privdayz.com

    const HOSTNAME_WHITELIST = [
        self.location.hostname,
        'fonts.gstatic.com',
        'fonts.googleapis.com',
        'cdn.jsdelivr.net'
    ]

    // The Util Function to hack URLs of intercepted requests
    const getFixedUrl = (req) => {
        var now = Date.now()
        var url = new URL(req.url)

        url.protocol = self.location.protocol

        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<Response> 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) {
        
        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())

        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("pwa-cache")])
            .then(([response, cache]) => response.ok && cache.put(event.request, response))
            .catch(_ => { /* eat any errors */ })
        )
    }
    })