Cameron the Dev

How to remove duplicate values in a Javascript array

September 21, 2020

A common task I need to do when I’m programming is to remove duplicate values from an array. The code to do this looks like:

const arrayWithDuplicates = [6, 7, 7, 7, 9, 9, 10]

const arrayWithOnlyUniqueValues = [ Set(arrayWithDuplicates)]

// arrayWithOnlyUniqueValues  contains -> [6, 7, 9, 10]

How does it work?

The code above uses the spread syntax and a Set in order to accomplish removing the duplicate values.

When we pass in an array to a Set it will remove all of the duplicate values (as a Set object will only store unique values).

new Set([6, 7, 7, 7, 9, 9, 10])

// The code above will return a set containing -> {6, 7, 9, 10}

We can then use the Spread syntax to expand the values from the set into a new array.