MPA Middleware — Logging, Authentication, Compression, and Error Handling

In this tutorial, you will learn about MPA Middleware. We cover key concepts, practical examples, and best practices to help you master this topic.

Middleware runs on every request in an MPA, providing cross-cutting concerns without repeating code in every route handler.

// Express middleware example
app.use(logger('dev'));
app.use(express.json());
app.use(session({ secret: 'keyboard cat' }));
app.use((req, res, next) => {
  if (!req.session.user && req.path !== '/login') {
    return res.redirect('/login');
  }
  next();
});