service-worker.js

var CACHE_NAME = 'du-scale-cache-v2';

var urlsToCache = [
  '/du-scales/',
  '/du-scales/index.html',
  '/du-scales/src/d3.min.js',
  '/du-scales/src/data/data.js',
  '/du-scales/src/du-scales.js',
  '/du-scales/src/du-style-prefixed.css',
  '/du-scales/src/logos/du-logo.svg',
  '/du-scales/src/logos/joke-logo.svg',
  '/du-scales/src/logos/du-logo-2.svg',
  '/du-scales/src/logos/d3-logo.svg',
  '/du-scales/src/logos/github-logo.svg',
  '/du-scales/src/images/logo-16x16.png',
  '/du-scales/src/images/logo-32x32.png',
  '/du-scales/src/images/logo-57x57.png',
  '/du-scales/src/images/logo-72x72.png',
  '/du-scales/src/images/logo-96x96.png',
  '/du-scales/src/images/logo-114x114.png',
  '/du-scales/src/images/logo-128x128.png',
  '/du-scales/src/images/logo-270x270.png',
  '/du-scales/src/images/logo-558x558.png'
];

self.addEventListener('install', function(event) {
  event.waitUntil(
    caches.open(CACHE_NAME)
      .then(function(cache) {
        console.log('Opened cache');
        return cache.addAll(urlsToCache);
      })
  );
});

self.addEventListener('fetch', function(event) {
  event.respondWith(
    caches.match(event.request)
      .then(function(response) {
        // Cache hit - return response
        if (response) {
          return response;
        }

        return fetch(event.request).then(
          function(response) {
            // Check if we received a valid response
            if(!response || response.status !== 200 || response.type !== 'basic') {
              return response;
            }

            // IMPORTANT: Clone the response. A response is a stream
            // and because we want the browser to consume the response
            // as well as the cache consuming the response, we need
            // to clone it so we have two streams.
            var responseToCache = response.clone();

            caches.open(CACHE_NAME)
              .then(function(cache) {
                cache.put(event.request, responseToCache);
              });

            return response;
          }
        );
      })
    );
});

self.addEventListener('activate', function(event) {

  var cacheWhitelist = ['du-scale-cache-v2'];

  event.waitUntil(
    caches.keys().then(function(cacheNames) {
      return Promise.all(
        cacheNames.map(function(cacheName) {
          if (cacheWhitelist.indexOf(cacheName) === -1) {
            return caches.delete(cacheName);
          }
        })
      );
    })
  );
});