diff --git a/build/logger.js b/build/logger.js
index bc6707c..645720d 100644
--- a/build/logger.js
+++ b/build/logger.js
@@ -50,39 +50,47 @@ function render(diff) {
     case 'D':
       return '' + path.join('.');
     case 'A':
-      return (path.join('.') + '[' + index + ']', item);
+      return path.join('.') + '[' + index + ']', item;
     default:
       return null;
   }
 }
 
-function logger(_ref) {
-  var getState = _ref.getState;
-
-  return function (next) {
-    return function (action) {
-      var prevState = getState();
-      var returnValue = next(action);
-      var newState = getState();
-      var time = new Date();
-
-      var diff = (0, _deepDiff2['default'])(prevState, newState);
-
-      console.group('diff @', time.getHours() + ':' + time.getMinutes() + ':' + time.getSeconds());
-      if (diff) {
-        diff.forEach(function (elem) {
-          var kind = elem.kind;
-
-          var output = render(elem);
-
-          console.log('%c ' + dictionary[kind].text, style(kind), output);
-        });
-      } else {
-        console.log('—— no diff ——');
-      }
-      console.groupEnd('diff');
-
-      return returnValue;
+function logger() {
+  var options = arguments.length <= 0 || arguments[0] === undefined ? {} : arguments[0];
+
+  return function (_ref) {
+    var getState = _ref.getState;
+    return function (next) {
+      return function (action) {
+        var _options$transformer = options.transformer;
+        var transformer = _options$transformer === undefined ? function (state) {
+          return state;
+        } : _options$transformer;
+
+        var prevState = transformer(getState());
+        var returnValue = next(action);
+        var newState = transformer(getState());
+        var time = new Date();
+
+        var diff = (0, _deepDiff2['default'])(prevState, newState);
+
+        console.group('diff @', time.getHours() + ':' + time.getMinutes() + ':' + time.getSeconds());
+        if (diff) {
+          diff.forEach(function (elem) {
+            var kind = elem.kind;
+
+            var output = render(elem);
+
+            console.log('%c ' + dictionary[kind].text, style(kind), output);
+          });
+        } else {
+          console.log('—— no diff ——');
+        }
+        console.groupEnd('diff');
+
+        return returnValue;
+      };
     };
   };
 }
diff --git a/src/logger.js b/src/logger.js
index 3e4f81d..8dc752f 100644
--- a/src/logger.js
+++ b/src/logger.js
@@ -41,11 +41,14 @@ function render(diff) {
   }
 }
 
-function logger({ getState }) {
-  return (next) => (action) => {
-    const prevState = getState();
+function logger(options = {}) {
+  return ({getState}) => (next) => (action) => {
+    const {
+      transformer = state => state,
+    } = options;
+    const prevState = transformer(getState());
     const returnValue = next(action);
-    const newState = getState();
+    const newState = transformer(getState());
     const time = new Date();
 
     const diff = differ(prevState, newState);