对字符，字符串的相关操作--js,jQuery

1、字符方法

charAt()和charCodeAt()，这两个方法都接收一个参数，及基于0的字符位置，charAt()返回的是给定位置的字符，charCodeAt()返回的是给定位置字符的字符编码。与charCodeAt()对应的一个方法是formCharCode()将字符编码转为字符串。 
如：

<code class="hljs xml has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">script</span>></span><span class="javascript" style="box-sizing: border-box;">
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">var</span> code = <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"future"</span>;
    console.log(code.charAt(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>)); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//t</span>
    console.log(code.charCodeAt(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>)) <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//116</span>
</span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">script</span>></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li></ul>

除了以上方法外，还可以通过方括号去访问特定位置的字符，如：

<code class="hljs xml has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">script</span>></span><span class="javascript" style="box-sizing: border-box;">
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">var</span> code = <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"future"</span>;
    console.log(code[<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>]); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//t</span>
</span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">script</span>></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>

使用方括号的方法在IE8，Firefox,Safari,Chrome和Opera中都可以支持，但是在IE7及更早版本中不支持，返回的值为undefined.

2、字符串操作方法

1、字符串拼接：concact()方法。

<code class="hljs rsl has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">var a = <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"my "</span>;
console.<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">log</span>(a.<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">concat</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"future"</span>));<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//my future</span>
console.<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">log</span>(a.<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">concat</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"future "</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"will"</span>));<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//my future will</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

2、基于子字符串创建新字符串：slice()、substr()和substring().这三个方法都返回操纵字符串的一个子字符串，而且都接收一到两个参数。 
第一个参数指定字符串的开始位置，第二个参数（可省略）表示子字符串到哪里结束。slice()和substring()的第二个参数指定的是子字符串最后一个字符后面的位置，而substr()的第二个参数指定的是返回的字符个数。如果省略第二个参数，则截取到字符串最后一个位置。

<code class="hljs rust has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">var <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span> = <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"We are family"</span>;
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>.slice(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">5</span>));    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// ar(从第2个位置开始，不包含第5个位置)</span>
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>.slice(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>));      <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//e are family（从第1个位置开始，一直到最后）</span>
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>.substring(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">3</span>));  <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//are family（从第3个位置开始，一直到最后）</span>
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>.substring(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">3</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">5</span>));<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//ar（从第3个位置开始，不包含第5个位置）</span>
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>.substr(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>));     <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// are family（从第2个位置开始，一直到最后）</span>
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>.substr(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">6</span>));   <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// are f(从第2个位置开始，截取6个字符)</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li></ul>

slice()和substring()方法在正值情况下，实现的功能一致，但是在传递的值为负值时，行为就不相同了。 
slice()方法会将传入的负值与字符串的长度相加（因此，如果两个参数都会负值，第二个参数必须要大于第一个参数，否则返回的是空字符串） 
substr()方法会将负的第一个参数加上字符串的长度，将将第二个参数转换为0。（如果第二个参数为负值，返回空的字符串） 
substring()方法将所有的负值参数都转换为0，substring始终会将较小的参数作为开始位置。

<code class="hljs rust has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">var <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span> = <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Wearefamily"</span>; <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//length为11</span>
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>.slice(-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">3</span>,-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">8</span>));<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//相当于str.slice(8,3)//返回空字符串</span>
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>.slice(-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">5</span>,-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>));<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//相当于str.slice(6,10)//返回ami</span>
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>.substring(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">3</span>,-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">4</span>));<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//相当于str.substring(3,0)//返回Wea</span>
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>.substring(-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">3</span>,-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">5</span>));<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//相当于str.substring(0,0)//返回空字符串</span>
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>.substr(-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">4</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">3</span>));<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//相当于substr(7,3)//返回mil</span>
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>.substr(-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">4</span>,-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">3</span>));<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//相当于substr(7,0)//返回空字符串</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li></ul>

3、字符串的位置方法

字符串的位置方法：indexOf()和lastIndexOf()。这两个方法都是从一个字符串中搜索给定的子字符串，然后返回子字符串的位置，没有找到，返回-1.indexOf()从字符串的开头向后搜索子字符串，而lastIndexOf()从字符串的末尾向前搜索子字符串。 

<code class="hljs rust has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">var <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span> = <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"WEAREFAMILY"</span>;
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>.indexOf(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"A"</span>));<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//2</span>
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>.lastIndexOf(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"A"</span>));<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//6</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

4.trim()方法

trim()用于去掉字符串收尾的空格

5、字符串大小写转换方法

转换为大写：toUpperCase()和toLocalUpperCase() 
转换为小写：toLowerCase()和toLocalLowerCase()

6、字符串的模式匹配

match(),replace(),search(),replace()以及split()方法是String类型定义的集中用于在字符串中匹配模式的几种方法。 
match方法只接收一个参数，要么是一个正则表达式，要么是一个RegExp对象。在字符串上调用match()方法，本质上和调用RegExp的exec()方法相同，返回的是一个数组

<code class="hljs rust has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">var <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span> = <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"we are weamy"</span>;
var pattern = /we/;
var matches = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">match</span>(pattern);
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(matches);<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//["we", index: 0, input: "we are weamy"]</span>
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(pattern.exec(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>));<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//["we", index: 0, input: "we are weamy"]</span>
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(matches.index);<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//0</span>
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(matches[<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>]);<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//we</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li></ul>

search()的参数与match()相同，不同在于search()返回的是字符串中第一个匹配项的索引；如果没有找到匹配项，返回-1. 
replace()方法，接收2个参数，第一个参数可以是一个RegExp对象或者是一个字符串，第二个参数是一个字符串或者是一个函数，如果第一个参数是字符串，那么只会替换第一个字符串，如果想要替换所有的字符串，那么必须使用正则表达式，并指定全局标志(g)

<code class="hljs rust has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">var <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span> = <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"cat, fat, sat, bat"</span>;
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>.replace(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"at"</span>,<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"ooo"</span>));<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//cooo, fat, sat, bat</span>
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>.replace(/at/g,<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"ooo"</span>));<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//cooo, fooo, sooo, booo</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

如果replace()的第二个参数是字符串，还可以使用一些特殊的字符序列，将正则表达式操作得到的值插入到结果字符中。 
$$ $ 
S& 匹配整个模式的子字符串 
Sn 匹配第n个捕获组的子字符串

<code class="hljs rust has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">var <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span> = <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"cat, fat, sat, bat"</span>;
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>.replace(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"at"</span>,<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"ooo"</span>));<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//cooo, fat, sat, bat</span>
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>.replace(/(.at)/g,<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"ooo ($1)"</span>));<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//ooo (cat), ooo (fat), ooo (sat), ooo (bat)</span>
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>.replace(/(.at)/g,<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"ooo ($&)"</span>));<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//ooo (cat), ooo (fat), ooo (sat), ooo (bat)</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>

split()方法接收一个参数作为分隔符，将字符串转变为数组。 
与之相对应的方法是join()，用作将数组转变为字符串。

7、LocalCompare()方法

这个方法用于字符串的比较。 
如果字符串在字母表中应该拍照字符串参数之前，则返回一个负数。（大多数情况下是-1，具体的值要视实现而定） 
如果字符串等于字符串参数，则返回0. 
如果字符串在字母表中的顺序排在字符串参数之后，则返回一个正数。（大多数情况下是1，具体的值要视实现而定）

<code class="hljs rust has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">var <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span> = <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"break"</span>;
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>.localeCompare(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"future"</span>)); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//-1</span>
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>.localeCompare(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"above"</span>));  <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//1</span>
console.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">log</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">str</span>.localeCompare(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"break"</span>));  <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//0</span></code>

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