How to Flatten an Array in JavaScript

Working with arrays in JavaScript is common — but what happens when an array contains other arrays inside it? That’s called a nested array, and sometimes, you just want to flatten it into one single-level array.

In this post, we’ll explore:

• ✅ What it means to flatten an array
• 🔧 Different methods to do it
• 💻 JavaScript code examples

🧱 What is a Nested Array?

A nested array means an array that contains one or more arrays inside it. For example:

arr = [1, [2, 3], [4, [5, 6]]];

Your goal is to flatten it to:

[1, 2, 3, 4, 5, 6]