docs/sw.js

   1 /* ===========================================================
   2  * docsify sw.js
   3  * ===========================================================
   4  * Copyright 2016 @huxpro
   5  * Licensed under Apache 2.0
   6  * Register service worker.
   7  * ========================================================== */
   8
   9 const RUNTIME = 'docsify'
  10 const HOSTNAME_WHITELIST = [
  11   self.location.hostname,
  12   'fonts.gstatic.com',
  13   'fonts.googleapis.com',
  14   'unpkg.com'
  15 ]
  16
  17 // The Util Function to hack URLs of intercepted requests
  18 const getFixedUrl = (req) => {
  19   var now = Date.now()
  20   var url = new URL(req.url)
  21
  22   // 1. fixed http URL
  23   // Just keep syncing with location.protocol
  24   // fetch(httpURL) belongs to active mixed content.
  25   // And fetch(httpRequest) is not supported yet.
  26   url.protocol = self.location.protocol
  27
  28   // 2. add query for caching-busting.
  29   // Github Pages served with Cache-Control: max-age=600
  30   // max-age on mutable content is error-prone, with SW life of bugs can even extend.
  31   // Until cache mode of Fetch API landed, we have to workaround cache-busting with query string.
  32   // Cache-Control-Bug: https://bugs.chromium.org/p/chromium/issues/detail?id=453190
  33   if (url.hostname === self.location.hostname) {
  34     url.search += (url.search ? '&' : '?') + 'cache-bust=' + now
  35   }
  36   return url.href
  37 }
  38
  39 /**
  40  *  @Lifecycle Activate
  41  *  New one activated when old isnt being used.
  42  *
  43  *  waitUntil(): activating ====> activated
  44  */
  45 self.addEventListener('activate', event => {
  46   event.waitUntil(self.clients.claim())
  47 })
  48
  49 /**
  50  *  @Functional Fetch
  51  *  All network requests are being intercepted here.
  52  *
  53  *  void respondWith(Promise<Response> r)
  54  */
  55 self.addEventListener('fetch', event => {
  56   // Skip some of cross-origin requests, like those for Google Analytics.
  57   if (HOSTNAME_WHITELIST.indexOf(new URL(event.request.url).hostname) > -1) {
  58     // Stale-while-revalidate
  59     // similar to HTTP's stale-while-revalidate: https://www.mnot.net/blog/2007/12/12/stale
  60     // Upgrade from Jake's to Surma's: https://gist.github.com/surma/eb441223daaedf880801ad80006389f1
  61     const cached = caches.match(event.request)
  62     const fixedUrl = getFixedUrl(event.request)
  63     const fetched = fetch(fixedUrl, { cache: 'no-store' })
  64     const fetchedCopy = fetched.then(resp => resp.clone())
  65
  66     // Call respondWith() with whatever we get first.
  67     // If the fetch fails (e.g disconnected), wait for the cache.
  68     // If there’s nothing in cache, wait for the fetch.
  69     // If neither yields a response, return offline pages.
  70     event.respondWith(
  71       Promise.race([fetched.catch(_ => cached), cached])
  72         .then(resp => resp || fetched)
  73         .catch(_ => { /* eat any errors */ })
  74     )
  75
  76     // Update the cache with the version we fetched (only for ok status)
  77     event.waitUntil(
  78       Promise.all([fetchedCopy, caches.open(RUNTIME)])
  79         .then(([response, cache]) => response.ok && cache.put(event.request, response))
  80         .catch(_ => { /* eat any errors */ })
  81     )
  82   }
  83 })