Webkit Notifications on Multiple Tabs

You just need to specify "tag" option for notification. Notifications with the same value in tag only shows once even if many tabs are opened.

For example:

var notification = new Notification('Hey!', {    body : 'So nice to hear from you',    tag : 'greeting-notify',    icon : 'https://mysite.com/my_funny_icon.png'});

A detailed explanation of Tagging notifications so only the last one appears is available on the MDN docs site

An excerpt of the code [just in case the docs go down]

The HTML

<button>Notify me!</button>

The JS

window.addEventListener('load', function () {  // At first, let's check if we have permission for notification  // If not, let's ask for it  if (Notification && Notification.permission !== "granted") {    Notification.requestPermission(function (status) {      if (Notification.permission !== status) {        Notification.permission = status;      }    });  }  var button = document.getElementsByTagName('button')[0];  button.addEventListener('click', function () {    // If the user agreed to get notified    // Let's try to send ten notifications    if (Notification && Notification.permission === "granted") {      for (var i = 0; i < 10; i++) {        // Thanks to the tag, we should only see the "Hi! 9" notification        var n = new Notification("Hi! " + i, {tag: 'soManyNotification'});      }    }    // If the user hasn't told if he wants to be notified or not    // Note: because of Chrome, we are not sure the permission property    // is set, therefore it's unsafe to check for the "default" value.    else if (Notification && Notification.permission !== "denied") {      Notification.requestPermission(function (status) {        if (Notification.permission !== status) {          Notification.permission = status;        }        // If the user said okay        if (status === "granted") {          for (var i = 0; i < 10; i++) {            // Thanks to the tag, we should only see the "Hi! 9" notification            var n = new Notification("Hi! " + i, {tag: 'soManyNotification'});          }        }        // Otherwise, we can fallback to a regular modal alert        else {          alert("Hi!");        }      });    }    // If the user refuses to get notified    else {      // We can fallback to a regular modal alert      alert("Hi!");    }  });});