Set.prototype.union()
Baseline 2024
Newly available
Since June 2024, this feature works across the latest devices and browser versions. This feature might not work in older devices or browsers.
The union()
method of Set
instances takes a set and returns a new set containing elements which are in either or both of this set and the given set.
Syntax
union(other)
Parameters
Return value
A new Set
object containing elements which are in either or both of this set and the other
set.
Description
In mathematical notation, union is defined as:
And using Venn diagram:
union()
accepts set-like objects as the other
parameter. It requires this
to be an actual Set
instance, because it directly retrieves the underlying data stored in this
without invoking any user code. Then, it iterates over other
by calling its keys()
method, and constructs a new set with all elements in this
, followed by all elements in other
that are not present in this
.
The order of elements in the returned set is first those in this
followed by those in other
.
Examples
Using union()
The following example computes the union between the set of even numbers (<10) and the set of perfect squares (<10). The result is the set of numbers that are either even or a perfect square, or both.
const evens = new Set([2, 4, 6, 8]);
const squares = new Set([1, 4, 9]);
console.log(evens.union(squares)); // Set(6) { 2, 4, 6, 8, 1, 9 }
Specifications
Specification |
---|
Set methods # sec-set.prototype.union |
Browser compatibility
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