Transpose a matrix in JavaScript

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.
@Further reading

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]

@Further reading

From 30-seconds-of-code: transpose-matrix