For more comfortable to use we need to take user permission to display web notification.

document.addEventListener('DOMContentLoaded', function () { 
 if (Notification.permission !== "granted")
 {
  Notification.requestPermission(); 
 }
});

if(window.Notification && Notification.permission !== "denied") {
  Notification.requestPermission(function(status) { // status is "granted", if accepted by user
  var n = new Notification('Title', {
   body: 'I am the body text!',
   icon: '/path/to/icon.png' // optional
  });
  }); 
}