Loader

EventDispatcher.js

var EventDispatcher = (function(){

    function EventDispatcher(){
        this._listeners = {};
    }

    EventDispatcher.prototype.dispatchEvent = function(event, data){
        var _this = this;
        if(!this._listeners || !this._listeners[event]) return;
        this._listeners[event].forEach(function(callback){
            callback.call(_this, data);
        });
    };

    EventDispatcher.prototype.addEventListener = function(event, listener){
        if(!this._listeners) this._listeners = {};
        if(!this._listeners[event]) this._listeners[event] = [];
        this._listeners[event].push(listener);
    };

    EventDispatcher.prototype.removeEventListener = function(event, listener){
        if(!this._listeners[event]) return;
        var index = this._listeners[event].indexOf(listener);
        if(index > -1) this._listeners[event].splice(index, 1);
    };

    EventDispatcher.implementation = function(proto){
        var prop;
        for(prop in EventDispatcher.prototype){
            proto[prop] = EventDispatcher.prototype[prop];
        }
    };

    return EventDispatcher;

})();

Loader.js

var Loader = (function(parent){

    function Loader(){
        this.data = {};
        this.imagesData = [];
    }

    Loader.prototype = new parent;

    Loader.prototype.constructor = Loader;

    Loader.prototype.loadImages = function(images){
        var _this = this;
        this.imageCounter = 0;
        (this.imagesData = images).forEach(function(image){
            _this.loadImage(image);
        });
    };

    Loader.prototype.loadImage = function(data){
        var _this = this, image = new Image();
        if(this.imagesData.length === 0) this.imagesData.push(data);
        if(this.imageCounter == void 0) this.imageCounter = 0;
        image.onload = function(){
            _this.data[data.id] = this;
            _this.imageCounter++;
            _this.dispatchEvent("update", _this.imageCounter);
            if(_this.imageCounter === _this.imagesData.length){
                _this.imagesData.length = 0;
                _this.imageCounter = void 0;
                _this.dispatchEvent("complete")
            }
        };
        image.src = data.src;
    };

    Loader.prototype.getResult = function(id){
        return this.data[id];
    };

    return Loader;

})(EventDispatcher);

test.js

var loader = new Loader();

loader.addEventListener("complete", function(){
});

loader.loadImages([
    {id: "sBackground", src: "images/Background/starBackground.png"},
    {id: "player", src: "images/player.png"},
    {id: "gLaser", src: "images/laserGreen.png"},
    {id: "gLaserShot", src: "images/laserGreenShot.png"},
    {id: "enemyShip", src: "images/enemyShip.png"},
    {id: "shield", src: "images/shield.png"},
    {id: "playerDamaged", src: "images/playerDamaged.png"},
    {id: "life", src: "images/life.png"},
    {id: "playerExplosion", src: "images/playerExplosion.png"},
    {id: "explosion", src: "images/explosion.png"}
]);