sw.js

const VERSION ='v1';

self. addEventListener('install', event=>{
  event.waitUntil(precache())
})

self.addEventListener('fetch', event=>{
  const request = event.request;
  //get
 if (request.method !== 'GET') {
    return;
  }

 // buscar en cache
  event.respondWith(cachedResponse(request));

  // actualizar el cache
  event.waitUntil(updateCache(request));

});


async function precache (){
  const cache = await  caches.open(VERSION)
  return cache.addAll([
    '/index.html',
   '/assets/*',
  ]);
}

async function cachedResponse (request){

  const cache = await caches.open(VERSION);
  const response = await cache.match(request);
  return  response || fetch(request);
}

async function updateCache (request){

  const cache = await caches.open(VERSION);
  const response = await fetch(request);
  return cache.put(request, response);
}