refactor: Remove unnecessary function calls

Author: ledsun

index.js

@@ -1,17 +1,19 @@
+const problem = require('./lib/problem')
+
 var jsing = require('workshopper-adventure')({
   appDir: __dirname,
   languages: ['en', 'ja', 'ko', 'es', 'zh-cn', 'zh-tw', 'pt-br', 'nb-no', 'uk', 'it', 'ru', 'fr'],
   header: require('workshopper-adventure/default/header'),
   footer: require('./lib/footer.js')
 })
 
-jsing.addAll(require('./menu.json').map(function (problem) {
+jsing.addAll(require('./menu.json').map(function (name) {
   return {
-    name: problem,
+    name,
     fn: function () {
-      var p = problem.toLowerCase().replace(/\s/g, '-')
+      var p = name.toLowerCase().replace(/\s/g, '-')
       var dir = require('path').join(__dirname, 'problems', p)
-      return require(dir)
+      return problem(dir)
     }
   }
 }))