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。
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Symbol.species 属性的属性特性: |
|
---|---|
writable | false |
enumerable | false |
configurable | false |
species 访问器属性允许子类覆盖对象的默认构造函数。
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
Specification | Status | Comment |
---|---|---|
ECMAScript 2015 (6th Edition, ECMA-262) Symbol.species |
Standard | Initial definition. |
ECMAScript Latest Draft (ECMA-262) Symbol.species |
Draft |
Desktop | Mobile | Server | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
species | Chrome Full support 51 | Edge Full support 13 | Firefox Full support 41 | IE No support No | Opera Full support 38 | Safari Full support 10 | WebView Android Full support 51 | Chrome Android Full support 51 | Edge Mobile Full support 14 | Firefox Android Full support 41 | Opera Android Full support 38 | Safari iOS Full support 10 | Samsung Internet Android Full support Yes | nodejs
Full support
6.5.0
|