Your service worker - sw.js

self.addEventListener('push', event => {
  const data = event.data.json();

  if (data.action === 'SW_REGISTRATION_SUBSCRIPTION') {
    self.registration.showNotification('BSB PUSH Service', {
      body: 'Messages will show up like this one.',
    });
  }
});
self.skipWaiting();

In site, reference this host and script.js

window.bsb.push will have your functions:

window.bsb.push.isAvailable() - is SW available

window.bsb.push.isRegistered() - is push registered

window.bsb.push.isSubscribed() - have you already subbed

window.bsb.push.unSubscribe() - unsubscribe

window.bsb.push.subscribe() - subscribe for push