A JavaScript Set is a collection of unique values.
Each value can only occur once in a Set.
The values can be of any type, primitive values or objects.
How to Create a Set
You can create a JavaScript Set by:
- Passing an array to new Set()
- Create an empty set and use add() to add values
The new Set() Method
Pass an array to the new Set() constructor:
Example
// Create a Set
const letters = new Set(["a","b","c"]);Example
// Create a Set
const letters = new Set();
// Add Values to the Set letters.add("a"); letters.add("b"); letters.add("c");Example
// Create a Set
const letters = new Set();
// Create Variables
const a = "a";
const b = "b";
const c = "c";
// Add Variables to the Set letters.add(a); letters.add(b); letters.add(c);The add() Method
letters.add("d");
letters.add("e");If you add equal elements, only the first will be saved:
letters.add("a");
letters.add("b");
letters.add("c");
letters.add("c");
letters.add("c");
letters.add("c");
letters.add("c");
letters.add("c");Listing the Elements
You can list all Set elements (values) with a for..of loop:
Example
// Create a Set
const letters = new Set(["a","b","c"]);
// List all Elements
let text = "";
for (const x of letters) {
text += x;
}Sets are Objects
typeofLearn More
JavaScript Set Methods
JavaScript Set Logic
JavaScript Weak Sets
JavaScript Set Reference
JavaScript Maps
Browser Support
Set is an ES6 feature .
ES6 is fully supported in all modern browsers since June 2017:
| Chrome 51 | Edge 15 | Firefox 54 | Safari 10 | Opera 38 |
|---|---|---|---|---|
| May 2016 | Apr 2017 | Jun 2017 | Sep 2016 | Jun 2016 |