Just

A library of zero-dependency npm modules that do just do one thing. A guilt-free alternative to those bulkier utility libraries. Ideal for PWA development or whenever bytes are precious.

Jump To API

We welcome contributions. Please follow our contribution guidelines.

Try 🍦

A REPL for every utility (powered by RunKit)

Read 📚

• TRADEOFFS.md -- When to use Just (and when not to).
• The Zen of Dependency-Free -- Why I wrote Just.

TypeScript

Right now, a handful of Just functions are type-defined in Definitely Typed. We welcome additions. When available, you can install type definitions for a Just function like this:

# npm
npm i just-extend && npm i @types/just-extend -D

# yarn
yarn add just-extend && yarn add @types/just-extend -D

Browser Support 💻

Data based on available saucelabs test browsers. It's likely Just is also fully supported by some older versions not verifiable via saucelabs.

Chrome	Safari	Firefox	IE/Edge	Node	Mobile Safari	Android
yes	yes	yes	IE9+	6+	iOS 8+	Android OS 5+

The Modules 📦

• Collections {}[]

  • just-diff
  • just-diff-apply
  • just-compare
  • just-clone
  • just-pluck-it
  • just-flush

• Objects {}

  • just-extend
  • just-merge
  • just-values
  • just-entries
  • just-pick
  • just-omit
  • just-filter-object
  • just-map-object
  • just-map-values
  • just-map-keys
  • just-reduce-object
  • just-is-empty
  • just-is-circular
  • just-is-primitive
  • just-safe-get
  • just-safe-set
  • just-typeof
  • just-flip-object

• Arrays []

  • just-unique
  • just-flatten-it
  • just-index
  • just-insert
  • just-intersect
  • just-compact
  • just-last
  • just-tail
  • just-random
  • just-shuffle
  • just-split
  • just-split-at
  • just-partition
  • just-range
  • just-remove
  • just-union
  • just-zip-it
  • just-group-by

• Statistics Σ

  • just-mean
  • just-median
  • just-mode
  • just-percentile
  • just-variance
  • just-stdev
  • just-skewness

• Strings ""

  • just-template
  • just-truncate
  • just-prune
  • just-squash
  • just-left-pad
  • just-right-pad
  • just-camel-case
  • just-kebab-case
  • just-snake-case
  • just-pascal-case
  • just-capitalize
  • just-replace-all

• Numbers +-

  • just-clamp
  • just-modulo

• Functions =>

  • just-compose
  • just-curry-it
  • just-demethodize
  • just-flip
  • just-partial-it
  • just-debounce-it
  • just-throttle
  • just-once

  Collections

  just-diff

  🍦Try It

  npm install just-diff

  Return an object representing the difference between two other objects Pass converter to format as http://jsonpatch.com

  import {diff} from 'just-diff';
  
  const obj1 = {a: 4, b: 5};
  const obj2 = {a: 3, b: 5};
  const obj3 = {a: 4, c: 5};
  
  diff(obj1, obj2);
  [
    { "op": "replace", "path": ['a'], "value": 3 }
  ]
  
  diff(obj2, obj3);
  [
    { "op": "remove", "path": ['b'] },
    { "op": "replace", "path": ['a'], "value": 4 }
    { "op": "add", "path": ['c'], "value": 5 }
  ]
  
  // arrays
  const obj4 = {a: 4, b: [1, 2, 3]};
  const obj5 = {a: 3, b: [1, 2, 4]};
  const obj6 = {a: 3, b: [1, 2, 4, 5]};
  
  diff(obj4, obj5);
  [
    { "op": "replace", "path": ['a'], "value": 3 }
    { "op": "replace", "path": ['b', 2], "value": 4 }
  ]
  
  diff(obj5, obj6);
  [
    { "op": "add", "path": ['b', 3], "value": 5 }
  ]
  
  // nested paths
  const obj7 = {a: 4, b: {c: 3}};
  const obj8 = {a: 4, b: {c: 4}};
  const obj9 = {a: 5, b: {d: 4}};
  
  diff(obj7, obj8);
  [
    { "op": "replace", "path": ['b', 'c'], "value": 4 }
  ]
  
  diff(obj8, obj9);
  [
    { "op": "replace", "path": ['a'], "value": 5 }
    { "op": "remove", "path": ['b', 'c']}
    { "op": "add", "path": ['b', 'd'], "value": 4 }
  ]
  
  // using converter to generate jsPatch standard paths
  import {diff, jsonPatchPathConverter} from 'just-diff'
  
  diff(obj1, obj2, jsonPatchPathConverter);
  [
    { "op": "replace", "path": '/a', "value": 3 }
  ]
  
  diff(obj2, obj3, jsonPatchPathConverter);
  [
    { "op": "remove", "path": '/b' },
    { "op": "replace", "path": '/a', "value": 4 }
    { "op": "add", "path": '/c', "value": 5 }
  ]

just-diff-apply

🍦Try It

npm install just-diff-apply

Apply a diff object to an object. Pass converter to apply a http://jsonpatch.com standard patch

  import diffApply from 'just-diff-apply';

  const obj1 = {a: 3, b: 5};
  diffApply(obj1,
    [
      { "op": "remove", "path": ['b'] },
      { "op": "replace", "path": ['a'], "value": 4 },
      { "op": "add", "path": ['c'], "value": 5 }
    ]
  );
  obj1; // {a: 4, c: 5}

  // arrays (array key can be string or numeric)
  const obj3 = {a: 4, b: [1, 2, 3]};
  diffApply(obj3, [
    { "op": "replace", "path": ['a'], "value": 3 }
    { "op": "replace", "path": ['b', 2], "value": 4 }
    { "op": "add", "path": ['b', 3], "value": 9 }
  ]);
  obj3; // {a: 3, b: [1, 2, 4, 9]}

  // nested paths
  const obj4 = {a: 4, b: {c: 3}};
  diffApply(obj4, [
    { "op": "replace", "path": ['a'], "value": 5 }
    { "op": "remove", "path": ['b', 'c']}
    { "op": "add", "path": ['b', 'd'], "value": 4 }
  ]);
  obj4; // {a: 5, b: {d: 4}}

  // using converter to apply jsPatch standard paths
  // see http://jsonpatch.com
  import {diffApply, jsonPatchPathConverter} from 'just-diff-apply'

  const obj2 = {a: 3, b: 5};
  diffApply(obj2, [
    { "op": "remove", "path": '/b' },
    { "op": "replace", "path": '/a', "value": 4 }
    { "op": "add", "path": '/c', "value": 5 }
  ], jsonPatchPathConverter);
  obj2; // {a: 4, c: 5}

just-compare

🍦Try It

npm install just-compare

import compare from "just-compare";

// primitives: value1 === value2
// functions: value1.toString == value2.toString
// arrays: if length, sequence and values of properties are identical
// objects: if length, names and values of properties are identical
compare([1, [2, 3]], [1, [2, 3]]); // true
compare([1, [2, 3], 4], [1, [2, 3]]); // false
compare({ a: 2, b: 3 }, { a: 2, b: 3 }); // true
compare({ a: 2, b: 3 }, { b: 3, a: 2 }); // true
compare({ a: 2, b: 3, c: 4 }, { a: 2, b: 3 }); // false
compare({ a: 2, b: 3 }, { a: 2, b: 3, c: 4 }); // false
compare([1, [2, { a: 4 }], 4], [1, [2, { a: 4 }]]); // false
compare([1, [2, { a: 4 }], 4], [1, [2, { a: 4 }], 4]); // true
compare(NaN, NaN); // true

just-clone

🍦Try It

npm install just-clone

import clone from "just-clone";

// Deep copies objects and arrays, doesn't clone functions

var arr = [1, 2, 3];
var subObj = { aa: 1 };
var obj = { a: 3, b: 5, c: arr, d: subObj };
var objClone = clone(obj);
arr.push(4);
objClone.d.bb = 2;
obj; // {a: 3, b: 5, c: [1, 2, 3, 4], d: {aa: 1}}
objClone; // {a: 3, b: 5, c: [1, 2, 3], d: {aa: 1, bb: 2}}

just-pluck-it

🍦Try It

npm install just-pluck-it

import pluck from "just-pluck-it";

pluck(
  [
    { a: 1, b: 2 },
    { a: 4, b: 3 },
    { a: 2, b: 5 }
  ],
  "a"
); // [1, 4, 2]
pluck({ x: { a: 1, b: 2 }, y: { a: 4, b: 3 }, z: { a: 2, b: 5 } }, "a"); // {x: 1, y: 4, z: 2}

just-flush

🍦Try It

npm install just-flush

import flush from "just-flush";

flush([1, undefined, 2, null, 3, NaN, 0]); // [1, 2, 3, NaN, 0]
flush([true, null, false, true, [null], undefined]); // [true, false, true, [null]]
flush({ a: 2, b: null, c: 4, d: undefined }); // {a: 2, c: 4}
flush("something"); // undefined
flush(); // undefined

Objects

just-extend

🍦Try It

npm install just-extend

import extend from 'just-extend';

var obj = {a: 3, b: 5};
extend(obj, {a: 4, c: 8}); // {a: 4, b: 5, c: 8}
obj; // {a: 4, b: 5, c: 8}

var obj = {a: 3, b: 5};
extend({}, obj, {a: 4, c: 8}); // {a: 4, b: 5, c: 8}
obj; // {a: 3, b: 5}

var arr = [1, 2, 3];
var obj = {a: 3, b: 5};
extend(obj, {c: arr}); // {a: 3, b: 5, c: [1, 2, 3]}
arr.push(4);
obj; // {a: 3, b: 5, c: [1, 2, 3, 4]}

var arr = [1, 2, 3];
var obj = {a: 3, b: 5};
extend(true, obj, {c: arr}); // {a: 3, b: 5, c: [1, 2, 3]}
arr.push(4);
obj; // {a: 3, b: 5, c: [1, 2, 3]}

extend({a: 4, b: 5}); // {a: 4, b: 5}
extend({a: 4, b: 5}, 3); {a: 4, b: 5}
extend({a: 4, b: 5}, true); {a: 4, b: 5}
extend('hello', {a: 4, b: 5}); // throws
extend(3, {a: 4, b: 5}); // throws

just-merge

🍦Try It

npm install just-merge

import merge from "just-merge";

let obj = { a: 3, b: 5 };
merge(obj, { a: 4, c: 8 }); // {a: 4, b: 5, c: 8}
obj; // {a: 4, b: 5, c: 8}

let obj = { a: 3, b: 5 };
merge({}, obj, { a: 4, c: 8 }); // {a: 4, b: 5, c: 8}
obj; // {a: 3, b: 5}

let arr = [1, 2, 3];
let obj = { a: 3, b: 5 };
merge(obj, { c: arr }); // {a: 3, b: 5, c: [1, 2, 3]}
arr.push[4];
obj; // {a: 3, b: 5, c: [1, 2, 3, 4]}

merge({ a: 4, b: 5 }); // {a: 4, b: 5}
merge(3, { a: 4, b: 5 }); // throws
merge({ a: 4, b: 5 }, 3); // throws
merge({ a: 4, b: 5 }, { b: 4, c: 5 }, "c"); // throws

just-values

🍦Try It

npm install just-values

import values from "just-values";

values({ a: 4, c: 8 }); // [4, 8]
values({ a: { aa: 2 }, b: { bb: 4 } }); // [{aa: 2}, {bb: 4}]
values({}); // []
values([1, 2, 3]); // [1, 2, 3]
values(function(a, b) {
  return a + b;
}); // []
values(String("hello")); // []
values(1); // throw exception
values(true); // throw exception
values(undefined); // throw exception
values(null); // throw exception

just-entries

🍦Try It

npm install just-entries

import entries from "just-entries";

// Object:
entries({ c: 8, a: 4 }); // [['c', 8], ['a', 4]]
entries({ b: { bb: 4 }, a: { aa: 2 } }); // [['b', {bb: 4}], ['a', {aa: 2}]]
entries({}); // []

// Array:
entries([{ c: 8 }, { a: 4 }]); // [[0, {c: 8}], [1, {a: 4}]]
entries(["À", "mauvais", "ouvrier", "point", "de", "bon", "outil"]);
// [[0, 'À'], [1, 'mauvais'] ... [6, 'outil']]
entries([]); // []

just-pick

🍦Try It

npm install just-pick

import pick from "just-pick";

var obj = { a: 3, b: 5, c: 9 };
pick(obj, ["a", "c"]); // {a: 3, c: 9}
pick(obj, "a", "c"); // {a: 3, c: 9}
pick(obj, ["a", "b", "d"]); // {a: 3, b: 5}
pick(obj, ["a", "a"]); // {a: 3}

just-omit

🍦Try It

npm install just-omit

import omit from "just-omit";

var obj = { a: 3, b: 5, c: 9 };
omit(obj, ["a", "c"]); // {b: 5}
omit(obj, "a", "c"); // {b: 5}
omit(obj, ["a", "b", "d"]); // {c: 9}
omit(obj, ["a", "a"]); // {b: 5, c: 9}

just-is-empty

🍦Try It

npm install just-is-empty

import isEmpty from 'just-is-empty';
 isEmpty({a: 3, b: 5}) // false
 isEmpty([1, 2]) // false
 isEmpty(new Set([1, 2, 2])) // false
 isEmpty((new Map()).set('a', 2)) // false
 isEmpty({}) // true
 isEmpty([]) // true
 isEmpty(new Set()) // true
 isEmpty(new Map()) // true
 isEmpty('abc') // false
 isEmpty('') // true
 isEmpty(0) // true
 isEmpty(1) // true
 isEmpty(true) // true
 isEmpty(Symbol('abc')); // true
 isEmpty(//); // true
 isEmpty(new String('abc')); // false
 isEmpty(new String('')); // true
 isEmpty(new Boolean(true)); // true
 isEmpty(null) // true
 isEmpty(undefined) // true

just-is-circular

🍦Try It

npm install just-is-circular

import isCircular from "just-is-circular";

const a = {};
a.b = a;
isCircular(a); // true

const a = {};
a.b = { c: a };
isCircular(a); // true

const a = {};
a.b = { c: 4 };
isCircular(a); // false

const a = [];
a.push(a);
isCircular(a); // true

isCircular({}); // false
isCircular("hi"); // false
isCircular(undefined); // false

just-is-primitive

🍦Try It

npm install just-is-primitive

import isPrimitive from "just-is-primitive";
isPrimitive("hi"); // true
isPrimitive(3); // true
isPrimitive(true); // true
isPrimitive(false); // true
isPrimitive(null); // true
isPrimitive(undefined); // true
isPrimitive(Symbol()); // true
isPrimitive({}); // false
isPrimitive([]); // false
isPrimitive(function() {}); // false
isPrimitive(new Date()); // false
isPrimitive(/a/); // false

just-filter-object

🍦Try It

npm install just-filter-object

import filter from "just-filter-object";

// returns a new object containing those original properties for which the predicate returns truthy
filter({ a: 3, b: 5, c: 9 }, (key, value) => value < 6); // {a: 3, b: 5}
filter({ a1: 3, b1: 5, a2: 9 }, (key, value) => key[0] == "a"); // {a1: 3, a2: 9}
filter({ a: 3, b: 5, c: null }, (key, value) => value); // {a: 3, b: 5}

just-map-object

🍦Try It

npm install just-map-object

import map from "just-map-object";

// DEPRECATED: use just-map-values
map({ a: 3, b: 5, c: 9 }, (key, value) => value + 1); // {a: 4, b: 6, c: 10}
map({ a: 3, b: 5, c: 9 }, (key, value) => key); // {a: 'a', b: 'b', c: 'c'}
map({ a: 3, b: 5, c: 9 }, (key, value) => key + value); // {a: 'a3', b: 'b5', c: 'c9'}

just-map-values

🍦Try It

npm install just-map-values

import map from "just-map-values";

// predicate updates values, receives (value, key, obj)
map({ a: 3, b: 5, c: 9 }, value => value + 1); // {a: 4, b: 6, c: 10}
map({ a: 3, b: 5, c: 9 }, (value, key) => value + key); // {a: 3a, b: 5b, c: 9c}
map({ a: 3, b: 5, c: 9 }, (value, key, obj) => obj.b); // {a: 5, b: 5, c: 5}

just-map-keys

🍦Try It

npm install just-map-keys

import map from "just-map-keys";

// predicate updates keys, receives (value, key, object)
map({ a: "cow", b: "sheep", c: "pig" }, value => value);
// {cow: 'cow', sheep: 'sheep', pig: 'pig'}
map([4, 5, 6], (value, key) => key + 1); // {1: 4, 2: 5, 3: 6}
map({ a: 3, b: 5, c: 9 }, (value, key) => key + value); // {a3: 3, b5: 5, c9: 9}
map({ a: 3, b: 5, c: 9 }, (value, key, obj) => obj.b + value + key);
// {'8a': 3, '10b': 5, '14c': 9}

just-reduce-object

🍦Try It

npm install just-reduce-object

import reduce from "just-reduce-object";

// applies a function against an accumulator and each key-value pairs of the object
// to reduce it to a single value
reduce(
  { a: 3, b: 5, c: 9 },
  (acc, key, value, index, keys) => {
    acc[value] = key;
    return acc;
  },
  {}
); // {3: 'a', 5: 'b', 9: 'c'}

reduce({ a: 3, b: 5, c: 9 }, (acc, key, value, index, keys) => {
  acc += value;
  return acc;
}); // 17

just-safe-get

🍦Try It

npm install just-safe-get

import get from "just-safe-get";

const obj = { a: { aa: { aaa: 2 } }, b: 4 };

get(obj, "a.aa.aaa"); // 2
get(obj, ["a", "aa", "aaa"]); // 2

get(obj, "b.bb.bbb"); // undefined
get(obj, ["b", "bb", "bbb"]); // undefined

get(obj.a, "aa.aaa"); // 2
get(obj.a, ["aa", "aaa"]); // 2

get(obj.b, "bb.bbb"); // undefined
get(obj.b, ["bb", "bbb"]); // undefined

get(obj.b, "bb.bbb", 5); // 5
get(obj.b, ["bb", "bbb"], true); // true

get(null, "a"); // undefined
get(undefined, ["a"]); // undefined

get(null, "a", 42); // 42
get(undefined, ["a"], 42); // 42

const obj = { a: {} };
const sym = Symbol();
obj.a[sym] = 4;
get(obj.a, sym); // 4

just-safe-set

🍦Try It

npm install just-safe-set

import set from "just-safe-set";

const obj1 = {};
set(obj1, "a.aa.aaa", 4); // true
obj1; // {a: {aa: {aaa: 4}}}

const obj2 = {};
set(obj2, [a, aa, aaa], 4); // true
obj2; // {a: {aa: {aaa: 4}}}

const obj3 = { a: { aa: { aaa: 2 } } };
set(obj3, "a.aa.aaa", 3); // true
obj3; // {a: {aa: {aaa: 3}}}

// don't clobber existing
const obj4 = { a: { aa: { aaa: 2 } } };
set(obj4, "a.aa", { bbb: 7 }); // false

const obj5 = { a: {} };
const sym = Symbol();
set(obj5.a, sym, 7); // true
obj5; // {a: {Symbol(): 7}}

just-typeof

🍦Try It

npm install just-typeof

import typeOf from "just-typeof";

typeOf({}); // 'object'
typeOf([]); // 'array'
typeOf(function() {}); // 'function'
typeOf(/a/); // 'regexp'
typeOf(new Date()); // 'date'
typeOf(null); // 'null'
typeOf(undefined); // 'undefined'
typeOf("a"); // 'string'
typeOf(1); // 'number'
typeOf(true); // 'boolean'

just-flip-object

🍦Try It

npm install just-flip-object

import flip from "just-flip-object";

// flip the key and value
flip({ a: "x", b: "y", c: "z" }); // {x: 'a', y: 'b', z: 'c'}
flip({ a: 1, b: 2, c: 3 }); // {'1': 'a', '2': 'b', '3': 'c'}
flip({ a: false, b: true }); // {false: 'a', true: 'b'}

just-has

🍦Try It

npm install just-has

import has from "just-has";

const obj = { a: { aa: { aaa: 2 } }, b: 4 };

has(obj, "a.aa.aaa"); // true
has(obj, ["a", "aa", "aaa"]); // true

has(obj, "b.bb.bbb"); // false
has(obj, ["b", "bb", "bbb"]); // false

has(obj.a, "aa.aaa"); // true
has(obj.a, ["aa", "aaa"]); // true

has(obj.b, "bb.bbb"); // false
has(obj.b, ["bb", "bbb"]); // false

has(null, "a"); // false
has(undefined, ["a"]); // false

const obj = { a: {} };
const sym = Symbol();
obj.a[sym] = 4;
has(obj.a, sym); // true

Arrays

just-unique

🍦Try It

npm install just-unique

import unique from "just-unique";

unique([1, 2, 3, 2, 3, 4, 3, 2, 1, 3]); // [1, 2, 3, 4]

var a = { a: 3 };
var b = { b: 4 };
var c = { c: 5 };
unique([a, a, b, c, b]); // [a, b, c]

unique([1, "1", 2, "2", 3, 2]); // [1, '1', 2, '2', 3]

// declaring sorted array for performance
unique([1, 1, "1", 2, 2, 5, "5", "5"], true); // [1, '1', 2, 5, '6']

// declaring strings array for performance
unique(["a", "c", "b", "c", "a"], false, true); // ['a', 'b', 'c']

just-flatten-it

🍦Try It

npm install just-flatten-it

import flatten from "just-flatten-it";

flatten([
  [1, [2, 3]],
  [[4, 5], 6, 7, [8, 9]]
]);
// [1, 2, 3, 4, 5, 6, 7, 8, 9]

just-index

🍦Try It

npm install just-index

import index from "just-index";

index(
  [
    { id: "first", val: 1 },
    { id: "second", val: 2 }
  ],
  "id"
);
// {first: {id: 'first', val: 1}, second: {id: 'second', val: 2}}
index([{ id: "first", val: 1 }, null], "id"); // {first: {id: 'first', val: 1}}
index([], "id"); // {}
index([], null); // throws
index({}, "id"); // throws

just-insert

🍦Try It

npm install just-insert

import insert from "just-insert";

insert([1, 2, 5, 6], ["a", "c", "e"], 2); // [1, 2, 'a', 'c', 'e', 5, 6]
insert([1, 2, 5, 6], "a", 2); // [1, 2, 'a', 5, 6]
insert([1, 2, 5, 6], ["a", "c", "e"], 0); // ['a', 'c', 'e', 1, 2, 5, 6]
insert([1, 2, 5, 6], ["a", "c", "e"]); // ['a', 'c', 'e', 1, 2, 5, 6]

just-intersect

🍦Try It

npm install just-intersect

import intersect from "just-intersect";

intersect([1, 2, 5, 6], [2, 3, 5, 6]); // [2, 5, 6]
intersect([1, 2, 2, 4, 5], [3, 2, 2, 5, 7]); // [2, 5]

just-compact

🍦Try It

npm install just-compact

import compact from "just-compact";

compact([1, null, 2, undefined, null, NaN, 3, 4, false, 5]); // [1, 2, 3, 4, 5]
compact([1, 2, [], 4, {}]); // [1, 2, [], 4, {}]
compact([]); // []
compact({}); // throws

just-last

🍦Try It

npm install just-last

import last from "just-last";

last([1, 2, 3, 4, 5]); // 5
last([{ a: 1 }, { b: 1 }, { c: 1 }]); // {c: 1}
last([true, false, [true, false]]); // [true, false]
last([]); // undefined
last(); // throws
last(null); // throws
last(undefined); // throws

just-tail

🍦Try It

npm install just-tail

import tail from "just-tail";

tail([1, 2, 3, 4, 5]); // [2, 3, 4, 5]
tail([{ a: 1 }, { b: 1 }, { c: 1 }]); // [{b: 1}, {c: 1}]
tail([true, false, [true, false]]); // [false, [true, false]]
tail([]); // []
tail(); // throws
tail(null); // throws
tail(undefined); // throws

just-random

🍦Try It

npm install just-random

import random from "just-random";

random([1, 2, 3]); // one of [1, 2, 3], at random

just-shuffle

🍦Try It

npm install just-shuffle

import shuffle from "just-shuffle";

shuffle([1, 2, 3]); 
// array with original elements randomly sorted
shuffle([1, 2, 3], {shuffleAll: true}); 
// array with original elements randomly sorted and all in new postions
shuffle([]); // []
shuffle([1]); // [1]
shuffle(); // undefined
shuffle(undefined); // undefined
shuffle(null); // undefined
shuffle({}); // undefined

just-split

🍦Try It

npm install just-split

import split from "just-split";

split([]); // []
split([1, 2, 3, 4, 5]); // [[1, 2, 3, 4, 5]]
split([1, 2, 3, 4, 5, 6, 7, 8, 9], 3); // [[1, 2, 3], [4, 5, 6], [7, 8, 9]];
split(["a", "b", "c", "d", "e"], 2); // [['a', 'b'], ['c', 'd'], ['e']];
split([1, 2, 3, 4, 5, 6, 7, 8], 3); // [[1, 2, 3], [4, 5, 6], [7, 8]];
split({}, 3); // throws
split(null, 3); // throws
split([1, 2, 3, 4, 5, 6], "3"); // throws

just-split-at

🍦Try It

npm install just-split-at

import splitAt from "just-split-at";

splitAt([1, 2, 3, 4, 5], 2); // [[1, 2], [3, 4, 5]]
splitAt([{ a: 1 }, { b: 1 }, { c: 1 }], -1); // [[{a: 1}, {b: 1}], [{c: 1}]]
splitAt([], 2); // [[], []]
splitAt(null, 1); // throws
splitAt(undefined, 1); // throws
splitAt([1, 2, 3, 4, 5], {}); // throws

just-partition

🍦Try It

npm install just-partition

import partition from "just-partition";

partition([1, 5, 2, 4, 3], n => n > 3); // [[5, 4],[1, 2, 3]]
partition(["a", 2, 3, "3"], x => typeof x == "string"); // [['a', '3'],[2, 3]]
partition([1, 2, 3, 4], x => typeof x == "number"); // [[1, 2, 3, 4],[]]
partition([1, 2, 3, 4], x => typeof x == "string"); // [[], [1, 2, 3, 4]]
partition([], n => n > 3); // [[], []]
partition({ a: 1, b: 2 }, n => n > 1); // throws
partition(null, n => n > 1); // throws
partition(undefined, n => n > 1); // throws

just-range

🍦Try It

npm install just-range

import range from "just-range";

range(1, 5); // [1, 2, 3, 4]
range(5); // [0, 1, 2, 3, 4]
range(-5); // [0, -1, -2, -3, -4]
range(0, 20, 5); // [0, 5, 10, 15]

just-remove

🍦Try It

npm install just-remove

import remove from "just-remove";

remove([1, 2, 3, 4, 5, 6], [1, 3, 6]); // [2, 4, 5]

just-union

🍦Try It

npm install just-union

import union from "just-union";

union([1, 2, 5, 6], [2, 3, 4, 6]); // [1, 2, 3, 4, 5, 6]

just-zip-it

🍦Try It

npm install just-zip-it

import zip from "just-zip-it";

zip([1, 2, 3]); // [[1], [2], [3]]
zip([1, 2, 3], ["a", "b", "c"]); // [[1, 'a'], [2, 'b'], [3, 'c']]
zip([1, 2], ["a", "b"], [true, false]); // [[1, 'a', true], [2, 'b', false]]
zip([1, 2, 3], ["a", "b"], [true]); // [[1, 'a', true], [2, 'b', undefined], [3, undefined, undefined]]
zip(undefined, {}, false, 1, "foo"); // throws
zip([1, 2], ["a", "b"], undefined, {}, false, 1, "foo"); // throws

just-group-by

🍦Try It

npm install just-group-by

import groupBy from "just-group-by";

groupBy([6.1, 4.2, 6.3], Math.floor); // { '4': [4.2], '6': [6.1, 6.3] }
groupBy([1,2,3,4,5,6,7,8], function(i) { return i % 2}); // { '0': [2, 4, 6, 8], '1': [1, 3, 5, 7] }
groupBy('string', Math.floor); // throws
groupBy([1,2,3,4], 'string'); // throws

Statistics

just-mean

🍦Try It

npm install just-mean

import mean from "just-mean";

mean([1, 2, 3, 2, 4, 1]); // 2.1666666667
mean(3, 2, 1); // 2
mean([4]); // 4
mean(["3", 2]); // throws
mean(); // throws

just-median

🍦Try It

npm install just-median

import median from "just-median";

median([1, 2, 3, 4, 5]); // 5
median([3, -1, 2]); // 2
median([9, 14, 14, 200, 15]); // 14
median(1, 2, 4, 3); // 2.5
median(["3", 2, 1]); // throws
median(); // throws

just-mode

🍦Try It

npm install just-mode

import mode from "just-mode";

mode([1, 2, 3, 2]); // 2
mode(4, 4, 1, 4); // 4
mode(100, 100, 101, 101); // [100, 101]
mode(4, 3, 2, 1); // [1, 2, 3, 4]
mode(["1", 2, 2, 1, 2]); // throws
mode(null); // throws

just-percentile

🍦Try It

npm install just-percentile

import percentile from "just-percentile";

percentile([1, 2, 3], 0); // 1
percentile([1, 2, 3], 50); // 2
percentile([1, 2, 3], 100); // 3

// See https://en.wikipedia.org/wiki/Percentile (linear interpolation method)
percentile([15, 20, 35, 40, 50], 5); // 15
percentile([15, 20, 35, 40, 50], 30); // 20
percentile([15, 20, 35, 40, 50], 40); // 27.5
percentile([15, 20, 35, 40, 50], 95); // 50

percentile(1, 2, 3, 50); // throws
percentile(["1", 2, 3], 50); // throws
percentile([], 50); // throws

just-variance

🍦Try It

npm install just-variance

import variance from "just-variance";

variance([1, 2, 3, 2, 4, 1]); // 1.3666666667
variance(3, 2, 1); // 1
variance([100, 100, 100.1, 100]); // 0.0025
variance(1, 2, 3, 4, 5, -6); // 15.5
variance([4]); // throws
variance(["3", 2]); // throws
variance(NaN, NaN); // throws
variance(); // throws

just-standard-deviation

🍦Try It

npm install just-standard-deviation

import standardDeviation from "just-standard-deviation";

standardDeviation([1, 2, 3, 2, 4, 1]); // 1.16904519
standardDeviation(3, 2, 1); // 1
standardDeviation([100, 100, 100.1, 100]); // 0.05
standardDeviation(1, 2, 3, 4, 5, -6); // 3.9370039
standardDeviation([4]); // throws
standardDeviation(["3", 2]); // throws
standardDeviation(NaN, NaN); // throws
standardDeviation(); // throws

just-skewness

🍦Try It

npm install just-skewness

import skewness from "just-skewness";

// Using Pearson's second skewness coefficient
skewness(3, 2, 1); // 0
skewness([1, 2, 3, 2, 4, 1]); // 0.4276994613841504
skewness(1, 2, 3, 4, 5, -6); // -0.762000762001143
skewness([1, 2, 3, 4, 9]); // 0.7705935588815224
skewness([4]); // throws
skewness(["3", 2]); // throws
skewness(NaN, NaN); // throws
skewness(); // throws

Strings

just-template

🍦Try It

npm install just-template

import template from "just-template";

const data = {
  a: {
    aa: {
      aaa: "apple",
      bbb: "pear"
    },
    bb: "orange"
  },
  b: "plum"
};
template(
  "2 {{a.aa.aaa}}s, a {{a.aa.bbb}}, 3 {{a.bb}}s and a {{b}}. Yes 1 {{a.aa.bbb}}.",
  data
);
// '2 apples, a pear, 3 oranges and a plum. Yes 1 pear.'

just-truncate

🍦Try It

npm install just-truncate

truncate("when shall we three meet again", 9); // 'when s...'
truncate("when shall we three meet again", 12, " (etc)"); // 'when s (etc)'
truncate("when shall we", 15); // 'when shall we'
truncate("when shall we", 15, "(more)"); // 'when shall we'
truncate("when shall we", 10, " (etc etc etc)"); // ' (etc etc etc)'

just-prune

🍦Try It

npm install just-prune

  prune('when shall we three meet again', 7); // 'when...'
  prune('when shall we three meet again', 7, ' (more)'; // 'when (more)'
  prune('when shall we', 15,); // 'when shall we'
  prune('when shall we', 15, ' (etc)'); // 'when shall we'
  prune('when shall we', 7, ' (more)'); // ' (more)'

just-squash

🍦Try It

npm install just-squash

squash("the cat sat on the mat"); // 'thecatsatonthemat'
squash(" the cat sat on the mat "); // 'thecatsatonthemat'
squash("\tthe cat\n sat \fon \vthe \rmat "); // '\tthecat\nsat\fon\vthe\rmat'
squash("\tthe cat\n sat \fon \vthe \rmat ", true); // 'thecatsatonthemat'
squash(
  `the cat
sat on the mat`,
  true
); // thecatsatonthemat

just-left-pad

🍦Try It

npm install just-left-pad

leftPad("hello", 9); // '    hello'
leftPad("hello", 3); // 'hello'
leftPad("hello", 9, "."); // '....hello'
leftPad("hello", 9, ".."); // '....hello'
leftPad("hello", 10, "ab"); // 'bababhello'
leftPad("hello", 9, "\uD83D\uDC04"); // '🐄🐄🐄🐄hello'
leftPad("hello", 10, "\uD83D\uDC11\uD83D\uDC04"), // '🐄🐑🐄🐑🐄hello'
  leftPad("hello", 7, "🐄"), // '🐄🐄hello'
  leftPad(null, 7); // throws
leftPad([], 4, "*"); // throws
leftPad("hello", 4, true); // throws
leftPad("hello", -4, true); // throws
leftPad("hello", 2.3, true); // throws

just-right-pad

🍦Try It

npm install just-right-pad

rightPad("hello", 9); // 'hello    '
rightPad("hello", 3); // 'hello'
rightPad("hello", 9, "."); // 'hello....'
rightPad("hello", 9, ".."); // 'hello....'
rightPad("hello", 10, "ab"); // 'helloababa'
rightPad("hello", 9, "\uD83D\uDC04"); // 'hello🐄🐄🐄🐄'
rightPad("hello", 10, "\uD83D\uDC11\uD83D\uDC04"), // 'hello🐑🐄🐑🐄🐑'
  rightPad("hello", 7, "🐄"), // 'hello🐄🐄'
  rightPad(null, 7); // throws
rightPad([], 4, "*"); // throws
rightPad("hello", 4, true); // throws
rightPad("hello", -4, true); // throws
rightPad("hello", 2.3, true); // throws

just-camel-case

🍦Try It

npm install just-camel-case

camelCase("the quick brown fox"); // 'theQuickBrownFox'
camelCase("the_quick_brown_fox"); // 'theQuickBrownFox'
camelCase("the-quick-brown-fox"); // 'theQuickBrownFox'
camelCase("theQuickBrownFox"); // 'theQuickBrownFox'
camelCase("thequickbrownfox"); // 'thequickbrownfox'
camelCase("the - quick * brown# fox"); // 'theQuickBrownFox'
camelCase("behold theQuickBrownFox"); // 'beholdTheQuickBrownFox'
camelCase("Behold theQuickBrownFox"); // 'beholdTheQuickBrownFox'
// all caps words are camel-cased
camelCase("The quick brown FOX"); // theQuickBrownFox
// all caps substrings >= 4 chars are camel-cased
camelCase("theQUickBrownFox"); // 'theQUickBrownFox'
camelCase("theQUIckBrownFox"); // 'theQUIckBrownFox'
camelCase("theQUICKBrownFox"); // 'theQuickBrownFox'

just-kebab-case

🍦Try It

npm install just-kebab-case

kebabCase("the quick brown fox"); // 'the-quick-brown-fox'
kebabCase("the-quick-brown-fox"); // 'the-quick-brown-fox'
kebabCase("the_quick_brown_fox"); // 'the-quick-brown-fox'
kebabCase("theQuickBrownFox"); // 'the-quick-brown-fox'
kebabCase("theQuickBrown Fox"); // 'the-quick-brown-fox'
kebabCase("thequickbrownfox"); // 'thequickbrownfox'
kebabCase("the - quick * brown# fox"); // 'the-quick-brown-fox'
kebabCase("theQUICKBrownFox"); // 'the-q-u-i-c-k-brown-fox'

just-snake-case

🍦Try It

npm install just-snake-case

snakeCase("the quick brown fox"); // 'the_quick_brown_fox'
snakeCase("the-quick-brown-fox"); // 'the_quick_brown_fox'
snakeCase("the_quick_brown_fox"); // 'the_quick_brown_fox'
snakeCase("theQuickBrownFox"); // 'the_quick_brown_fox'
snakeCase("theQuickBrown Fox"); // 'the_quick_brown_Fox'
snakeCase("thequickbrownfox"); // 'thequickbrownfox'
snakeCase("the - quick * brown# fox"); // 'the_quick_brown_fox'
snakeCase("theQUICKBrownFox"); // 'the_q_u_i_c_k_brown_fox'

just-pascal-case

🍦Try It

npm install just-pascal-case

pascalCase("the quick brown fox"); // 'TheQuickBrownFox'
pascalCase("the_quick_brown_fox"); // 'TheQuickBrownFox'
pascalCase("the-quick-brown-fox"); // 'TheQuickBrownFox'
pascalCase("theQuickBrownFox"); // 'TheQuickBrownFox'
pascalCase("thequickbrownfox"); // 'Thequickbrownfox'
pascalCase("the - quick * brown# fox"); // 'TheQuickBrownFox'
pascalCase("theQUICKBrownFox"); // 'TheQUICKBrownFox'

just-capitalize

🍦Try It

npm install just-capitalize

capitalize("capitals"); // 'Capitals'
capitalize("Capitals"); // 'Capitals'
// all remaining characters are lowercased
capitalize("CAPITALS"); // 'Capitals'
capitalize("CaPiTaLs"); // 'Capitals'
capitalize(" capitals"); // ' capitals'
capitalize("Capi tals"); // 'Capit als'
capitalize("Capi Tals"); // 'Capi tals'
capitalize("!capitals"); // '!capitals'

just-replace-all

🍦Try It

npm install just-replace-all

replaceAll('hello, world', 'l', 'q'); // 'heqqo, worqd'
replaceAll('hello, world', 'l', 'qq'); // 'heqqqqo, worqqd'
replaceAll('hello, world', 'll', 'q'); // 'heqo, world'
replaceAll('hello, world', '', 'q'); // 'hello, world'
replaceAll('hello, world', 'l', ''); // 'heo, word'
replaceAll('hello, world', null, 'q'); // 'hello, world'
replaceAll('hello, world', 'l'); // throw
replaceAll('hello, world'); // throw
replaceAll(); // throw
replaceAll(null, 'l', 'q'); // throw
replaceAll('hello, world', null, 'q'); // throw
replaceAll('hello, world', 'l', null); // throw

Numbers

just-clamp

🍦Try It

npm install just-clamp

import clamp from "just-clamp";

var n = 5;
clamp(1, n, 12); // 5
clamp(3, n, 1); // 3
clamp(8, n, 9); // 8
clamp(0, n, 0); // 0

var n = -5;
clamp(1, n, 12); // 1
clamp(-7, n, -8); // -7

clamp(NaN, n, 8); // NaN
clamp(3, n, NaN); // NaN
clamp(3, NaN, 8); // NaN

clamp(undefined, n, 8); // throws
clamp(3, n, "h"); // throws
clamp(3, false, 8); // throws

just-modulo

🍦Try It

npm install just-modulo

import modulo from "just-modulo";

modulo(7, 5); // 2
modulo(17, 23); // 17
modulo(16.2, 3.8); // 1
modulo(5.8, 3.4); //2.4
modulo(4, 0); // 4
modulo(-7, 5); // 3
modulo(-2, 15); // 13
modulo(-5.8, 3.4); // 1
modulo(12, -1); // NaN
modulo(-3, -8); // NaN
modulo(12, "apple"); // NaN
modulo("bee", 9); // NaN
modulo(null, undefined); // NaN

Functions

just-compose

🍦Try It

npm install just-compose

import compose from "just-compose";

const sqRootBiggest = compose(Math.max, Math.sqrt, Math.trunc);
sqRootBiggest(10, 5); // 3
sqRootBiggest(7, 0, 16); // 4

just-curry-it

🍦Try It

npm install just-curry-it

import curry from "just-curry-it";

function add(a, b, c) {
  return a + b + c;
}
curry(add)(1)(2)(3); // 6
curry(add)(1)(2)(2); // 5
curry(add)(2)(4, 3); // 9

function add(...args) {
  return args.reduce((sum, n) => sum + n, 0);
}
var curryAdd4 = curry(add, 4);
curryAdd4(1)(2, 3)(4); // 10

function converter(ratio, input) {
  return (input * ratio).toFixed(1);
}
const curriedConverter = curry(converter);
const milesToKm = curriedConverter(1.62);
milesToKm(35); // 56.7
milesToKm(10); // 16.2

just-demethodize

🍦Try It

npm install just-demethodize

const demethodize = require("just-demethodize");

const trimFn = demethodize("".trim);
["hello ", " goodbye", "hello again"].map(trimFn);

just-flip

🍦Try It

npm install just-flip

import flip from "just-flip";

flip(console.log)(1, 2, 3); // 2, 1, 3

just-partial-it

🍦Try It

npm install just-partial-it

import partial from "just-partial-it";

const cubedRoot = partial(Math.pow, _, 1 / 3);
cubedRoot(64); // 4

const getRoot = partial(Math.pow, 64);
getRoot(1 / 2); // 8

just-debounce-it

🍦Try It

npm install just-debounce-it

import debounce from "just-debounce-it";

const fn1 = debounce(() => console.log("Hello"), 500);
fn1();
fn1();
fn1();
// 500ms later logs 'hello' once

const fn2 = debounce(() => console.log("Hello"), 500, true);
fn2(); // logs hello immediately
fn2();
fn2();
// 500ms later logs 'hello' once

just-throttle

🍦Try It

npm install just-throttle

import throttle from "just-throttle";

const fn1 = throttle(() => console.log("hello"), 500, true);
setInterval(fn1, 400);
// logs 'hello' immediately and then every 500ms

const fn2 = throttle(() => console.log("hello"), 500);
setInterval(fn2, 400);
// logs 'hello' after 500ms and then every 500ms

just-once

🍦Try It

npm install just-once

import once from "just-once";

const fn = once(() => console.log("hello"));

fn();
// logs 'hello'
fn();
// does nothing

Testing

Run all tests as a single test suite with

npm run test

Cross browser tests (via saucelabs) are in the sauce branch

Contribute!

https://github.com/angus-c/just/blob/master/CONTRIBUTING.md