TheisSupersetOf() method ofSet instances takes a set and returns a boolean indicating if all elements of the given set are in this set.

Syntax

isSupersetOf(other)

Parameters

other

ASet object, orset-like object.

Return value

true if all elements in theother set are also in this set, andfalse otherwise.

Description

In mathematical notation,superset is defined as:

And using Venn diagram:

isSupersetOf() 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 fewer elements inthis thanother.size, then it directly returnsfalse.
• Otherwise, it iterates overother by calling itskeys() method, and if any element inother is not present inthis, it returnsfalse (and closes thekeys() iterator by calling itsreturn() method). Otherwise, it returnstrue.

Examples

Using isSupersetOf()

The set of even numbers (<20) is a superset of multiples of 4 (<20):

const evens = new Set([2, 4, 6, 8, 10, 12, 14, 16, 18]);const fours = new Set([4, 8, 12, 16]);console.log(evens.isSupersetOf(fours)); // true

The set of all odd numbers (<20) is not a superset of prime numbers (<20), because 2 is prime but not odd:

const primes = new Set([2, 3, 5, 7, 11, 13, 17, 19]);const odds = new Set([3, 5, 7, 9, 11, 13, 15, 17, 19]);console.log(odds.isSupersetOf(primes)); // false

Equivalent sets are supersets of each other:

const set1 = new Set([1, 2, 3]);const set2 = new Set([1, 2, 3]);console.log(set1.isSupersetOf(set2)); // trueconsole.log(set2.isSupersetOf(set1)); // true

Specifications

Browser compatibility

See also

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