https://okoptica.ru/pwabuilder-sw.js

1// This is the "Offline page" service worker
2
3importScripts('https://storage.googleapis.com/workbox-cdn/releases/5.1.2/workbox-sw.js');
4
5const CACHE = 'pwabuilder-page';
6
7const offlineFallbackPage = '/offline.html';
8
9self.addEventListener('message', (event) => {
10    if (event.data && event.data.type === 'SKIP_WAITING') {
11        self.skipWaiting();
12    }
13});
14
15self.addEventListener('install', async(event) => {
16    event.waitUntil(
17        caches.open(CACHE)
18              .then((cache) => cache.add(offlineFallbackPage))
19    );
20});
21
22if (workbox.navigationPreload.isSupported()) {
23    workbox.navigationPreload.enable();
24}
25
26self.addEventListener('fetch', (event) => {
27    if (event.request.mode === 'navigate') {
28        event.respondWith((async() => {
29            try {
30                const preloadResp = await event.preloadResponse;
31
32                if (preloadResp) {
33                    return preloadResp;
34                }
35
36                const networkResp = await fetch(event.request);
37                return networkResp;
38            } catch (error) {
39
40                const cache      = await caches.open(CACHE);
41                const cachedResp = await cache.match(offlineFallbackPage);
42                return cachedResp;
43            }
44        })());
45    }
46});