tileset.js

var TILEDMapClass = Class.extend({
    currMapData: null,

    numXTiles: 100,
    numYTiles: 100,

    tileSize: {
        "x": 64,
        "y": 64
    },

    pixelSize: {
        "x": 64,
        "y": 64
    },

    imgLoadCount: 0,

    fullyLoaded: false,

    load: function (map) {
        xhrGet(map, function (data) {
            gMap.parseMapJSON(data.responseText);
        });
    },

    parseMapJSON: function (mapJSON) {
        var map = gMap.currMapData;

        gMap.numXTiles = map.width;
        gMap.numYTiles = map.height;

        gMap.tileSize.x = map.tilewidth;
        gMap.tileSize.y = map.tileheight;
      
        gMap.pixelSize.x = gMap.numXTiles * gMap.tileSize.x;
        gMap.pixelSize.y = gMap.numYTiles * gMap.tileSize.y;

        for(var i = 0; i < map.tilesets.length; i++){
            var img = new Image();
            img.onload = gMap.onloaded(map.tilesets);
            img.src = "../data/" + map.tilesets[i].image.replace(/^.*[\\\/])/, '');
        }
    },
    
    onloaded: function(tile){
        gMap.imgLoadCount++;
        if (gMap.imgLoadCount === tile.length){
            gMap.fullyLoaded = true;
        }
    }
});

var gMap = new TILEDMapClass();