follow along with tests

parts/4/blogApp/src/utils.js

@@ -0,0 +1,16 @@
+const reverse = (string) => {
+  return string.split("").reverse().join("");
+};
+
+const average = (array) => {
+  const reducer = (sum, item) => {
+    return sum + item;
+  };
+
+  return array.length === 0 ? 0 : array.reduce(reducer, 0) / array.length;
+};
+
+module.exports = {
+  reverse,
+  average,
+};