Show desktop notification (chrome) when the duego.com pre-register page updates

duego-preregister.user.js

// ==UserScript==
// @match http://duego.com/preregister*
// @require http://code.jquery.com/jquery-1.4.2.min.js
// ==/UserScript==

var load,execute,loadAndExecute;load=function(a,b,c){var d;d=document.createElement("script"),d.setAttribute("src",a),b!=null&&d.addEventListener("load",b),c!=null&&d.addEventListener("error",c),document.body.appendChild(d);return d},execute=function(a){var b,c;typeof a=="function"?b="("+a+")();":b=a,c=document.createElement("script"),c.textContent=b,document.body.appendChild(c);return c},loadAndExecute=function(a,b){return load(a,function(){return execute(b)})};

loadAndExecute("//ajax.googleapis.com/ajax/libs/jquery/1.6.2/jquery.min.js", function() {
	function Notifier() {};

	// Returns "true" if this browser supports notifications.
	Notifier.prototype.HasSupport = function() {
		if (window.webkitNotifications) {
			return true;
		} else {
			return false;
		}
	}

	// Request permission for this page to send notifications. If allowed,
	// calls function "cb" with true.
	Notifier.prototype.RequestPermission = function(cb) {
		if (window.webkitNotifications.checkPermission() != 0) {
			window.webkitNotifications.requestPermission(function() {
				if (cb) { cb(window.webkitNotifications.checkPermission() == 0); }
			});
		}
	}

	// Popup a notification with icon, title, and body. Returns false if
	// permission was not granted.
	Notifier.prototype.Notify = function(icon, title, body) {
		if (window.webkitNotifications.checkPermission() == 0) {
			var popup = window.webkitNotifications.createNotification(
				icon, title, body);
			popup.show();

			return true;
		}

		return false;
	}

	var notifier = new Notifier();
	notifier.RequestPermission();

	var current = false;

	if (!notifier.HasSupport()) {
		console.log("No support for desktop notifications");
		return;
	}

	$("<input type=\"button\" value=\"Show desktop notifications!\" id=\"req_perm\" />")
		.hide()
		.appendTo('body')
		.css('position', 'absolute')
		.css('left', '0px')
		.css('top', '0px')
		.css('height', '100%')
		.css('width', '100%')
		.css('z-index', '100')
		.css('font-size', '5em')
		.click(function() {
			notifier.RequestPermission(function(allowed) {
				if (allowed) {
					notifier.Notify("http://static.duego.com/images/badges/duego-107x106.png?version=DEV", "Duego", "Notifications active");
				}
			});
			$('#req_perm').hide();
		});

	if (window.webkitNotifications.checkPermission() != 0) {
		$('#req_perm').show();
	}

	function updateCount() {
		notifier.RequestPermission();
		$.get("http://duego.com/preregister", function(data){
			var matches = data.match("<strong>([0-9]*)</strong>");
			if (matches.length > 1) {
				var n = matches[1];
				if (false === current) {
					current = n;
					return;
				}
				if (n < current) {
					console.log("New number of signups left: " + n);
					// show popup
					if (!notifier.Notify("http://static.duego.com/images/badges/duego-107x106.png?version=DEV", "Duego", "Only " + n + " signups to go!")) {
						console.log('No permission to show desktop notifications.');
						$('#req_perm').show();
						//notifier.RequestPermission();
					}
					current = n;
				}
			}
		});
	}

	updateCount();
	setInterval(updateCount, 60000);
});