Flatten Multidimensional array with Javascript

[blackkspydo]

---

description: Flatten your deeply nested multi-dimentional array with this simple Javascript trick.
category: snippets
slug: flatten-multi-dimentional-array
canonical: https://blackkspydo.com/blog/flatten-multi-dimentional-array
image: https://user-images.githubusercontent.com/58302072/194879157-5cbb3229-2e6a-416a-a342-22166ef93875.png

Problem

You have a multidimensional array and you want to flatten it into a single array.

const arr = [[1, 2], [3, 4], [5, 6, [7, 8, [9, 10]]]];

Solution

Here, we use the Array.prototype.reduce() method to flatten the array. We use the Array.isArray() method to check if the current element is an array. If it is, we recursively call the flatten() function on it and concatenate the result to the accumulator. If it is not, we simply concatenate the element to the accumulator.

const flatten = arr => arr.reduce((acc, val) => Array.isArray(val) ? acc.concat(flatten(val)) : acc.concat(val), []);

Usage

flatten(arr); // [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

References

• Array.prototype.reduce()
• Array.prototype.concat()