Map[@@species]
访问器属性会返回一个 Map
构造函数.
Map[Symbol.species]
The species accessor property returns the default constructor for Map
objects. Subclass constructors may over-ride it to change the constructor assignment.
The species property returns the default constructor function, which is the Map
constructor for Map
objects:
Map[Symbol.species]; // function Map()
In a derived collection object (e.g. your custom map MyMap
), the MyMap
species is the MyMap
constructor. However, you might want to overwrite this, in order to return parent Map
objects in your derived class methods:
class MyMap extends Map {
// 重写覆盖 MyMap species to the parent Map constructor
static get [Symbol.species]() { return Map; }
}
Specification | Status | Comment |
---|---|---|
ECMAScript 2015 (6th Edition, ECMA-262) get Map [ @@species ] |
Standard | Initial definition. |
ECMAScript Latest Draft (ECMA-262) get Map [ @@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 13 | Firefox Android Full support 41 | Opera Android Full support 38 | Safari iOS Full support 10 | Samsung Internet Android Full support 5.0 | nodejs
Full support
6.5.0
|