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) {
     });
   });
 } 
-*/
 
 /**
  *
@@ -90,21 +88,11 @@ self.addEventListener('fetch', (event) => {
   }
 
   event.respondWith(caches.match(event.request).then(function(cachedResponse) {
-    // caches.match() always resolves
-    // 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;
-    });
-  }));
+      // caches.match() always resolves
+      // but in case of success response will have value
+      if (cachedResponse !== undefined) 
+        return cachedResponse;
+      return self.fetch_and_cache(event.request)
+    }));
 
   });