---
title: String.prototype.toLowerCase()
slug: Web/JavaScript/Reference/Global_Objects/String/toLowerCase
translation_of: Web/JavaScript/Reference/Global_Objects/String/toLowerCase
---
<div>{{JSRef}}</div>

<p><strong><code>toLowerCase()</code></strong> 函式会回传将字符串转换为英文小写字母后的结果。</p>

<div>{{EmbedInteractiveExample("pages/js/string-tolowercase.html")}}</div>



<h2 id="语法">语法</h2>

<pre class="syntaxbox"><code><var>str</var>.toLowerCase()</code></pre>

<h3 id="回传值">回传值</h3>

<p>回传一组将原字串英文内容转换成英文小写字母后的结果。</p>

<h2 id="描述">描述</h2>

<p>The <code>toLowerCase()</code> 函式会回传一组将原字符串英文内容转换成英文小写字母后的结果。 <code>toLowerCase()</code> 并不会影响到原字符串 <code>str</code> 的内容值。</p>

<h2 id="范例">范例</h2>

<h3 id="使用toLowerCase()">使用<code>toLowerCase()</code></h3>

<pre class="brush: js">console.log('ALPHABET'.toLowerCase()); // 'alphabet'
</pre>

<h2 id="规范">规范</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">规范</th>
   <th scope="col">状态</th>
   <th scope="col">注解</th>
  </tr>
  <tr>
   <td>{{SpecName('ES1')}}</td>
   <td>{{Spec2('ES1')}}</td>
   <td>Initial definition. Implemented in JavaScript 1.0.</td>
  </tr>
  <tr>
   <td>{{SpecName('ES5.1', '#sec-15.5.4.16', 'String.prototype.toLowerCase')}}</td>
   <td>{{Spec2('ES5.1')}}</td>
   <td></td>
  </tr>
  <tr>
   <td>{{SpecName('ES6', '#sec-string.prototype.tolowercase', 'String.prototype.toLowerCase')}}</td>
   <td>{{Spec2('ES6')}}</td>
   <td></td>
  </tr>
  <tr>
   <td>{{SpecName('ESDraft', '#sec-string.prototype.tolowercase', 'String.prototype.toLowerCase')}}</td>
   <td>{{Spec2('ESDraft')}}</td>
   <td></td>
  </tr>
 </tbody>
</table>

<h2 id="浏览器相容性">浏览器相容性</h2>

<p>{{Compat("javascript.builtins.String.toLowerCase")}}</p>

<h2 id="参考">参考</h2>

<ul>
 <li>{{jsxref("String.prototype.toLocaleLowerCase()")}}</li>
 <li>{{jsxref("String.prototype.toLocaleUpperCase()")}}</li>
 <li>{{jsxref("String.prototype.toUpperCase()")}}</li>
</ul>