code: function update(request) {
    // don't automatically put 3D models in the cache
    if(request.url.match(/https:\/\/storage.3d.io/)) return fetch(request);
  
    return caches.open(CACHE).then(function (cache) {
      return fetch(request).then(function (response) {
        return cache.put(request, response);
      });
    });
  }
docs: Update consists in opening the cache, performing a network request and storing the new response data.