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Set.prototype.add()

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨July 2015⁩.

The add() method of Set instances inserts the specified value into this set, if it is not already present.

Try it

const set = new Set();

set.add(42);
set.add(42);
set.add(13);

for (const item of set) {
  console.log(item);
  // Expected output: 42
  // Expected output: 13
}

Syntax

add(value)

Parameters

value: The value to add to the Set object. Objects are compared by reference, not by value.

Return value

The Set object.

Examples

Using add()

const mySet = new Set();

mySet.add(1);
mySet.add(5).add("some text"); // chainable

console.log(mySet);
// Set [1, 5, "some text"]

Specifications

Specification
ECMAScript® 2026 Language Specification> # sec-set.prototype.add>

Browser compatibility

	Desktop					Mobile							Server
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet	WebView Android	WebView on iOS	Bun	Deno	Node.js
`add`	38	12	13	25	8	38	14	25	8	3.0	38	8	1.0.0	1.0	0.12.0