Get (two-dimensional) array position

1

I found the tutorial about getting the index of something in an array, but i need the same for a twodimensional array, so i get [0][1] for example. How do i alter this code to do so?

Array.prototype.getIndex = function(data) {
 for (i=0; f=0; i<this.length; ++i; ) {
  if (this* == data) {
   return i;
  }
 }
 return -1;
};