---
title: Math.sign()
slug: Web/JavaScript/Reference/Global_Objects/Math/sign
tags:
  - JavaScript
  - Math
  - Math.sign()
translation_of: Web/JavaScript/Reference/Global_Objects/Math/sign
---
<div>{{JSRef}}</div>

<div> </div>

<p><strong><code>Math.sign()</code></strong> 函数返回一个数字的符号, 指示数字是正数，负数还是零。</p>

<h2 id="Syntax" name="Syntax">语法</h2>

<pre class="syntaxbox"><code>Math.sign(<em>x</em>);</code></pre>

<h3 id="Parameters" name="Parameters">参数</h3>

<dl>
 <dt><code>x</code></dt>
 <dd>任意数字.</dd>
</dl>

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

<p>因为 <code>sign </code>是 <code>Math </code>的一个静态方法，所以你应该使用 Math.sign() ，而不是作为你创建的一个Math对象的一种方法 （Math不是一个构造函数）。</p>

<p>而不是作为您创建的Math对象的一种方法（Math不是构造函数）。</p>

<p>此函数共有5种返回值, 分别是<strong> 1, -1, 0, -0, NaN.</strong> 代表的各是<strong>正数, 负数, 正零, 负零, NaN</strong>。</p>

<p>传入该函数的参数会被<strong>隐式转换</strong>成数字类型。</p>

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

<h3 id="使用Math.sign()">使用Math.sign()</h3>

<pre class="brush:js">Math.sign(3);     //  1
Math.sign(-3);    // -1
Math.sign("-3");  // -1
Math.sign(0);     //  0
Math.sign(-0);    // -0
Math.sign(NaN);   // NaN
Math.sign("foo"); // NaN
Math.sign();      // NaN
</pre>

<h2 id="Compatibility" name="Compatibility">Polyfill</h2>

<pre class="brush: js  language-js"><code class="language-js"><span class="keyword token">function</span> <span class="function token">sign<span class="punctuation token">(</span></span>x<span class="punctuation token">)</span> <span class="punctuation token">{</span>
    x <span class="operator token">=</span> <span class="operator token">+</span>x<span class="comment token"> ;// convert to a number
</span>    <span class="keyword token">if</span> <span class="punctuation token">(</span>x <span class="operator token">===</span> <span class="number token">0</span> <span class="operator token">||</span> <span class="function token">isNaN<span class="punctuation token">(</span></span>x<span class="punctuation token">)</span><span class="punctuation token">)</span>
        <span class="keyword token">return</span> x;
    <span class="keyword token">return</span> x <span class="operator token">&gt;</span> <span class="number token">0</span> <span class="operator token">?</span> <span class="number token">1</span> <span class="punctuation token">:</span> <span class="operator token">-</span><span class="number token">1;</span>
<span class="punctuation token">}</span></code></pre>

<p> </p>

<pre><code>if (!Math.sign) {
  Math.sign = function(x) {
    // If x is NaN, the result is NaN.
    // If x is -0, the result is -0.
    // If x is +0, the result is +0.
    // If x is negative and not -0, the result is -1.
    // If x is positive and not +0, the result is +1.
    x = +x; // convert to a number
    if (x === 0 || isNaN(x)) {
      return Number(x);
    }
    return x &gt; 0 ? 1 : -1;
  };
}</code></pre>

<p> </p>

<h2 id="规范">规范</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
  <tr>
   <td>{{SpecName('ES6', '#sec-math.sign', 'Math.sign')}}</td>
   <td>{{Spec2('ES6')}}</td>
   <td>Initial definition.</td>
  </tr>
 </tbody>
</table>

<h2 id="浏览器兼容性">浏览器兼容性</h2>

<p>{{ CompatibilityTable() }}</p>

<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>38</td>
   <td>{{CompatGeckoDesktop("25")}}</td>
   <td>{{CompatNo}}</td>
   <td>25</td>
   <td>{{CompatNo}}</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>{{CompatNo}}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatGeckoMobile("25")}}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatNo}}</td>
  </tr>
 </tbody>
</table>
</div>

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

<ul>
 <li>{{jsxref("Global_Objects/Math", "Math")}} 对象</li>
</ul>