sw.js

var CACHE = 'v1.1'
var filesToCache = [
  './',
  './resources/js/jquery.min.js',
  './resources/js/highlight.min.js',
  './resources/js/json-go-struct.js',
  './resources/js/common.js',
  './resources/js/example.js',
  './resources/js/gofmt.js',
  './resources/css/tomorrow.highlight.css',
  './resources/css/common.css',
  './resources/images/json-go-struct.png',
]
self.addEventListener('install', function (evt) {
  console.log('Attempting service worker installation.')
  // Wait until promise resolves
  evt.waitUntil(precache())
})
// On fetch, return from cache
self.addEventListener('fetch', function (evt) {
  evt.respondWith(serve(evt.request))
})
// Opens cache and loads filesToCache into cache for using them in future
function precache() {
  return caches.open(CACHE).then(function (cache) {
    return cache.addAll(filesToCache)
  })
}
// When a resource is requested first serve from service worker and if service
// worker hasn't cached that request, then fetch that resource and then serve it
// This strategy is cache first.
function serve(request) {
  return caches.open(CACHE).then(function (cache) {
    return cache
      .match(request)
      .then(function (matching) {
        return matching || fetch(request)
      })
      .catch(console.error)
  })
}