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authorPeter Bengtsson <mail@peterbe.com>2020-12-08 14:40:17 -0500
committerPeter Bengtsson <mail@peterbe.com>2020-12-08 14:40:17 -0500
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+---
+title: Symbol.species
+slug: Web/JavaScript/Reference/Global_Objects/Symbol/species
+tags:
+ - ECMAScript 2015
+ - JavaScript
+ - Property
+ - Symbol
+translation_of: Web/JavaScript/Reference/Global_Objects/Symbol/species
+---
+<div>{{JSRef}}</div>
+
+<p>知名的<strong> </strong><code><strong>Symbol.species</strong></code> 是个函数值属性,其被构造函数用以创建派生对象。</p>
+
+<div>{{EmbedInteractiveExample("pages/js/symbol-species.html")}}</div>
+
+
+
+<div>{{js_property_attributes(0,0,0)}}</div>
+
+<h2 id="描述">描述</h2>
+
+<p>species 访问器属性允许子类覆盖对象的默认构造函数。</p>
+
+<h2 id="示例">示例</h2>
+
+<p>你可能想在扩展数组类 <code>MyArray </code>上返回 {{jsxref("Array")}} 对象。 例如,当使用例如 {{jsxref("Array.map", "map()")}} 这样的方法返回默认的构造函数时,你希望这些方法能够返回父级的 Array 对象,以取代 <code>MyArray</code> 对象。<code>Symbol.species</code> 允许你这么做:</p>
+
+<pre class="brush: js">class MyArray extends Array {
+ // 覆盖 species 到父级的 Array 构造函数上
+ static get [Symbol.species]() { return Array; }
+}
+var a = new MyArray(1,2,3);
+var mapped = a.map(x =&gt; x * x);
+
+console.log(mapped instanceof MyArray); // false
+console.log(mapped instanceof Array); // true
+</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>{{SpecName('ES6', '#sec-symbol.species', 'Symbol.species')}}</td>
+ <td>{{Spec2('ES6')}}</td>
+ <td>Initial definition.</td>
+ </tr>
+ <tr>
+ <td>{{SpecName('ESDraft', '#sec-symbol.species', 'Symbol.species')}}</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.species")}}</p>
+
+<h2 id="相关链接">相关链接</h2>
+
+<ul>
+ <li>{{jsxref("Map.@@species", "Map[@@species]")}}</li>
+ <li>{{jsxref("Set.@@species", "Set[@@species]")}}</li>
+</ul>