sw.js

var cacheName = 'bpm-v6';
var filesToCache = [
  '/',
  '/index.html',
  '/index.js',
  '/styles.css'
];

self.addEventListener('install', function(e) {
  console.log('[ServiceWorker] Install');
  e.waitUntil(
    caches.open(cacheName).then(function(cache) {
      console.log('[ServiceWorker] Caching app shell');
      return cache.addAll(filesToCache);
    })
  );
});

self.addEventListener('activate', event => {
  console.log('[ServiceWorker] Activate');
  event.waitUntil(
    caches.keys().then(function(keyList) {
      return Promise.all(keyList.map(function(key) {
        if (key !== cacheName) {
          console.log('[ServiceWorker] Removing old cache', key);
          return caches.delete(key);
        }
      }));
    })
  );

  return self.clients.claim();
});

self.addEventListener('fetch', event => {
  console.log('[ServiceWorker] Fetch', event.request.url);
  event.respondWith(
    caches.match(event.request, {ignoreSearch:true}).then(response => {
      return response || fetch(event.request);
    })
  );
});