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140 lines
12 KiB
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<article id="wikiArticle">
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<div></div>
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<p><strong><code>Object.isSealed()</code></strong> 方法判断一个对象是否被密封。</p>
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<h2 id="语法">语法</h2>
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<pre><code class="language-javascript"><code>Object.isSealed(<em>obj</em>)</code></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>要被检查的对象。</dd>
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</dl>
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<h3 id="返回值">返回值</h3>
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<p>表示给定对象是否被密封的一个<a href="Reference/Boolean" title="此页面仍未被本地化, 期待您的翻译!"><code>Boolean</code></a> 。</p>
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<h2 id="描述">描述</h2>
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<p>如果这个对象是密封的，则返回 <code>true</code>，否则返回 <code>false</code>。密封对象是指那些不可 <a href="Reference/Global_Objects/Object/isExtensible" title="Object.isExtensible() 方法判断一个对象是否是可扩展的（是否可以在它上面添加新的属性）。"><code>扩展</code></a> 的，且所有自身属性都不可配置且因此不可删除（但不一定是不可写）的对象。</p>
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<h2 id="Examples" name="Examples">例子</h2>
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<pre><code class="language-javascript">// 新建的对象默认不是密封的.
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var empty = {};
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Object.isSealed(empty); // === false
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// 如果你把一个空对象变的不可扩展,则它同时也会变成个密封对象.
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Object.preventExtensions(empty);
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Object.isSealed(empty); // === true
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// 但如果这个对象不是空对象,则它不会变成密封对象,因为密封对象的所有自身属性必须是不可配置的.
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var hasProp = { fee: "fie foe fum" };
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Object.preventExtensions(hasProp);
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Object.isSealed(hasProp); // === false
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// 如果把这个属性变的不可配置,则这个对象也就成了密封对象.
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Object.defineProperty(hasProp, "fee", { configurable: false });
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Object.isSealed(hasProp); // === true
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// 最简单的方法来生成一个密封对象,当然是使用Object.seal.
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var sealed = {};
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Object.seal(sealed);
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Object.isSealed(sealed); // === true
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// 一个密封对象同时也是不可扩展的.
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Object.isExtensible(sealed); // === false
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// 一个密封对象也可以是一个冻结对象,但不是必须的.
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Object.isFrozen(sealed); // === true ，所有的属性都是不可写的
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var s2 = Object.seal({ p: 3 });
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Object.isFrozen(s2); // === false， 属性"p"可写
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var s3 = Object.seal({ get p() { return 0; } });
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Object.isFrozen(s3); // === true ，访问器属性不考虑可写不可写,只考虑是否可配置</code></pre>
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<h2 id="注意" style="margin-bottom: 20px; line-height: 30px;">注意</h2>
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<p>在ES5中，如果这个方法的参数不是一个对象（一个原始类型），那么它会导致<a href="Reference/Global_Objects/TypeError" title="TypeError（类型错误） 对象用来表示值的类型非预期类型时发生的错误。"><code>TypeError</code></a>。在ES2015中，非对象参数将被视为是一个密封的普通对象，只返回<code>true</code>。</p>
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<pre><code class="language-javascript">Object.isSealed(1);
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// TypeError: 1 is not an object (ES5 code)
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Object.isSealed(1);
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// true (ES2015 code)</code></pre>
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<h2 id="规范" style="margin-bottom: 20px; line-height: 30px;">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://www.ecma-international.org/ecma-262/5.1/#sec-15.2.3.11" hreflang="en" lang="en" rel="noopener">ECMAScript 5.1 (ECMA-262)<br/><small lang="zh-CN">Object.isSealed</small></a></td>
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<td><span class="spec-Standard">Standard</span></td>
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<td>Initial definition.<br/>
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Implemented in JavaScript 1.8.5</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-262/6.0/#sec-object.issealed" hreflang="en" lang="en" rel="noopener">ECMAScript 2015 (6th Edition, ECMA-262)<br/><small lang="zh-CN">Object.isSealed</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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<tr>
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<td><a class="external" href="https://tc39.github.io/ecma262/#sec-object.issealed" hreflang="en" lang="en" rel="noopener">ECMAScript Latest Draft (ECMA-262)<br/><small lang="zh-CN">Object.isSealed</small></a></td>
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<td><span class="spec-Draft">Draft</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">
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<p>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.</p>
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</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>isSealed</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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6</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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12</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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4</td><td class="bc-supports-yes bc-browser-ie"><span class="bc-browser-name">IE</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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9</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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12</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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5.1</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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Yes</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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Yes</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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4</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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Yes</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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Yes</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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Yes</td><td class="bc-supports-yes bc-browser-nodejs"><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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Yes</td></tr></tbody></table><section class="bc-legend" id="sect1"><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></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="Reference/Global_Objects/Object/seal" title="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 https://github.com/mdn/interactive-examples and send us a pull request."><code>Object.seal()</code></a></li>
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<li><a href="Reference/Global_Objects/Object/preventExtensions" title="Object.preventExtensions()方法让一个对象变的不可扩展，也就是永远不能再添加新的属性。"><code>Object.preventExtensions()</code></a></li>
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<li><a href="Reference/Global_Objects/Object/isExtensible" title="Object.isExtensible() 方法判断一个对象是否是可扩展的（是否可以在它上面添加新的属性）。"><code>Object.isExtensible()</code></a></li>
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<li><a href="Reference/Global_Objects/Object/freeze" title="Object.freeze() 方法可以冻结一个对象。一个被冻结的对象再也不能被修改；冻结了一个对象则不能向这个对象添加新的属性，不能删除已有属性，不能修改该对象已有属性的可枚举性、可配置性、可写性，以及不能修改已有属性的值。此外，冻结一个对象后该对象的原型也不能被修改。freeze() 返回和传入的参数相同的对象。"><code>Object.freeze()</code></a></li>
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<li><a href="Reference/Global_Objects/Object/isFrozen" title="Object.isFrozen()方法判断一个对象是否被冻结。"><code>Object.isFrozen()</code></a></li>
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</ul>
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</article> |