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JavaScript Objects HTML DOM Objects


JavaScript Sets

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"]);
Try it Yourself »

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");
Try it Yourself »

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);
Try it Yourself »

The add() Method

Example

letters.add("d");
letters.add("e");
Try it Yourself »

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");
Try it Yourself »


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;
}
Try it Yourself »

Sets are Objects

typeof returns object:

typeof letters;      // Returns object
Try it Yourself »

instanceof Set returns true:

letters instanceof Set;  // Returns true
Try it Yourself »

Complete Set Reference

For a complete reference, go to our:

Complete JavaScript Set Reference.

The reference contains descriptions and examples of all Set Properties and Methods.


Browser Support

Set is an ES6 feature (JavaScript 2015).

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

Set is not supported in Internet Explorer.


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