Chalarangelo/30-seconds-of-code

---
title: Transpose a matrix in JavaScript
shortTitle: Transpose matrix
type: tip
language: javascript
tags: [array]
cover: camera-zoom
excerpt: Learn how to transpose a two-dimensional array in JavaScript.
listed: true
dateModified: 2024-07-18
---

A **matrix transpose** is an operation that switches the rows and columns of a two-dimensional array. In other words, it converts the rows of the matrix into columns and vice versa.

In order to perform this operation in JavaScript, we can use `Array.prototype.map()` to create a new array where **each column of the original matrix becomes a row in the transposed matrix**. We can achieve this by mapping over the columns of the original matrix and creating a new row by mapping over the rows and selecting the corresponding element.

```js
const transpose = arr => arr[0].map((col, i) => arr.map(row => row[i]));

transpose([[1, 2, 3], [4, 5, 6], [7, 8, 9], [10, 11, 12]]);
// [[1, 4, 7, 10], [2, 5, 8, 11], [3, 6, 9, 12]
```