Progressive Web Application receiving data to trigger notification

Hello i'm newbie and im hardly to understand this notification in service-worker, and because my knowledge isn't good yet then probably i will unable to explain my problem clearly.

so here's the code :

// triggered everytime, when a push notification is received.
self.addEventListener('push', function(event) {

  console.info('Event: Push');

  var title = 'New commit on Github Repo: RIL';

  var body = {
    'body': 'Click to see the latest commit',
    'tag': 'pwa',
    'icon': './images/48x48.png'
  };

  event.waitUntil(
    self.registration.showNotification(title, body)
  );
});

this is the code that trigger to POP the notification, what I do not understand is where the argument to accept/ receive the data ?

I've been searched a lot: https://auth0.com/blog/introduction-to-progressive-web-apps-push-notifications-part-3/ , https://developers.google.com/web/updates/2015/03/push-notifications-on-the-open-web there's some new data JSON or from git-server or push api, but I still hardly to understand where's to accept the data.

sorry if you still do not understand what's my problem.

Here to make it simple what I want :

1. Let's say i make a button, and everytime i click the button it will value as 'True' and I want that 'True' value to pass into argument and trigger the push of notication in service-worker.

2. 2nd questions: am I able to trigger notification with header or text in html ? since we can manipulate the text with DOM ?

3. am I able to trigger notification without GCM, or API cause I just want a simple notification in serivce-worker like above without passing much data.

4. If you give more advice or maybe notification without service-worker but real time , I am surely happy to read it but I hope Im able to understand.

via Dell Watson