Implemented the middlewares to handle extracting user data in express

Author: gai93003

middleware.js

@@ -0,0 +1,45 @@
+// ...existing code...
+const express = require('express');
+// ...existing code...
+const app = express();
+
+app.use(express.json());
+
+const userdata = [];
+const info = [];
+
+const usernameValidator = (req, res, next) => {
+  const username = req.headers['x-username'];
+  userdata.push(username);
+
+  const userInfo = `You are authenticated as ${username}`;
+
+  console.log('req.body =', req.body); // debug
+
+  let userMessage = 'No subjects requested';
+  if (Array.isArray(req.body) && req.body.length > 0) {
+    info.push(...req.body); // push items first
+    userMessage = `You have requested information about ${req.body.length} subjects: ${req.body.join(', ')}`;
+  }
+
+  console.log(info);
+
+  console.log(`
+    ${userInfo}
+    ${userMessage}
+  `);
+
+  next();
+}
+
+app.use(usernameValidator);
+
+app.post('/', (req, res) => {
+  const username = req.headers['x-username']; // use lowercase key
+  res.send(`Username is ${username}, Subjects: ${JSON.stringify(info)}`);
+});
+
+app.listen(3000, () => {
+  console.log('Server listening on port 3000');
+})
+// ...existing code...