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155 lines
14 KiB
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<article id="wikiArticle">
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<div></div>
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<div><code><strong>Object.entries()</strong></code>方法返回一个给定对象自身可枚举属性的键值对数组，其排列与使用 <a href="Reference/Statements/for...in" title="for...in语句以任意顺序遍历一个对象的可枚举属性。对于每个不同的属性，语句都会被执行。"><code>for...in</code></a> 循环遍历该对象时返回的顺序一致（区别在于 for-in 循环也枚举原型链中的属性）。</div>
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<div><iframe class="interactive interactive-js" frameborder="0" height="250" src="https://interactive-examples.mdn.mozilla.net/pages/js/object-entries.html" width="100%"></iframe></div>
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<p class="hidden">The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone <a class="external" href="https://github.com/mdn/interactive-examples" rel="noopener">https://github.com/mdn/interactive-examples</a> and send us a pull request.</p>
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<h2 id="语法">语法</h2>
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<pre><code class="language-javascript">Object.entries(<var>obj</var>)</code></pre>
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<h3 id="参数">参数</h3>
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<dl>
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<dt><code>obj</code></dt>
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<dd>可以返回其可枚举属性的键值对的对象。</dd>
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</dl>
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<h3 id="返回值">返回值</h3>
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<dl>
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<dd>给定对象自身可枚举属性的键值对数组。</dd>
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</dl>
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<h2 id="描述">描述</h2>
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<p><code>Object.entries()</code>返回一个数组，其元素是与直接在<code>object</code>上找到的可枚举属性键值对相对应的数组。属性的顺序与通过手动循环对象的属性值所给出的顺序相同。</p>
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<h2 id="示例">示例</h2>
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<pre><code class="language-javascript">const obj = { foo: 'bar', baz: 42 };
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console.log(Object.entries(obj)); // [ ['foo', 'bar'], ['baz', 42] ]
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// array like object
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const obj = { 0: 'a', 1: 'b', 2: 'c' };
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console.log(Object.entries(obj)); // [ ['0', 'a'], ['1', 'b'], ['2', 'c'] ]
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// array like object with random key ordering
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const anObj = { 100: 'a', 2: 'b', 7: 'c' };
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console.log(Object.entries(anObj)); // [ ['2', 'b'], ['7', 'c'], ['100', 'a'] ]
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// getFoo is property which isn't enumerable
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const myObj = Object.create({}, { getFoo: { value() { return this.foo; } } });
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myObj.foo = 'bar';
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console.log(Object.entries(myObj)); // [ ['foo', 'bar'] ]
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// non-object argument will be coerced to an object
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console.log(Object.entries('foo')); // [ ['0', 'f'], ['1', 'o'], ['2', 'o'] ]
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// iterate through key-value gracefully
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const obj = { a: 5, b: 7, c: 9 };
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for (const [key, value] of Object.entries(obj)) {
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console.log(`${key} ${value}`); // "a 5", "b 7", "c 9"
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}
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// Or, using array extras
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Object.entries(obj).forEach(([key, value]) => {
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console.log(`${key} ${value}`); // "a 5", "b 7", "c 9"
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});</code></pre>
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<h3 id="将Object转换为Map">将<code>Object</code>转换为<code>Map</code></h3>
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<p><a href="Reference/Map" title="此页面仍未被本地化, 期待您的翻译!"><code>new Map()</code></a> 构造函数接受一个可迭代的<code>entries</code>。借助<code>Object.entries</code>方法你可以很容易的将<a href="Reference/Global_Objects/Object" title="Object 构造函数创建一个对象包装器。"><code>Object</code></a>转换为<a href="Reference/Map" title="此页面仍未被本地化, 期待您的翻译!"><code>Map</code></a>:</p>
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<pre><code class="language-javascript">var obj = { foo: "bar", baz: 42 };
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var map = new Map(Object.entries(obj));
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console.log(map); // Map { foo: "bar", baz: 42 }</code></pre>
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<h2 id="Polyfill">Polyfill</h2>
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<p>要在较旧环境中添加兼容的<code>Object.entries</code>支持，你可以在 <a class="external" href="https://github.com/tc39/proposal-object-values-entries" rel="noopener">tc39/proposal-object-values-entries</a> 中找到Object.entries的示例（如果你不需要任何对IE的支持），在 <a class="external" href="https://github.com/es-shims/Object.entries" rel="noopener">es-shims/Object.entries</a> 资料库中的一个polyfill，或者你可以使用下面列出的简易 polyfill。</p>
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<pre><code class="language-javascript">if (!Object.entries)
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Object.entries = function( obj ){
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var ownProps = Object.keys( obj ),
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i = ownProps.length,
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resArray = new Array(i); // preallocate the Array
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while (i--)
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resArray[i] = [ownProps[i], obj[ownProps[i]]];
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return resArray;
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};</code></pre>
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<p>对于上述 polyfill 代码片段，如果你需要 IE9 以下的支持，那么你还需要一个 Object.keys polyfill（如 <a href="Reference/Global_Objects/Object/keys" title="Object.keys() 方法会返回一个由一个给定对象的自身可枚举属性组成的数组，数组中属性名的排列顺序和使用 for...in 循环遍历该对象时返回的顺序一致 。"><code>Object.keys</code></a>页面上的）。</p>
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<h2 id="规范">规范</h2>
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<table class="standard-table">
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<tbody>
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<tr>
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<th scope="col">Specification</th>
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<th scope="col">Status</th>
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<th scope="col">Comment</th>
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</tr>
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<tr>
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<td><a class="external" href="https://tc39.github.io/ecma262/#sec-object.entries" hreflang="en" lang="en" rel="noopener">ECMAScript Latest Draft (ECMA-262)<br/><small lang="zh-CN">Object.entries</small></a></td>
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<td><span class="spec-Draft">Draft</span></td>
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<td>Initial definition.</td>
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</tr>
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<tr>
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<td><a class="external" href="https://www.ecma-international.org/ecma-262/8.0/#sec-object.entries" hreflang="en" lang="en" rel="noopener">ECMAScript 2017 (ECMA-262)<br/><small lang="zh-CN">Object.entries</small></a></td>
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<td><span class="spec-Standard">Standard</span></td>
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<td> </td>
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</tr>
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</tbody>
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</table>
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<h2 id="浏览器兼容">浏览器兼容</h2>
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<div class="hidden">The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out <a class="external" href="https://github.com/mdn/browser-compat-data" rel="noopener">https://github.com/mdn/browser-compat-data</a> and send us a pull request.</div>
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<p></p><div class="bc-data"><a class="bc-github-link external" href="https://github.com/mdn/browser-compat-data" rel="noopener">Update compatibility data on GitHub</a><table class="bc-table bc-table-js"><thead><tr class="bc-platforms"><td></td><th class="bc-platform-desktop" colspan="6"><span>Desktop</span></th><th class="bc-platform-mobile" colspan="7"><span>Mobile</span></th><th class="bc-platform-server" colspan="1"><span>Server</span></th></tr><tr class="bc-browsers"><td></td><th class="bc-browser-chrome"><span class="bc-head-txt-label bc-head-icon-chrome">Chrome</span></th><th class="bc-browser-edge"><span class="bc-head-txt-label bc-head-icon-edge">Edge</span></th><th class="bc-browser-firefox"><span class="bc-head-txt-label bc-head-icon-firefox">Firefox</span></th><th class="bc-browser-ie"><span class="bc-head-txt-label bc-head-icon-ie">Internet Explorer</span></th><th class="bc-browser-opera"><span class="bc-head-txt-label bc-head-icon-opera">Opera</span></th><th class="bc-browser-safari"><span class="bc-head-txt-label bc-head-icon-safari">Safari</span></th><th class="bc-browser-webview_android"><span class="bc-head-txt-label bc-head-icon-webview_android">Android webview</span></th><th class="bc-browser-chrome_android"><span class="bc-head-txt-label bc-head-icon-chrome_android">Chrome for Android</span></th><th class="bc-browser-edge_mobile"><span class="bc-head-txt-label bc-head-icon-edge_mobile">Edge Mobile</span></th><th class="bc-browser-firefox_android"><span class="bc-head-txt-label bc-head-icon-firefox_android">Firefox for Android</span></th><th class="bc-browser-opera_android"><span class="bc-head-txt-label bc-head-icon-opera_android">Opera for Android</span></th><th class="bc-browser-safari_ios"><span class="bc-head-txt-label bc-head-icon-safari_ios">Safari on iOS</span></th><th class="bc-browser-samsunginternet_android"><span class="bc-head-txt-label bc-head-icon-samsunginternet_android">Samsung Internet</span></th><th class="bc-browser-nodejs"><span class="bc-head-txt-label bc-head-icon-nodejs">Node.js</span></th></tr></thead><tbody><tr><th scope="row"><code>entries</code></th><td class="bc-supports-yes bc-browser-chrome"><span class="bc-browser-name">Chrome</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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54</td><td class="bc-supports-yes bc-browser-edge"><span class="bc-browser-name">Edge</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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14</td><td class="bc-supports-yes bc-browser-firefox"><span class="bc-browser-name">Firefox</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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47</td><td class="bc-supports-no bc-browser-ie"><span class="bc-browser-name">IE</span><abbr class="bc-level-no only-icon" title="No support">
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<span>No support</span>
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</abbr>
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No</td><td class="bc-supports-yes bc-browser-opera"><span class="bc-browser-name">Opera</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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41</td><td class="bc-supports-yes bc-browser-safari"><span class="bc-browser-name">Safari</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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10.1</td><td class="bc-supports-yes bc-browser-webview_android"><span class="bc-browser-name">WebView Android</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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54</td><td class="bc-supports-yes bc-browser-chrome_android"><span class="bc-browser-name">Chrome Android</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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54</td><td class="bc-supports-yes bc-browser-edge_mobile"><span class="bc-browser-name">Edge Mobile</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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Yes</td><td class="bc-supports-yes bc-browser-firefox_android"><span class="bc-browser-name">Firefox Android</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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47</td><td class="bc-supports-yes bc-browser-opera_android"><span class="bc-browser-name">Opera Android</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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41</td><td class="bc-supports-yes bc-browser-safari_ios"><span class="bc-browser-name">Safari iOS</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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10.1</td><td class="bc-supports-yes bc-browser-samsunginternet_android"><span class="bc-browser-name">Samsung Internet Android</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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6.0</td><td class="bc-supports-yes bc-browser-nodejs bc-has-history"><span class="bc-browser-name">nodejs</span><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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7.0.0<div class="bc-icons"></div><section class="bc-history" id="sect1"><dl><dt class="bc-supports-yes bc-supports"><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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7.0.0<div class="bc-icons"></div></dt><dd></dd><dt class="bc-supports-yes bc-supports"><abbr class="bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr>
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6.5.0<div class="bc-icons"><abbr class="only-icon" title="User must explicitly enable this feature."><span>Disabled</span><i class="ic-disabled"></i></abbr> </div></dt><dd><abbr class="only-icon" title="User must explicitly enable this feature."><span>Disabled</span><i class="ic-disabled"></i></abbr> From version 6.5.0: this feature is behind the <code>--harmony</code> runtime flag.</dd></dl></section></td></tr></tbody></table><section class="bc-legend" id="sect2"><h3 class="offscreen" id="Legend">Legend</h3><dl><dt><span class="bc-supports-yes bc-supports">
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<abbr class="bc-level bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr></span></dt><dd>Full support</dd><dt><span class="bc-supports-no bc-supports">
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<abbr class="bc-level bc-level-no only-icon" title="No support">
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<span>No support</span>
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</abbr></span></dt><dd>No support</dd><dt><abbr class="only-icon" title="User must explicitly enable this feature."><span>User must explicitly enable this feature.</span><i class="ic-disabled"></i></abbr></dt><dd>User must explicitly enable this feature.</dd></dl></section></div><p></p>
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<h2 id="相关链接">相关链接</h2>
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<ul>
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<li><a href="Enumerability_and_ownership_of_properties">属性的可枚举性和所有权</a></li>
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<li><a href="Reference/Global_Objects/Object/keys" title="Object.keys() 方法会返回一个由一个给定对象的自身可枚举属性组成的数组，数组中属性名的排列顺序和使用 for...in 循环遍历该对象时返回的顺序一致 。"><code>Object.keys()</code></a></li>
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<li><a href="Reference/Global_Objects/Object/values" title="Object.values()方法返回一个给定对象自身的所有可枚举属性值的数组，值的顺序与使用for...in循环的顺序相同 ( 区别在于 for-in 循环枚举原型链中的属性 )。"><code>Object.values()</code></a> <span title="这是一个实验性的 API，请尽量不要在生产环境中使用它。"><i class="icon-beaker"> </i></span></li>
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<li><a href="Reference/Global_Objects/Object/propertyIsEnumerable" title="propertyIsEnumerable() 方法返回一个布尔值，表示指定的属性是否可枚举。"><code>Object.prototype.propertyIsEnumerable()</code></a></li>
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<li><a href="Reference/Global_Objects/Object/create" title="Object.create()方法创建一个新对象，使用现有的对象来提供新创建的对象的__proto__。 （请打开浏览器控制台以查看运行结果。）"><code>Object.create()</code></a></li>
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<li><a href="Reference/Global_Objects/Object/getOwnPropertyNames" title="Object.getOwnPropertyNames()方法返回一个由指定对象的所有自身属性的属性名（包括不可枚举属性但不包括Symbol值作为名称的属性）组成的数组。"><code>Object.getOwnPropertyNames()</code></a></li>
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</ul>
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</article> |