function matrix(width, height, callback) {
    return (' '.repeat(height).split('').map((_, j) => {
        return (' '.repeat(width).split('').map((_, i) => {
            return typeof callback === 'function' ? callback(i, j, width, height) : undefined;
        }));
    }));
}

// console.log(matrix(0, 0));
// []

// console.log(matrix(8, 8, (i, j, w) => j * w + i));
// [ [ 0, 1, 2, 3, 4, 5, 6, 7 ],
//   [ 8, 9, 10, 11, 12, 13, 14, 15 ],
//   [ 16, 17, 18, 19, 20, 21, 22, 23 ],
//   [ 24, 25, 26, 27, 28, 29, 30, 31 ],
//   [ 32, 33, 34, 35, 36, 37, 38, 39 ],
//   [ 40, 41, 42, 43, 44, 45, 46, 47 ],
//   [ 48, 49, 50, 51, 52, 53, 54, 55 ],
//   [ 56, 57, 58, 59, 60, 61, 62, 63 ] ]