Caching configuration to prefer forEach.

Author: gajus

src/makeConfiguration.js

@@ -1,4 +1,9 @@
 import _ from 'lodash';
+import Map from 'es6-map';
+
+let userConfigurationIndex;
+
+userConfigurationIndex = new Map();
 
 /**
  * @typedef CSSModules~Options
@@ -14,6 +19,12 @@ import _ from 'lodash';
 export default (userConfiguration = {}) => {
     let configuration;
 
+    configuration = userConfigurationIndex.get(userConfiguration);
+
+    if (configuration) {
+        return configuration;
+    }
+
     configuration = {
         allowMultiple: false,
         errorWhenNotFound: true
@@ -31,5 +42,7 @@ export default (userConfiguration = {}) => {
         configuration[name] = value;
     });
 
+    userConfigurationIndex.set(userConfiguration, configuration);
+
     return configuration;
 };