The Set[@@species] static accessor property is an unused accessor property specifying how to copy Set objects.
Syntax
Set[Symbol.species]
Return value
The value of the constructor (this) on which get @@species was called. The return value is used to construct copied Set instances.
Description
The @@species accessor property returns the default constructor for Set objects. Subclass constructors may override it to change the constructor assignment.
Note: This property is currently unused by all
Setmethods.
Examples
Species in ordinary objects
The @@species property returns the default constructor function, which is the Set constructor for Set.
Set[Symbol.species]; // function Set()
Species in derived objects
In an instance of a custom Set subclass, such as MySet, the MySet species is the MySet constructor. However, you might want to overwrite this, in order to return parent Set objects in your derived class methods:
class MySet extends Set {
// Overwrite MySet species to the parent Set constructor
static get [Symbol.species]() {
return Set;
}
}