text: 'use strict'
  
  // Give the service worker access to Firebase Messaging.
  // Note that you can only use Firebase Messaging here, other Firebase libraries
  // are not available in the service worker.
  importScripts('https://www.gstatic.com/firebasejs/5.3.1/firebase-app.js')
  importScripts('https://www.gstatic.com/firebasejs/5.3.1/firebase-messaging.js')
  
  // Initialize the Firebase app in the service worker by passing in the
  // messagingSenderId.
  firebase.initializeApp({
    messagingSenderId: 'SENDER_ID'
  })
  
  // Retrieve an instance of Firebase Messaging so that it can handle background
  // messages.
  const messaging = firebase.messaging()
  
  messaging.setBackgroundMessageHandler((e) => {
    console.log('[Service Worker] Push Received', e)
    // Customize notification here
    const title = 'Push Title'
    const options = {
      body: e.data.text
    }
  
    return self.registration.showNotification(title, options)
  })
  