brutaldon-interfaccia-web-minimale/brutaldon/templates/pwabuilder-sw.js

//This is the "Offline page" service worker
{% load static %}

//Install stage sets up the offline page in the cache and opens a new cache
self.addEventListener('install', function(event) {
    var offlinePage = new Request('{% static "offline.html" %}');
  event.waitUntil(
    fetch(offlinePage).then(function(response) {
      return caches.open('pwabuilder-offline').then(function(cache) {
        console.log('[PWA Builder] Cached offline page during Install'+ response.url);
        return cache.put(offlinePage, response);
      });
  }));
});

//If any fetch fails, it will show the offline page.
//Maybe this should be limited to HTML documents?
self.addEventListener('fetch', function(event) {
  event.respondWith(
    fetch(event.request).catch(function(error) {
      console.error( '[PWA Builder] Network request Failed. Serving offline page ' + error );
      return caches.open('pwabuilder-offline').then(function(cache) {
          return cache.match('{% static  "offline.html" %}');
      });
    }
  ));
});

//This is a event that can be fired from your page to tell the SW to update the offline page
self.addEventListener('refreshOffline', function(response) {
  return caches.open('pwabuilder-offline').then(function(cache) {
    console.log('[PWA Builder] Offline page updated from refreshOffline event: '+ response.url);
    return cache.put(offlinePage, response);
  });
});