index.js

self.addEventListener('install', () => {
  console.log('ServiceWorker がインストールされました');
});

self.addEventListener('push', ev => {
  // payloadの取得
  const {title, msg, icon} = ev.data.json();
  self.registration.showNotification(title, {
    icon: icon,
    body: msg
  });
  self.registration.pushManager.getSubscription().then(subscription => {
    console.log(subscription);
  }, err => console.log(err));
});