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authorPeter Bengtsson <mail@peterbe.com>2020-12-08 14:40:17 -0500
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+---
+title: Object.isSealed()
+slug: Web/JavaScript/Reference/Global_Objects/Object/isSealed
+tags:
+ - ECMAScript5
+ - JavaScript
+ - Method
+ - Object
+translation_of: Web/JavaScript/Reference/Global_Objects/Object/isSealed
+---
+<div>{{JSRef}}</div>
+
+<p><strong><code>Object.isSealed()</code></strong> 方法判断一个对象是否被密封。</p>
+
+<h2 id="语法">语法</h2>
+
+<pre class="syntaxbox notranslate"><code>Object.isSealed(<em>obj</em>)</code></pre>
+
+<h3 id="参数">参数</h3>
+
+<dl>
+ <dt><code>obj</code></dt>
+ <dd>要被检查的对象。</dd>
+</dl>
+
+<h3 id="返回值">返回值</h3>
+
+<p>表示给定对象是否被密封的一个{{jsxref("Boolean")}} 。</p>
+
+<h2 id="描述">描述</h2>
+
+<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 {{jsxref("Object.isExtensible", "扩展")}} 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>
+
+<h2 id="Examples" name="Examples">例子</h2>
+
+<pre class="brush: js notranslate">// 新建的对象默认不是密封的.
+var empty = {};
+Object.isSealed(empty); // === false
+
+// 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.
+Object.preventExtensions(empty);
+Object.isSealed(empty); // === true
+
+// 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.
+var hasProp = { fee: "fie foe fum" };
+Object.preventExtensions(hasProp);
+Object.isSealed(hasProp); // === false
+
+// 如果把这个属性变的不可配置,则这个属性也就成了密封对象.
+Object.defineProperty(hasProp, "fee", { configurable: false });
+Object.isSealed(hasProp); // === false
+Object.isSealed(hasProp.fee); // === true
+
+// 最简单的方法来生成一个密封对象,当然是使用Object.seal.
+var sealed = {};
+Object.seal(sealed);
+Object.isSealed(sealed); // === true
+
+// 一个密封对象同时也是不可扩展的.
+Object.isExtensible(sealed); // === false
+
+// 一个密封对象也可以是一个冻结对象,但不是必须的.
+Object.isFrozen(sealed); // === true ,所有的属性都是不可写的
+var s2 = Object.seal({ p: 3 });
+Object.isFrozen(s2); // === false, 属性"p"可写
+
+var s3 = Object.seal({ get p() { return 0; } });
+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</pre>
+
+<h2 id="注意" style="margin-bottom: 20px; line-height: 30px;">注意</h2>
+
+<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{{jsxref("TypeError")}}。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>
+
+<pre class="brush: js notranslate">Object.isSealed(1);
+// TypeError: 1 is not an object (ES5 code)
+
+Object.isSealed(1);
+// true (ES2015 code)</pre>
+
+<h2 id="规范" style="margin-bottom: 20px; line-height: 30px;">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('ES5.1', '#sec-15.2.3.11', 'Object.isSealed')}}</td>
+ <td>{{Spec2('ES5.1')}}</td>
+ <td>Initial definition.<br>
+ Implemented in JavaScript 1.8.5</td>
+ </tr>
+ <tr>
+ <td>{{SpecName('ES6', '#sec-object.issealed', 'Object.isSealed')}}</td>
+ <td>{{Spec2('ES6')}}</td>
+ <td></td>
+ </tr>
+ <tr>
+ <td>{{SpecName('ESDraft', '#sec-object.issealed', 'Object.isSealed')}}</td>
+ <td>{{Spec2('ESDraft')}}</td>
+ <td></td>
+ </tr>
+ </tbody>
+</table>
+
+<h2 id="浏览器兼容">浏览器兼容</h2>
+
+<div class="hidden">
+<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 href="https://github.com/mdn/browser-compat-data">https://github.com/mdn/browser-compat-data</a> and send us a pull request.</p>
+</div>
+
+<p>{{Compat("javascript.builtins.Object.isSealed")}}</p>
+
+<h2 id="相关链接">相关链接</h2>
+
+<ul>
+ <li>{{jsxref("Object.seal()")}}</li>
+ <li>{{jsxref("Object.preventExtensions()")}}</li>
+ <li>{{jsxref("Object.isExtensible()")}}</li>
+ <li>{{jsxref("Object.freeze()")}}</li>
+ <li>{{jsxref("Object.isFrozen()")}}</li>
+</ul>