Issue HowProgrammingWorks#4: Task four.

Author: Dmitry Porokhnya

Exercises/4-count-types.js

@@ -1,5 +1,13 @@
 'use strict';
 
-const countTypesInArray = null;
+
+const countTypesInArray = arr => {
+  const obj = {};
+  for (const item of arr) {
+    const type = typeof item;
+    type in obj ? obj[type]++ : obj[type] = 1;
+  }
+  return obj;
+};
 
 module.exports = { countTypesInArray };