Reverting to previously nonworking service worker to check cache

static/service-worker.js

@@ -35,10 +35,13 @@ self.addEventListener('activate', function (event) {
 
 self.addEventListener('fetch', function (event) {
     event.respondWith(
-        fetch(event.request).catch(function() {
-            return caches.match(event.request);
+        caches.match(event.request).then(function(res){
+            if(res){
+                return res;
+            }
+            requestBackend(event);
         })
-    );
+    )
 });
 
 function requestBackend(event){