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114 lines
10 KiB
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<article id="wikiArticle">
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<div></div>
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<p>静态方法 <code><strong>Reflect</strong></code><strong><code>.preventExtensions()</code></strong> 方法阻止新属性添加到对象 例如：防止将来对对象的扩展被添加到对象中)。该方法与 <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>相似，但有一些不同点。详情可见 <a href="#Difference_to_Object.preventExtensions()">differences</a>。</p>
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<h2 id="语法">语法</h2>
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<pre><code class="language-javascript">Reflect.preventExtensions(target)
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</code></pre>
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<h3 id="参数">参数</h3>
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<dl>
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<dt><code>target</code></dt>
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<dd>阻止扩展的目标对象。</dd>
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</dl>
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<h3 id="返回值">返回值</h3>
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<p>返回一个 <a href="Reference/Boolean" title="此页面仍未被本地化, 期待您的翻译!"><code>Boolean</code></a> 值表明目标对象是否成功被设置为不可扩展。</p>
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<h3 id="异常">异常</h3>
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<p>抛出一个 <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> 错误，如果对象不是 <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>。</p>
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<h2 id="描述">描述</h2>
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<p><code>Reflect.preventExtensions</code> 方法阻止新属性添加到对象 例如：防止将来对对象的扩展被添加到对象中)。该方法与 <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> 方法一致。</p>
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<h2 id="示例">示例</h2>
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<h3 id="使用_Reflect.preventExtensions()">使用 <code>Reflect.preventExtensions()</code></h3>
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<p>详情可见 <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>.</p>
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<pre><code class="language-javascript">// Objects are extensible by default.
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var empty = {};
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Reflect.isExtensible(empty); // === true
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// ...but that can be changed.
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Reflect.preventExtensions(empty);
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Reflect.isExtensible(empty); // === false
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</code></pre>
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<h3 id="与_Object.preventExtensions()_的不同点">与 <code>Object.preventExtensions()</code> 的不同点</h3>
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<p>如果该方法的第一个参数不是一个对象（原始值），那么将造成一个 <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> 异常。 对于<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> 方法， 非对象的第一个参数将被强制转换为对象。</p>
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<pre><code class="language-javascript">Reflect.preventExtensions(1);
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// TypeError: 1 is not an object
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Object.preventExtensions(1);
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// 1
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</code></pre>
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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://www.ecma-international.org/ecma-262/6.0/#sec-reflect.preventextensions" hreflang="en" lang="en" rel="noopener">ECMAScript 2015 (6th Edition, ECMA-262)<br/><small lang="zh-CN">Reflect.preventExtensions</small></a></td>
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<td><span class="spec-Standard">Standard</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://tc39.github.io/ecma262/#sec-reflect.preventextensions" hreflang="en" lang="en" rel="noopener">ECMAScript Latest Draft (ECMA-262)<br/><small lang="zh-CN">Reflect.preventExtensions</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="浏览器兼容性">浏览器兼容性</h2>
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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>preventExtensions</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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49</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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42</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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36</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</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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49</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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49</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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42</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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36</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</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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5.0</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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6.0.0</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><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></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/Reflect" title="Reflect 是一个内置的对象，它提供拦截 JavaScript 操作的方法。这些方法与处理器对象的方法相同。Reflect不是一个函数对象，因此它是不可构造的。"><code>Reflect</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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</ul>
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</article> |