Array Deduplication Challenge (3 Ways)

April 16, 2026~1 min read

💡TL;DR

Can you remove duplicate values from an array using 3 different approaches in JavaScript?

Today’s challenge is simple but powerful 👇

You have an array:

JavaScript

const arr = [1, 2, 2, 3, 4, 4, 5];

Your task:

Remove duplicates using 3 different approaches.

Try these methods:

Using Set
Using filter
Using reduce

Expected Output:

JavaScript

[1, 2, 3, 4, 5]

Bonus:

Maintain original order
Try with objects (hard mode)

Solutions:

JavaScript

// 1. Using Set
const unique1 = [...new Set(arr)];

// 2. Using filter
const unique2 = arr.filter((item, index) => arr.indexOf(item) === index);

// 3. Using reduce
const unique3 = arr.reduce((acc, curr) => {
  if (!acc.includes(curr)) acc.push(curr);
  return acc;
}, []);