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---
title: 量词
slug: Web/JavaScript/Guide/Regular_Expressions/Quantifiers
translation_of: Web/JavaScript/Guide/Regular_Expressions/Quantifiers
original_slug: Web/JavaScript/Guide/Regular_Expressions/量词
---
<p>{{jsSidebar("JavaScript Guide")}}</p>
<p>量词表示要匹配的字符或表达式的数量。</p>
<div>{{EmbedInteractiveExample("pages/js/regexp-quantifiers.html", "taller")}}</div>
<h2 id="类型">类型</h2>
<div class="hidden">The following table is also duplicated on <a href="/en-US/docs/Web/JavaScript/Guide/Regular_Expressions/Cheatsheet">this cheatsheet</a>. Do not forget to edit it as well, thanks!</div>
<table class="standard-table">
<thead>
<tr>
<th scope="col">Characters</th>
<th scope="col">Meaning</th>
</tr>
</thead>
<tbody>
<tr>
<td><code><em>x</em>*</code></td>
<td>
<p>将前面的项“x”匹配0次或更多次。例如，/bo*/匹配“A ghost booooed”中的“boooo”和“A bird warbled”中的“b”，但在“A goat grunt”中没有匹配。</p>
</td>
</tr>
<tr>
<td><code><em>x</em>+</code></td>
<td>
<p>将前一项“x”匹配1次或更多次。等价于{1,}。例如，/a+/匹配“candy”中的“a”和“caaaaaaandy”中的“a”。</p>
</td>
</tr>
<tr>
<td><code><em>x</em>?</code></td>
<td>
<p>将前面的项“x”匹配0或1次。例如,/e?le?/匹配angel中的el和angle中的le。</p>
<p>如果立即在任何量词*、+、?或{}之后使用，则使量词是非贪婪的(匹配最小次数)，而不是默认的贪婪的(匹配最大次数)。</p>
</td>
</tr>
<tr>
<td><code><em>x</em>{<em>n</em>}</code></td>
<td>
<p>其中“n”是一个正整数，与前一项“x”的n次匹配。例如，<code>/a{2}/ </code>不匹配“candy”中的“a”，但它匹配“caandy”中的所有“a”，以及“caaandy”中的前两个“a”。</p>
</td>
</tr>
<tr>
<td><code><em>x</em>{<em>n</em>,}</code></td>
<td>
<p>其中，“n”是一个正整数，与前一项“x”至少匹配“n”次。例如，<code>/a{2，}/</code>不匹配“candy”中的“a”，但匹配“caandy”和“caaaaaaandy”中的所有a。</p>
</td>
</tr>
<tr>
<td><code><em>x</em>{<em>n</em>,<em>m</em>}</code></td>
<td>
<p>其中，“n”是0或一个正整数，“m”是一个正整数，而m > n至少与前一项“x”匹配，最多与“m”匹配。例如，/a{1,3}/不匹配“cndy”中的“a”，“candy”中的“a”，“caandy”中的两个“a”，以及“caaaaaaandy”中的前三个“a”。注意，当匹配“caaaaaaandy”时，匹配的是“aaa”，即使原始字符串中有更多的“a”。</p>
</td>
</tr>
<tr>
<td>
<p><code><em>x</em>*?</code><br>
<code><em>x</em>+?</code><br>
<code><em>x</em>??</code><br>
<code><em>x</em>{n}?</code><br>
<code><em>x</em>{n,}?</code><br>
<code><em>x</em>{n,m}?</code></p>
</td>
<td>
<p>默认情况下，像 <code>* </code>和 <code>+ </code>这样的量词是“贪婪的”，这意味着它们试图匹配尽可能多的字符串。?量词后面的字符使量词“非贪婪”：意思是它一旦找到匹配就会停止。例如，给定一个字符串“some <foo> <bar> new </bar> </foo> thing”:</p>
<ul>
<li><code>/<.*>/</code> will match "<foo> <bar> new </bar> </foo>"</li>
<li><code>/<.*?>/</code> will match "<foo>"</li>
</ul>
</td>
</tr>
</tbody>
</table>
<h2 id="举例说明">举例说明</h2>
<h3 id="重复模式">重复模式</h3>
<pre class="brush: js">var wordEndingWithAs = /\w+a+/;
var delicateMessage = "This is Spartaaaaaaa";
console.table(delicateMessage.match(wordEndingWithAs)); // [ "Spartaaaaaaa" ]</pre>
<h3 id="计算字符集">计算字符集</h3>
<pre class="brush: js">var singleLetterWord = /\b\w\b/g;
var notSoLongWord = /\b\w{1,6}\b/g;
var loooongWord = /\b\w{13,}\b/g;
var sentence = "Why do I have to learn multiplication table?";
console.table(sentence.match(singleLetterWord)); // ["I"]
console.table(sentence.match(notSoLongWord)); // [ "Why", "do", "I", "have", "to", "learn", "table" ]
console.table(sentence.match(loooongWord)); // ["multiplication"]可选可选字符
</pre>
<h3 id="可选字符"> 可选字符</h3>
<pre class="brush: js">var britishText = "He asked his neighbour a favour.";
var americanText = "He asked his neighbor a favor.";
var regexpEnding = /\w+ou?r/g;
// \w+ One or several letters
// o followed by an "o",
// u? optionally followed by a "u"
// r followed by an "r"
console.table(britishText.match(regexpEnding));
// ["neighbour", "favour"]
console.table(americanText.match(regexpEnding));
// ["neighbor", "favor"]
</pre>
<h3 id="贪婪_与_非贪婪的">贪婪 与 非贪婪的</h3>
<pre class="brush: js">var text = "I must be getting somewhere near the centre of the earth.";
var greedyRegexp = /[\w ]+/;
// [\w ] a letter of the latin alphabet or a whitespace
// + one or several times
console.log(text.match(greedyRegexp)[0]);
// "I must be getting somewhere near the centre of the earth"
// almost all of the text matches (leaves out the dot character)
var nonGreedyRegexp = /[\w ]+?/; // Notice the question mark
console.log(text.match(nonGreedyRegexp));
// "I"
// The match is the smallest one possible
</pre>
<h2 id="规范"><strong>规范</strong></h2>
<table class="standard-table">
<tbody>
<tr>
<th scope="col">Specification</th>
</tr>
<tr>
<td>{{SpecName('ESDraft', '#sec-quantifier', 'RegExp: Quantifiers')}}</td>
</tr>
</tbody>
</table>
<h2 id="浏览器支持">浏览器支持</h2>
<p>For browser compatibility information, check out the <a href="/en-US/docs/Web/JavaScript/Guide/Regular_Expressions#Browser_compatibility">main Regular Expressions compatibility table</a>.</p>
<h2 id="See_also">See also</h2>
<ul>
<li><a href="/en-US/docs/Web/JavaScript/Guide/Regular_Expressions">Regular expressions guide</a>
<ul>
<li><a href="/en-US/docs/Web/JavaScript/Guide/Regular_Expressions/Character_Classes">Character classes</a></li>
<li><a href="/en-US/docs/Web/JavaScript/Guide/Regular_Expressions/Assertions">Assertions</a></li>
<li><a href="/en-US/docs/Web/JavaScript/Guide/Regular_Expressions/Unicode_Property_Escapes">Unicode property escapes</a></li>
<li><a href="/en-US/docs/Web/JavaScript/Guide/Regular_Expressions/Groups_and_Ranges">Groups and ranges</a></li>
</ul>
</li>
<li><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp">The <code>RegExp()</code> constructor</a></li>
</ul>
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