service-worker.js

"use strict";

// see https://github.com/chriscoyier/Simple-Offline-Site
var version = 'v1::';

var offlineResources = [
  '',
  'dist/bundle.js',
  'dist/style.css'
];

self.addEventListener("install", function(event) {
  event.waitUntil(
    caches
      .open(version + 'anvaka-send')
      .then(function(cache) {
        return cache.addAll(offlineResources);
      })
  );
});

self.addEventListener("fetch", function(event) {
  if (event.request.method !== 'GET') {
    return;
  }
  event.respondWith(
    caches
      .match(event.request)
      .then(function(cached) {
        var networked = fetch(event.request)
          .then(fetchedFromNetwork, unableToResolve)
          .catch(unableToResolve);

        return cached || networked;

        function fetchedFromNetwork(response) {
          var cacheCopy = response.clone();

          caches
            .open(version + 'pages')
            .then(function add(cache) {
              cache.put(event.request, cacheCopy);
            });

          return response;
        }

        function unableToResolve () {
          return new Response('<h1>Service Unavailable</h1>', {
            status: 503,
            statusText: 'Service Unavailable',
            headers: new Headers({
              'Content-Type': 'text/html'
            })
          });
        }
      })
  );
});

self.addEventListener("activate", function(event) {
  event.waitUntil(
    caches
      .keys()
      .then(function (keys) {
        return Promise.all(
          keys.filter(function (key) {
              return !key.startsWith(version);
            })
            .map(function (key) {
              return caches.delete(key);
            })
        );
      })
  );
});