Express.js Applications with Middleware

Middleware is a core concept in Express.js that allows you to add additional functionality to your Node.js applications. In this article, we’ll explore what middleware is, how it works, and how you can use it to build robust APIs.

What is Middleware?

Middleware functions are functions that have access to the request object (req), the response object (res), and the next middleware function in the application’s request-response cycle. Middleware can execute code, modify the request/response, end the request-response cycle, or call the next middleware in the stack.

app.use((req, res, next) => {
      console.log(\`Request URL: \${req.url}\`);
      next();
    });

Types of Middleware

• Application-level middleware
• Router-level middleware
• Error-handling middleware
• Built-in middleware
• Third-party middleware

Why Use Middleware?

• Logging and debugging
• Authentication and authorization
• Parsing request bodies
• Error handling
• Serving static files

"Middleware makes your Express.js apps modular, reusable, and maintainable."

Mastering middleware is essential for building scalable and maintainable Node.js applications with Express.js.