Set.prototype.forEach()

set.forEach(callbackFn, thisArg)

Returns: undefined · Updated March 13, 2026 · Map and Set

set foreach iteration

The forEach() method executes a provided function once for each value in the Set.

Syntax

set.forEach(callbackFn, thisArg)

Parameters

Parameter	Type	Default	Description
`callbackFn`	`function`	—	Function executed for each value
`value`	`any`	—	The current value
`value`	`any`	—	Same as first argument (for Map compatibility)
`set`	`Set`	—	The Set being iterated
`thisArg`	`any`	`undefined`	Value to use as `this`

The callbackFn receives three arguments (the second is the same as the first for Set compatibility with Map):

Examples

Basic usage

const numbers = new Set([1, 2, 3]);

numbers.forEach((value, sameValue, set) => {
  console.log(`Value: ${value}, Set size: ${set.size}`);
});
// Value: 1, Set size: 3
// Value: 2, Set size: 3
// Value: 3, Set size: 3

Using thisArg

const multiplier = {
  factor: 10
};

const nums = new Set([1, 2, 3]);

nums.forEach(function(value) {
  console.log(value * this.factor);
}, multiplier);
// 10
// 20
// 30

Processing unique values

const duplicates = [1, 2, 2, 3, 3, 3, 4, 4, 5];
const uniqueSet = new Set(duplicates);

const doubled = [Global_Objects::eval];
uniqueSet.forEach(value => {
  doubled.push(value * 2);
});
console.log(doubled);
// [2, 4, 6, 8, 10]