var Asset = new Hash({

        javascript: function(source, properties){
                properties = $extend({
                        onload: $empty,
                        document: document,
                        check: $lambda(true)
                }, properties);
                
                var script = new Element('script', {'src': source, 'type': 'text/javascript'});
                
                var load = properties.onload.bind(script), check = properties.check, doc = properties.document;
                delete properties.onload; delete properties.check; delete properties.document;
                
                script.addEvents({
                        load: load,
                        readystatechange: function(){
                                if (['loaded', 'complete'].contains(this.readyState)) load();
                        }
                }).setProperties(properties);
                
                
                if (Browser.Engine.webkit419) var checker = (function(){
                        if (!$try(check)) return;
                        $clear(checker);
                        load();
                }).periodical(50);
                
                return script.inject(doc.head);
        },

        css: function(source, properties){
                return new Element('link', $merge({
                        'rel': 'stylesheet', 'media': 'screen', 'type': 'text/css', 'href': source
                }, properties)).inject(document.head);
        },

        image: function(source, properties){
                properties = $merge({
                        'onload': $empty,
                        'onabort': $empty,
                        'onerror': $empty
                }, properties);
                var image = new Image();
                var element = $(image) || new Element('img');
                ['load', 'abort', 'error'].each(function(name){
                        var type = 'on' + name;
                        var event = properties[type];
                        delete properties[type];
                        image[type] = function(){
                                if (!image) return;
                                if (!element.parentNode){
                                        element.width = image.width;
                                        element.height = image.height;
                                }
                                image = image.onload = image.onabort = image.onerror = null;
                                event.delay(1, element, element);
                                element.fireEvent(name, element, 1);
                        };
                });
                image.src = element.src = source;
                if (image && image.complete) image.onload.delay(1);
                return element.setProperties(properties);
        },

        images: function(sources, options){
                options = $merge({
                        onComplete: $empty,
                        onProgress: $empty
                }, options);
                if (!sources.push) sources = [sources];
                var images = [];
                var counter = 0;
                sources.each(function(source){
                        var img = new Asset.image(source, {
                                'onload': function(){
                                        options.onProgress.call(this, counter, sources.indexOf(source));
                                        counter++;
                                        if (counter == sources.length) options.onComplete();
                                }
                        });
                        images.push(img);
                });
                return new Elements(images);
        }

});