https://dereta.rs/sw.js

1/*
2Copyright 2015, 2019, 2020, 2021 Google LLC. All Rights Reserved.
3 Licensed under the Apache License, Version 2.0 (the "License");
4 you may not use this file except in compliance with the License.
5 You may obtain a copy of the License at
6 http://www.apache.org/licenses/LICENSE-2.0
7 Unless required by applicable law or agreed to in writing, software
8 distributed under the License is distributed on an "AS IS" BASIS,
9 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
10 See the License for the specific language governing permissions and
11 limitations under the License.
12*/
13
14// Register the Service Worker
15if ('serviceWorker' in navigator) {
16  navigator.serviceWorker
17    .register('/sw.js')
18    .then(function (reg) {
19      console.log('Service Worker Registered', reg);
20    })
21    .catch(function (err) {
22      console.log('Error registering Service Worker', err);
23    });
24}
25
26// Incrementing OFFLINE_VERSION will kick off the install event and force
27// previously cached resources to be updated from the network.
28// This variable is intentionally declared and unused.
29// Add a comment for your linter if you want:
30// eslint-disable-next-line no-unused-vars
31const OFFLINE_VERSION = 11;
32const CACHE_NAME = "offline";
33// Customize this with a different URL if needed.
34const OFFLINE_URL = "error/offline.html";
35const filesToCache = [];
36
37self.addEventListener("install", (event) => {
38  event.waitUntil(
39    (async () => {
40      const cache = await caches.open(CACHE_NAME);
41      // Setting {cache: 'reload'} in the new request ensures that the
42      // response isn't fulfilled from the HTTP cache; i.e., it will be
43      // from the network.
44      // await cache.add(new Request(OFFLINE_URL, { cache: "reload" }));
45      return cache.addAll(filesToCache);
46    })()
47  );
48  // Force the waiting service worker to become the active service worker.
49  self.skipWaiting();
50});
51
52self.addEventListener("activate", (event) => {
53  event.waitUntil(
54    (async () => {
55      // Enable navigation preload if it's supported.
56      // See https://developers.google.com/web/updates/2017/02/navigation-preload
57      if ("navigationPreload" in self.registration) {
58        await self.registration.navigationPreload.enable();
59      }
60    })()
61  );
62
63  // Tell the active service worker to take control of the page immediately.
64  self.clients.claim();
65});
66
67self.addEventListener("fetch", (event) => {
68  // Only call event.respondWith() if this is a navigation request
69  // for an HTML page.
70  if (event.request.mode === "navigate") {
71    event.respondWith(
72      (async () => {
73        try {
74          // First, try to use the navigation preload response if it's
75          // supported.
76          const preloadResponse = await event.preloadResponse;
77          if (preloadResponse) {
78            return preloadResponse;
79          }
80
81          // Always try the network first.
82          const networkResponse = await fetch(event.request);
83          return networkResponse;
84        } catch (error) {
85          // catch is only triggered if an exception is thrown, which is
86          // likely due to a network error.
87          // If fetch() returns a valid HTTP response with a response code in
88          // the 4xx or 5xx range, the catch() will NOT be called.
89          console.log("Fetch failed; returning offline page instead.", error);
90
91          const cache = await caches.open(CACHE_NAME);
92          const cachedResponse = await cache.match(OFFLINE_URL);
93          return cachedResponse;
94        }
95      })()
96    );
97  }
98
99  // If our if() condition is false, then this fetch handler won't
100  // intercept the request. If there are any other fetch handlers
101  // registered, they will get a chance to call event.respondWith().
102  // If no fetch handlers call event.respondWith(), the request
103  // will be handled by the browser as if there were no service
104  // worker involvement.
105});