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diff --git a/files/zh-cn/web/javascript/guide/regular_expressions/quantifiers/index.html b/files/zh-cn/web/javascript/guide/regular_expressions/quantifiers/index.html new file mode 100644 index 0000000000..fa89245988 --- /dev/null +++ b/files/zh-cn/web/javascript/guide/regular_expressions/quantifiers/index.html @@ -0,0 +1,171 @@ +--- +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 ?勒?/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 notranslate">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 notranslate">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)); // <span class="message-body-wrapper"><span class="message-flex-body"><span class="devtools-monospace message-body"><span class="objectBox objectBox-array"><span class="arrayLeftBracket">[ </span><span class="objectBox objectBox-string">"Why"</span>, <span class="objectBox objectBox-string">"do"</span>, <span class="objectBox objectBox-string">"I"</span>, <span class="objectBox objectBox-string">"have"</span>, <span class="objectBox objectBox-string">"to"</span>, <span class="objectBox objectBox-string">"learn"</span>, <span class="objectBox objectBox-string">"table"</span><span class="arrayRightBracket"> ]</span></span></span></span></span> +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 notranslate">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 notranslate">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> |