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118 lines
5.0 KiB
HTML
<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>.has()</code></strong> 作用与 <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/in"><code>in</code> 操作符</a> 相同。</p>
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<h2 id="句法">句法</h2>
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<pre><code class="language-javascript">Reflect.has(target, propertyKey)
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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>目标对象.</dd>
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<dt><code>propertyKey</code></dt>
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<dd>属性名，需要检查目标对象是否存在此属性。</dd>
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</dl>
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<h3 id="返回值">返回值</h3>
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<p>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> 类型的对象指示是否存在此属性。</p>
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<h3 id="异常">异常</h3>
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<p>如果目标对象并非<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> 类型，抛出<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>。</p>
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<h2 id="描述">描述</h2>
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<p><code>Reflect.has</code> 用于检查一个对象是否拥有某个属性， 相当于<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/in"><code>in</code> 操作符</a> 。</p>
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<h2 id="示例">示例</h2>
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<h3 id="使用_Reflect.has()">使用 <code>Reflect.has()</code></h3>
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<pre><code class="language-javascript">Reflect.has({x: 0}, "x"); // true
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Reflect.has({x: 0}, "y"); // false
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// 如果该属性存在于原型链中，返回true
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Reflect.has({x: 0}, "toString");
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// Proxy 对象的 .has() 句柄方法
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obj = new Proxy({}, {
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has(t, k) { return k.startsWith("door"); }
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});
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Reflect.has(obj, "doorbell"); // true
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Reflect.has(obj, "dormitory"); // false
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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.has" hreflang="en" lang="en" rel="noopener">ECMAScript 2015 (6th Edition, ECMA-262)<br/><small lang="zh-CN">Reflect.has</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.has" hreflang="en" lang="en" rel="noopener">ECMAScript Latest Draft (ECMA-262)<br/><small lang="zh-CN">Reflect.has</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="blockIndicator warning"><strong><a class="external" href="https://github.com/mdn/browser-compat-data" rel="noopener">We're converting our compatibility data into a machine-readable JSON format</a></strong>.
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This compatibility table still uses the old format,
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because we haven't yet converted the data it contains.
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<strong><a class="new" href="/zh-CN/docs/MDN/Contribute/Structures/Compatibility_tables" rel="nofollow">Find out how you can help!</a></strong></div>
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<div class="htab">
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<a id="AutoCompatibilityTable" name="AutoCompatibilityTable"></a>
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<ul>
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<li class="selected"><a>Desktop</a></li>
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<li><a>Mobile</a></li>
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</ul>
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</div><p></p>
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<div id="compat-desktop">
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<table class="compat-table">
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<tbody>
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<tr>
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<th>Feature</th>
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<th>Chrome</th>
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<th>Firefox (Gecko)</th>
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<th>Internet Explorer</th>
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<th>Opera</th>
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<th>Safari</th>
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</tr>
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<tr>
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<td>Basic support</td>
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<td>49</td>
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<td><a href="/en-US/Firefox/Releases/42" title="Released on 2015-11-03.">42</a> (42)</td>
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<td><span style="color: #f00;">未实现</span></td>
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<td><span style="color: #f00;">未实现</span></td>
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<td><span style="color: #f00;">未实现</span></td>
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</tr>
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</tbody>
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</table>
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</div>
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<div id="compat-mobile">
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<table class="compat-table">
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<tbody>
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<tr>
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<th>Feature</th>
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<th>Android</th>
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<th>Chrome for Android</th>
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<th>Firefox Mobile (Gecko)</th>
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<th>IE Mobile</th>
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<th>Opera Mobile</th>
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<th>Safari Mobile</th>
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</tr>
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<tr>
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<td>Basic support</td>
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<td><span style="color: #f00;">未实现</span></td>
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<td><span style="color: #f00;">未实现</span></td>
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<td>42.0 (42)</td>
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<td><span style="color: #f00;">未实现</span></td>
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<td><span style="color: #f00;">未实现</span></td>
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<td><span style="color: #f00;">未实现</span></td>
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</tr>
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</tbody>
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</table>
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</div>
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<h2 id="相关连接">相关连接</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="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/in"><code>in</code> operator</a></li>
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</ul>
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</article> |