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authorPeter Bengtsson <mail@peterbe.com>2020-12-08 14:40:17 -0500
committerPeter Bengtsson <mail@peterbe.com>2020-12-08 14:40:17 -0500
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+---
+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>