imagePreloader.js

// instantiate like
// var images = new imagePreloader('/path/to/image1.jpg', '/path/to/image2.jpg', ...);

var imagePreloader = function() {
	var _this = this;
	_this.cache = {};

	_this.load = function(src, callback) {
		var cacheImage = document.createElement('img');
		cacheImage.src = src;
		if(cacheImage.complete && callback && typeof(callback) == "function") {
			callback();
			return cacheImage;
		}
		if(callback && typeof(callback) == "function") {
			cacheImage.onload = callback();
		}
		_this.cache[src] = cacheImage;
		return cacheImage;
	};
	
	_this.loaded = function(src, callback) {
		if(_this.cache[src]) {
			return true;
		} else {
			var cacheImage = _this.load(src, callback);
			if(cacheImage.complete) {
				return true;
			}
		}
		return false;
	};

	var argsLen = arguments.length;
	
	if(argsLen == 2 && typeof(arguments[0]) == "string" && typeof(arguments[1]) == "function") {
		_this.load(arguments[0], arguments[1]);
		return;
	}
	
	for (var i = argsLen; i--;) {
		if(typeof(arguments[i]) == "string")
			_this.load(arguments[i]);
	}
	
};