Skip to content

How to remove duplicates from a JavaScript array

FULL-STACK WEB DEVELOPMENT BOOTCAMP

2024 COHORT SIGNUPS END TOMORROW

Given an array, how can you remove duplicate values in it?

Let’s say you have an array containing a series of primitive values, for example numbers or strings.

Some of those elements are repeated.

Like in this example:

const list = [1, 2, 3, 4, 4, 3]

We can generare a new array containing the same values, without the duplicates, in this way:

const uniqueList = [...new Set(list)]

uniqueList will now be a new array with the values [1, 2, 3, 4] in it.

How does this work?

Set is a new data structure, introduced in ES6 in 2015, and its main characteristic is to be a container for data that can’t be repeated in the same set. See my full guide on Set here.

By initializing a Set with a destructured array (see the ... operator before new Set()), we pass values and Set automatically removes the duplicates. Then we convert it to an array by wrapping it into square brackets [].

This method works with anything that’s not an object: numbers, strings, booleans, symbols.

  • Learn modern web development in my BOOTCAMP (SIGNUP END TOMORROW FEB 20, 2024)
  • THE VALLEY OF CODE (+ PRO), your web development manual
  • I wrote 15+ coding BOOKS, all available in THE VALLEY OF CODE PRO
  • Indie solopreneur internet business masterclass SOLO LAB (summer 2024)