JavaScript Set Methods

A Set in JavaScript provides several built-in methods to add, remove, check, and iterate over elements.

1. add()

Adds a new value to the Set. Duplicate values are ignored.

• Returns the Set itself (can be chained).
• Maintains insertion order.

const numbers = new Set();
numbers.add(1);
numbers.add(2);
numbers.add(2); // Duplicate ignored
console.log(numbers); // Set { 1, 2 }

2. delete()

Removes a specific value from the Set.

• true if the value existed and was removed.
• false if the value did not exist.

const numbers = new Set([1, 2, 3]);
numbers.delete(2);
console.log(numbers); // Set { 1, 3 }

3. has()

Checks if a value exists in the Set.

const numbers = new Set([1, 2, 3]);
console.log(numbers.has(2)); // true
console.log(numbers.has(4)); // false

4. clear()

Removes all elements from the Set.

const numbers = new Set([1, 2, 3]);
numbers.clear();
console.log(numbers); // Set {}

5. size

Returns the number of unique elements in the Set.

const numbers = new Set([1, 2, 3]);
console.log(numbers.size); // 3

6. entries()

Returns an iterator of [value, value] pairs (for Map compatibility).

const numbers = new Set([1, 2]);
console.log([...numbers.entries()]); // [[1,1],[2,2]]

7. keys()

Returns an iterator of the Set’s values (same as values()).

console.log([...numbers.keys()]); // [1, 2]

8. values()

Returns an iterator of the Set’s values (redundant with keys() but part of the API).

console.log([...numbers.values()]); // [1, 2]

9. Iterating Over a Set

Sets are iterable. You can loop over them using:

a. for...of Loop

const numbers = new Set([1, 2, 3]);
for (const num of numbers) {
  console.log(num);
}
// Output: 1, 2, 3

b. forEach() Method

numbers.forEach((value) => console.log(value));
// Output: 1, 2, 3

c. Spread Operator

const numbersArray = [...numbers];
console.log(numbersArray); // [1, 2, 3]

10. Converting Set to Array

Sets can be easily converted to arrays for further operations:

const numbers = new Set([1, 2, 3]);
const numbersArray = Array.from(numbers);
console.log(numbersArray); // [1, 2, 3]

Summary Table of Key Set Methods

Method / Property	Description
add(value)	Adds a new element to the Set
delete(value)	Removes a specific element
has(value)	Checks if a value exists
clear()	Removes all elements
size	Returns the number of elements
forEach()	Executes a function for each element
Spread / Array.from()	Convert Set to Array