Example

HTML

<button onclick="notifyMe()">Notify me!</button>

JavaScript

// reference:
// https://tools.ietf.org/html/bcp47#section-4.1.2
// https://www.w3.org/TR/notifications/#notificationdirection
// https://developer.mozilla.org/en-US/docs/Web/API/notification

var options = {
  dir: 'rtl',
  lang: 'ar'
}

var message = 'مرحبا العالم';

function notifyMe() {
  // Let's check if the browser supports notifications
  if (!("Notification" in window)) {
    alert("This browser does not support desktop notification");
  }

  // Let's check whether notification permissions have already been granted
  else if (Notification.permission === "granted") {
    // If it's okay let's create a notification
    var notification = new Notification(message, options);
  }

  // Otherwise, we need to ask the user for permission
  else if (Notification.permission !== "denied") {
    Notification.requestPermission(function(permission) {
      // If the user accepts, let's create a notification
      if (permission === "granted") {
        var notification = new Notification(message, options);
      }
    });
  }

  // At last, if the user has denied notifications, and you 
  // want to be respectful there is no need to bother them any more.
}