code: function getTileId(x, y) {
           var tile = this.getTile(x, y);
           return tile ? tile.tileId : null;
         }
docs: Return the TileId of the Tile at the specified position
  @name getTileId
  @memberOf me.TMXLayer
  @public
  @function
  @param {Number} x X coordinate (in world/pixels coordinates)
  @param {Number} y Y coordinate (in world/pixels coordinates)
  @return {Number} TileId or null if there is no Tile at the given position