sw.js

const CACHE_NAME = 'gradus-v1';

const ASSETS = [
  './',
  './index.html',
  './icon.png',
  './icon-192.png',
  './icon-512.png',
  './manifest.webmanifest'
];

self.addEventListener('install', event => {
  event.waitUntil(
    caches.open(CACHE_NAME).then(cache => {
      return cache.addAll(ASSETS);
    })
  );
  self.skipWaiting();
});

self.addEventListener('activate', event => {
  event.waitUntil(
    caches.keys().then(keys => {
      return Promise.all(
        keys
          .filter(key => key !== CACHE_NAME)
          .map(key => caches.delete(key))
      );
    })
  );
  self.clients.claim();
});

self.addEventListener('fetch', event => {
  event.respondWith(
    caches.match(event.request).then(response => {
      return response || fetch(event.request);
    })
  );
});