typo

serviceWorker.js

@@ -34,7 +34,7 @@ self.addEventListener('install', function(event){
             return caches.open(myCache.name)
                 .then(function (cache){
                     console.log("[Cache] opened: ", myCache.name);
-                    return caches.addAll(myCache.urls);
+                    return cache.addAll(myCache.urls);
                 });
         })
     ))