JavaScript Set keys()
Syntax & Examples

Set.keys() method

The keys() method of the Set object in JavaScript is an alias for the values() method. It returns a new iterator object that contains the values for each element in the Set object in insertion order.

Syntax of Set.keys()

The syntax of Set.keys() method is:

keys()

This keys() method of Set an alias for Set.prototype.values().

Return Type

Set.keys() returns value of type Iterator.


✐ Examples

1 Using keys() to iterate over a Set

In JavaScript, we can use the keys() method to get an iterator object and use it to iterate over the elements of a Set.

For example,

  1. Create a new Set object letters with initial values 'a', 'b', and 'c'.
  2. Use the keys() method to get an iterator object iterator for the letters Set.
  3. Use a for...of loop to iterate over the iterator and log each value to the console using console.log().

JavaScript Program

const letters = new Set(['a', 'b', 'c']);
const iterator = letters.keys();
for (const value of iterator) {
  console.log(value);
}

Output

a
b
c

2 Using keys() to convert a Set to an array

In JavaScript, we can use the keys() method to convert a Set object to an array.

For example,

  1. Create a new Set object numbers with initial values 1, 2, and 3.
  2. Use the keys() method to get an iterator object iterator for the numbers Set.
  3. Convert the iterator to an array using the Array.from() method and store it in the variable arrayOfKeys.
  4. Log arrayOfKeys to the console using console.log().

JavaScript Program

const numbers = new Set([1, 2, 3]);
const iterator = numbers.keys();
const arrayOfKeys = Array.from(iterator);
console.log(arrayOfKeys);

Output

[ 1, 2, 3 ]

3 Using keys() with a Set of objects

In JavaScript, we can use the keys() method to iterate over a Set object containing objects.

For example,

  1. Create a new Set object people with initial objects representing different people.
  2. Use the keys() method to get an iterator object iterator for the people Set.
  3. Use a for...of loop to iterate over the iterator and log each value to the console using console.log().

JavaScript Program

const person1 = { name: 'John' };
const person2 = { name: 'Jane' };
const people = new Set([person1, person2]);
const iterator = people.keys();
for (const value of iterator) {
  console.log(value);
}

Output

{ name: 'John' }
{ name: 'Jane' }

Summary

In this JavaScript tutorial, we learned about keys() method of Set: the syntax and few working examples with output and detailed explanation for each example.