index.js

var urlsToCache = [
  '/',
  '/bower_components/jquery/dist/jquery.min.js',
  '/bower_components/hifive/h5.js',
  '/bower_components/hifive/h5.css',
  '/bower_components/hifive/ejs-h5mod.js',
  '/ncmb.min.js',
  '/app.js'
];

self.addEventListener('install', function(event) {
  return install(event);
});

self.addEventListener('message', function(event) {
  return install(event);
});

const install = (event) => {
  return event.waitUntil(
    caches.open(CACHE_NAME)
      .then(function(cache) {
        urlsToCache.map(url => {
          return fetch(new Request(url)).then(response => {
            return cache.put(url, response);
          });
        })
      })
      .catch(function(err) {
        console.log(err);
      })
  );
}