Doors in tile based games

i’m going through tony pa’s tutorials on tile-based games and have a question relating to the way he organises doors between maps

here is the door code:

game.Doors = function (newmap, newcharx, newchary) {

game.Doors.prototype.walkable = true;
game.Doors.prototype.frame = 3;
game.Doors.prototype.door = true;
game.Tile2 = function () { };
game.Tile2.prototype = new game.Doors(2, 1, 4);
game.Tile3 = function () { };
game.Tile3.prototype = new game.Doors(1, 6, 4);

doing it this way, every door you place on your maps is going to look the same (ie ‘frame three’ of the map component movie clip). waht’s the most efficient way to amend this so that each door (Tilex) could have one of, say, four graphics (so it can be installed n, s, e, w).

thanks in advance for any suggestions

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