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116 lines
4.4 KiB
HTML
116 lines
4.4 KiB
HTML
<article id="wikiArticle">
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<p></p><p></p>
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<h2 id="概述">概述</h2>
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<p><strong><code>Symbol.hasInstance 用于判断某对象是否为某构造器的实例。</code></strong> 因此你可以用它自定义 <a href="Reference/Operators/instanceof" title="instanceof运算符用于测试构造函数的prototype属性是否出现在对象的原型链中的任何位置"><code>instanceof</code></a> 操作符在某个类上的行为。</p>
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<div><table class="standard-table">
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<thead>
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<tr>
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<th class="header" colspan="2"><code>Symbol.hasInstance</code> 属性的属性特性：</th>
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</tr>
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</thead>
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<tbody>
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<tr>
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<td>writable</td>
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<td>false</td>
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</tr>
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<tr>
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<td>enumerable</td>
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<td>false</td>
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</tr>
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<tr>
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<td>configurable</td>
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<td>false</td>
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</tr>
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</tbody>
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</table></div>
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<h2 id="示例">示例</h2>
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<p><code><font face="Open Sans, Arial, sans-serif">例如，你可以这样来自定义 </font></code>MyArray 的 <code>instanceof </code>行为:</p>
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<pre><code class="language-javascript">class MyArray {
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static [Symbol.hasInstance](instance) {
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return Array.isArray(instance);
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}
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}
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console.log([] instanceof MyArray); // true</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">文档</th>
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<th scope="col">状态</th>
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<th scope="col">备注</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-symbol.hasinstance" hreflang="en" lang="en" rel="noopener">ECMAScript 2015 (6th Edition, ECMA-262)<br/><small lang="zh-CN">Symbol.hasInstance</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-symbol.hasinstance" hreflang="en" lang="en" rel="noopener">ECMAScript Latest Draft (ECMA-262)<br/><small lang="zh-CN">Symbol.hasInstance</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>51</td>
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<td><a href="/en-US/Firefox/Releases/50" title="Released on 2016-11-08.">50</a> (50)</td>
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<td><span style="color: #f00;">未实现</span></td>
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<td><span style="color: rgb(255, 153, 0);" title="Compatibility unknown; please update this.">?</span></td>
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<td><span style="color: rgb(255, 153, 0);" title="Compatibility unknown; please update this.">?</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: rgb(255, 153, 0);" title="Compatibility unknown; please update this.">?</span></td>
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<td><span style="color: rgb(255, 153, 0);" title="Compatibility unknown; please update this.">?</span></td>
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<td>50.0 (50)</td>
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<td><span style="color: #f00;">未实现</span></td>
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<td><span style="color: rgb(255, 153, 0);" title="Compatibility unknown; please update this.">?</span></td>
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<td><span style="color: rgb(255, 153, 0);" title="Compatibility unknown; please update this.">?</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="参考">参考</h2>
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<ul>
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<li><a href="Reference/Operators/instanceof" title="instanceof运算符用于测试构造函数的prototype属性是否出现在对象的原型链中的任何位置"><code>instanceof</code></a></li>
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</ul>
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</article> |