get Map[@@species] - JavaScript 编辑

The Map[@@species] accessor property returns the Map constructor.

Description

The species accessor property returns the default constructor for Map objects. Subclass constructors may over-ride it to change the constructor assignment.

Examples

Species in ordinary objects

The species property returns the default constructor function, which is the Map constructor for Map objects:

Map[Symbol.species]; // function Map()

Species in derived objects

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 {
  // Overwrite MyMap species to the parent Map constructor
  static get [Symbol.species]() { return Map; }
}

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• Map
• Symbol.species