Service Worker example for controlling what is cached - See https://malloc.fi/fix-duplicate-redirects-service-worker-caching

sw.js

self.addEventListener('install', function (event) {
    event.waitUntil(preLoad());
});

var preLoad = function () {
    //    console.log('[PWA Builder] Install Event processing');
    return caches.open('pwabuilder-offline').then(function (cache) {
        //        console.log('[PWA Builder] Cached index and offline page during Install');
        return cache.addAll(['/offline.html', '/']);
    });
}

self.addEventListener('fetch', function (event) {
    //    console.log('The service worker is serving the asset.');
    event.respondWith(checkResponse(event.request).catch(function () {
        return returnFromCache(event.request)
    }
    ));

    var storeInCache = true;
    var dontCache = [
        'sw.js',
        '/_redirect'
    ];

    dontCache.forEach(function (element) {
        if (event.request.url.includes(element)) {
            storeInCache = false;
        }
    }, this);
    
    if (storeInCache) {
        event.waitUntil(addToCache(event.request));
    } else {
        console.log('do not cache ' + event.request.url);
    }
});

var checkResponse = function (request) {
    return new Promise(function (fulfill, reject) {
        fetch(request).then(function (response) {
            if (response.status !== 404) {
                fulfill(response)
            } else {
                reject()
            }
        }, reject)
    });
};

var addToCache = function(request){
    return caches.open('pwabuilder-offline').then(function (cache) {
      return fetch(request).then(function (response) {
//        console.log('[PWA Builder] add page to offline'+response.url)
        return cache.put(request, response);
      });
    });
  };

var returnFromCache = function (request) {
    return caches.open('pwabuilder-offline').then(function (cache) {
        return cache.match(request).then(function (matching) {
            if (!matching || matching.status == 404) {
                return cache.match('offline.html')
            } else {
                return matching
            }
        });
    });
};