---
title: Math.atan2()
slug: Web/JavaScript/Reference/Global_Objects/Math/atan2
translation_of: Web/JavaScript/Reference/Global_Objects/Math/atan2
---
<div>{{JSRef("Global_Objects", "Math")}}</div>

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

<p><code><strong>Math.atan2(</strong></code><code><strong>)</strong></code> 返回从原点(0,0)到(x,y)点的线段与x轴正方向之间的平面角度(弧度值)，也就是Math.atan2(y,x)</p>

<h2 id="Syntax" name="Syntax">语法</h2>

<pre class="syntaxbox">Math.atan2(<em>y</em>, <em>x</em>) </pre>

<h2 id="Parameters" name="Parameters">参数</h2>

<dl>
 <dt><code>y, x</code></dt>
 <dd>数值</dd>
</dl>

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

<p><code>atan2</code> 方法返回一个 -pi 到 pi 之间的数值，表示点 (x, y) 对应的偏移角度。这是一个逆时针角度，以弧度为单位，正X轴和点 (x, y) 与原点连线 之间。注意此函数接受的参数：先传递 y 坐标，然后是 x 坐标。</p>

<p><code>atan2</code> 接受单独的 x 和 y 参数，而 <code>atan</code> 接受两个参数的比值。</p>

<p>由于 <code>atan2</code> 是 <code>Math</code> 的静态方法，所以应该像这样使用：<code>Math.atan2()</code>，而不是作为你创建的 <code>Math</code> 实例的方法。</p>

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

<h3 id="Example_Using_Math.atan2" name="Example:_Using_Math.atan2">例子：使用 <code>Math.atan2</code></h3>

<pre class="brush:js">Math.atan2(90, 15) // 1.4056476493802699
Math.atan2(15, 90) // 0.16514867741462683

<code>Math.atan2( ±0, -0 )</code>               // <code>±PI</code>.
<code>Math.atan2( ±0, +0 )</code>               // <code>±0</code>.
<code>Math.atan2( ±0, -x )</code>               // <code>±PI</code> for x &gt; 0.
<code>Math.atan2( ±0, x )</code>                // <code>±0</code> for x &gt; 0.
<code>Math.atan2( </code><code>-y, ±0 )</code>               // -<code>PI/2</code> for y &gt; 0.
<code>Math.atan2( </code><code>y, ±0 )</code>                // <code>PI/2</code> for y &gt; 0.
<code>Math.atan2( ±y, -Infinity )</code>        // <code>±PI</code> for finite y &gt; 0.
<code>Math.atan2( ±y, +Infinity )</code>        // <code>±0</code> for finite y &gt; 0.
<code>Math.atan2( ±Infinity, x )</code>         // <code>±PI/2</code> for finite x.
<code>Math.atan2( ±Infinity, -Infinity )</code> // <code>±3*PI/4</code>.
<code>Math.atan2( ±Infinity, +Infinity )</code> // <code>±PI/4</code>.
</pre>

<h2 id="规范">规范</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">规范版本</th>
   <th scope="col">规范状态</th>
   <th scope="col">注解</th>
  </tr>
  <tr>
   <td>ECMAScript 1st Edition. Implemented in JavaScript 1.0</td>
   <td>Standard</td>
   <td>Initial definition.</td>
  </tr>
  <tr>
   <td>{{SpecName('ES5.1', '#sec-15.8.2.5', 'Math.atan2')}}</td>
   <td>{{Spec2('ES5.1')}}</td>
   <td></td>
  </tr>
  <tr>
   <td>{{SpecName('ES6', '#sec-math.atan2', 'Math.atan2')}}</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>

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

<div>
<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>
<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>The {{jsxref("Global_Objects/Math", "Math")}} object it belongs to.</li>
 <li>{{jsxref("Math.acos()")}}</li>
 <li>{{jsxref("Math.asin()")}}</li>
 <li>{{jsxref("Math.atan()")}}</li>
 <li>{{jsxref("Math.cos()")}}</li>
 <li>{{jsxref("Math.sin()")}}</li>
 <li>{{jsxref("Math.tan()")}}</li>
</ul>