Loads the assets to be cached by the browser.

preloader.js

// depends on jQuery

var PreloaderClass = function (urls) {
  // holds the URLs passed
	this.urls = urls;

  // base loading
	this.loadUrl = function ( url ) {
		var supported, deferredLoading, xhr;

		deferredLoading = jQuery.Deferred();

		supported = typeof new XMLHttpRequest().responseType === 'string';
		if (supported) {
			xhr = new XMLHttpRequest();
			xhr.open('GET', url, true);
			xhr.responseType = 'arraybuffer';

			xhr.onreadystatechange = function () {
				if (xhr.readyState === 4) {
					if (xhr.status === 200) {
						deferredLoading.resolve( xhr );
					} else {
						deferredLoading.reject( xhr );
					}
				}
			};

			xhr.onprogress = function (evt) {
				if(evt.lengthComputable) {
					deferredLoading.notify(evt.loaded, evt.total);
				}
			};

			xhr.send(null);
		}

		return deferredLoading;
	};

  // action method
	this.preload = function () {
		var self = this;

		var deferredLoads = [];
		this.urls.forEach(function (url) {
			var getDeferredLoad = self.loadUrl( url );
			deferredLoads.push(
				getDeferredLoad
			);
		})
		
		return $.when.apply($, deferredLoads); 
	}

};

//preloader usage
(function () {
  var url_set = [
    //enter URLs here  
  ];
  
  // creates instance
	window.Preloader = new PreloaderClass( url_set );

  // execute preloading
  Preloader.preload();
})();