---
title: Number.prototype.valueOf()
slug: Web/JavaScript/Reference/Global_Objects/Number/valueOf
tags:
  - JavaScript
  - Method
  - Number
  - valueOf()
translation_of: Web/JavaScript/Reference/Global_Objects/Number/valueOf
---
<div>{{JSRef("Global_Objects", "Number")}}</div>

<h2 id="Summary" name="Summary">概述</h2>

<p><strong><code>valueOf()</code></strong> 方法返回一个被 {{jsxref("Global_Objects/Number", "Number")}} 对象包装的原始值。</p>

<h2 id="Syntax" name="Syntax">语法</h2>

<pre class="syntaxbox"><code><var>numObj</var>.valueOf()</code></pre>

<h3 id="Parameters" name="Parameters">返回值</h3>

<p>表示指定 {{jsxref("Number")}} 对象的原始值的数字</p>

<h2 id="Description" name="Description">描述</h2>

<p>该方法通常是由 JavaScript 引擎在内部隐式调用的，而不是由用户在代码中显式调用的。</p>

<h2 id="Examples" name="Examples">示例</h2>

<pre class="brush: js">var numObj = new Number(10);
console.log(typeof numObj); // object

var num = numObj.valueOf();
console.log(num);           // 10
console.log(typeof num);    // number
</pre>

<h2 id="规范">规范</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">规范名称</th>
   <th scope="col">规范状态</th>
   <th scope="col">备注</th>
  </tr>
  <tr>
   <td>ECMAScript 1st Edition.</td>
   <td>Standard</td>
   <td> </td>
  </tr>
  <tr>
   <td>{{SpecName('ES5.1', '#sec-15.7.4.4', 'Number.prototype.valueOf')}}</td>
   <td>{{Spec2('ES5.1')}}</td>
   <td> </td>
  </tr>
  <tr>
   <td>{{SpecName('ES6', '#sec-number.prototype.valueof', 'Number.prototype.valueOf')}}</td>
   <td>{{Spec2('ES6')}}</td>
   <td> </td>
  </tr>
 </tbody>
</table>

<h2 id="浏览器兼容性">浏览器兼容性</h2>

<div>{{CompatibilityTable}}</div>

<div id="compat-desktop">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Chrome</th>
   <th>Firefox (Gecko)</th>
   <th>Internet Explorer</th>
   <th>Opera</th>
   <th>Safari</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<div id="compat-mobile">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Android</th>
   <th>Chrome for Android</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>IE Mobile</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<h2 id="See_also" name="See_also">相关链接</h2>

<ul>
 <li>{{jsxref("Number.prototype.toSource()")}}</li>
</ul>