function sendNotification() {
  new Notification('Notification title', {
    body: 'This is the notification body'
  })
}

document.getElementById('notification').addEventListener('click', function () {
  if (Notification.permission === 'default') {
    Notification.requestPermission().then(function (response) {
      if (response === 'granted') {
        sendNotification()
      } else {
        registerResponse('Permission is ' + response)
      }
    }).catch(registerResponse)
  } else if (Notification.permission === 'granted') {
    sendNotification()
  } else {
    registerResponse('Permission is denied')
  }
})