Set
A collection of unique values.
Available since: ES2015
Syntax
new Set(iterable)Parameters
| Parameter | Type | Description |
|---|---|---|
| iterable | Iterable | Optional. An array or another collection to start with. |
Return value
SetA new set.
Examples
Duplicates are removed automatically:
const tags = new Set(['js', 'css', 'js']);
console.log(tags.size);Output:
2The unique elements of an array:
const numbers = [3, 1, 3, 2, 1];
console.log([...new Set(numbers)].join(', '));Output:
3, 1, 2Notes
Uniqueness is checked like ===, so identical-looking objects count as different. The order is the insertion order.
See also
- Set.prototype.add — Adds a value to a Set if it is not there yet.
- Set.prototype.has — Checks whether a value is in a Set.
- Map — A collection of key–value pairs where a key can be anything.
- Array.from — Creates an array from a string, Set, Map or another iterable.
Related recipes
In the tutorial
- Map and Set — The Map and Set collections in JavaScript: a dictionary with keys of any type and a set of unique values.