Divided the middleware file into separate functions to handle tiny tasks

Author: gai93003

middleware.js

@@ -6,35 +6,57 @@ app.use(express.json());
 const userdata = [];
 const info = [];
 
-const usernameValidator = (req, res, next) => {
+const getUsernameFromHeader = (req, res, next) => {
   const username = req.headers['x-username'];
   userdata.push(username);
+  res.locals.username = username;
+  next();
+};
 
-  const userInfo = `You are authenticated as ${username}`;
+const checkBodyIsArray = (req, res, next) => {
+  if (req.body === undefined || req.body === null) {
+    res.locals.subjects = [];
+    return next();
+  }
 
-  console.log('req.body =', req.body);
+  if (!Array.isArray(req.body)) {
+    return res.status(400).send('Request body must be an array of subjects');
+  }
+
+  res.locals.subjects = req.body;
+  next();
+};
+
+const prepareReturnValue = (req, res, next) => {
+  const username = res.locals.username;
+  const subjects = res.locals.subjects ?? [];
 
-  let userMessage = 'No subjects requested';
-  if (Array.isArray(req.body) && req.body.length > 0) {
-    info.push(...req.body); 
-    userMessage = `You have requested information about ${req.body.length} subjects: ${req.body.join(', ')}`;
+  if (subjects.length > 0) {
+    info.push(...subjects);
   }
 
-  console.log(info);
+  const userInfo = `You are authenticated as ${username}`;
+  const userMessage = subjects.length > 0
+    ? `You have requested information about ${subjects.length} subjects: ${subjects.join(', ')}`
+    : 'No subjects requested';
 
+  console.log('req.body =', req.body);
+  console.log(info);
   console.log(`
     ${userInfo}
     ${userMessage}
   `);
 
+  res.locals.responseMessage = `Username is ${username}, Subjects: ${JSON.stringify(info)}`;
   next();
-}
+};
 
-app.use(usernameValidator);
+app.use(getUsernameFromHeader);
+app.use(checkBodyIsArray);
+app.use(prepareReturnValue);
 
 app.post('/', (req, res) => {
-  const username = req.headers['x-username']; 
-  res.send(`Username is ${username}, Subjects: ${JSON.stringify(info)}`);
+  res.send(res.locals.responseMessage);
 });
 
 app.listen(3000, () => {