Yes, sure.
First of all, I have used GitHub - danhper/elixir-web-push-encryption: Elixir implementation of Web Push Payload encryption..

I have a JavaScript file for service worker, sw.js

self.addEventListener('push', function(event) {
  console.log('Push Notification received', JSON.parse(event.data.text()));

  var data = {title: 'New!', content: 'Something new happened!', openUrl: '/'};

  if (event.data) {
    data = JSON.parse(event.data.text());
  }

  var options = {
    body: data.content,
    icon: '/src/images/icons/app-icon-96x96.png',
    badge: '/src/images/icons/app-icon-96x96.png',
    data: {
      url: data.openUrl
    }
  };

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

This is a addEventListener with push event and my service worker is registered in my app.js

app.js

if ('serviceWorker' in navigator) {
  navigator.serviceWorker
    .register('/sw.js')
    .then(function () {
      console.log('Service worker registered!');
    })
    .catch(function (err) {
      console.log(err);
    });
}

After that, you need user permission, for example when he/her clicks on a button. Like this:

var enableNotificationsButtons = document.querySelectorAll('.enable-notifications');

if ('Notification' in window && 'serviceWorker' in navigator) {
  for (var i = 0; i < enableNotificationsButtons.length; i++) {
    enableNotificationsButtons[i].style.display = 'inline-block';
    enableNotificationsButtons[i].addEventListener('click', askForNotificationPermission);
  }
}

I got all the buttons with .enable-notifications class CSS and gave them addEventListener with click event.

You can see my app.js here: app.js · GitHub

finally, I use the elixir library:

body = ~s({"title":"New Post","content":"New Post added!","openUrl":"/help"})
subscription = %{
  keys: %{
    p256dh: "CODE_OF_p256dh", 
    auth: "CODE_OF_auth" 
  }, 
  endpoint: "https://fcm.googleapis.com/fcm/send/FCM_TOKEN"
}

{:ok, response} = WebPushEncryption.send_web_push(body, subscription)

Thanks, much appreciated! I’ll give it another go