服务工作者也用于onMessage:

The service worker is also used for the onMessage:

/**
 * Check out https://googlechromelabs.github.io/sw-toolbox/ for
 * more info on how to use sw-toolbox to custom configure your service worker.
 */


'use strict';
//importScripts('./build/sw-toolbox.js');
importScripts('https://www.gstatic.com/firebasejs/4.8.1/firebase-app.js');
importScripts('https://www.gstatic.com/firebasejs/4.8.1/firebase-messaging.js');

firebase.initializeApp({
  'messagingSenderId': '147703423097'
});

const messaging = firebase.messaging();

messaging.setBackgroundMessageHandler(function(payload) {
  console.log('[firebase-messaging-sw.js] Received background message ', payload);
  // Customize notification here
  const notificationTitle = 'Background Message Title';
  const notificationOptions = {
    body: 'Background Message body.',
    icon: '/firebase-logo.png'
  };

  return self.registration.showNotification(notificationTitle,
      notificationOptions);
});