知名的 Symbol.species 是个函数值属性,其被构造函数用以创建派生对象。

Symbol.species 属性的属性特性:
writable false
enumerable false
configurable false

描述

species 访问器属性允许子类覆盖对象的默认构造函数。

示例

你可能想在扩展数组类 MyArray 上返回 Array 对象。 例如,当使用例如 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 MyArray 对象。Symbol.species 允许你这么做:

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 => x * x);

console.log(mapped instanceof MyArray); // false
console.log(mapped instanceof Array);   // true

规范

Specification Status Comment
ECMAScript 2015 (6th Edition, ECMA-262)
Symbol.species
Standard Initial definition.
ECMAScript Latest Draft (ECMA-262)
Symbol.species
Draft  

浏览器兼容性

Update compatibility data on GitHub
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung InternetNode.js
Basic supportChrome Full support 51Edge Full support 14Firefox Full support 41IE No support NoOpera Full support 38Safari Full support 10WebView Android Full support YesChrome Android Full support YesEdge Mobile Full support 14Firefox Android Full support 41Opera Android Full support 38Safari iOS Full support 10Samsung Internet Android Full support Yesnodejs Full support 6.5.0
Full support 6.5.0
Full support 6.0.0
Disabled
Disabled From version 6.0.0: this feature is behind the --harmony runtime flag.

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