Set in JavaScript - Part 2

Published July 25, 2020

We have looked at the basics of Set in JavaScript including creating a new set, adding a new element, deleting an element, clearing all elements, and checking if an element is present in a set In the last blog post.

Now let's look at more operations we can do with Set in JavaScript.

Loop over Set in JavaScript

To loop over a Set collection we can use the forEach() method available in set or use a for..of statement.

// arr
const arr = [1, 2, 3, 4];

// convert to set
const set = new Set(arr);

// loop over the new set
// using the forEach() method
set.forEach((element) => {
  console.log(element);
});

// loop over the new set
// using the for...of statement
for (let element of set) {
  console.log(element);
}

Convert Set to an Array

To convert a Set collection into an Array we can use the Array.from() method or use the spread operator ... .

// arr
const arr = [1, 2, 3, 4];

// convert to set
const set = new Set(arr);

// using Array.from()
let arrFromSet = Array.from(set);

// using the spread operator
arrFromSet = [...set];

console.log(arrFromSet); // [1,2,3,4]

Caveats with Set in JavaScript

  • You can't pass an object when creating a set with new Set() constructor function as it accepts only iterable and since the object type is not iterable it will throw an error.
// obj
const obj = {
  name: "John Doe",
};

// make a set from the object
const set = new Set(obj); // error

But you can pass an object after the creation of an empty Set using the add() method available in the set.

// obj
const obj = {
  name: "John Doe",
};

// make an empty set
const set = new Set();

// add object to the set using the add() method
set.add(obj);

console.log(set);

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