Javascript Spiral Matrix Problem

spiral.js

function spiralMatrix(n) {
  var total = n * n,
    sides = n,
    x = 0,
    y = 0,
    dx = 1,
    dy = 0,
    matrix = [],
    i = 0,
    j = 0;

  while(sides--) {
    matrix[sides] = [];
  }

  sides = n;

  while(i < total) {
    matrix[y][x] = i++;

    if (++j === sides) {
      var dyVal = dy;
      j = 0;

      if(dx == 0) {
        dyVal = -dy;
        dx = -dx;
      }
      
      dy = dx;
      dx = dyVal;

      if (dx == 0) {
        sides--;
      }
    }

    x += dx;
    y += dy;
  }

  return matrix;
}