How to check if object of type set - JavaScript

In this article we will learn how to check if object of type set in JavaScript.

It is very common to check if object of type set in JavaScript in JavaScript.

Problem

Now we have a problem which is that we want to check if object of type set.

Imagine we have set like this:

const set = new Set([1, 2, 3, 4]);

And we want to check if this object is typeof set or not.

How to solve this problem?

Use the instanceof operator to check if an object is a Set, e.g. myObj instanceof Set.

Solution:

The instanceof operator returns true if the prototype property of a constructor appears in the prototype chain otherwise returns false.

Let's see an example

// Set
const set = new Set([1, 2, 3, 4]);

// Tests:
console.log(set instanceof Set);
console.log('set' instanceof Set);
console.log(new Map() instanceof Set);
console.log({} instanceof Set);

Output

true
false
false
false

This approach would also work if you extend the Set class.

class CustomSet extends Set {
  example() {
    console.log('Do something');
  }
}

const set = new CustomSet();

// Tests:
console.log(set instanceof Set); // true
console.log(new Set([1, 2, 3]) instanceof Set); // true
console.log(new Map() instanceof Set); // false
console.log({} instanceof Set); // false

Output

true
true
false
false

Thank you for reading

Thank you for reading my blog. 🚀