Theintersection() method ofSet instances takes a set and returns a new set containing elements in both this set and the given set.

Syntax

intersection(other)

Parameters

other

ASet object, orset-like object.

Return value

A newSet object containing elements in both this set and theother set.

Description

In mathematical notation,intersection is defined as:

And using Venn diagram:

intersection() 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, its behavior depends on the sizes ofthis andother:

• If there are more elements inthis thanother.size, then it iterates overother by calling itskeys() method, and constructs a new set with all elements produced that are also present inthis.
• Otherwise, it iterates over the elements inthis, and constructs a new set with all elementse inthis that causeother.has(e) to return atruthy value.

Because of this implementation, the efficiency ofintersection() mostly depends on the size of the smaller set betweenthis andother (assuming sets can be accessed in sublinear time). The order of elements in the returned set is the same as that of the smaller ofthis andother.

Examples

Using intersection()

The following example computes the intersection between the set of odd numbers (<10) and the set of perfect squares (<10). The result is the set of odd numbers that are perfect squares.

const odds = new Set([1, 3, 5, 7, 9]);const squares = new Set([1, 4, 9]);console.log(odds.intersection(squares)); // Set(2) { 1, 9 }

Specifications

Browser compatibility

See also

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