bounce in a two-dimensional array

bounce-array

export function* bounce(arr) {
  let x = 0;
  let y = 0;
  let mx = 1;
  let my = 1;
  const w = arr.length - 1;
  const h = arr[0].length - 1;
  while (true) {
    if (mx + x > w || mx + x < 0) {
      mx = mx * -1;
    }
    if (my + y > h || my + y < 0) {
      my = my * -1;
    }
    x = x + mx;
    y = y + my;
    yield arr[x][y];
  }
}