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JS正则
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<p>JS中的正则</p>
<a id="more"></a>
<h2 id="一-正则表达式简介">一.正则表达式简介</h2>
<blockquote>
<p>百度百科:正则表达式, 又称规则表达式. (英语: Regular Expression, 在代码中常简写为regex、regexp或RE), 计算机科学的一个概念. 正则表达式通常被用来检索、替换那些符合某个模式(规则)的文本.</p>
<p>正则表达式用于定义一些字符串的规则, 计算机根据正则表达式, 来检查是否符合规则, 获取、提取字符串中符合规则的内容.</p>
</blockquote>
<h3 id="1-创建RegExp对象">1.创建RegExp对象</h3>
<p>正则表达式对象即RegExp对象, JS内置的对象.</p>
<p>RegExp对象的test()方法, 检索字符串中指定的值, 返回 true 或 false</p>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//语法:</span></span><br><span class="line"><span class="comment">//var 变量名 = new RegExp("正则表达式","匹配模式");</span></span><br><span class="line"><span class="comment">//匹配模式:i 忽略大小写;g 全局匹配;m 多行匹配;</span></span><br><span class="line"><span class="keyword">var</span> reg = <span class="keyword">new</span> <span class="built_in">RegExp</span>(<span class="string">"a"</span>,<span class="string">"i"</span>);</span><br><span class="line"><span class="keyword">var</span> str = <span class="string">"ABCD"</span>;</span><br><span class="line"><span class="keyword">var</span> result = reg.test(str);<span class="comment">//检查字符串中是否含A</span></span><br><span class="line"><span class="built_in">console</span>.log(result);<span class="comment">//true</span></span><br></pre></td></tr></table></figure>
<h3 id="2-字面量创建RegExp对象">2.字面量创建RegExp对象</h3>
<p>字面量的方式创建更加简单, 使用构造函数创建更加灵活(可以传参数).</p>
<p><font style = 'font-size:1.2em;'><center>语法: var 变量名 = /正则表达式/匹配模式;</center></font></p>
<p><font style = 'font-size:1.2em;color:red;'>注意: 语法中没有引号</font></p>
<table>
<thead>
<tr>
<th>表达式</th>
<th>描述</th>
</tr>
</thead>
<tbody>
<tr>
<td>[abc]</td>
<td>查找方括号之间的任何字符</td>
</tr>
<tr>
<td>[^abc]</td>
<td>查找任何不在方括号之间的字符</td>
</tr>
<tr>
<td>[0-9]</td>
<td>查找任何从 0 至 9 的数字</td>
</tr>
<tr>
<td>[a-z]</td>
<td>查找任何从小写 a 到小写 z 的字符</td>
</tr>
<tr>
<td>[A-Z]</td>
<td>查找任何从大写 A 到大写 Z 的字符</td>
</tr>
<tr>
<td>[A-z]</td>
<td>查找任何从大写 A 到小写 z 的字符</td>
</tr>
<tr>
<td>[adgk]</td>
<td>查找给定集合内的任何字符</td>
</tr>
<tr>
<td>[^adgk]</td>
<td>查找给定集合外的任何字符</td>
</tr>
<tr>
<td>(red blue green)</td>
<td>查找任何指定的选项</td>
</tr>
</tbody>
</table>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">var</span> reg = <span class="regexp">/a/i</span>;<span class="comment">//等价于:var reg = new RegExp("a","i");</span></span><br><span class="line"><span class="comment">//1.创建一个正则表达式检查一个字符串中是否含有a或b</span></span><br><span class="line">reg = <span class="regexp">/a|b/</span>;</span><br><span class="line"></span><br><span class="line"><span class="comment">//2.创建一个正则表达式检查一个字符串中是否含有字母</span></span><br><span class="line">reg = <span class="regexp">/[A-z]/</span>;<span class="comment">//中括号表示或的意思</span></span><br><span class="line"></span><br><span class="line"><span class="comment">//3.检查一个字符串中是否含有abc或adc或aec</span></span><br><span class="line">reg = <span class="regexp">/a[bde]c/</span>;<span class="comment">//以a开头,c结尾,中间为b或d或e</span></span><br><span class="line"></span><br><span class="line">reg = <span class="regexp">/[^0-9]/</span>;<span class="comment">//检查除了数字之外的内容</span></span><br><span class="line">reg = <span class="regexp">/(abc)/</span>;<span class="comment">//abc连续出现</span></span><br><span class="line">reg = <span class="regexp">/(a|b|c)/</span>;<span class="comment">//出现过a或b或c</span></span><br></pre></td></tr></table></figure>
<h2 id="二-字符串与正则相关的方法">二.字符串与正则相关的方法</h2>
<h3 id="1-split">1.split</h3>
<ul>
<li>根据参数将字符串拆分为字符数组</li>
<li>参数可以是正则表达式</li>
<li>正则不需要设置全局匹配, split默认将所有符合条件的拆分</li>
</ul>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">var</span> str = <span class="string">"1a2b3c4d5e6f7g8"</span>;</span><br><span class="line"><span class="keyword">var</span> arr = str.split(<span class="regexp">/[A-z]/</span>);<span class="comment">//根据任意字母拆分</span></span><br><span class="line"><span class="built_in">console</span>.log(arr);<span class="comment">//1,2,3,4,5,6,7,8</span></span><br></pre></td></tr></table></figure>
<h3 id="2-search">2.search</h3>
<ul>
<li>检索与正则表达式相匹配的值</li>
<li>如果可以搜索到指定内容, 则返回第一次出现过的位置, 没搜索到返回-1</li>
<li>它能接受一个正则表达式作为参数, 然后根据正则表达式检索字符串</li>
<li>search正则查找时不能设置全局匹配</li>
</ul>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//功能和indexOf()类似</span></span><br><span class="line"><span class="keyword">var</span> str = <span class="string">"hello abc hello adc hello aec"</span>;</span><br><span class="line"><span class="comment">//搜索字符串中是否含有abc或adc或aec</span></span><br><span class="line"><span class="keyword">var</span> result = str.search(<span class="regexp">/a[bde]c/</span>);</span><br><span class="line"><span class="built_in">console</span>.log(result);<span class="comment">//6</span></span><br></pre></td></tr></table></figure>
<h3 id="3-match">3.match</h3>
<ul>
<li>可以根据正则表达式, 从一个字符串中将符合条件的内容提取出来</li>
<li>默认情况下, match只会找第一个符合条件的内容, 找到后停止检索, 我们可以将正则表达式设置为全局匹配模式, 这样match会找到所有符合条件的内容</li>
<li>可以为正则表达式设置多个匹配模式, 且顺序无所谓</li>
<li>match会将匹配到的内容封装到一个数组中返回, 即使只查询到一个结果.</li>
<li>可以将一个没有规则的长串中, 有规则的内容提取出来, 很实用</li>
</ul>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">var</span> str = <span class="string">"1A2B3C4d5e6f7g8"</span>;</span><br><span class="line"><span class="keyword">var</span> result = str.match(<span class="regexp">/[a-z]/gi</span>);</span><br><span class="line"><span class="built_in">console</span>.log(<span class="built_in">Array</span>.isArray(result));<span class="comment">//true;</span></span><br><span class="line"><span class="built_in">console</span>.log(result);<span class="comment">//A,B,C,d,e,f,g</span></span><br><span class="line"><span class="built_in">console</span>.log(result[<span class="number">0</span>]);<span class="comment">//A</span></span><br><span class="line"></span><br><span class="line"><span class="comment">//筛选出所有的QQ号</span></span><br><span class="line"><span class="keyword">var</span> str = <span class="string">"826720408abhfe826720407"</span>+</span><br><span class="line"> <span class="string">"freaf826720405C826720"</span>+</span><br><span class="line"> <span class="string">"404d826720405e8267204"</span>+</span><br><span class="line"> <span class="string">"00f826720409g826720401"</span>;</span><br><span class="line"><span class="keyword">var</span> result = str.match(<span class="regexp">/[0-9]{8,10}/g</span>);</span><br><span class="line"><span class="built_in">console</span>.log(<span class="built_in">Array</span>.isArray(result));<span class="comment">//true;</span></span><br><span class="line"><span class="built_in">console</span>.log(result);</span><br></pre></td></tr></table></figure>
<h3 id="4-replace">4.replace</h3>
<ul>
<li>将字符串中指定的内容替换为新的内容, 不影响原字符串</li>
<li>参数:①被替换的内容, 可以接受一个正则表达式作为参数</li>
<li>②新的内容</li>
<li>默认只会替换一个,可以为正则表达式设置全局匹配模式替换所有内容</li>
</ul>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">var</span> str = <span class="string">"1A2B3C4d5e6f7g8"</span>;</span><br><span class="line"><span class="comment">//将所有字母替换为""</span></span><br><span class="line"><span class="keyword">var</span> result = str.replace(<span class="regexp">/[a-z]/gi</span>,<span class="string">""</span>);</span><br><span class="line"><span class="built_in">console</span>.log(result);<span class="comment">//12345678</span></span><br></pre></td></tr></table></figure>
<h2 id="三-正则表达式语法补充">三.正则表达式语法补充</h2>
<h3 id="1-量词">1.量词</h3>
<ul>
<li>量词: 可以设置一个内容出现的次数, 它只对它前面的一个内容起作用</li>
</ul>
<table>
<thead>
<tr>
<th style="text-align:left">量词</th>
<th>描述</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align:left">n+</td>
<td>匹配任何包含至少一个 n 的字符串, 相当于n{1, }</td>
</tr>
<tr>
<td style="text-align:left">n*</td>
<td>匹配任何包含零个或多个 n 的字符串, 相当于n{0, }</td>
</tr>
<tr>
<td style="text-align:left">n?</td>
<td>匹配任何包含零个或一个 n 的字符串, 相当于n{0,1}</td>
</tr>
<tr>
<td style="text-align:left">n{x}</td>
<td>匹配包含 x 个 n 的序列的字符串</td>
</tr>
<tr>
<td style="text-align:left">n{x,y}</td>
<td>匹配包含 x ~ y 个 n 的序列的字符串</td>
</tr>
<tr>
<td style="text-align:left">n{x, }</td>
<td>匹配包含至少 x 个 n 的序列的字符串</td>
</tr>
<tr>
<td style="text-align:left">n$</td>
<td>匹配任何结尾为 n 的字符串</td>
</tr>
<tr>
<td style="text-align:left">^n</td>
<td>匹配任何开头为 n 的字符串</td>
</tr>
<tr>
<td style="text-align:left">?=n</td>
<td>匹配任何其后紧接指定字符串 n 的字符串</td>
</tr>
<tr>
<td style="text-align:left">?!n</td>
<td>匹配任何其后没有紧接指定字符串 n 的字符串</td>
</tr>
</tbody>
</table>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">var</span> reg = <span class="regexp">/a{3}/</span>;</span><br><span class="line"><span class="built_in">console</span>.log(reg.test(<span class="string">"xaaax"</span>));<span class="comment">//只有字符串中连续出现3个a时为true</span></span><br><span class="line">reg = <span class="regexp">/(ab){3}/</span>;</span><br><span class="line"><span class="built_in">console</span>.log(reg.test(<span class="string">"xabababx"</span>));<span class="comment">//只有字符串中连续出现3个ab时为true</span></span><br><span class="line">reg = <span class="regexp">/ab{3,5}c/</span>;</span><br><span class="line"><span class="built_in">console</span>.log(reg.test(<span class="string">"xabbbbcx"</span>));<span class="comment">//只有字符串中a和c之间有3~5个b时为true</span></span><br><span class="line">reg = <span class="regexp">/ab{3,}c/</span>;</span><br><span class="line"><span class="built_in">console</span>.log(reg.test(<span class="string">"xabbbcx"</span>));<span class="comment">//只有字符串中a和c之间有2个以上b时为true</span></span><br><span class="line"></span><br><span class="line">reg = <span class="regexp">/^a$/</span>;</span><br><span class="line"><span class="built_in">console</span>.log(reg.test(<span class="string">"a"</span>));<span class="comment">//只有字符串为"a"时,结果为true</span></span><br><span class="line">reg = <span class="regexp">/^a|a$/</span>;</span><br><span class="line"><span class="built_in">console</span>.log(reg.test(<span class="string">"abc"</span>));<span class="comment">//字符串以a开头或以a结尾时为true</span></span><br></pre></td></tr></table></figure>
<p><font style='color:red;font-size:1.2em;font-weight:blod;'>注意: 在正则表达式中同时使用了 ^ 和 $ 量词, 则要求字符串必须完全符合正则表达式.</font></p>
<h3 id="练习-手机号的正则表达式">练习: 手机号的正则表达式</h3>
<p>匹配手机号的正则表达式: <font style='color:red;font-size:1.2em;font-weight:bold;'>/^1[3-9][0-9]{9}$/</font></p>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/*手机号的规则:</span></span><br><span class="line"><span class="comment"> *1. 以1开头</span></span><br><span class="line"><span class="comment"> *2. 第二位为3-9任意数字</span></span><br><span class="line"><span class="comment"> *3. 第三位之后为任意数字9个</span></span><br><span class="line"><span class="comment"> * ^ 和 $ 量词是必须的</span></span><br><span class="line"><span class="comment"> * ^1 [3-9] [0-9]{9}$</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="keyword">var</span> phoneNumReg = <span class="regexp">/^1[3-9][0-9]{9}$/</span>;</span><br><span class="line"><span class="built_in">console</span>.log(phoneNumReg.test(<span class="string">"15555555555"</span>));<span class="comment">//true</span></span><br></pre></td></tr></table></figure>
<h3 id="2-元字符">2.元字符</h3>
<table>
<thead>
<tr>
<th>元字符</th>
<th>描述</th>
</tr>
</thead>
<tbody>
<tr>
<td>.</td>
<td>查找单个字符, 除了换行和行结束符</td>
</tr>
<tr>
<td>\w</td>
<td>查找单词字符(字母、数字、下划线)</td>
</tr>
<tr>
<td>\W</td>
<td>查找非单词字符</td>
</tr>
<tr>
<td>\d</td>
<td>查找数字</td>
</tr>
<tr>
<td>\D</td>
<td>查找非数字字符</td>
</tr>
<tr>
<td>\s</td>
<td>查找空白字符</td>
</tr>
<tr>
<td>\S</td>
<td>查找非空白字符</td>
</tr>
<tr>
<td>\b</td>
<td>匹配单词边界</td>
</tr>
<tr>
<td>\B</td>
<td>匹配非单词边界</td>
</tr>
<tr>
<td>\0</td>
<td>查找 NULL 字符</td>
</tr>
<tr>
<td>\n</td>
<td>查找换行符</td>
</tr>
<tr>
<td>\f</td>
<td>查找换页符</td>
</tr>
<tr>
<td>\r</td>
<td>查找回车符</td>
</tr>
<tr>
<td>\t</td>
<td>查找制表符</td>
</tr>
<tr>
<td>\v</td>
<td>查找垂直制表符</td>
</tr>
<tr>
<td>\xxx</td>
<td>查找以八进制数 xxx 规定的字符</td>
</tr>
<tr>
<td>\xdd</td>
<td>查找以十六进制数 dd 规定的字符</td>
</tr>
<tr>
<td>\uxxxx</td>
<td>查找以十六进制数 xxxx 规定的 Unicode 字符</td>
</tr>
</tbody>
</table>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//查找字符串中是否有.</span></span><br><span class="line"><span class="comment">//正则字面量:</span></span><br><span class="line"><span class="comment">//由于.是元字符,我们要用\.来代替.</span></span><br><span class="line"><span class="comment">//而\表示转义,要用\\来代替\</span></span><br><span class="line"><span class="keyword">var</span> reg = <span class="regexp">/\./</span>;</span><br><span class="line"><span class="built_in">console</span>.log(reg.test(<span class="string">"adsC.dSf l"</span>));<span class="comment">//true</span></span><br><span class="line"></span><br><span class="line"><span class="comment">//正则构造函数:</span></span><br><span class="line"><span class="comment">//由于函数的参数为字符串,而在字符串中\代表转义字符</span></span><br><span class="line"><span class="comment">//故在字面量中的一个\要用\\来代替</span></span><br><span class="line"><span class="keyword">var</span> reg1 = <span class="keyword">new</span> <span class="built_in">RegExp</span>(<span class="string">"\\."</span>);<span class="comment">//等价于reg</span></span><br><span class="line"><span class="built_in">console</span>.log(reg1);<span class="comment">//输出:/\./</span></span><br><span class="line"></span><br><span class="line"><span class="comment">//查找字符串是否含单词child</span></span><br><span class="line">reg = <span class="regexp">/\bchild\b/</span>;</span><br><span class="line"><span class="built_in">console</span>.log(reg.test(<span class="string">"hello children"</span>));<span class="comment">//false</span></span><br><span class="line"><span class="built_in">console</span>.log(reg.test(<span class="string">"hello child ren"</span>));<span class="comment">//true</span></span><br></pre></td></tr></table></figure>
<h3 id="练习-A-去除字符串的前后空格">练习: A.去除字符串的前后空格</h3>
<p>匹配开头和结尾空格的正则表达式: <font style='color:red;font-size:1.2em;font-weight:bold;'> /^\s*|\s*$/g</font></p>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//可以考虑replace用空串替换空格</span></span><br><span class="line"><span class="keyword">var</span> str = <span class="string">" Aaron Bob "</span>;</span><br><span class="line"><span class="comment">//str = str.replace(/\s/g,"");//去除所有空格</span></span><br><span class="line"><span class="comment">//str = str.replace(/^\s*/,"");//去除开头的空格</span></span><br><span class="line"><span class="comment">//str = str.replace(/\s*$/,"");//去除结尾的空格</span></span><br><span class="line"></span><br><span class="line"><span class="comment">//综合一下:</span></span><br><span class="line">str = str.replace(<span class="regexp">/^\s*|\s*$/g</span>,<span class="string">""</span>);</span><br><span class="line"><span class="comment">//因为是或的关系,若不加全局匹配,方法匹配完开头的空格就返回了</span></span><br><span class="line"><span class="built_in">console</span>.log(str);</span><br></pre></td></tr></table></figure>
<h3 id="练习-B-email的正则表达式">练习: B.email的正则表达式</h3>
<figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/*电子邮件格式:</span></span><br><span class="line"><span class="comment"> * hello .hello @ abc .com .cn</span></span><br><span class="line"><span class="comment"> * </span></span><br><span class="line"><span class="comment"> * 任意字母数字下划线 .任意字母数字下划线 @ 任意字母数字 .任意字母(2-5位) .任意字母(2-5位)</span></span><br><span class="line"><span class="comment"> * </span></span><br><span class="line"><span class="comment"> * \w{3,} (\.\w+)* @ [A-z0-9]+ (\.[A-z]{2,5}){1,2}</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="keyword">var</span> emailReg = <span class="regexp">/^\w{3,}(\.\w+)*@[A-z0-9]+(\.[A-z]{2,5}){1,2}$/</span>;</span><br><span class="line"><span class="keyword">var</span> email = <span class="string">"[email protected]"</span>;</span><br><span class="line"><span class="built_in">console</span>.log(emailReg.test(email));<span class="comment">//true</span></span><br></pre></td></tr></table></figure>
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