---
title: Symbol.hasInstance
slug: Web/JavaScript/Reference/Global_Objects/Symbol/hasInstance
translation_of: Web/JavaScript/Reference/Global_Objects/Symbol/hasInstance
---
<p>{{JSRef}}</p>

<p><strong><code>Symbol.hasInstance</code></strong>用于判断某对象是否为某构造器的实例。因此你可以用它自定义 {{jsxref("Operators/instanceof", "instanceof")}} 操作符在某个类上的行为。</p>

<div>
<div>{{EmbedInteractiveExample("pages/js/symbol-hasinstance.html")}}</div>

<div>{{js_property_attributes(0,0,0)}}</div>

<h2 id="示例">示例</h2>

<p>你可实现一个自定义的<code>instanceof</code> 行为，例如：</p>

<pre class="brush: js">class MyArray {
  static [Symbol.hasInstance](instance) {
    return Array.isArray(instance);
  }
}
console.log([] instanceof MyArray); // true</pre>

<h2 id="规范">规范</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">文档</th>
   <th scope="col">状态</th>
   <th scope="col">备注</th>
  </tr>
  <tr>
   <td>{{SpecName('ES6', '#sec-symbol.hasinstance', 'Symbol.hasInstance')}}</td>
   <td>{{Spec2('ES6')}}</td>
   <td>Initial definition.</td>
  </tr>
  <tr>
   <td>{{SpecName('ESDraft', '#sec-symbol.hasinstance', 'Symbol.hasInstance')}}</td>
   <td>{{Spec2('ESDraft')}}</td>
   <td></td>
  </tr>
 </tbody>
</table>

<h2 id="浏览器兼容性">浏览器兼容性</h2>

<p>{{Compat("javascript.builtins.Symbol.hasInstance")}}</p>

<h2 id="参见">参见</h2>

<ul>
 <li>{{jsxref("Operators/instanceof", "instanceof")}}</li>
</ul>