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<article id="wikiArticle">
<div></div>
<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>
<h2 id="句法">句法</h2>
<pre><code class="language-javascript">Reflect.has(target, propertyKey)
</code></pre>
<h3 id="参数">参数</h3>
<dl>
<dt><code>target</code></dt>
<dd>目标对象.</dd>
<dt><code>propertyKey</code></dt>
<dd>属性名,需要检查目标对象是否存在此属性。</dd>
</dl>
<h3 id="返回值">返回值</h3>
<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>
<h3 id="异常">异常</h3>
<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>
<h2 id="描述">描述</h2>
<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>
<h2 id="示例">示例</h2>
<h3 id="使用_Reflect.has()">使用 <code>Reflect.has()</code></h3>
<pre><code class="language-javascript">Reflect.has({x: 0}, "x"); // true
Reflect.has({x: 0}, "y"); // false
// 如果该属性存在于原型链中返回true
Reflect.has({x: 0}, "toString");
// Proxy 对象的 .has() 句柄方法
obj = new Proxy({}, {
has(t, k) { return k.startsWith("door"); }
});
Reflect.has(obj, "doorbell"); // true
Reflect.has(obj, "dormitory"); // false
</code></pre>
<h2 id="规范">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><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>
<td><span class="spec-Standard">Standard</span></td>
<td>Initial definition.</td>
</tr>
<tr>
<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>
<td><span class="spec-Draft">Draft</span></td>
<td> </td>
</tr>
</tbody>
</table>
<h2 id="浏览器兼容性">浏览器兼容性</h2>
<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>.
This compatibility table still uses the old format,
because we haven't yet converted the data it contains.
<strong><a class="new" href="/zh-CN/docs/MDN/Contribute/Structures/Compatibility_tables" rel="nofollow">Find out how you can help!</a></strong></div>
<div class="htab">
<a id="AutoCompatibilityTable" name="AutoCompatibilityTable"></a>
<ul>
<li class="selected"><a>Desktop</a></li>
<li><a>Mobile</a></li>
</ul>
</div><p></p>
<div id="compat-desktop">
<table class="compat-table">
<tbody>
<tr>
<th>Feature</th>
<th>Chrome</th>
<th>Firefox (Gecko)</th>
<th>Internet Explorer</th>
<th>Opera</th>
<th>Safari</th>
</tr>
<tr>
<td>Basic support</td>
<td>49</td>
<td><a href="/en-US/Firefox/Releases/42" title="Released on 2015-11-03.">42</a> (42)</td>
<td><span style="color: #f00;">未实现</span></td>
<td><span style="color: #f00;">未实现</span></td>
<td><span style="color: #f00;">未实现</span></td>
</tr>
</tbody>
</table>
</div>
<div id="compat-mobile">
<table class="compat-table">
<tbody>
<tr>
<th>Feature</th>
<th>Android</th>
<th>Chrome for Android</th>
<th>Firefox Mobile (Gecko)</th>
<th>IE Mobile</th>
<th>Opera Mobile</th>
<th>Safari Mobile</th>
</tr>
<tr>
<td>Basic support</td>
<td><span style="color: #f00;">未实现</span></td>
<td><span style="color: #f00;">未实现</span></td>
<td>42.0 (42)</td>
<td><span style="color: #f00;">未实现</span></td>
<td><span style="color: #f00;">未实现</span></td>
<td><span style="color: #f00;">未实现</span></td>
</tr>
</tbody>
</table>
</div>
<h2 id="相关连接">相关连接</h2>
<ul>
<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>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/in"><code>in</code> operator</a></li>
</ul>
</article>