merge

src/controller/MainController.jsx

@@ -18,7 +18,7 @@ store.sub(['navigation.current', 'loaded.cards'], async function(page, loaded) {
       const result = await AsyncAuthAjax.get( API.ENDPOINTS.GET_USER_NEW_CARDS() );
 
       result.forEach(function(card) {
-        cards.set(card.id+'', {...card, seen: false})
+        cards.set(card.id+'', Object.assign({},card, {seen: false}));
       });
       store.set('loaded.cards', true);
 

src/core/Ajax.jsx

 const transformCfg = function(cfg) {
-  return {
-    ...cfg,
-    headers: {
-      'Content-Type': 'application/json',
-      ...(cfg && cfg.headers || {})
-    }
-  }
+  return Object.assign({}, cfg, {
+    headers: Object.assign(
+      {'Content-Type': 'application/json'},
+      cfg && cfg.headers || {}
+    )
+  });
 };
 const xhrProceed = function(method, xhr, cfg, cb) {
   xhr.open(method, cfg.url, true);