Better example of custom service worker cache keys

service-worker-cache-example.js

var jsonDataRe = /example\.com\/(.*\.json)/;

self.addEventListener('fetch', function(event) {
    var request = event.request,
        match = jsonDataRe.exec(request.url);

    if (match) {
        // Use regex capturing to grab only the bit of the URL
        // that we care about, ignoring query string, etc.
        var cacheRequest = new Request(match[1]);
        event.respondWith(
            caches.match(cacheRequest).then(function(response) {
                return response || fetch(request).then(function(response) {
                    caches.open('mycache').then(function(cache) {
                      cache.put(cacheRequest, response);
                    })
                    return response;
                });
            })
        );
    }
});