Add middleware example 2 for arrow function and color query

Author: mabelleeyanhwa

middleware_example_2.js

@@ -0,0 +1,36 @@
+const express = require("express");
+const app = express();
+const PORT = 3000;
+
+const arrowFunction = (req, res, next) => {
+  console.log("I am an arrow function!");
+  next();
+};
+
+app.use(arrowFunction);
+
+const checkColor = () => {
+  return (req, res, next) => {
+    if (req.query.color) {
+      res.send("I have blue!");
+    } else {
+      next();
+    }
+  };
+};
+
+app.use(checkColor());
+
+app.get("/users", function(req, res) {
+  console.log("users list was shown");
+  res.send("Here is a list of users:....");
+});
+
+app.get("/books", function(req, res) {
+  console.log("books list was shown");
+  res.send("Here is a list of books:....");
+});
+
+const server = app.listen(PORT, () => {
+  console.log(`Server running at http://localhost:${PORT}`);
+});