serviceWorker.js

const VERSION = 'v3'

self.addEventListener('fetch', function (event) {
	event.respondWith(
		caches.open(VERSION).then(function (cache) {
			return cache.match(event.request).then(function (response) {
				var fetchPromise = fetch(event.request).then(function (
					networkResponse,
				) {
					cache.put(event.request, networkResponse.clone())
					return networkResponse
				})
				return response || fetchPromise
			})
		}),
	)
})