Set.prototype.difference()

The difference() method of {{jsxref("Set")}} instances takes a set and returns a new set containing elements in this set but not in the given set.

Syntax#

difference(other)

Parameters#

• other
• : A {{jsxref("Set")}} object, or set-like object.

Return value#

A new {{jsxref("Set")}} object containing elements in this set but not in the other set.

Description#

In mathematical notation, difference is defined as:

And using Venn diagram:

difference() accepts set-like objects as the other parameter. It requires {{jsxref("this")}} to be an actual {{jsxref("Set")}} instance, because it directly retrieves the underlying data stored in this without invoking any user code. Then, its behavior depends on the sizes of this and other:

• If there are more elements in this than other.size, then it iterates over other by calling its keys() method, and constructs a new set with all elements in this that are not seen in other.
• Otherwise, it iterates over the elements in this, and constructs a new set with all elements e in this that cause other.has(e) to return a falsy value.

The order of elements in the returned set is the same as in this.

Examples#

Using difference()#

The following example computes the difference between the set of odd numbers (<10) and the set of perfect squares (<10). The result is the set of odd numbers that are not perfect squares.

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

Specifications#

{{Specifications}}

Browser compatibility#

{{Compat}}

See also#

• Polyfill of Set.prototype.difference in core-js
• es-shims polyfill of Set.prototype.difference
• {{jsxref("Set.prototype.intersection()")}}
• {{jsxref("Set.prototype.isDisjointFrom()")}}
• {{jsxref("Set.prototype.isSubsetOf()")}}
• {{jsxref("Set.prototype.isSupersetOf()")}}
• {{jsxref("Set.prototype.symmetricDifference()")}}
• {{jsxref("Set.prototype.union()")}}