resSW.js

// Chrome's currently missing some useful cache methods,
// this polyfill adds them.
importScripts('serviceworker-cache-polyfill.js');

// install event!
self.addEventListener('install', function(event) {
  // We pass a promise to event.waitUntil to signal how 
  // long install takes, and if it failed
  event.waitUntil(
    // We open a cache…
    caches.open('res-sw-1').then(function(cache) {
      // And add resources to it
      return cache.addAll([
        './', 
        'index.html',
       'restaurant.html',
        'css/styles.css', 
        'js/dbhelper.js', 
        'js/main.js', 
        'js/restaurant_info.js',
         'data/restaurants.json' 
    ]);
    })
  );
});

// The fetch event happens for the page request with the
// ServiceWorker's scope, and any request made within that
// page
self.addEventListener('fetch', function(event) {
  // Calling event.respondWith means we're in charge
  // of providing the response. We pass in a promise
  // that resolves with a response object
  event.respondWith(
    // First we look for something in the caches that
    // matches the request
    caches.match(event.request).then(function(response) {
      // If we get something, we return it, otherwise
      // it's null, and we'll pass the request to
      // fetch, which will use the network.
      return response || fetch(event.request);
    })
  );
});