const RUNTIME = 'docsify' const HOSTNAME_WHITELIST = [ self.location.hostname, 'fonts.gstatic.com', 'fonts.googleapis.com', 'unpkg.com' ] // The Util Function to hack URLs of intercepted requests const getFixedUrl = (req) => { var now = Date.now() var url = new URL(req.url) // 1. fixed http URL // Just keep syncing with location.protocol // fetch(httpURL) belongs to active mixed content. // And fetch(httpRequest) is not supported yet. url.protocol = self.location.protocol // 2. add query for caching-busting. // Github Pages served with Cache-Control: max-age=600 // max-age on mutable content is error-prone, with SW life of bugs can even extend. // Until cache mode of Fetch API landed, we have to workaround cache-busting with query string. // Cache-Control-Bug: https://bugs.chromium.org/p/chromium/issues/detail?id=453190 if (url.hostname === self.location.hostname) { url.search += (url.search ? '&' : '?') + 'cache-bust=' + now } return url.href } /** * @Lifecycle Activate * New one activated when old isnt being used. * * waitUntil(): activating ====> activated */ self.addEventListener('activate', event => { event.waitUntil(self.clients.claim()) }) /** * @Functional Fetch * All network requests are being intercepted here. * * void respondWith(Promise r) */ self.addEventListener('fetch', event => { // Skip some of cross-origin requests, like those for Google Analytics. if (HOSTNAME_WHITELIST.indexOf(new URL(event.request.url).hostname) > -1) { // Stale-while-revalidate // similar to HTTP's stale-while-revalidate: https://www.mnot.net/blog/2007/12/12/stale // Upgrade from Jake's to Surma's: https://gist.github.com/surma/eb441223daaedf880801ad80006389f1 const cached = caches.match(event.request) const fixedUrl = getFixedUrl(event.request) const fetched = fetch(fixedUrl, { cache: 'no-store' }) const fetchedCopy = fetched.then(resp => resp.clone()) // Call respondWith() with whatever we get first. // If the fetch fails (e.g disconnected), wait for the cache. // If there’s nothing in cache, wait for the fetch. // If neither yields a response, return offline pages. event.respondWith( Promise.race([fetched.catch(_ => cached), cached]) .then(resp => resp || fetched) .catch(_ => { /* eat any errors */ }) ) // Update the cache with the version we fetched (only for ok status) event.waitUntil( Promise.all([fetchedCopy, caches.open(RUNTIME)]) .then(([response, cache]) => response.ok && cache.put(event.request, response)) .catch(_ => { /* eat any errors */ }) ) } })