Swap the rows and columns of a matrix

JavaScript version
const transpose = (matrix) => matrix[0].map((col, i) => matrix.map((row) => row[i]));
// Or
const transpose = (matrix) => matrix[0].map((col, c) => matrix.map((row, r) => matrix[r][c]));
// Or
const transpose = (matrix) => matrix.reduce((prev, next) => next.map((item, i) => (prev[i] || []).concat(next[i])), []);
TypeScript version
const transpose = <T,>(matrix: T[][]): T[][] => matrix[0].map((col, i) => matrix.map((row) => row[i]));
// Or
const transpose = <T,>(matrix: T[][]): T[][] => matrix[0].map((col, c) => matrix.map((row, r) => matrix[r][c]));
// Or
const transpose = <T,>(matrix: T[][]): T[][] => (
matrix.reduce((prev, next) => next.map((item, i) => (prev[i] || []).concat(next[i])), [] as T[][])
);
Examples
transpose([
// [
[1, 2, 3], // [1, 4, 7],
[4, 5, 6], // [2, 5, 8],
[7, 8, 9], // [3, 6, 9],
]); // ]