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

Syntax

Map[Symbol.species]

Description

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

Examples

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

Specifications

Specification Status Comment
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'get Map [ @@species ]' in that specification.
Standard Initial definition.
ECMAScript Latest Draft (ECMA-262)
The definition of 'get Map [ @@species ]' in that specification.
Draft  

Browser compatibility

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ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung InternetNode.js
Basic supportChrome Full support 51Edge Full support 13Firefox Full support 41IE No support NoOpera Full support 38Safari Full support 10WebView Android Full support 51Chrome Android Full support 51Edge Mobile Full support 13Firefox Android Full support 41Opera Android Full support 38Safari iOS Full support 10Samsung Internet Android Full support 5.0nodejs 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.

Legend

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See also

Document Tags and Contributors

Contributors to this page: fscholz, jameshkramer, kdex, arai
Last updated by: fscholz,