如何在PWA中实现推送通知？

Notification.requestPermission().then(function(permission) {
  if (permission === 'granted') {
    console.log('用户已授权');
  } else {
    console.log('用户未授权');
  }
});

self.addEventListener('push', function(event) {
  console.log('收到推送通知');
  const payload = event.data.json();
  const title = payload.title;
  const options = {
    body: payload.body,
    icon: payload.icon
  };
  event.waitUntil(self.registration.showNotification(title, options));
});