add interceptors to http client

static/js/services/httpClient.js

@@ -1,8 +1,16 @@
-(function collonadeClosure() {
+(function () {
   'use strict';
 
   window.HttpClient = (function() {
 
+    var _responseInterceptors = [];
+
+    function addResponseInterceptor(interceptor) {
+      if (typeof interceptor === 'function') {
+        _responseInterceptors.push(interceptor);
+      }
+    }
+
     function _fetch(url, method, additionalHeaders, body) {
       var requestOptions = {
         credentials: 'same-origin',
@@ -15,7 +23,17 @@
         requestOptions.headers[headerKey] = additionalHeaders[headerKey];
       });
 
-      return fetch(url, requestOptions);
+      return fetch(url, requestOptions).then(
+        function(response) {
+          _responseInterceptors.forEach(function(interceptor) { interceptor(response); });
+          return Promise.resolve(response);
+        },
+        function(error) {
+          return Promise.reject(error);
+        }
+      ).catch(function(error) {
+        console.error(error);
+      });
     }
 
     return {
@@ -25,6 +43,7 @@
       post: function(url, headers, body) {
         return _fetch(url, 'POST', headers, body);
       },
+      addResponseInterceptor: addResponseInterceptor,
     }
   })();
 })();