---
title: Map.prototype.keys()
slug: Web/JavaScript/Reference/Global_Objects/Map/keys
tags:
  - ECMAScript 2015
  - Iterator
  - JavaScript
  - Map
  - Method
  - Prototype
translation_of: Web/JavaScript/Reference/Global_Objects/Map/keys
original_slug: Web/JavaScript/Reference/Global_Objects/Map/keys
browser-compat: javascript.builtins.Map.keys
---
<div>{{JSRef}}</div>

<p><code><strong>keys()</strong></code> 返回一个引用的 <code><strong>Iterator</strong></code> 对象。它包含按照顺序插入 <code>Map</code> 对象中每个元素的key值。</p>

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



<h2 id="语法">语法</h2>

<pre class="syntaxbox notranslate"><code><em>myMap</em>.keys()</code></pre>

<h3 id="返回值">返回值</h3>

<p>一个存在引用关系的 {{jsxref("Map")}} iterator 对象.</p>

<h2 id="例子">例子</h2>

<h3 id="使用_keys">使用 <code>keys()</code></h3>

<pre class="brush:js notranslate">var myMap = new Map();
myMap.set("0", "foo");
myMap.set(1, "bar");
myMap.set({}, "baz");

var mapIter = myMap.keys();

console.log(mapIter.next().value); // "0"
console.log(mapIter.next().value); // 1
console.log(mapIter.next().value); // Object
</pre>

<h2 id="规范">规范</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">规范</th>
   <th scope="col">状态</th>
   <th scope="col">备注</th>
  </tr>
  <tr>
   <td>{{SpecName('ES2015', '#sec-map.prototype.keys', 'Map.prototype.keys')}}</td>
   <td>{{Spec2('ES2015')}}</td>
   <td>Initial definition.</td>
  </tr>
  <tr>
   <td>{{SpecName('ESDraft', '#sec-map.prototype.keys', 'Map.prototype.keys')}}</td>
   <td>{{Spec2('ESDraft')}}</td>
   <td></td>
  </tr>
 </tbody>
</table>

<h2 id="浏览器兼容性">浏览器兼容性</h2>



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

<h2 id="参见">参见</h2>

<ul>
 <li>{{jsxref("Map.prototype.entries()")}}</li>
 <li>{{jsxref("Map.prototype.values()")}}</li>
</ul>