function transpose(matrix) {
    const rows = matrix.length
    const col = matrix[0].length

    const transposedMatrix = []

    for(let j = 0; j < col; j++) {
        transposedMatrix[j] = []
        for(let i = 0; i < rows; i++) {
            transposedMatrix[j][i] = matrix[i][j]
        }
    }

    return transposedMatrix
}

let matrix = [[1,2,3],[4,5,6],[7,8,9]]

console.log(transpose(matrix))