// An image preloader without using Image class nor document.images
// Built for a Facebook environment where those two are forbiden. May not work in a regular web page.
// Just change 
 
function Preloader(options) {
	var defaultSettings = {
		preloaderID: "preloader_id",
		container: document.body
	};
 
	this.settings = this.extend(defaultSettings, options || {});
	this.buildPreloader();
};
 
Preloader.prototype = {
	extend: function(destination, source) {
		for (var property in source)
			destination[property] = source[property];
		return destination;
	},
 
	// Prepare the preloader. Just a IMG html element hidden with css.
	buildPreloader: function(preloaderId) {
		var image = document.createElement('IMG')
			.setId(this.settings.preloaderId)
			.setStyle({display: 'none'});
		this.settings.container.appendChild(image);
	},
 
	// Update de src attribute of our hidden tag with the passing url.
	// Having the src updated will make the tag to load the image.
	preloadPic: function(imageUrl) {
		var preloader = document.getElementById(this.settings.preloaderId);
		if (preloader) {
			preloader.setSrc(imageUrl);
			// Don't know why, setting the src make the picture visible. 
			// Have to hide it again.
			preloader.setStyle({display: 'none'});
		}
	}
 
};