refactor($http): clean up code

Closes #14921

Author: gkalpak

src/ng/http.js

@@ -586,7 +586,7 @@ function $HttpProvider() {
      *
      * ### Overriding the Default Transformations Per Request
      *
-     * If you wish override the request/response transformations only for a single request then provide
+     * If you wish to override the request/response transformations only for a single request then provide
      * `transformRequest` and/or `transformResponse` properties on the configuration object passed
      * into `$http`.
      *
@@ -959,25 +959,23 @@ function $HttpProvider() {
       config.paramSerializer = isString(config.paramSerializer) ?
           $injector.get(config.paramSerializer) : config.paramSerializer;
 
-      var chain = [serverRequest, undefined];
+      var requestInterceptors = [];
+      var responseInterceptors = [];
       var promise = $q.when(config);
 
       // apply interceptors
       forEach(reversedInterceptors, function(interceptor) {
         if (interceptor.request || interceptor.requestError) {
-          chain.unshift(interceptor.request, interceptor.requestError);
+          requestInterceptors.unshift(interceptor.request, interceptor.requestError);
         }
         if (interceptor.response || interceptor.responseError) {
-          chain.push(interceptor.response, interceptor.responseError);
+          responseInterceptors.push(interceptor.response, interceptor.responseError);
         }
       });
 
-      while (chain.length) {
-        var thenFn = chain.shift();
-        var rejectFn = chain.shift();
-
-        promise = promise.then(thenFn, rejectFn);
-      }
+      promise = chainInterceptors(promise, requestInterceptors);
+      promise = promise.then(serverRequest);
+      promise = chainInterceptors(promise, responseInterceptors);
 
       if (useLegacyPromise) {
         promise.success = function(fn) {
@@ -1004,6 +1002,20 @@ function $HttpProvider() {
 
       return promise;
 
+
+      function chainInterceptors(promise, interceptors) {
+        for (var i = 0, ii = interceptors.length; i < ii;) {
+          var thenFn = interceptors[i++];
+          var rejectFn = interceptors[i++];
+
+          promise = promise.then(thenFn, rejectFn);
+        }
+
+        interceptors.length = 0;
+
+        return promise;
+      }
+
       function executeHeaderFns(headers, config) {
         var headerContent, processedHeaders = {};