---
title: Array.prototype.keys()
slug: Web/JavaScript/Reference/Global_Objects/Array/keys
tags:
  - Array
  - ECMAScript 2015
  - Iterator
  - JavaScript
  - Method
  - Prototype
translation_of: Web/JavaScript/Reference/Global_Objects/Array/keys
---
<div>{{JSRef}}</div>

<p> <code><strong>keys() </strong></code>方法返回一个包含数组中每个索引键的<code><strong>Array Iterator</strong></code>对象。</p>

<div>{{EmbedInteractiveExample("pages/js/array-keys.html")}}</div>

<h2 id="Syntax" name="Syntax">语法</h2>

<pre class="syntaxbox"><code><var>arr</var>.keys()</code>
</pre>

<h3 id="返回值">返回值 </h3>

<p>一个新的 {{jsxref("Array")}} 迭代器对象。</p>

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

<h3 id="索引迭代器会包含那些没有对应元素的索引">索引迭代器会包含那些没有对应元素的索引</h3>

<pre class="brush: js">var arr = ["a", , "c"];
var sparseKeys = Object.keys(arr);
var denseKeys = [...arr.keys()];
console.log(sparseKeys); // ['0', '2']
console.log(denseKeys);  // [0, 1, 2]
</pre>

<h2 id="Specifications" name="Specifications">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('ES2015', '#sec-array.prototype.keys', 'Array.prototype.keys')}}</td>
   <td>{{Spec2('ES2015')}}</td>
   <td>Initial definition.</td>
  </tr>
  <tr>
   <td>{{SpecName('ESDraft', '#sec-array.prototype.keys', 'Array.prototype.keys')}}</td>
   <td>{{Spec2('ESDraft')}}</td>
   <td> </td>
  </tr>
 </tbody>
</table>

<h2 id="Browser_compatibility" name="Browser_compatibility">浏览器兼容性</h2>

<div>
<div>


<p>{{Compat("javascript.builtins.Array.keys")}}</p>
</div>
</div>

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

<ul>
 <li>{{jsxref("Array.prototype.values()")}}</li>
 <li>{{jsxref("Array.prototype.entries()")}}</li>
 <li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols">Iteration protocols</a></li>
</ul>