I’m learning Express.js and I’m a bit confused about the difference between middleware functions and route handlers. I understand that middleware functions usually have the next argument, but I’m not clear on when a function is considered middleware and when it is a route handler.

Are Route Handlers Considered Middleware in Node.js Express?

Questions:

1. Does the following code have middlewares?

2. Are the functions like app.get(‘/’, …), app.post(‘/verify’, …), app.get(‘/home’, …), and app.get(‘/logout’, …) considered middlewares?

3. Do middleware functions always need to have the next argument?

4. Can you explain the role of middleware versus route handlers in Express.js?

   const express = require(‘express’);
   const app = express();
   const hbs = require(‘hbs’);
   const nocache = require(‘nocache’);
   const session = require(‘express-session’);

   app.use(express.static(‘public’));
   app.set(‘view engine’, ‘hbs’);
   app.use(express.urlencoded({ extended: true }));
   app.use(express.json());

   app.use(session({
   secret: ‘keyboard cat’,
   resave: false,
   saveUninitialized: true,
   }));

   app.use(nocache());

   const username = ‘admin’;
   const password = ‘admin@123’;

   app.get(‘/’, (req, res) => {
   if (req.session.user) {
   res.render(‘home’);
   } else {
   if (req.session.passwordwrong) {
   res.render(‘login’, { msg: “invalid credentials” });
   req.session.passwordwrong = false;
   } else {
   res.render(‘login’);
   }
   }
   });

   app.post(‘/verify’, (req, res) => {
   if (req.body.username === username && req.body.password === password) {
   req.session.user = req.body.username;
   res.redirect(‘/home’);
   } else {
   req.session.passwordwrong = true;
   res.redirect(‘/’);
   }
   });

   app.get(‘/home’, (req, res) => {
   if (req.session.user) {
   res.render(‘home’, { username: username });
   } else {
   if (req.session.passwordwrong) {
   req.session.passwordwrong = false;
   res.render(‘login’, { msg: “invalid credentials” });
   } else {
   res.render(‘login’);
   }
   }
   });

   app.get(‘/logout’, (req, res) => {
   req.session.destroy();
   res.render(‘login’, { msg: ‘logged out’ });
   });

   app.listen(3000, () => console.log(‘server running on port 3000’));