentifierName.
+ A UnicodeEscapeSequence
+ cannot be used to put a character into an IdentifierName that would otherwise be illegal. In other words, if a \
+ UnicodeEscapeSequence
+ sequence were replaced by its UnicodeEscapeSequence's
+ CV, the result must still be a valid IdentifierName that has the exact same sequence of characters as the
+ original IdentifierName.
+ All interpretations of identifiers within this specification are
+ based upon their actual characters regardless of whether or not an
+ escape sequence was used to contribute any particular characters.
+ Two + IdentifierName that + are canonically equivalent according to the Unicode standard are not + equal unless they are represented by the exact same sequence of code + units (in other words, conforming ECMAScript implementations are + only required to do bitwise comparison on IdentifierName values). + The intent is that the incoming source text has been converted to + normalised form C before it reaches the compiler.
++ ECMAScript + implementations may recognize identifier characters defined in later + editions of the Unicode Standard. If portability is a concern, + programmers should only employ identifier characters defined in + Unicode 3.0.
++ Syntax
++ Identifier ::
++ IdentifierName but + not ReservedWord
++ IdentifierName + ::
+
+ IdentifierStart
IdentifierName
+ IdentifierPart
+ IdentifierStart ::
+
+ UnicodeLetter$
_\
+ UnicodeEscapeSequence
+ IdentifierPart ::
+
+ IdentifierStart
UnicodeCombiningMark
UnicodeDigit
UnicodeConnectorPunctuation
<ZWNJ>
<ZWJ>
+ UnicodeLetter
++ any + character in the Unicode categories “Uppercase letter (Lu)”, + “Lowercase letter (Ll)”, “Titlecase letter (Lt)”, “Modifier + letter (Lm)”, “Other letter (Lo)”, or “Letter number (Nl)”.
++ UnicodeCombiningMark
++ any + character in the Unicode categories “Non-spacing mark (Mn)” or + “Combining spacing mark (Mc)”
++ UnicodeDigit
++ any + character in the Unicode category “Decimal number (Nd)”
++ UnicodeConnectorPunctuation
++ any + character in the Unicode category “Connector punctuation (Pc)”
++ UnicodeEscapeSequence
++ see + 7.8.4.
++ A + reserved word is an IdentifierName + that cannot be used as an Identifier.
++ Syntax
++ ReservedWord + ::
+
+ Keyword
FutureReservedWord
NullLiteral
BooleanLiteral
+ The + following tokens are ECMAScript keywords and may not be used as + Identifiers in + ECMAScript programs.
++ Syntax
++ Keyword :: one + of
+|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+ + | +
|
+
+ |
+
+
+ |
+
+
+ |
+ + | +
+ The + following words are used as keywords in proposed extensions and are + therefore reserved to allow for the possibility of future adoption + of those extensions.
++ Syntax
++ FutureReservedWord + :: + one + of
+|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+ + | +
+ The + following tokens are also considered to be FutureReservedWords + when they occur within strict mode code (see 10.1.1). The + occurrence of any of these tokens within strict mode code in any + context where the occurrence of a FutureReservedWord + would produce an error must also produce an equivalent error:
+|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+ + | +
+ Syntax
++ Punctuator :: one + of
+|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+ + | +
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+
+
+ |
+ + | +
+ DivPunctuator :: one + of
+|
+
+ |
+
+
+ |
+ + | ++ | ++ | ++ | +
+ Syntax
++ Literal ::
+
+ NullLiteral
BooleanLiteral
NumericLiteral
StringLiteral
+
RegularExpressionLiteral
+ Syntax
++ NullLiteral ::
+
+ null
+ Semantics
+
+ The
+ value of the null literal null
+ is the sole value of the Null type, namely null.
+ Syntax
++ BooleanLiteral ::
+
+ true
false
+ Semantics
+
+ The
+ value of the Boolean literal true
+ is a value of the Boolean type, namely true.
+ The
+ value of the Boolean literal false
+ is a value of the Boolean type, namely false.
+ Syntax
++ NumericLiteral + ::
+
+ DecimalLiteral
HexIntegerLiteral
+ DecimalLiteral ::
+
+ DecimalIntegerLiteral . DecimalDigitsopt ExponentPartopt. DecimalDigits ExponentPartopt
DecimalIntegerLiteral
+ ExponentPartopt
+ DecimalIntegerLiteral + ::
+
+ 0
NonZeroDigit
+ DecimalDigitsopt
+ DecimalDigits ::
+
+ DecimalDigit
DecimalDigits
+ DecimalDigit
+ DecimalDigit :: + one + of
+
+ 0
+ 1 2 3 4 5 6 7 8 9
+ NonZeroDigit :: + one + of
+
+ 1
+ 2 3 4 5 6 7 8 9
+ ExponentPart ::
++ ExponentIndicator + SignedInteger
++ ExponentIndicator :: + one + of
+
+ e
+ E
+ SignedInteger + ::
+
+ DecimalDigits+ DecimalDigits- DecimalDigits
+ HexIntegerLiteral ::
+
+ 0x HexDigit0X HexDigit
HexIntegerLiteral HexDigit
+ HexDigit :: one + of
+
+ 0
+ 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F
+ The + source character immediately following a NumericLiteral + must not be an IdentifierStart + or DecimalDigit.
++
NOTE For example:
+3in
is
+ an error and not the two input elements 3
+ and in.
+ Semantics
++ A + numeric literal stands for a value of the Number type. This value is + determined in two steps: first, a mathematical value (MV) is derived + from the literal; second, this mathematical value is rounded as + described below.
++ The + MV of NumericLiteral :: + DecimalLiteral is the MV of + DecimalLiteral.
++ The + MV of NumericLiteral :: + HexIntegerLiteral is the MV + of HexIntegerLiteral.
+
+ The
+ MV of DecimalLiteral ::
+ DecimalIntegerLiteral .
+ is the MV of
+ DecimalIntegerLiteral.
+ The
+ MV of DecimalLiteral ::
+ DecimalIntegerLiteral . DecimalDigits is
+ the MV of DecimalIntegerLiteral plus
+ (the MV of DecimalDigits times
+ 10–n),
+ where n is the
+ number of characters in DecimalDigits.
+ The
+ MV of DecimalLiteral ::
+ DecimalIntegerLiteral . ExponentPart is the MV of
+ DecimalIntegerLiteral times
+ 10e,
+ where e is
+ the MV of ExponentPart.
+ The
+ MV of DecimalLiteral ::
+ DecimalIntegerLiteral . DecimalDigits ExponentPart is
+ (the MV of DecimalIntegerLiteral plus
+ (the MV of DecimalDigits times
+ 10–n))
+ times 10e,
+ where n is the
+ number of characters in DecimalDigits and
+ e is the MV of
+ ExponentPart.
+ The
+ MV of DecimalLiteral ::. DecimalDigits is the MV of
+ DecimalDigits times
+ 10–n,
+ where n is the
+ number of characters in DecimalDigits.
+ The
+ MV
+ of DecimalLiteral ::. DecimalDigits ExponentPart is
+ the MV of DecimalDigits times
+ 10e–n,
+ where n is the
+ number of characters in DecimalDigits and
+ e is the MV of
+ ExponentPart.
+ The + MV of DecimalLiteral :: + DecimalIntegerLiteral is + the MV of DecimalIntegerLiteral.
++ The + MV of DecimalLiteral :: + DecimalIntegerLiteral ExponentPart is + the MV of DecimalIntegerLiteral times + 10e, + where e is the MV of + ExponentPart.
+
+ The
+ MV of DecimalIntegerLiteral ::
+ 0 is 0.
+ The + MV of DecimalIntegerLiteral :: + NonZeroDigit DecimalDigits is + (the MV of NonZeroDigit times + 10n) plus + the MV of DecimalDigits, + where n + is the number of characters in DecimalDigits.
++ The + MV of DecimalDigits :: + DecimalDigit is the MV of + DecimalDigit.
++ The + MV of DecimalDigits :: + DecimalDigits DecimalDigit is + (the MV of DecimalDigits times + 10) plus the MV of DecimalDigit.
++ The + MV of ExponentPart :: + ExponentIndicator SignedInteger is + the MV of SignedInteger.
++ The + MV of SignedInteger :: + DecimalDigits is + the MV of DecimalDigits.
+
+ The
+ MV of SignedInteger ::
+ + DecimalDigits is
+ the MV of DecimalDigits.
+ The
+ MV of SignedInteger ::
+ - DecimalDigits is
+ the negative of the MV of DecimalDigits.
+ The
+ MV of DecimalDigit ::
+ 0 or
+ of HexDigit ::
+ 0 is
+ 0.
+ The
+ MV of DecimalDigit ::
+ 1 or
+ of NonZeroDigit ::
+ 1 or
+ of HexDigit ::
+ 1 is
+ 1.
+ The
+ MV of DecimalDigit ::
+ 2 or
+ of NonZeroDigit ::
+ 2 or
+ of HexDigit ::
+ 2 is
+ 2.
+ The
+ MV of DecimalDigit ::
+ 3 or
+ of NonZeroDigit ::
+ 3 or
+ of HexDigit ::
+ 3 is
+ 3.
+ The
+ MV of DecimalDigit ::
+ 4 or
+ of NonZeroDigit ::
+ 4 or
+ of HexDigit ::
+ 4 is
+ 4.
+ The
+ MV of DecimalDigit ::
+ 5 or
+ of NonZeroDigit ::
+ 5 or
+ of HexDigit ::
+ 5 is
+ 5.
+ The
+ MV of DecimalDigit ::
+ 6 or
+ of NonZeroDigit ::
+ 6 or
+ of HexDigit ::
+ 6 is
+ 6.
+ The
+ MV of DecimalDigit ::
+ 7 or
+ of NonZeroDigit ::
+ 7 or
+ of HexDigit ::
+ 7 is
+ 7.
+ The
+ MV of DecimalDigit ::
+ 8 or
+ of NonZeroDigit ::
+ 8 or
+ of HexDigit ::
+ 8 is
+ 8.
+ The
+ MV of DecimalDigit ::
+ 9 or
+ of NonZeroDigit ::
+ 9 or
+ of HexDigit ::
+ 9 is
+ 9.
+ The
+ MV of HexDigit ::
+ a or
+ of HexDigit ::
+ A is
+ 10.
+ The
+ MV of HexDigit ::
+ b or
+ of HexDigit ::
+ B is
+ 11.
+ The
+ MV of HexDigit ::
+ c or
+ of HexDigit ::
+ C is
+ 12.
+ The
+ MV of HexDigit ::
+ d or
+ of HexDigit ::
+ D is
+ 13.
+ The
+ MV of HexDigit ::
+ e or
+ of HexDigit ::
+ E is
+ 14.
+ The
+ MV of HexDigit ::
+ f or
+ of HexDigit ::
+ F is
+ 15.
+ The
+ MV of HexIntegerLiteral ::
+ 0x HexDigit
+ is the MV of HexDigit.
+ The
+ MV of HexIntegerLiteral ::
+ 0X HexDigit
+ is the MV of HexDigit.
+ The + MV of HexIntegerLiteral :: + HexIntegerLiteral HexDigit is + (the MV of HexIntegerLiteral times + 16) plus the MV of + HexDigit.
+
+ Once
+ the exact MV for a numeric literal has been determined, it is then
+ rounded to a value of the Number type. If the MV is 0, then the
+ rounded value is +0;
+ otherwise, the rounded value must be the Number value for the
+ MV (as specified in 8.5), unless the literal is a DecimalLiteral
+ and the literal has more than 20 significant digits, in which case
+ the Number value may be either the Number value for the MV of a
+ literal produced by replacing each significant digit after the 20th
+ with a 0 digit or
+ the Number value for the MV of a literal produced by replacing each
+ significant digit after the 20th with a 0
+ digit and then incrementing the literal at the 20th significant
+ digit position. A digit is significant if it is not part of
+ an ExponentPart
+ and
+ it
+ is not 0;
+ or
+ there + is a nonzero digit to its left and there is a nonzero digit, not + in the ExponentPart, + to its right.
++ A + conforming implementation, when processing strict mode code (see + 10.1.1), must not extend the syntax of NumericLiteral + to include OctalIntegerLiteral + as described in B.1.1.
++ A + string literal is zero or more characters enclosed in single or + double quotes. Each character may be represented by an escape + sequence. All characters may appear literally in a string literal + except for the closing quote character, backslash, carriage return, + line separator, paragraph separator, and line feed. Any character + may appear in the form of an escape sequence.
++ Syntax
++ StringLiteral ::
+
+ " DoubleStringCharactersopt
+ " SingleStringCharactersopt
''
+ DoubleStringCharacters ::
++ DoubleStringCharacter + DoubleStringCharactersopt
++ SingleStringCharacters ::
++ SingleStringCharacter + SingleStringCharactersopt
++ DoubleStringCharacter ::
+
+ SourceCharacter but
+ not double-quote "
+ or
+ backslash \ or
+ LineTerminator\
+ EscapeSequence
LineContinuation
+ SingleStringCharacter ::
+
+ SourceCharacter but
+ not single-quote '
+ orbackslash \ or
+ LineTerminator\
+ EscapeSequence
LineContinuation
+ LineContinuation ::
+
+ \
+ LineTerminatorSequence
+ EscapeSequence ::
+
+ CharacterEscapeSequence0 [lookahead
+ ∉
+ DecimalDigit]
HexEscapeSequence
UnicodeEscapeSequence
+ CharacterEscapeSequence ::
+
+ SingleEscapeCharacter
NonEscapeCharacter
+ SingleEscapeCharacter :: + one + of
+
+ '
+ " \ b f n r t v
+ NonEscapeCharacter + ::
++ SourceCharacter + but + not EscapeCharacter or + LineTerminator
++ EscapeCharacter ::
+
+ SingleEscapeCharacter
DecimalDigitx u
+ HexEscapeSequence ::
+
+ x
+ HexDigit HexDigit
+ UnicodeEscapeSequence ::
+
+ u HexDigit HexDigit HexDigit HexDigit
+ The + definitions of the nonterminal HexDigit + is given in 7.6. SourceCharacter + is defined in clause 6.
++ Semantics
++ A + string literal stands for a value of the String type. The String + value (SV) of the literal is described in terms of character values + (CV) contributed by the various parts of the string literal. As part + of this process, some characters within the string literal are + interpreted as having a mathematical value (MV), as described below + or in 7.8.3.
+
+ The
+ SV of StringLiteral ::
+ "" is
+ the empty character sequence.
+ The
+ SV of StringLiteral ::
+ '' is
+ the empty character sequence.
+ The
+ SV of StringLiteral ::
+ "
+ DoubleStringCharacters "
+ is the SV of
+ DoubleStringCharacters.
+ The
+ SV of StringLiteral ::
+ '
+ SingleStringCharacters '
+ is the SV of
+ SingleStringCharacters.
+ The + SV of DoubleStringCharacters :: + DoubleStringCharacter is a + sequence of one character, the CV of DoubleStringCharacter.
++ The + SV of DoubleStringCharacters :: + DoubleStringCharacter DoubleStringCharacters is + a sequence of the CV of DoubleStringCharacter + followed by all the characters in + the SV of DoubleStringCharacters + in order.
++ The + SV of SingleStringCharacters :: + SingleStringCharacter is a + sequence of one character, the CV of + SingleStringCharacter.
++ The + SV of SingleStringCharacters :: + SingleStringCharacter SingleStringCharacters + is a sequence of the CV of SingleStringCharacter + followed by all the characters in + the SV of SingleStringCharacters in + order.
+
+ The
+ SV of LineContinuation ::
+ \
+ LineTerminatorSequence is
+ the empty character sequence.
+ The
+ CV of DoubleStringCharacter ::
+ SourceCharacter but not
+ double-quote "
+ or backslash
+ \ or
+ LineTerminator is theSourceCharacter character
+ itself.
+ The
+ CV of DoubleStringCharacter ::
+ \
+ EscapeSequence is
+ the CV of the EscapeSequence.
The +CV of DoubleStringCharacter :: +LineContinuation is the +empty character sequence.
+ The
+ CV of SingleStringCharacter ::
+ SourceCharacter but not
+ single-quote '
+ or backslash
+ \ or
+ LineTerminator is theSourceCharacter character
+ itself.
+ The
+ CV of SingleStringCharacter ::
+ \
+ EscapeSequence is
+ the CV of the EscapeSequence.
The +CV of SingleStringCharacter :: +LineContinuation is +the empty character sequence.
+ The + CV of EscapeSequence :: + CharacterEscapeSequence is + the CV of the CharacterEscapeSequence.
+
+ The
+ CV of EscapeSequence ::
+ 0 [lookahead
+ ∉
+ DecimalDigit]
+ is a <NUL>
+ character (Unicode value 0000).
+ The + CV of EscapeSequence :: + HexEscapeSequence is the CV + of the HexEscapeSequence.
++ The + CV of EscapeSequence :: + UnicodeEscapeSequence is + the CV of the UnicodeEscapeSequence.
++ The CV of CharacterEscapeSequence ::SingleEscapeCharacter is the + character whose code unit value is determined by theSingleEscapeCharacter according + to Table 4:
+|
+ + Escape + Sequence + |
+
+ + Code + Unit Value + |
+
+ + Name + |
+
+ + Symbol + |
+
|
+
+ |
+
+
+ |
+
+ + backspace + |
+
+ + <BS> + |
+
|
+
+ |
+
+
+ |
+
+ + horizontal + tab + |
+
+ + <HT> + |
+
|
+
+ |
+
+
+ |
+
+ + line + feed (new line) + |
+
+ + <LF> + |
+
|
+
+ |
+
+
+ |
+
+ + vertical + tab + |
+
+ + <VT> + |
+
|
+
+ |
+
+
+ |
+
+ + form + feed + |
+
+ + <FF> + |
+
|
+
+ |
+
+
+ |
+
+ + carriage + return + |
+
+ + <CR> + |
+
|
+
+ |
+
+
+ |
+
+ + double + quote + |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+ + single + quote + |
+
+
+ |
+
|
+
+ |
+
+
+ |
+
+ + backslash + |
+
+
+ |
+
+ The + CV of CharacterEscapeSequence :: + NonEscapeCharacter is the + CV of the NonEscapeCharacter.
++ The + CV of NonEscapeCharacter :: + SourceCharacter but + not EscapeCharacter or + LineTerminator is the + SourceCharacter character + itself.
+
+ The
+ CV of HexEscapeSequence ::
+ x HexDigit
+ HexDigit is the character
+ whose code unit value is (16
+ times the MV of the first HexDigit)
+ plus the MV of the second HexDigit.
+ The
+ CV of UnicodeEscapeSequence ::
+ u HexDigit
+ HexDigit HexDigit HexDigit is the
+ character whose code unit value is (4096
+ times the MV of the first HexDigit)
+ plus (256 times the MV of
+ the second HexDigit)
+ plus (16 times the MV of
+ the third HexDigit)
+ plus the MV of the fourth HexDigit.
+ A + conforming implementation, when processing strict mode code (see + 10.1.1), may not extend the syntax of EscapeSequence + to include OctalEscapeSequence + as described in B.1.2.
++
NOTE A line
+ terminator character cannot appear in a string literal, except as
+ part of a LineContinuation
+ to produce the empty character sequence. The correct way to cause a
+ line terminator character to be part of the String value of a string
+ literal is to use an escape sequence such as \n
+ or \u000A.
+ A
+ regular expression literal is an input element that is converted to
+ a RegExp object (see 15.10) each time the literal is evaluated. Two
+ regular expression literals in a program evaluate to regular
+ expression objects that never compare as ===
+ to each other even if the two literals' contents are identical. A
+ RegExp object may also be created at runtime by new
+ RegExp (see 15.10.4) or calling the RegExp
+ constructor as a function (15.10.3).
+ The + productions below describe the syntax for a regular expression + literal and are used by the input element scanner to find the end of + the regular expression literal. The Strings of characters comprising + the RegularExpressionBody + and the RegularExpressionFlags + are passed uninterpreted to the regular expression constructor, + which interprets them according to its own, more stringent grammar. + An implementation may extend the regular expression constructor's + grammar, but it must not extend the RegularExpressionBody + and RegularExpressionFlags + productions or the productions used by these productions.
++ Syntax
++ RegularExpressionLiteral ::
+
+ / RegularExpressionBody /
+ RegularExpressionFlags
+ RegularExpressionBody + ::
++ RegularExpressionFirstChar + RegularExpressionChars
++ RegularExpressionChars ::
+
+ [empty]
RegularExpressionChars
+ RegularExpressionChar
+ RegularExpressionFirstChar ::
+
+ RegularExpressionNonTerminator but
+ not *
+ or
+ \ or
+ /
+ or
+ [
RegularExpressionBackslashSequence
RegularExpressionClass
+ RegularExpressionChar ::
+
+ RegularExpressionNonTerminator
+ but
+ not \
+ or
+ /
+ or
+ [
RegularExpressionBackslashSequence
RegularExpressionClass
+ RegularExpressionBackslashSequence ::
+
+ \ RegularExpressionNonTerminator
+ RegularExpressionNonTerminator ::
++ SourceCharacter + but + not LineTerminator
++ RegularExpressionClass ::
+
+ [
+ RegularExpressionClassChars
+ ]
+ RegularExpressionClassChars
+ ::
+ [empty]
RegularExpressionClassChars
+ RegularExpressionClassChar
+ RegularExpressionClassChar
+ ::
+ RegularExpressionNonTerminator
+ but
+ not ]
+ or
+ \
RegularExpressionBackslashSequence
+ RegularExpressionFlags + ::
+
+ [empty]
RegularExpressionFlags
+ IdentifierPart
NOTE Regular
+ expression literals may not be empty; instead of representing an
+ empty regular expression literal, the characters //
+ start a single-line comment. To specify an empty regular expression,
+ use: /(?:)/.
+ Semantics
+
+ A
+ regular expression literal evaluates to a value of the Object type
+ that is an instance of the standard built-in constructor RegExp.
+ This value is determined in two steps: first, the characters
+ comprising the regular expression's RegularExpressionBody
+ and RegularExpressionFlags
+ production expansions are collected uninterpreted into two Strings
+ Pattern and Flags, respectively. Then each time the literal is
+ evaluated, a new object is created as if by the expression new
+ RegExp(Pattern,
+ Flags)
+ where RegExp is the standard built-in constructor with that name.
+ The newly constructed object becomes the value of the
+ RegularExpressionLiteral.
+ If the call to new RegExp
+ would generate an error as specified in 15.10.4.1, the error must be
+ treated as an early error (Clause 16).
+ Certain
+ ECMAScript statements (empty statement, variable statement,
+ expression statement, do-while
+ statement, continue
+ statement, break
+ statement, return
+ statement, and throw
+ statement) must be terminated with semicolons. Such semicolons may
+ always appear explicitly in the source text. For convenience,
+ however, such semicolons may be omitted from the source text in
+ certain situations. These situations are described by saying that
+ semicolons are automatically inserted into the source code token
+ stream in those situations.
+ There + are three basic rules of semicolon insertion:
++ When, + as the program is parsed from left to right, a token (called the + offending token) + is encountered that is not allowed by any production of the + grammar, then a semicolon is automatically inserted before the + offending token if one or more of the following conditions is + true:
++ The + offending token is separated from the previous token by at least + one LineTerminator.
+
+ The
+ offending token is }.
+ When, + as the program is parsed from left to right, the end of the input + stream of tokens is encountered and the parser is unable to parse + the input token stream as a single complete ECMAScript Program, + then a semicolon is automatically inserted at the end of the + input stream.
++ When, + as the program is parsed from left to right, a token is + encountered that is allowed by some production of the grammar, + but the production is a restricted + production and the + token would be the first token for a terminal or nonterminal + immediately following the annotation “[no LineTerminator here]” + within the restricted production + (and therefore such a token is called a restricted token), and + the restricted token is separated from the previous token by at + least one LineTerminator, + then a semicolon is automatically inserted before the restricted + token.
+
+ However,
+ there is an additional overriding condition on the preceding rules:
+ a semicolon is never inserted automatically if the semicolon would
+ then be parsed as an empty statement or if that semicolon would
+ become one of the two semicolons in the header of a for
+ statement (see 12.6.3).
+ +
NOTE The following + are the only restricted productions in the grammar:
++ PostfixExpression :
+
+ LeftHandSideExpression
+ [no LineTerminator here]
+ ++
LeftHandSideExpression
+ [no LineTerminator here]
+ --
+ ContinueStatement :
+
+ continue [no LineTerminator here] Identifier;
+ BreakStatement :
+
+ break [no LineTerminator here] Identifier;
+ ReturnStatement :
+
+ return [no LineTerminator here] Expression;
+ ThrowStatement + :
+
+ throw [no LineTerminator here] Expression;
+ The + practical effect of these restricted productions is as follows:
+
+ When
+ a ++
+ or --
+ token is encountered where the parser would treat it as a postfix
+ operator, and at least one LineTerminator
+ occurred between the preceding token and the ++
+ or --
+ token, then a semicolon is automatically inserted before the ++
+ or --
+ token.
+ When
+ a continue,
+ break,
+ return,
+ or throw
+ token is encountered and a LineTerminator
+ is encountered before the next token, a semicolon is automatically
+ inserted after the continue,
+ break,
+ return,
+ or throw
+ token.
+ The + resulting practical advice to ECMAScript programmers is:
+
+ A
+ postfix ++
+ or --
+ operator should appear on the same line as its operand.
+ An
+ Expression
+ in a return
+ or throw
+ statement should start on the same line as the return
+ or throw
+ token.
+ A
+ Identifier
+ in a break
+ or continue
+ statement should be on the same line as the break
+ or continue
+ token.
+ The + source
+
+ {
+ 1 2 } 3
is + not a valid sentence in the ECMAScript grammar, even with the + automatic semicolon insertion rules. In contrast, the source
+
+ {
+ 1
2 } 3
is + also not a valid ECMAScript sentence, but is transformed by + automatic semicolon insertion into the following:
+
+ {
+ 1
;2 ;} 3;
+ which + is a valid ECMAScript sentence.
+The + source
+
+ for
+ (a; b
)
+ is
+ not a valid ECMAScript sentence and is not altered by automatic
+ semicolon insertion because the semicolon is needed for the header
+ of a for
+ statement. Automatic semicolon insertion never inserts one of the
+ two semicolons in the header of a for
+ statement.
The + source
+return
a
+ + b
is + transformed by automatic semicolon insertion into the following:
+
+ return;
a
+ + b;
NOTE The
+ expression a + b
+ is not treated as a value to be returned by the return
+ statement, because a LineTerminator
+ separates it from the token return.
The + source
+
+ a
+ = b
++c
is + transformed by automatic semicolon insertion into the following:
+
+ a
+ = b;
++c;
NOTE The
+ token ++ is not
+ treated as a postfix operator applying to the variable b,
+ because a LineTerminator
+ occurs between b
+ and ++.
The + source
+
+ if
+ (a > b)
else c = d
+ is
+ not a valid ECMAScript sentence and is not altered by automatic
+ semicolon insertion before the else
+ token, even though no production of the grammar applies at that
+ point, because an automatically inserted semicolon would then be
+ parsed as an empty statement.
The + source
+
+ a
+ = b + c
(d + e).print()
is + not transformed by automatic semicolon insertion, because the + parenthesised expression that begins the second line can be + interpreted as an argument list for a function call:
+
+ a
+ = b + c(d + e).print()
+ In + the circumstance that an assignment statement must begin with a left + parenthesis, it is a good idea for the programmer to provide an + explicit semicolon at the end of the preceding statement rather than + to rely on automatic semicolon insertion.
+ \ No newline at end of file diff --git a/x8.html b/x8.html new file mode 100644 index 0000000..a8723e5 --- /dev/null +++ b/x8.html @@ -0,0 +1,2386 @@ + +‟Ex igne vita”
+ ++ Algorithms + within this specification manipulate values each of which has an + associated type. The possible value types are exactly those defined + in this clause. Types are further subclassified into ECMAScript + language types and specification types.
++ An + ECMAScript language type corresponds to values that are directly + manipulated by an ECMAScript programmer using the ECMAScript + language. The ECMAScript language types are +Undefined, +Null, +Boolean, +String, +Number, +and +Object.
++ A + specification type corresponds to meta-values that are used within + algorithms to describe the semantics of ECMAScript language + constructs and ECMAScript language types. The specification types + are +Reference, +List, +Completion, +Property Descriptor, +Property Identifier, +Lexical Environment, +and +Environment Record. + Specification type values are specification artefacts that do not + necessarily correspond to any specific entity within an ECMAScript + implementation. Specification type values may be used to describe + intermediate results of ECMAScript expression evaluation but such + values cannot be stored as properties of objects or values of + ECMAScript language variables.
++ Within + this specification, the notation “Type(x)” + is used as shorthand for “the + type of x” + where “type” refers + to the ECMAScript language and specification types defined in this + clause.
++ The + Undefined type has exactly one value, called undefined. Any + variable that has not been assigned a value has the value undefined.
++ The + Null type has exactly one value, called null.
++ The + Boolean type represents a logical entity having two values, called + true and false.
++ The + String type is the set of all finite ordered sequences of zero or + more 16-bit unsigned integer values (“elements”). The String + type is generally used to represent textual data in a running + ECMAScript program, in which case each element in the String is + treated as a code unit value (see Clause 6). Each element is + regarded as occupying a position within the sequence. These + positions are indexed with nonnegative integers. The first element + (if any) is at position 0, the next element (if any) at position 1, + and so on. The length of a String is the number of elements (i.e., + 16-bit values) within it. The empty String has length zero and + therefore contains no elements.
++ When + a String contains actual textual data, each element is considered to + be a single UTF-16 code unit. Whether or not this is the actual + storage format of a String, the characters within a String are + numbered by their initial code unit element position as though they + were represented using UTF-16. All operations on Strings (except as + otherwise stated) treat them as sequences of undifferentiated 16-bit + unsigned integers; they do not ensure the resulting String is in + normalised form, nor do they ensure language-sensitive results.
+NOTE The + rationale behind this design was to keep the implementation of + Strings as simple and high-performing as possible. The intent is + that textual data coming into the execution environment from outside + (e.g., user input, text read from a file or received over the + network, etc.) be converted to Unicode Normalised Form C before the + running program sees it. Usually this would occur at the same time + incoming text is converted from its original character encoding to + Unicode (and would impose no additional overhead). Since it is + recommended that ECMAScript source code be in Normalised Form C, + string literals are guaranteed to be normalised (if source text is + guaranteed to be normalised), as long as they do not contain any + Unicode escape sequences.
+
+ The
+ Number type has exactly 18437736874454810627
+ (that is, 264−253+3)
+ values, representing the double-precision 64-bit format IEEE 754
+ values as specified in the IEEE Standard for Binary Floating-Point
+ Arithmetic, except that the 9007199254740990
+ (that is, 253−2)
+ distinct “Not-a-Number” values of the IEEE Standard are
+ represented in ECMAScript as a single special NaN value.
+ (Note that the NaN value is produced by the program
+ expression NaN.)
+ In some implementations, external code might be able to detect a
+ difference between various Not-a-Number values, but such behaviour
+ is implementation-dependent; to ECMAScript code, all NaN values are
+ indistinguishable from each other.
+ There
+ are two other special values, called positive Infinity and
+ negative Infinity. For brevity, these values are also
+ referred to for expository purposes by the symbols +∞
+ and −∞, respectively.
+ (Note that these two infinite Number values are produced by the
+ program expressions +Infinity
+ (or simply Infinity)
+ and -Infinity.)
+ The + other 18437736874454810624 + (that is, 264−253) + values are called the finite numbers. Half of these are positive + numbers and half are negative numbers; for every finite positive + Number value there is a corresponding negative value having the same + magnitude.
+
+ Note
+ that there is both a positive zero and a negative zero.
+ For brevity, these values are also referred to for expository
+ purposes by the symbols +0
+ and −0,
+ respectively. (Note that these two different zero Number values are
+ produced by the program expressions +0
+ (or simply 0) and
+ -0.)
+ The + 18437736874454810622 + (that is, 264−253−2) + finite nonzero values are of two kinds:
++ 18428729675200069632 + (that is, 264−254) + of them are normalised, having the form
++ s + × m × + 2e
++ where + s is +1 + or −1, + m is a positive + integer less than 253 + but not less than 252, + and e is an + integer ranging from −1074 + to 971, inclusive.
++ The + remaining 9007199254740990 + (that is, 253−2) + values are denormalised, having the form
++ s + × m × + 2e
++ where + s + is +1 or −1, + m is a positive + integer less than 252, + and e is −1074.
+
+ Note
+ that all the positive and negative integers whose magnitude is no
+ greater than 253
+ are representable in the Number type (indeed, the integer 0
+ has two representations, +0
+ and -0).
+ A + finite number has an odd significand if it is nonzero and the + integer m used to + express it (in one of the two forms shown above) is odd. Otherwise, + it has an even significand.
++ In + this specification, the phrase “the + Number value for x” + where x represents + an exact nonzero real mathematical quantity (which might even be an + irrational number such as π) + means a Number value chosen in the following manner. Consider the + set of all finite values of the Number type, with −0 + removed and with two additional values added to it that are not + representable in the Number type, namely 21024 + (which is +1 × + 253× + 2971) + and −21024 + (which is −1 + × + 253× + 2971). + Choose the member of this set that is closest in value to x. + If two values of the set are equally close, then the one with an + even significand is chosen; for this purpose, the two extra values + 21024 + and −21024 + are considered to have even significands. Finally, if 21024 + was chosen, replace it with +∞; + if −21024 + was chosen, replace it with −∞; + if +0 was chosen, + replace it with −0 + if and only if x + is less than zero; any other chosen value is used unchanged. The + result is the Number value for x. + (This procedure corresponds exactly to the behaviour of the IEEE 754 + “round to nearest” mode.)
++ Some + ECMAScript operators deal only with integers in the range −231 + through 231−1, + inclusive, or in the range 0 + through 232−1, + inclusive. These operators accept any value of the Number type but + first convert each such value to one of 232 + integer values. See the descriptions of the ToInt32 and ToUint32 + operators in 9.5 and 9.6, respectively.
++ An + Object is a collection of properties. Each property is either + a named data property, a named accessor property, or an internal + property:
++ A + named data property associates a name with an ECMAScript + language value and a set of Boolean attributes.
++ A + named accessor property associates a name with one or two + accessor functions, and a set of Boolean attributes. The accessor + functions are used to store or retrieve an ECMAScript language + value that is associated with the property. +
++ An + internal property has no name and is not directly accessible + via ECMAScript language operators. Internal properties exist purely + for specification purposes. +
++ There + are two kinds of access for named (non-internal) properties: get and put, corresponding to retrieval and assignment, + respectively.
++ Attributes + are used in this specification to define and explain the state of + named properties. A named data property associates a name with the + attributes listed in Table 5
+|
+ + Attribute + Name + |
+
+ + Value + Domain + |
+
+ + Description + |
+
|
+ + [[Value]] + + + |
+
+ + Any + ECMAScript language type + |
+
+ + The + value retrieved by reading the property. + |
+
|
+ + [[Writable]] + + + |
+
+ + Boolean + |
+
+ + If + false, attempts by ECMAScript code to change the + property’s [[Value]] attribute using [[Put]] will not succeed. + |
+
|
+ + [[Enumerable]] + |
+
+ + Boolean + |
+
+ + If + true, the property will be enumerated by a for-in + enumeration (see 12.6.4). Otherwise, the property is said to be + non-enumerable. + |
+
|
+ + [[Configurable]] + |
+
+ + Boolean + |
+
+ + If + false, attempts to delete the property, change the + property to be an accessor property, or change its attributes + (other than [[Value]]) will fail. + |
+
+ A + named accessor property associates a name with the attributes listed + in Table 6.
+|
+ + Attribute + Name + |
+
+ + Value + Domain + |
+
+ + Description + |
+
|
+ + [[Get]] + |
+
+ + Object + or Undefined + |
+
+ + If + the value is an Object it must be a function Object. The + function’s [[Call]] internal method (8.6.2) is called with an + empty arguments list to return the property value each time a + get access of the property is performed. + |
+
|
+ + [[Set]] + |
+
+ + Object + or Undefined + |
+
+ + If + the value is an Object it must be a function Object. The + function’s [[Call]] internal method (8.6.2) is called with an + arguments list containing the assigned value as its sole + argument each time a set access of the property is performed. + The effect of a property's [[Set]] internal method may, but is + not required to, have an effect on the value returned by + subsequent calls to the property's [[Get]] internal method. + |
+
|
+ + [[Enumerable]] + |
+
+ + Boolean + |
+
+ + If + true, the property is to be enumerated by a for-in + enumeration (see 12.6.4). Otherwise, the property is said to be + non-enumerable. + |
+
|
+ + [[Configurable]] + |
+
+ + Boolean + |
+
+ + If + false, attempts to delete the property, change the + property to be a data property, or change its attributes will + fail. + |
+
+ If + the value of an attribute is not explicitly specified by this + specification for a named property, the default value defined in + Table 7 is used.
+|
+ + Attribute + Name + |
+
+ + Default + Value + |
+
|
+ + [[Value]] + |
+
+ + undefined + |
+
|
+ + [[Get]] + |
+
+ + undefined + |
+
|
+ + [[Set]] + |
+
+ + undefined + |
+
|
+ + [[Writable]] + |
+
+ + false + |
+
|
+ + [[Enumerable]] + |
+
+ + false + |
+
|
+ + [[Configurable]] + |
+
+ + false + |
+
+ This + specification uses various internal properties to define the + semantics of object values. These internal properties are not part + of the ECMAScript language. They are defined by this specification + purely for expository purposes. An implementation of ECMAScript must + behave as if it produced and operated upon internal properties in + the manner described here. The names of internal properties are + enclosed in double square brackets [[ ]]. When an algorithm uses an + internal property of an object and the object does not implement the + indicated internal property, a TypeError exception is thrown.
++ The + Table 8 summarises the internal properties used by this + specification that are applicable to all ECMAScript objects. The + Table 9 summarises the internal properties used by this + specification that are only applicable to some ECMAScript objects. + The descriptions in these tables indicates their behaviour for + native ECMAScript objects, unless stated otherwise in this document + for particular kinds of native ECMAScript objects. Host objects may + support these internal properties with any implementation-dependent + behaviour as long as it is consistent with the specific host object + restrictions stated in this document.
++ The + “Value Type Domain” columns of the following tables define the + types of values associated with internal properties. The type names + refer to the types defined in Clause 8 augmented by the following + additional names. “any” means the value may be any + ECMAScript language type. “primitive” means Undefined, + Null, Boolean, String, or Number. “SpecOp” means the + internal property is an internal method, an implementation provided + procedure defined by an abstract operation specification. “SpecOp” + is followed by a list of descriptive parameter names. If a parameter + name is the same as a type name then the name describes the type of + the parameter. If a “SpecOp” returns a value, its parameter list + is followed by the symbol “→” and the type of the returned + value.
+|
+ + Internal + Property + |
+
+ + Value + Type Domain + |
+
+ + Description + |
+
|
+ + [[Prototype]] + |
+
+ + Object + or Null + |
+
+ + The + prototype of this object. + |
+
|
+ + [[Class]] + |
+
+ + String + |
+
+ + A + String value indicating a specification defined classification + of objects. + |
+
|
+ + [[Extensible]] + |
+
+ + Boolean + |
+
+ + If + true, own properties may be added to the object. + |
+
|
+ + [[Get]] + |
+
+ + SpecOp(propertyName) + → any + |
+
+ + Returns + the value of the named property. + |
+
|
+ + [[GetOwnProperty]] + |
+
+ + SpecOp + (propertyName) → ++ Undefinedor + Property Descriptor + |
+
+ + Returns + the Property Descriptor of the named own property of this + object, or undefined if absent. + |
+
|
+ + [[GetProperty]] + |
+
+ + SpecOp + (propertyName) → ++ Undefinedor + Property Descriptor + |
+
+ + Returns + the fully populated Property Descriptor of the named property of + this object, or undefined if absent. + |
+
|
+ + [[Put]] + |
+
+ + SpecOp + (propertyName, any, Boolean) + |
+
+ + Sets + the specified named property to the value of the second + parameter. The flag controls failure handling. + |
+
|
+ + [[CanPut]] + |
+
+ + SpecOp + (propertyName) → + Boolean + |
+
+ + Returns + a Boolean value indicating whether a [[Put]] operation with + PropertyName can be performed. + |
+
|
+ + [[HasProperty]] + |
+
+ + SpecOp + (propertyName) → + Boolean + |
+
+ + Returns + a Boolean value indicating whether the object already has a + property with the given name. + |
+
|
+ + [[Delete]] + |
+
+ + SpecOp + (propertyName, Boolean) → + Boolean + |
+
+ + Removes + the specified named own property from the object. The flag + controls failure handling. + |
+
|
+ + [[DefaultValue]] + |
+
+ + SpecOp + (Hint) → + primitive + |
+
+ + Hint + is a String. Returns a default value for the object. + |
+
|
+ + [[DefineOwnProperty]] + |
+
+ + SpecOp + (propertyName, PropertyDescriptor, Boolean) + → Boolean + |
+
+ + Creates + or alters the named own property to have the state described by + a Property Descriptor. The flag controls failure handling. + |
+
+ Every + object (including host objects) must implement all of the internal + properties listed in Table 8. However, the [[DefaultValue]] internal + method may, for some objects, simply throw a TypeError + exception.
++ All + objects have an internal property called [[Prototype]]. The value of + this property is either null or an object and is used for + implementing inheritance. Whether or not a native object can have a + host object as its [[Prototype]] depends on the implementation. + Every [[Prototype]] chain must have finite length (that is, starting + from any object, recursively accessing the [[Prototype]] internal + property must eventually lead to a null value). Named data + properties of the [[Prototype]] object are inherited (are visible as + properties of the child object) for the purposes of get access, but + not for put access. Named accessor properties are inherited for both + get access and put access.
++ Every + ECMAScript object has a Boolean-valued [[Extensible]] internal + property that controls whether or not named properties may be added + to the object. If the value of the [[Extensible]] internal property + is false then additional named properties may not be added to + the object. In addition, if [[Extensible]] is false the + value of the [[Class]] and [[Prototype]] internal properties of the + object may not be modified. Once the value of an [[Extensible]] + internal property has been set to false it may not be + subsequently changed to true.
+NOTE This + specification defines no ECMAScript language operators or built-in + functions that permit a program to modify an object’s [[Class]] or + [[Prototype]] internal properties or to change the value of + [[Extensible]] from false to true. Implementation + specific extensions that modify [[Class]], [[Prototype]] or + [[Extensible]] must not violate the invariants defined in the + preceding paragraph.
+
+ The
+ value of the [[Class]] internal property is defined by this
+ specification for every kind of built-in object. The value of the
+ [[Class]] internal property of a host object may be any String value
+ except one of "Arguments",
+ "Array",
+ "Boolean",
+ "Date",
+ "Error",
+ "Function",
+ "JSON",
+ "Math",
+ "Number",
+ "Object",
+ "RegExp",
+ and "String".
+ The value of a [[Class]] internal property is used internally to
+ distinguish different kinds of objects. Note that this specification
+ does not provide any means for a program to access that value except
+ through Object.prototype.toString
+ (see 15.2.4.2).
+ Unless + otherwise specified, the common internal methods of native + ECMAScript objects behave as described in 8.12. Array objects have a + slightly different implementation of the [[DefineOwnProperty]] + internal method (see 15.4.5.1) and String objects have a slightly + different implementation of the [[GetOwnProperty]] internal method + (see 15.5.5.2). Arguments objects (10.6) have different + implementations of [[Get]], [[GetOwnProperty]], + [[DefineOwnProperty]], and [[Delete]]. Function objects (15.3) have + a different implementation of [[Get]].
++ Host + objects may implement these internal methods in any manner unless + specified otherwise; for example, one possibility is that [[Get]] + and [[Put]] for a particular host object indeed fetch and store + property values but [[HasProperty]] always generates false. + However, if any specified manipulation of a host object's internal + properties is not supported by an implementation, that manipulation + must throw a TypeError exception when attempted.
++ The + [[GetOwnProperty]] internal method of a host object must conform to + the following invariants for each property of the host object:
++ If a + property is described as a data property and it may return + different values over time, then either or both of the [[Writable]] + and [[Configurable] attributes must be true even if no + mechanism to change the value is exposed via the other internal + methods.
++ If a + property is described as a data property and its [[Writable]] and + [[Configurable]] are both false, then the SameValue + (according to 9.12) must be returned for the [[Value]] attribute of + the property on all calls to [[GetOwnProperty]].
++ If + the attributes other than [[Writable]] may change over time or if + the property might disappear, then the [[Configurable]] attribute + must be true.
++ If + the [[Writable]] attribute may change from false to true, + then the [[Configurable]] attribute must be true.
++ If + the value of the host object’s [[Extensible]] internal property + is has been observed by ECMAScript code to be false, then if + a call to [[GetOwnProperty]] describes a property as non-existent + all subsequent calls must also describe that property as + non-existent.
++ The + [[DefineOwnProperty]] internal method of a host object must not + permit the addition of a new property to a host object if the + [[Extensible]] internal property of that host object has been + observed by ECMAScript code to be false. +
++ If + the [[Extensible]] internal property of that host object has been + observed by ECMAScript code to be false then it must not + subsequently become true.
+|
+ + Internal + Property + |
+
+ + Value + Type Domain + |
+
+ + Description + |
+
|
+ + [[PrimitiveValue]] + |
+
+ + primitive + |
+
+ + Internal + state information associated with this object. Of the standard + built-in ECMAScript objects, only Boolean, Date, Number, and + String objects implement [[PrimitiveValue]]. + |
+
|
+ + [[Construct]] + |
+ + + | +
+
+ Creates
+ an object. Invoked via the |
+
|
+ + [[Call]] + |
+ + + | +
+ + Executes + code associated with the object. Invoked via a function call + expression. The arguments to the SpecOp are a this object and a + list containing the arguments passed to the function call + expression. Objects that implement this internal method are + callable. Only callable objects that are host objects may + return Reference values. + |
+
|
+ + [[HasInstance]] + |
+
+ + SpecOp(any) + → + Boolean + |
+
+ + Returns + a Boolean value indicating whether the argument is likely an + Object that was constructed by this object. Of the standard + built-in ECMAScript objects, only Function objects implement + [[HasInstance]]. + |
+
|
+ + [[Scope]] + |
+ + + | +
+ + A + lexical environment that defines the environment in which a + Function object is executed. Of the standard built-in ECMAScript + objects, only Function objects implement [[Scope]]. + |
+
|
+ + [[FormalParameters]] + |
+
+ + List + of Strings + |
+
+ + A + possibly empty List containing the identifier Strings of a + Function’s FormalParameterList. + Of the standard built-in ECMAScript objects, only Function + objects implement [[FormalParameterList]]. + |
+
|
+ + [[Code]] + |
+
+ + ECMAScript + code + |
+
+ + The + ECMAScript code of a function. Of the standard built-in + ECMAScript objects, only Function objects implement [[Code]]. + |
+
|
+ + [[TargetFunction]] + |
+
+ + Object + |
+
+ + The + target function of a function object created using the standard + built-in Function.prototype.bind method. Only ECMAScript objects + created using Function.prototype.bind have a [[TargetFunction]] + internal property. + |
+
|
+ + [[BoundThis]] + |
+
+ + any + |
+
+ + The + pre-bound this value of a function Object created using the + standard built-in Function.prototype.bind method. Only + ECMAScript objects created using Function.prototype.bind have a + [[BoundThis]] internal property. + |
+
|
+ + [[BoundArguments]] + |
+
+ + List + of any + |
+
+ + The + pre-bound argument values of a function Object created using the + standard built-in Function.prototype.bind method. Only + ECMAScript objects created using Function.prototype.bind have a + [[BoundArguments]] internal property. + |
+
|
+ + [[Match]] + |
+
+ + SpecOp(String, + index) → + MatchResult + |
+
+ + Tests + for a regular expression match and returns a MatchResult value + (see 15.10.2.1). Of the standard built-in ECMAScript objects, + only RegExp objects implement [[Match]]. + |
+
|
+ + [[ParameterMap]] + |
+
+ + Object + |
+
+ + Provides + a mapping between the properties of an arguments object (see + 10.6) and the formal parameters of the associated function. Only + ECMAScript objects that are arguments objects have a + [[ParameterMap]] internal property. + |
+
+ The
+ Reference type is used to explain the behaviour of such operators as
+ delete, typeof,
+ and the assignment operators. For example, the left-hand operand of
+ an assignment is expected to produce a reference. The behaviour of
+ assignment could, instead, be explained entirely in terms of a case
+ analysis on the syntactic form of the left-hand operand of an
+ assignment operator, but for one difficulty: function calls are
+ permitted to return references. This possibility is admitted purely
+ for the sake of host objects. No built-in ECMAScript function
+ defined by this specification returns a reference and there is no
+ provision for a user-defined function to return a reference.
+ (Another reason not to use a syntactic case analysis is that it
+ would be lengthy and awkward, affecting many parts of the
+ specification.)
+ A + Reference is a resolved name binding. A Reference consists of + three components, the base value, the referenced + name and the Boolean valued strict + reference flag. The base value is either undefined, + an Object, a Boolean, a String, a Number, or an environment record + (10.2.1). A base value of undefined indicates that the + reference could not be resolved to a binding. The referenced name is + a String.
++ The + following abstract operations are used in this specification to + access the components of references:
+GetBase(V). + Returns the base value component of the reference V.
+GetReferencedName(V). + Returns the referenced name component of the reference V.
+IsStrictReference(V). + Returns the strict reference component of the reference V.
+HasPrimitiveBase(V). + Returns true if the base value is a Boolean, String, or + Number.
+IsPropertyReference(V). + Returns true if either the base value is an object or + HasPrimitiveBase(V) is true; otherwise returns false.
+IsUnresolvableReference(V). + Returns true if the base value is undefined and false + otherwise.
++ The + following abstract operations are used in this specification to + operate on references:
++ Let + base be the result of calling GetBase(V).
++ If + IsUnresolvableReference(V), throw a ReferenceError + exception.
++ If + IsPropertyReference(V), then
++ If + HasPrimitiveBase(V) is false, then let get be + the [[Get]] internal method of base, otherwise let get + be the special [[Get]] internal method defined below.
++ Return + the result of calling the get internal method using base as its this value, and passing GetReferencedName(V) + for the argument.
++ Else, + base must be an environment record.
++ Return + the result of calling the GetBindingValue (see 10.2.1) concrete + method of base passing GetReferencedName(V) and + IsStrictReference(V) as arguments.
++ The + following [[Get]] internal method is used by GetValue when V + is a property reference with a primitive base value. It is called + using base as its + this value and with property P + as its argument. The following steps are taken:
++ Let + O be ToObject(base).
++ Let + desc be the result of calling the [[GetProperty]] internal + method of O with property name P.
++ If + desc is undefined, return undefined.
++ If + IsDataDescriptor(desc) is true, return + desc.[[Value]].
++ Otherwise, + IsAccessorDescriptor(desc) must be true so, let + getter be desc.[[Get]].
++ If + getter is undefined, return undefined.
++ Return + the result calling the [[Call]] internal method of getter providing base as the this value and providing no + arguments.
+NOTE The + object that may be created in step 1 is not accessible outside of + the above method. An implementation might choose to avoid the actual + creation of the object. The only situation where such an actual + property access that uses this internal method can have visible + effect is when it invokes an accessor function.
++ If + Type(V) is not Reference, + throw a ReferenceError + exception.
++ Let + base be the result of calling GetBase(V).
++ If + IsUnresolvableReference(V), then
++ If + IsStrictReference(V) is true, then
++ Throw + ReferenceError exception.
++ Call + the [[Put]] internal method of the global object, passing + GetReferencedName(V) for the property name, W for + the value, and false for the Throw flag.
++ Else + if IsPropertyReference(V), then
++ If + HasPrimitiveBase(V) is false, then let put be + the [[Put]] internal method of base, otherwise let put + be the special [[Put]] internal method defined below.
++ Call + the put internal method using base as its this + value, and passing GetReferencedName(V) for the + property name, W for the value, and IsStrictReference(V) + for the Throw flag.
++ Else + base must be a reference whose base is an environment record. So,
++ Call + the SetMutableBinding (10.2.1) concrete method of base, + passing GetReferencedName(V), W, and + IsStrictReference(V) as arguments.
++ Return.
++ The + following [[Put]] internal method is used by PutValue when V + is a property reference with a primitive base value. It is called + using base as its + this value and with property P, + value W, and + Boolean flag Throw + as arguments. The following steps are taken:
++ Let + O be ToObject(base).
++ If + the result of calling the [[CanPut]] internal method of O + with argument P is false, then
++ If + Throw is true, then throw a TypeError + exception.
++ Else + return.
++ Let + ownDesc be the result of calling the [[GetOwnProperty]] + internal method of O with argument P.
++ If + IsDataDescriptor(ownDesc) is true, then
++ If + Throw is true, then throw a TypeError + exception.
++ Else + Return.
++ Let + desc be the result of calling the [[GetProperty]] internal + method of O with argument P. This may be either an + own or inherited accessor property descriptor + or an inherited data property descriptor.
++ If + IsAccessorDescriptor(desc) is true, then
++ Let + setter be desc.[[Set]] which cannot be undefined.
++ Call + the [[Call]] internal method of setter providing base + as the this value and an argument list containing only W.
++ Else, + this is a request to create an own property on the transient object + O
++ If + Throw is true, then throw a TypeError + exception.
++ Return.
+NOTE The + object that may be created in step 1 is not accessible outside of + the above method. An implementation might choose to avoid the + actual creation of that transient object. The only situations where + such an actual property assignment that uses this internal method + can have visible effect are when it either invokes an accessor + function or is in violation of a Throw + predicated error check. When Throw + is true any property assignment that would create a new + property on the transient object throws an error.
+
+ The
+ List type is used to explain the evaluation of argument lists (see
+ 11.2.4) in new
+ expressions, in function calls, and in other algorithms where a
+ simple list of values is needed. Values of the List type are simply
+ ordered sequences of values. These sequences may be of any length.
+ The
+ Completion type is used to explain the behaviour of statements
+ (break, continue,
+ return and throw)
+ that perform nonlocal transfers of control. Values of the Completion
+ type are triples of the form (type, value, target),
+ where type is one of normal, break, continue,
+ return, or throw, value is any ECMAScript
+ language value or empty, and target is any ECMAScript
+ identifier or empty.
+ The + term “abrupt completion” refers to any completion with a type + other than normal.
++ The + Property Descriptor type is used to explain the manipulation and + reification of named property attributes. Values of the Property + Descriptor type are records composed of named fields where each + field’s name is an attribute name and its value is a corresponding + attribute value as specified in 8.6.1. In addition, any field may be + present or absent.
++ Property + Descriptor values may be further classified as data property + descriptors and accessor property descriptors based upon the + existence or use of certain fields. A data property descriptor is + one that includes any fields named either [[Value]] or [[Writable]]. + An accessor property descriptor is one that includes any fields + named either [[Get]] or [[Set]]. Any property descriptor may have + fields named [[Enumerable]] and [[Configurable]]. A Property + Descriptor value may not be both a data property descriptor and an + accessor property descriptor; however, it may be neither. A generic + property descriptor is a Property Descriptor value that is neither a + data property descriptor nor an accessor property descriptor. + A fully populated property descriptor is one that is either an + accessor property descriptor or a data property descriptor and that + has all of the fields that correspond to the property attributes + defined in either 8.6.1 Table 5 or Table 6.
++ For + notational convenience within this specification, an object + literal-like syntax can be used to define a property descriptor + value. For example, Property Descriptor {[[Value]]: 42, + [[Writable]]: false, [[Configurable]]: true} defines a + data property descriptor. Field name order is not significant. Any + fields that are not explicitly listed are considered to be absent.
++ In + specification text and algorithms, dot notation may be used to refer + to a specific field of a Property Descriptor. For example, if D is a + property descriptor then D.[[Value]] is shorthand for “the field + of D named [[Value]]”.
++ The + Property Identifier type is used to associate a property name with a + Property Descriptor. Values of the Property Identifier type are + pairs of the form (name, descriptor), where name is a String and + descriptor is a Property Descriptor value. +
++ The + following abstract operations are used in this specification to + operate upon Property Descriptor values:
++ When + the abstract operation IsAccessorDescriptor is called with property descriptor Desc, + the following steps are taken:
++ If + Desc + is undefined, + then return false.
++ If + both Desc.[[Get]] + and Desc.[[Set]] + are absent, then return false.
++ Return + true.
++ When + the abstract operation IsDataDescriptor is called with property descriptor Desc, + the following steps are taken:
++ If + Desc + is undefined, + then return false.
++ If + both Desc.[[Value]] + and Desc.[[Writable]] + are absent, then return false.
++ Return + true.
++ When + the abstract operation IsGenericDescriptor is called with property descriptor Desc, + the following steps are taken:
++ If + Desc + is undefined, + then return false.
++ If + IsAccessorDescriptor(Desc) + and IsDataDescriptor(Desc) + are both false, + then return true.
++ Return + false.
++ When + the abstract operation FromPropertyDescriptor is called with + property descriptor Desc, + the following steps are taken:
++ The + following algorithm assumes that Desc is a fully populated Property Descriptor, such as that + returned from [[GetOwnProperty]] (see 8.12.1).
++ If + Desc + is undefined, + then return undefined.
++ Let + obj be + the result of creating a new object as if by the expression new + Object() where + Object is the + standard built-in constructor with that name.
++ If + IsDataDescriptor(Desc) + is true, + then +
+
+ Call
+ the [[DefineOwnProperty]] internal method of obj
+ with arguments "value",
+ Property Descriptor {[[Value]]: Desc.[[Value]],
+ [[Writable]]: true,
+ [[Enumerable]]: true,
+ [[Configurable]]: true},
+ and false.
+
+
+ Call
+ the [[DefineOwnProperty]] internal method of obj
+ with arguments "writable",
+ Property Descriptor {[[Value]]: Desc.[[Writable]],
+ [[Writable]]: true,
+ [[Enumerable]]: true,
+ [[Configurable]]: true},
+ and false.
+
+
+ Else, + IsAccessorDescriptor(Desc) + must be true, + so
+
+ Call
+ the [[DefineOwnProperty]] internal method of obj
+ with arguments "get",
+ Property Descriptor {[[Value]]: Desc.[[Get]],
+ [[Writable]]: true,
+ [[Enumerable]]: true,
+ [[Configurable]]: true},
+ and false.
+ Call
+ the [[DefineOwnProperty]] internal method of obj
+ with arguments "set",
+ Property Descriptor {[[Value]]: Desc.[[Set]],
+ [[Writable]]: true,
+ [[Enumerable]]: true,
+ [[Configurable]]: true},
+ and false.
+
+
+ Call
+ the [[DefineOwnProperty]] internal method of obj
+ with arguments "enumerable",
+ Property Descriptor {[[Value]]: Desc.[[Enumerable]],
+ [[Writable]]: true,
+ [[Enumerable]]: true,
+ [[Configurable]]: true},
+ and false.
+
+
+ Call
+ the [[DefineOwnProperty]] internal method of obj
+ with arguments "configurable",
+ Property Descriptor {[[Value]]: Desc.[[Configurable]],
+ [[Writable]]: true,
+ [[Enumerable]]: true,
+ [[Configurable]]: true},
+ and false.
+
+
+ Return + obj.
++ When + the abstract operation ToPropertyDescriptor is called with object + Desc, the + following steps are taken:
++ If + Type(Obj) is not Object throw a TypeError exception.
++ Let + desc be the result of creating a new Property Descriptor + that initially has no fields.
+
+ If
+ the result of calling the [[HasProperty]] internal method of Obj
+ with argument "enumerable"
+ is true, then
+ Let
+ enum be the result of calling the [[Get]] internal method
+ of Obj with "enumerable".
+ Set + the [[Enumerable]] field of desc to ToBoolean(enum).
+
+ If
+ the result of calling the [[HasProperty]] internal method of Obj
+ with argument "configurable"
+ is true, then
+ Let
+ conf be the result of calling the [[Get]] internal method
+ of Obj with argument "configurable".
+ Set + the [[Configurable]] field of desc to ToBoolean(conf).
+
+ If
+ the result of calling the [[HasProperty]] internal method of Obj
+ with argument "value"
+ is true, then
+ Let
+ value be the result of calling the [[Get]] internal method
+ of Obj with argument “value”.
+ Set + the [[Value]] field of desc to value.
+
+ If
+ the result of calling the [[HasProperty]] internal method of Obj
+ with argument "writable"
+ is true, then
+ Let
+ writable be the result of calling the [[Get]] internal
+ method of Obj with argument "writable".
+ Set + the [[Writable]] field of desc to ToBoolean(writable).
+
+ If
+ the result of calling the [[HasProperty]] internal method of Obj
+ with argument "get"
+ is true, then
+ Let
+ getter be the result of calling the [[Get]] internal method
+ of Obj with argument "get".
+ If + IsCallable(getter) is false and getter is not + undefined, then throw a TypeError exception.
++ Set + the [[Get]] field of desc to getter.
+
+ If
+ the result of calling the [[HasProperty]] internal method of Obj
+ with argument "set"
+ is true, then
+ Let
+ setter be the result of calling the [[Get]] internal method
+ of Obj with argument "set".
+ If + IsCallable(setter) is false and setter is not + undefined, then throw a TypeError exception.
++ Set + the [[Set]] field of desc to setter.
++ If + either desc.[[Get]] or desc.[[Set]] are present, then
++ If + either desc.[[Value]] or desc.[[Writable]] are + present, then throw a TypeError exception.
++ Return + desc.
++ The + Lexical Environment and Environment Record types are used to explain + the behaviour of name resolution in nested functions and blocks. + These types and the operations upon them are defined in Clause 10.
++ In + the following algorithm descriptions, assume O + is a native ECMAScript object, P + is a String, Desc + is a Property Description record, and Throw + is a Boolean flag.
++ When + the [[GetOwnProperty]] internal method of O + is called with property name P, + the following steps are taken:
++ If + O doesn’t have an own property with name P, return + undefined.
++ Let + D be a newly created Property Descriptor with no fields.
++ Let + X be O’s own property named P.
++ If + X is a data property, then
++ Set + D.[[Value]] to the value of X’s [[Value]] + attribute.
++ Set + D.[[Writable]] to the value of X’s [[Writable]] + attribute
++ Else + X is an accessor property, so
++ Set + D.[[Get]] to the value of X’s [[Get]] attribute.
++ Set + D.[[Set]] to the value of X’s [[Set]] attribute.
++ Set + D.[[Enumerable]] to the value of X’s [[Enumerable]] + attribute.
++ Set + D.[[Configurable]] to the value of X’s + [[Configurable]] attribute.
++ Return + D.
++ However, + if O is a String + object it has a more elaborate [[GetOwnProperty]] internal method + defined in 15.5.5.2.
++ When + the [[GetProperty]] internal method of O + is called with property name P, + the following steps are taken:
++ Let + prop be the result of calling the [[GetOwnProperty]] + internal method of O with property name P.
++ If + prop is not undefined, return prop.
++ Let + proto be the value of the [[Prototype]] internal property of + O.
++ If + proto is null, return undefined.
++ Return + the result of calling the [[GetProperty]] internal method of proto + with argument P.
++ When + the [[Get]] internal method of O + is called with property name P, + the following steps are taken:
++ Let + desc be the result of calling the [[GetProperty]] internal + method of O with property name P.
++ If + desc is undefined, return undefined.
++ If + IsDataDescriptor(desc) is true, return + desc.[[Value]].
++ Otherwise, + IsAccessorDescriptor(desc) must be true so, let getter + be desc.[[Get]].
++ If + getter is undefined, return undefined.
++ Return + the result calling the [[Call]] internal method of getter providing O as the this value and providing no + arguments.
++ When + the [[CanPut]] internal method of O is called with property name P, + the following steps are taken:
++ Let + desc be the result of calling the [[GetOwnProperty]] + internal method of O with argument P.
++ If + desc is not undefined, then
++ If + IsAccessorDescriptor(desc) is true, then
++ If + desc.[[Set]] is undefined, then return false.
++ Else + return true.
++ Else, + desc must be a DataDescriptor so return the value of + desc.[[Writable]].
++ Let + proto be the [[Prototype]] internal property of O.
++ If + proto is null, then return the value of the + [[Extensible]] internal property of O.
++ Let + inherited be the result of calling the [[GetProperty]] + internal method of proto with property name P.
++ If + inherited is undefined, return the value of the + [[Extensible]] internal property of O.
++ If + IsAccessorDescriptor(inherited) is true, then
++ If + inherited.[[Set]] is undefined, then return false.
++ Else + return true.
++ Else, + inherited must be a DataDescriptor
++ If + the [[Extensible]] internal property of O is false, + return false.
++ Else + return the value of inherited.[[Writable]].
+Host + objects may define additional constraints upon [[Put]] operations. + If possible, host objects should not allow [[Put]] operations in + situations where this definition of [[CanPut]] returns false.
++ When + the [[Put]] internal method of O + is called with property P, + value V, and + Boolean flag Throw, + the following steps are taken:
++ If + the result of calling the [[CanPut]] internal method of O with + argument P is false, then
++ If + Throw is true, then throw a TypeError exception.
++ Else + return.
++ Let + ownDesc be the result of calling the [[GetOwnProperty]] + internal method of O with argument P.
++ If + IsDataDescriptor(ownDesc) is true, then
++ Let + valueDesc be the Property Descriptor {[[Value]]: V}.
++ Call + the [[DefineOwnProperty]] internal method of O passing P, + valueDesc, and Throw as arguments.
++ Return.
++ Let + desc be the result of calling the [[GetProperty]] internal + method of O with argument P. This may be either an + own or inherited accessor property descriptor + or an inherited data property descriptor.
++ If + IsAccessorDescriptor(desc) is true, then
++ Let + setter be desc.[[Set]] which cannot be undefined.
++ Call + the [[Call]] internal method of setter providing O as + the this value and providing V as the sole argument.
++ Else, + create a named data property named P on object O as + follows
+
+ Let
+ newDesc be the Property Descriptor
{[[Value]]: V,
+ [[Writable]]: true, [[Enumerable]]: true,
+ [[Configurable]]: true}.
+ Call + the [[DefineOwnProperty]] internal method of O passing P, + newDesc, and Throw as arguments.
++ Return.
++ When + the [[HasProperty]] internal method of O + is called with property name P, + the following steps are taken:
++ Let + desc be the result of calling the [[GetProperty]] internal + method of O with property name P.
++ If + desc is undefined, then return false.
++ Else + return true.
++ When + the [[Delete]] internal method of O + is called with property name P and the Boolean flag Throw, + the following steps are taken:
++ Let + desc be the result of calling the [[GetOwnProperty]] + internal method of O with property name P.
++ If + desc is undefined, then return true.
++ If + desc.[[Configurable]] is true, then
++ Remove + the own property with name P from O.
++ Return + true.
++ Else + if Throw, then throw a TypeError exception.
++ Return + false.
++ When + the [[DefaultValue]] internal method of O + is called with hint String, the following steps are taken:
+
+ Let
+ toString be the result of calling the [[Get]] internal
+ method of object O with argument "toString".
+ If + IsCallable(toString) is true then,
++ Let + str be the result of calling the [[Call]] internal method + of toString, with O as the this value and an + empty argument list.
++ If + str is a primitive value, return str.
+
+ Let
+ valueOf be the result of calling the [[Get]] internal method
+ of object O with argument "valueOf".
+ If + IsCallable(valueOf) is true then, +
++ Let + val be the result of calling the [[Call]] internal method + of valueOf, with O as the this value and an empty + argument list.
++ If + val is a primitive value, return val.
++ Throw + a TypeError exception.
++ When + the [[DefaultValue]] internal method of O + is called with hint Number, the following steps are taken:
+
+ Let
+ valueOf be the result of calling the [[Get]] internal method
+ of object O with argument "valueOf".
+ If + IsCallable(valueOf) is true then,
++ Let + val be the result of calling the [[Call]] internal method + of valueOf, with O as the this value and an + empty argument list.
++ If + val is a primitive value, return val.
+
+ Let
+ toString be the result of calling the [[Get]] internal
+ method of object O with argument "toString".
+ If + IsCallable(toString) is true then,
++ Let + str be the result of calling the [[Call]] internal method + of toString, with O as the this value and an empty + argument list.
++ If + str is a primitive value, return str.
++ Throw + a TypeError exception.
++ When + the [[DefaultValue]] internal method of O + is called with no hint, then it behaves as if the hint were Number, + unless O is a Date + object (see 15.9.6), in which case it behaves as if the hint were + String.
++ The + above specification of [[DefaultValue]] for native objects can + return only primitive values. If a host object implements its own + [[DefaultValue]] internal method, it must ensure that its + [[DefaultValue]] internal method can return only primitive values.
++ In + the following algorithm, the term “Reject” means “If Throw + is true, then throw a TypeError exception, otherwise + return false”. The algorithm contains steps that test + various fields of the Property Descriptor Desc + for specific values. The fields that are tested in this manner need + not actually exist in Desc. + If a field is absent then its value is considered to be false.
++ When + the [[DefineOwnProperty]] internal method of O + is called with property name P, + property descriptor Desc, + and Boolean flag Throw, + the following steps are taken:
++ Let + current be the result of calling the [[GetOwnProperty]] + internal method of O with property name P.
++ Let + extensible be the value of the [[Extensible]] internal + property of O.
++ If + current is undefined and extensible is false, + then Reject.
++ If + current is undefined and extensible is true, + then
++ If + IsGenericDescriptor(Desc) or IsDataDescriptor(Desc) + is true, then
++ Create + an own data property named P of object O whose + [[Value]], [[Writable]], [[Enumerable]] and [[Configurable]] + attribute values are described by Desc. If the value of an + attribute field of Desc is absent, the attribute of the + newly created property is set to its default value.
++ Else, + Desc must be an + accessor Property Descriptor so,
++ Create + an own accessor property named P of object O whose + [[Get]], [[Set]], [[Enumerable]] and [[Configurable]] attribute + values are described by Desc. If the value of an attribute + field of Desc is absent, the attribute of the newly + created property is set to its default value.
++ Return + true.
++ Return + true, if every field in Desc is absent.
++ Return + true, if every field in Desc also occurs in current + and the value of every field in Desc is the same value as + the corresponding field in current when compared using the + SameValue algorithm (9.12).
++ If + the [[Configurable]] field of current is false then
++ If + IsGenericDescriptor(Desc) is true, then no further + validation is required.
++ Else, + if IsDataDescriptor(current) and IsDataDescriptor(Desc) + have different results, then
++ Reject, + if the [[Configurable]] field of current is false. +
++ If + IsDataDescriptor(current) is true, then
++ Convert + the property named P of object O from a data + property to an accessor property. Preserve the existing values of + the converted property’s [[Configurable]] and [[Enumerable]] + attributes and set the rest of the property’s attributes to + their default values.
++ Else,
++ Convert + the property named P of object O from an accessor + property to a data property. Preserve the existing values of the + converted property’s [[Configurable]] and [[Enumerable]] + attributes and set the rest of the property’s attributes to + their default values.
++ Else, + if IsDataDescriptor(current) and IsDataDescriptor(Desc) + are both true, then
++ If + the [[Configurable]] field of current is false, then
++ else, + the [[Configurable]] field of current is true, so + any change is acceptable.
++ Else, + IsAccessorDescriptor(current) and IsAccessorDescriptor(Desc) + are both true so,
++ For + each attribute field of Desc that is present, set the + correspondingly named attribute of the property named P of + object O to the value of the field.
++ Return + true.
++ However, + if O is an Array + object, it has a more elaborate [[DefineOwnProperty]] internal + method defined in 15.4.5.1.
+NOTE Step + 10.b allows any field of Desc to be different from the corresponding + field of current if current’s [[Configurable]] field is true. + This even permits changing the [[Value]] of a property whose + [[Writable]] attribute is false. This is allowed because a + true [[Configurable]] attribute would permit an equivalent + sequence of calls where [[Writable]] is first set to true, a + new [[Value]] is set, and then [[Writable]] is set to false.
+ \ No newline at end of file diff --git a/x9.html b/x9.html new file mode 100644 index 0000000..0808deb --- /dev/null +++ b/x9.html @@ -0,0 +1,1334 @@ + +‟Ex igne vita”
+ ++ The + ECMAScript runtime system performs automatic type conversion as + needed. To clarify the semantics of certain constructs it is useful + to define a set of conversion abstract operations. These abstract + operations are not a part of the language; they are defined here to + aid the specification of the semantics of the language. The + conversion abstract operations are polymorphic; that is, they can + accept a value of any ECMAScript language type, but not of + specification types.
++ The + abstract operation ToPrimitive takes an input + argument and an optional argument PreferredType. + The abstract operation ToPrimitive converts its input + argument to a non-Object type. If an object is capable of converting + to more than one primitive type, it may use the optional hint + PreferredType to + favour that type. Conversion occurs according to Table 10:
+|
+ + Input + Type + |
+
+ + Result + |
+
|
+ + Undefined + |
+
+ + The + result equals the input + argument (no conversion). + |
+
|
+ + Null + |
+
+ + The + result equals the input + argument (no conversion). + |
+
|
+ + Boolean + |
+
+ + The + result equals the input + argument (no conversion). + |
+
|
+ + Number + |
+
+ + The + result equals the input + argument (no conversion). + |
+
|
+ + String + |
+
+ + The + result equals the input + argument (no conversion). + |
+
|
+ + Object + |
+
+ + Return + a default value for the Object. The default value of an object + is retrieved by calling the [[DefaultValue]] internal method of + the object, passing the optional hint PreferredType. + The behaviour of the [[DefaultValue]] internal method is defined + by this specification for all native ECMAScript objects in + 8.12.8. + |
+
+ The + abstract operation ToBoolean converts its argument to a value of + type Boolean according to Table 11:
+|
+ + Argument + Type + |
+
+ + Result + |
+
|
+ + Undefined + |
+
+ + false + |
+
|
+ + Null + |
+
+ + false + |
+
|
+ + Boolean + |
+
+ + The + result equals the input argument (no conversion). + |
+
|
+ + Number + |
+
+ + The + result is false if the argument is +0, −0, + or NaN; otherwise the result is true. + + |
+
|
+ + String + |
+
+ + The + result is false if the argument is the empty String (its + length is zero); otherwise the result is true. + |
+
|
+ Object + |
+
+ true + |
+
+ The + abstract operation ToNumber converts its argument to a value of type + Number according to Table 12:
+|
+ + Argument + Type + |
+
+ + Result + |
+
|
+ + Undefined + |
+
+ + NaN + |
+
|
+ + Null + |
+
+ + +0 + |
+
|
+ + Boolean + |
+
+ + The + result is 1 if the argument is true. The result is + +0 if the argument is false. + |
+
|
+ + Number + |
+
+ + The + result equals the input argument (no conversion). + |
+
|
+ + String + |
+
+ + See + grammar and note below. + |
+
|
+ + Object + |
+
+ + Apply + the following steps: +
|
+
+ ToNumber + applied to Strings applies the following grammar to the input + String. If the grammar cannot interpret the String as an expansion + of StringNumericLiteral, + then the result of ToNumber is NaN.
++ StringNumericLiteral :::
+
+ StrWhiteSpaceopt
StrWhiteSpaceoptStrNumericLiteral StrWhiteSpaceopt
+ StrWhiteSpace :::
++ StrWhiteSpaceChar + StrWhiteSpaceopt
++ StrWhiteSpaceChar :::
+
+ WhiteSpace
LineTerminator
+ StrNumericLiteral :::
+
+ StrDecimalLiteral
HexIntegerLiteral
+ StrDecimalLiteral :::
+
+ StrUnsignedDecimalLiteral+
+ StrUnsignedDecimalLiteral-
+ StrUnsignedDecimalLiteral
+ StrUnsignedDecimalLiteral :::
+
+ Infinity
+ DecimalDigits . DecimalDigitsoptExponentPartopt. DecimalDigits ExponentPartopt
DecimalDigits
+ ExponentPartopt
+ DecimalDigits :::
+
+ DecimalDigit
DecimalDigits
+ DecimalDigit
+ DecimalDigit ::: + one + of
+
+ 0
+ 1 2 3 4 5 6 7 8 9
+ ExponentPart :::
++ ExponentIndicator + SignedInteger
++ ExponentIndicator ::: + one + of
+
+ e
+ E
+ SignedInteger :::
+
+ DecimalDigits+
+ DecimalDigits-
+ DecimalDigits
+ HexIntegerLiteral :::
+
+ 0x HexDigit0X HexDigit
HexIntegerLiteral HexDigit
+ HexDigit ::: one + of
+
+ 0
+ 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F
+ Some + differences should be noted between the syntax of a + StringNumericLiteral + and a NumericLiteral + (see 7.8.3):
++ A + StringNumericLiteral + may be preceded and/or followed by white space and/or line + terminators.
+
+ A
+ StringNumericLiteral
+ that is decimal may have any number of leading 0
+ digits.
+ A
+ StringNumericLiteral
+ that is decimal may be preceded by +
+ or - to indicate
+ its sign.
+ A + StringNumericLiteral + that is empty or contains only white space is converted to +0.
++ The + conversion of a String to a Number value is similar overall to the + determination of the Number value for a numeric literal (see 7.8.3), + but some of the details are different, so the process for converting + a String numeric literal to a value of Number type is given here in + full. This value is determined in two steps: first, a mathematical + value (MV) is derived from the String numeric literal; second, this + mathematical value is rounded as described below.
++ The + MV of StringNumericLiteral + ::: [empty] + is 0.
++ The + MV of StringNumericLiteral + ::: StrWhiteSpace + is 0.
++ The + MV of StringNumericLiteral + ::: StrWhiteSpaceoptStrNumericLiteral + StrWhiteSpaceopt + is the MV of StrNumericLiteral, + no matter whether white space is present or not.
++ The + MV of StrNumericLiteral + ::: StrDecimalLiteral + is the MV of StrDecimalLiteral.
++ The + MV of StrNumericLiteral + ::: HexIntegerLiteral + is the MV of HexIntegerLiteral.
++ The + MV of StrDecimalLiteral + ::: StrUnsignedDecimalLiteral + is the MV of StrUnsignedDecimalLiteral.
+
+ The
+ MV of StrDecimalLiteral
+ ::: +
+ StrUnsignedDecimalLiteral
+ is the MV of StrUnsignedDecimalLiteral.
+ The
+ MV of StrDecimalLiteral
+ ::: -
+ StrUnsignedDecimalLiteral
+ is the negative of the MV of StrUnsignedDecimalLiteral.
+ (Note that if the MV of StrUnsignedDecimalLiteral
+ is 0, the negative of this MV is also 0. The rounding rule
+ described below handles the conversion of this signless
+ mathematical zero to a floating-point +0 or −0
+ as appropriate.)
+ The
+ MV of StrUnsignedDecimalLiteral:::
+ Infinity
+ is 1010000
+ (a value so large that it will round to +∞).
+ The
+ MV of StrUnsignedDecimalLiteral:::
+ DecimalDigits.
+ is the MV of DecimalDigits.
+ The
+ MV of StrUnsignedDecimalLiteral:::
+ DecimalDigits . DecimalDigits
+ is the MV of the first DecimalDigits
+ plus (the MV of the second DecimalDigits
+ times 10−n),
+ where n is the
+ number of characters in the second DecimalDigits.
+ The
+ MV of StrUnsignedDecimalLiteral::: DecimalDigits. ExponentPart is the MV of
+ DecimalDigits times 10e, where e
+ is the MV of ExponentPart.
+ The
+ MV of StrUnsignedDecimalLiteral::: DecimalDigits. DecimalDigits ExponentPart is (the MV of the first
+ DecimalDigits plus (the MV of the second DecimalDigits
+ times 10−n))
+ times 10e, where n is the number of
+ characters in the second DecimalDigits and e is
+ the MV of ExponentPart.
+ The
+ MV of StrUnsignedDecimalLiteral:::. DecimalDigits is the MV of
+ DecimalDigits times 10−n,
+ where n is the number of characters in DecimalDigits.
+ The
+ MV of StrUnsignedDecimalLiteral:::. DecimalDigits ExponentPart is
+ the MV of DecimalDigits times 10e−n,
+ where n is the number of characters in DecimalDigits
+ and e is the MV of
+ ExponentPart.
+ The + MV of StrUnsignedDecimalLiteral::: DecimalDigits + is the MV of DecimalDigits.
++ The + MV of StrUnsignedDecimalLiteral::: DecimalDigits + ExponentPart is the MV of + DecimalDigits times 10e, where e + is the MV of ExponentPart.
++ The + MV of DecimalDigits ::: DecimalDigit is + the MV of DecimalDigit.
++ The + MV of DecimalDigits ::: DecimalDigits + DecimalDigit is (the MV of DecimalDigits times 10) + plus the MV of DecimalDigit.
++ The + MV of ExponentPart ::: ExponentIndicator + SignedInteger is + the MV of SignedInteger.
++ The + MV of SignedInteger ::: DecimalDigits + is the MV of DecimalDigits.
+
+ The
+ MV of SignedInteger ::: + DecimalDigits is
+ the MV of DecimalDigits.
+ The
+ MV of SignedInteger ::: - DecimalDigits is the negative of the MV of
+ DecimalDigits.
+ The
+ MV of DecimalDigit ::: 0
+ or of HexDigit :::
+ 0 is 0.
+ The
+ MV of DecimalDigit ::: 1
+ or of HexDigit :::
+ 1 is 1.
+ The
+ MV of DecimalDigit ::: 2
+ or of HexDigit :::
+ 2 is 2.
+ The
+ MV of DecimalDigit ::: 3
+ or of HexDigit :::
+ 3 is 3.
+ The
+ MV of DecimalDigit ::: 4
+ or of HexDigit :::
+ 4 is 4.
+ The
+ MV of DecimalDigit ::: 5
+ or of HexDigit :::
+ 5 is 5.
+ The
+ MV of DecimalDigit ::: 6
+ or of HexDigit :::
+ 6 is 6.
+ The
+ MV of DecimalDigit ::: 7
+ or of HexDigit :::
+ 7 is 7.
+ The
+ MV of DecimalDigit ::: 8
+ or of HexDigit :::
+ 8 is 8.
+ The
+ MV of DecimalDigit ::: 9
+ or of HexDigit :::
+ 9 is 9.
+ The
+ MV of HexDigit ::: a
+ or of HexDigit :::
+ A is 10.
+ The
+ MV of HexDigit ::: b
+ or of HexDigit :::
+ B is 11.
+ The
+ MV of HexDigit ::: c
+ or of HexDigit :::
+ C is 12.
+ The
+ MV of HexDigit ::: d
+ or of HexDigit :::
+ D is 13.
+ The
+ MV of HexDigit ::: e
+ or of HexDigit :::
+ E is 14.
+ The
+ MV of HexDigit ::: f
+ or of HexDigit :::
+ F is 15.
+ The
+ MV of HexIntegerLiteral ::: 0x
+ HexDigit is the MV of
+ HexDigit.
+ The
+ MV of HexIntegerLiteral ::: 0X
+ HexDigit is the MV of
+ HexDigit.
+ The + MV of HexIntegerLiteral ::: HexIntegerLiteral + HexDigit is (the MV of HexIntegerLiteral times 16) + plus the MV of HexDigit.
+
+ Once
+ the exact MV for a String numeric literal has been determined, it is
+ then rounded to a value of the Number type. If the MV is 0, then the
+ rounded value is +0 unless the first non white space character in
+ the String numeric literal is ‘-’,
+ in which case the rounded value is −0.
+ Otherwise, the rounded value must be the Number value for the MV (in
+ the sense defined in 8.5), unless the literal includes a
+ StrUnsignedDecimalLiteral
+ and the literal has more than 20 significant digits, in which case
+ the Number value may be either the Number value for the MV of a
+ literal produced by replacing each significant digit after the 20th
+ with a 0 digit or the Number value for the MV of a literal produced
+ by replacing each significant digit after the 20th with a 0 digit
+ and then incrementing the literal at the 20th digit position. A
+ digit is significant if it is not part of an ExponentPart
+ and
+ it + is not 0; + or
++ there + is a nonzero digit to its left and there is a nonzero digit, not in + the ExponentPart, + to its right.
++ The + abstract operation ToInteger converts its argument to an integral + numeric value. This abstract operation functions as follows:
++ Let + number be the result of calling ToNumber on the input + argument.
++ If + number is NaN, return +0.
++ If + number is +0, −0, + +∞, or −∞, + return number.
++ Return + the result of computing sign(number) * floor(abs(number)).
++ The + abstract operation ToInt32 converts its argument to one of 232 + integer values in the range −231 + through 231−1, + inclusive. This abstract operation functions as follows:
++ Let + number be the result of calling ToNumber on the input + argument.
++ If + number is NaN, +0, −0, + +∞, or −∞, + return +0.
++ Let + int32bit be posInt modulo 232; that is, a + finite integer value k of Number type with positive sign and less + than 232 in magnitude such that the mathematical + difference of posInt and k is mathematically an integer + multiple of 232.
++ If + int32bit is greater than or equal to 231, return + int32bit − 232, + otherwise return int32bit.
++
NOTE Given the above definition of ToInt32:
++ The ToInt32 + abstract operation is idempotent: if applied to a result that it + produced, the second application leaves that value unchanged.
++ ToInt32(ToUint32(x)) + is equal to ToInt32(x) + for all values of x. + (It is to preserve this latter property that +∞ + and −∞ + are mapped to +0.)
++ ToInt32 maps −0 + to +0.
++ The + abstract operation ToUint32 converts its argument to one of 232 + integer values in the range 0 + through 232−1, + inclusive. This abstraction operation functions as follows:
++ Let + number be the result of calling ToNumber on the input + argument.
++ If + number is NaN, +0, −0, + +∞, or −∞, + return +0.
++ Let + int32bit be posInt modulo 232; that is, a + finite integer value k of Number type with positive sign and less + than 232 in magnitude such that the mathematical + difference of posInt and k is mathematically an integer + multiple of 232.
++ Return + int32bit.
++
NOTE Given the above definition of ToUInt32:
++ Step 5 is the + only difference between ToUint32 and ToInt32.
++ The ToUint32 + abstract operation is idempotent: if applied to a result that it + produced, the second application leaves that value unchanged.
++ ToUint32(ToInt32(x)) + is equal to ToUint32(x) + for all values of x. + (It is to preserve this latter property that +∞ + and −∞ are mapped to + +0.)
++ ToUint32 maps −0 + to +0.
++ The + abstract operation ToUint16 converts its argument to one of 216 + integer values in the range 0 + through 216−1, + inclusive. This abstract operation functions as follows:
++ Let + number be the result of calling ToNumber on the input + argument.
++ If + number is NaN, +0, −0, + +∞, or −∞, + return +0.
++ Let + int16bit be posInt modulo 216; that is, a + finite integer value k of Number type with positive sign and + less than 216 in magnitude such that the mathematical + difference of posInt and k is mathematically an + integer multiple of 216.
++ Return + int16bit.
++
NOTE Given the above definition of ToUint16:
++ The substitution + of 216 + for 232 + in step 4 is the only difference between ToUint32 and ToUint16.
++ ToUint16 maps −0 + to +0.
++ The + abstract operation ToString converts its argument to a value of type + String according to Table 13:
+|
+ + Argument + Type + |
+
+ + Result + |
+
|
+ + Undefined + |
+
+
|
+
|
+ + Null + |
+
+
|
+
|
+ + Boolean + |
+
+ If
+ the argument is true, then the result is If
+ the argument is false, then the result is |
+
|
+ + Number + |
+
+ See + 9.8.1. + |
+
|
+ + String + |
+
+ Return + the input argument (no conversion) + |
+
|
+ + Object + |
+
+ Apply + the following steps: ++ 1. + Let primValue + be ToPrimitive(input argument, hint String). ++ 2. + Return ToString(primValue). + |
+
+ The + abstract operation ToString converts a Number m + to String format as follows:
+
+ If
+ m is NaN, return the String "NaN".
+ If
+ m is +0 or −0,
+ return the String "0".
+ If
+ m is less than zero, return the String concatenation of the
+ String "-"
+ and ToString(−m).
+ If
+ m is infinity, return the String "Infinity".
+ Otherwise, + let n, k, and s be integers such that k + ≥ 1, 10k−1≤ s < 10k, + the Number value for s × + 10n−k + is m, and k is as small as possible. Note that k + is the number of digits in the decimal representation of s, + that s is not divisible by 10, and that the least + significant digit of s is not necessarily uniquely + determined by these criteria.
+
+ If
+ k ≤ n ≤
+ 21, return the String consisting of the k digits of the
+ decimal representation of s (in order, with no leading zeroes),
+ followed by n−k
+ occurrences of the character ‘0’.
+ If
+ 0 < n ≤ 21, return the
+ String consisting of the most significant n digits of the
+ decimal representation of s, followed by a decimal point
+ ‘.’, followed
+ by the remaining k−n
+ digits of the decimal representation of s.
+ If
+ −6 < n ≤
+ 0, return the String consisting of the character ‘0’,
+ followed by a decimal point ‘.’,
+ followed by −n
+ occurrences of the character ‘0’,
+ followed by the k digits of the decimal representation of s.
+ Otherwise,
+ if k = 1, return the String consisting of the single digit
+ of s, followed by lowercase character ‘e’,
+ followed by a plus sign ‘+’
+ or minus sign ‘−’
+ according to whether n−1
+ is positive or negative, followed by the decimal representation of
+ the integer abs(n−1)
+ (with no leading zeros).
+ Return + the String consisting of the most significant digit of the decimal + representation of s, followed by a decimal point ‘.’, followed + by the remaining k−1 digits of + the decimal representation of s, followed by the lowercase + character ‘e’, followed by a plus sign ‘+’ or minus sign + ‘−’ according to whether + n−1 is positive or negative, + followed by the decimal representation of the integer abs(n−1) + (with no leading zeros).
+NOTE 1 The following observations may be useful as guidelines for + implementations, but are not part of the normative requirements of + this Standard:
++ If x is any + Number value other than −0, + then ToNumber(ToString(x)) is exactly the same Number value as x.
++ The least + significant digit of s is not always uniquely determined by the + requirements listed in step 5.
+NOTE 2 For implementations that provide more accurate conversions than + required by the rules above, it is recommended that the following + alternative version of step 5 be used as a guideline:
++ Otherwise, + let n, + k, + and s + be integers such that k + ≥ + 1, 10k−1≤ + s + < 10k, + the Number value for s + × + 10n−k + is m, + and k + is as small as possible. If there are multiple possibilities for s, + choose the value of s + for which s + × + 10n−k + is closest in value to m. + If there are two such possible values of s, + choose the one that is even. Note that k + is the number of digits in the decimal representation of s + and that s + is not divisible by 10.
+NOTE 3 Implementers of ECMAScript may find useful the paper and code + written by David M. Gay for binary-to-decimal conversion of + floating-point numbers:
+
+ Gay, David M.
+ Correctly Rounded Binary-Decimal and Decimal-Binary Conversions.
+ Numerical Analysis, Manuscript 90-10. AT&T Bell Laboratories
+ (Murray Hill, New Jersey). November 30, 1990. Available
+ as
+
http://cm.bell-labs.com/cm/cs/doc/90/4-10.ps.gz.
+ Associated code available
+ as
+
http://cm.bell-labs.com/netlib/fp/dtoa.c.gz
+ and as
+
http://cm.bell-labs.com/netlib/fp/g_fmt.c.gz
+ and may also be found at the various netlib
+ mirror sites.
+ The + abstract operation ToObject converts its argument to a value of type + Object according to Table 14:
+|
+ + Argument + Type + |
+
+ + Result + |
+
|
+ + Undefined + |
+
+ + Throw + a TypeError exception. + |
+
|
+ + Null + |
+
+ + Throw + a TypeError exception. + |
+
|
+ + Boolean + |
+
+ + Create + a new Boolean object whose [[PrimitiveValue]] internal property + is set to the value of the argument. See 15.6 for a description + of Boolean objects. + |
+
|
+ + Number + |
+
+ + Create + a new Number object whose [[PrimitiveValue]] internal property + is set to the value of the argument. See 15.7 for a description + of Number objects. + |
+
|
+ + String + |
+
+ + Create + a new String object whose [[PrimitiveValue]] internal property + is set to the value of the argument. See 15.5 for a description + of String objects. + |
+
|
+ Object + |
+
+ The + result is the input argument (no conversion). + |
+
+ The + abstract operation CheckObjectCoercible throws an error if its + argument is a value that cannot be converted to an Object using + ToObject. It is defined by Table 15:
+|
+ + Argument + Type + |
+
+ + Result + |
+
|
+ + Undefined + |
+
+ + Throw + a TypeError exception. + |
+
|
+ + Null + |
+
+ + Throw + a TypeError exception. + |
+
|
+ + Boolean + |
+
+ + Return + |
+
|
+ + Number + |
+
+ + Return + |
+
|
+ + String + |
+
+ + Return + |
+
|
+ Object + |
+
+ Return + |
+
+ The + abstract operation IsCallable determines if its argument, which must + be an ECMAScript language value, is a callable function Object + according to Table 16:
+|
+ + Argument + Type + |
+
+ + Result + |
+
|
+ + Undefined + |
+
+ + Return + false. + |
+
|
+ + Null + |
+
+ + Return + false. + |
+
|
+ + Boolean + |
+
+ + Return + false. + |
+
|
+ + Number + |
+
+ + Return + false. + |
+
|
+ + String + |
+
+ + Return + false. + |
+
|
+ Object + |
+
+ If + the argument object has an [[Call]] internal method, then return + true, otherwise return false. + |
+
+ The + internal comparison abstract operation SameValue(x, + y), where x + and y are + ECMAScript language values, produces true or false. + Such a comparison is performed as follows:
++ If + Type(x) is Undefined, return true.
++ If + Type(x) is Null, return true.
++ If + Type(x) is Number, then.
++ If + x is NaN and y is NaN, return true.
++ If + x is +0 and y is -0, return false.
++ If + x is -0 and y is +0, return false.
++ If + x is the same Number value as y, return true.
++ Return + false.
++ If + Type(x) is String, then return true if x and y + are exactly the same sequence of characters (same length and same + characters in corresponding positions); otherwise, return false.
++ If + Type(x) is Boolean, return true if x and y + are both true or both false; otherwise, return false.
++ Return + true if x and y refer to the same object. Otherwise, + return false.
+