https://yzune.github.io/sw.js

1/* ===========================================================
2 * sw.js
3 * ===========================================================
4 * Copyright 2016 @huxpro
5 * Licensed under Apache 2.0 
6 * Register service worker.
7 * ========================================================== */
8
9const PRECACHE = 'precache-v1';
10const RUNTIME = 'runtime';
11const HOSTNAME_WHITELIST = [
12  self.location.hostname,
13  "huangxuan.me",
14  "yanshuo.io",
15  "cdnjs.cloudflare.com"
16]
17
18
19// The Util Function to hack URLs of intercepted requests
20const getFixedUrl = (req) => {
21  var now = Date.now();
22  url = new URL(req.url)
23
24  // 1. fixed http URL
25  // Just keep syncing with location.protocol 
26  // fetch(httpURL) belongs to active mixed content. 
27  // And fetch(httpRequest) is not supported yet.
28  url.protocol = self.location.protocol
29
30  // 2. add query for caching-busting.
31  // Github Pages served with Cache-Control: max-age=600
32  // max-age on mutable content is error-prone, with SW life of bugs can even extend.
33  // Until cache mode of Fetch API landed, we have to workaround cache-busting with query string.
34  // Cache-Control-Bug: https://bugs.chromium.org/p/chromium/issues/detail?id=453190
35  url.search += (url.search ? '&' : '?') + 'cache-bust=' + now;
36  return url.href
37}
38
39// The Util Function to detect and polyfill req.mode="navigate"
40// request.mode of 'navigate' is unfortunately not supported in Chrome
41// versions older than 49, so we need to include a less precise fallback,
42// which checks for a GET request with an Accept: text/html header.
43const isNavigationReq = (req) => (req.mode === 'navigate' || (req.method === 'GET' && req.headers.get('accept').includes('text/html')))
44
45// The Util Function to detect if a req is end with extension
46// Accordin to Fetch API spec <https://fetch.spec.whatwg.org/#concept-request-destination>
47// Any HTML's navigation has consistently mode="navigate" type="" and destination="document" 
48// including requesting an img (or any static resources) from URL Bar directly.
49// So It ends up with that regExp is still the king of URL routing ;)
50// P.S. An url.pathname has no '.' can not indicate it ends with extension (e.g. /api/version/1.2/)
51const endWithExtension = (req) => Boolean(new URL(req.url).pathname.match(/\.\w+$/))
52
53// Redirect in SW manually fixed github pages arbitray 404s on things?blah 
54// what we want:
55//    repo?blah -> !(gh 404) -> sw 302 -> repo/?blah 
56//    .ext?blah -> !(sw 302 -> .ext/?blah -> gh 404) -> .ext?blah 
57// If It's a navigation req and it's url.pathname isn't end with '/' or '.ext'
58// it should be a dir/repo request and need to be fixed (a.k.a be redirected)
59// Tracking https://twitter.com/Huxpro/status/798816417097224193
60const shouldRedirect = (req) => (isNavigationReq(req) && new URL(req.url).pathname.substr(-1) !== "/" && !endWithExtension(req))
61
62// The Util Function to get redirect URL
63// `${url}/` would mis-add "/" in the end of query, so we use URL object.
64// P.P.S. Always trust url.pathname instead of the whole url string.
65const getRedirectUrl = (req) => {
66  url = new URL(req.url)
67  url.pathname += "/"
68  return url.href
69}
70
71/**
72 *  @Lifecycle Install
73 *  Precache anything static to this version of your app.
74 *  e.g. App Shell, 404, JS/CSS dependencies...
75 *
76 *  waitUntil() : installing ====> installed
77 *  skipWaiting() : waiting(installed) ====> activating
78 */
79self.addEventListener('install', e => {
80  e.waitUntil(
81    caches.open(PRECACHE).then(cache => {
82      return cache.add('offline.html')
83      .then(self.skipWaiting())
84      .catch(err => console.log(err))
85    })
86  )
87});
88
89
90/**
91 *  @Lifecycle Activate
92 *  New one activated when old isnt being used.
93 *
94 *  waitUntil(): activating ====> activated
95 */
96self.addEventListener('activate',  event => {
97  console.log('service worker activated.')
98  event.waitUntil(self.clients.claim());
99});
100
101
102/**
103 *  @Functional Fetch
104 *  All network requests are being intercepted here.
105 * 
106 *  void respondWith(Promise<Response> r);
107 */
108self.addEventListener('fetch', event => {
109  // logs for debugging
110  console.log(`fetch ${event.request.url}`)
111  //console.log(` - type: ${event.request.type}; destination: ${event.request.destination}`)
112  //console.log(` - mode: ${event.request.mode}, accept: ${event.request.headers.get('accept')}`)
113
114  // Skip some of cross-origin requests, like those for Google Analytics.
115  if (HOSTNAME_WHITELIST.indexOf(new URL(event.request.url).hostname) > -1) {
116    
117    // Redirect in SW manually fixed github pages 404s on repo?blah 
118    if(shouldRedirect(event.request)){
119      event.respondWith(Response.redirect(getRedirectUrl(event.request)))
120      return;
121    }
122
123    // Stale-while-revalidate 
124    // similar to HTTP's stale-while-revalidate: https://www.mnot.net/blog/2007/12/12/stale
125    // Upgrade from Jake's to Surma's: https://gist.github.com/surma/eb441223daaedf880801ad80006389f1

126    const cached = caches.match(event.request);
127    const fixedUrl = getFixedUrl(event.request);
128    const fetched = fetch(fixedUrl, {cache: "no-store"});
129    const fetchedCopy = fetched.then(resp => resp.clone());
130
131    // Call respondWith() with whatever we get first.
132    // If the fetch fails (e.g disconnected), wait for the cache.
133    // If there’s nothing in cache, wait for the fetch. 
134    // If neither yields a response, return offline pages.
135    event.respondWith(
136      Promise.race([fetched.catch(_ => cached), cached])
137        .then(resp => resp || fetched)
138        .catch(_ => caches.match('offline.html'))
139    );
140
141    // Update the cache with the version we fetched (only for ok status)
142    event.waitUntil(
143      Promise.all([fetchedCopy, caches.open(RUNTIME)])
144        .then(([response, cache]) => response.ok && cache.put(event.request, response))
145        .catch(_ => {/* eat any errors */})
146    );
147  }
148});