Refactor middleware functions for clarity and reuse

Author: Luke-Manyamazi

Middleware-custom/app.js

@@ -3,54 +3,69 @@ const app = express();
 const PORT = 3000;
 
 // Middleware 1: Check username header
-app.use((req, res, next) => {
+function checkUsername(req, res, next) {
   req.username = req.headers['x-username'] || null;
   next();
-});
+}
 
-// Middleware 2: Parse JSON and check if body is string array
-app.use((req, res, next) => {
+// Middleware 2: Parse JSON
+function parseJson(req, res, next) {
   if (req.method !== 'POST') return next();
-  
+
   let body = '';
+
   req.on('data', chunk => {
     body += chunk.toString();
   });
-  
+
   req.on('end', () => {
     try {
       req.body = JSON.parse(body);
+      next();
     } catch (error) {
-      return res.status(400).send('Error: Invalid JSON');
-    }
-    
-    // Simple array check
-    if (!Array.isArray(req.body)) {
-      return res.status(400).send('Error: Send a JSON array');
+      res.status(400).send('Error: Invalid JSON');
     }
-    
-    // Simple string check
-    for (let item of req.body) {
-      if (typeof item !== 'string') {
-        return res.status(400).send('Error: All items must be strings');
-      }
-    }
-    
-    req.subjects = req.body;
-    next();
   });
-});
+}
+
+// Middleware 3: Validate array of strings
+function validateStringArray(req, res, next) {
+  if (req.method !== 'POST') return next();
+
+  if (!Array.isArray(req.body)) {
+    return res.status(400).send('Error: Send a JSON array');
+  }
+
+  for (const item of req.body) {
+    if (typeof item !== 'string') {
+      return res.status(400).send('Error: All items must be strings');
+    }
+  }
+
+  req.subjects = req.body;
+  next();
+}
+
+// Register middleware
+app.use(checkUsername);
+app.use(parseJson);
+app.use(validateStringArray);
 
 // POST endpoint
 app.post('/', (req, res) => {
-  const name = req.username ? `authenticated as ${req.username}` : 'not authenticated';
+  const name = req.username
+    ? `authenticated as ${req.username}`
+    : 'not authenticated';
+
   const count = req.subjects.length;
   const word = count === 1 ? 'subject' : 'subjects';
   const list = req.subjects.join(', ');
-  
-  res.send(`You are ${name}.\n\nYou asked about ${count} ${word}: ${list}.`);
+
+  res.send(
+    `You are ${name}.\n\nYou asked about ${count} ${word}: ${list}.`
+  );
 });
 
 app.listen(PORT, () => {
-  console.log('Custom server started on port 3000');
-});
+  console.log(`Custom server started on port ${PORT}`);
+});