more readability: use fetch and cache

cachersw.js

@@ -52,9 +52,8 @@ self.addEventListener('install', (event) => {
      *
      *
      */
-/*
 self.fetch_and_cache = function (evreq) {
-  fetch(evreq).then((response) => {
+  return fetch(evreq).then((response) => {
     return caches.open('v1').then((cache) => {
       console.log('fetch and cache ' + evreq);
       cache.put(evreq, response.clone());
@@ -64,7 +63,6 @@ self.fetch_and_cache = function (evreq) {
     });
   });
 } 
-*/
 
 /**
  *
@@ -94,17 +92,7 @@ self.addEventListener('fetch', (event) => {
       // but in case of success response will have value
       if (cachedResponse !== undefined) 
         return cachedResponse;
-    return fetch(event.request).then(function (response) {
-      // response may be used only once
-      // we need to save clone to put one copy in cache
-      // and serve second one
-      let responseClone = response.clone();
-      
-      caches.open('v1').then(function (cache) {
-        cache.put(event.request, responseClone);
-      });
-      return response;
-    });
+      return self.fetch_and_cache(event.request)
     }));
 
   });