greasemonkey/googleplus-notification.user.js

// ==UserScript==
// @name          Google+ desktop notification
// @namespace     https://www.schtobia.de/
// @version       0.1.0
// @description   Google+ desktop notification (based on HTML5)
// @include       http*://plus.google.com/*
// @include       http*://encrypted.google.com/*
// @include       http*://google.com/*
// @grant         GM_getValue
// @run-at        document-end
// @downloadURL   https://github.com/schtobia/greasemonkey/raw/master/googleplus-notification.user.js
// @updateURL     https://github.com/schtobia/greasemonkey/raw/master/googleplus-notification.user.js
// ==/UserScript==
//

var Notification = window.Notification || window.mozNotification || window.webkitNotification;

var notificationsElement = document.getElementsByClassName("gb_Fa")[0];
var newNotifications = 0;

var lastNotifications = 0;
var notificationInstance = null;

var timeout = GM_getValue("timeout", 10000);

var intervalID = null;

notify = function()
{
	newNotifications = notificationsElement.innerHTML;

	if (newNotifications > lastNotifications)
	{
		var msg = (newNotifications - lastNotifications) + " new Notification(s)";

		console.log(GM_info.script.name + ": Trying to set notification...", msg);

		notificationInstance = new Notification("Google+ (" + newNotifications + ')',
			{
				"dir" : "auto",
				"body" : msg,
				"icon" : "https://ssl.gstatic.com/s2/oz/images/faviconr3.ico"
			}
		)

		lastNotifications = newNotifications;
	}
}

registerNotification = function()
{
	Notification.requestPermission(function(grantedPermission){
		if (grantedPermission === "granted")
		{
			console.log(GM_info.script.name + ": permission granted");
			intervalID = setInterval(notify, timeout);
			console.log(GM_info.script.name + ": intervalID: " + intervalID);
		}
		else
		{
			console.log(GM_info.script.name + ": permission NOT granted");
		}
	});
}

/* Normal flow of operations below! */
if (!Notification)
{
	alert("Notifications are not supported for this browser version yet.");
}
else
	registerNotification();