{
    "name": "Progressive Web App",
    "short_name": "PWA",
    "icons": [{
      "src": "./icon-256.png",
        "sizes": "256x256",
        "type": "image/png"
      }],
    "lang": "en-US",
    "start_url": "./index.html",
    "display": "standalone",
    "background_color": "white",
    "theme_color": "white"
}

<script>
    // register ServiceWorker
    window.onload = () => {
        'use strict';
        if ('serviceWorker' in navigator) {
            navigator.serviceWorker
                    .register('./service_worker.js');
        }
    }
</script>

var cacheName = 'pwa';
var filesToCache = [
  './',
  './index.html',
  './build/bundle.js',
  './build/bundle.wasm'
];
/* Start the service worker and cache all of the app's content */
self.addEventListener('install', function(e) {
  e.waitUntil(
    caches.open(cacheName).then(function(cache) {
      return cache.addAll(filesToCache);
    })
  );
});
/* Serve cached content when offline */
self.addEventListener('fetch', function(e) {
  e.respondWith(
    caches.match(e.request).then(function(response) {
      return response || fetch(e.request);
    })
  );
});