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"]);
Create a Set and add values:
Example
// Create a Set
const letters = new Set();
// Add Values to the Set
letters.add("a");
letters.add("b");
letters.add("c");
Create a Set and add variables:
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
Example
letters.add("d");
letters.add("e");
If you add equal elements, only the first will be saved:
Example
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
typeof letters; // Returns object
Note: Learn 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:
