Theunion() method ofSet 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

other

ASet object, orset-like object.

Return value

A newSet object containing elements which are in either or both of this set and theother set.

Description

In mathematical notation,union is defined as:

And using Venn diagram:

union() acceptsset-like objects as theother parameter. It requiresthis to be an actualSet instance, because it directly retrieves the underlying data stored inthis without invoking any user code. Then, it iterates overother by calling itskeys() method, and constructs a new set with all elements inthis, followed by all elements inother that are not present inthis.

The order of elements in the returned set is first those inthis followed by those inother.

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

Browser compatibility

See also

• Polyfill ofSet.prototype.union incore-js
• es-shims polyfill ofSet.prototype.union
• Set.prototype.difference()
• Set.prototype.intersection()
• Set.prototype.isDisjointFrom()
• Set.prototype.isSubsetOf()
• Set.prototype.isSupersetOf()
• Set.prototype.symmetricDifference()