The well-known symbol Symbol.species
specifies a function-valued property that the constructor function uses to create derived objects.
Symbol.species
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Description
The species
accessor property allows subclasses to override the default constructor for objects.
Property attributes of Symbol.species |
|
---|---|
Writable | no |
Enumerable | no |
Configurable | no |
Examples
Using species
You might want to return Array
objects in your derived array class MyArray
. For example, when using methods such as map()
that return the default constructor, you want these methods to return a parent Array
object, instead of the MyArray
object. The species
symbol lets you do this:
class MyArray extends Array { // Overwrite species to the parent Array constructor static get [Symbol.species]() { return Array; } } let a = new MyArray(1,2,3); let mapped = a.map(x => x * x); console.log(mapped instanceof MyArray); // false console.log(mapped instanceof Array); // true
Specifications
Specification |
---|
ECMAScript Language Specification # sec-symbol.species |
Browser compatibility
Desktop | Mobile | Server | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | Deno | Node.js | |
species |
51
|
13
|
41
|
No
|
38
|
10
|
51
|
51
|
41
|
41
|
10
|
5.0
|
1.0
|
6.5.0
6.0.0
|
See also
© 2005–2022 MDN contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/species