Today, I concentrated on building middleware for user authorization, a crucial backend component that safeguards sensitive routes and ensures that only authenticated users can access protected pages or APIs. This achievement is a major advancement in improving the application's security and user management.

I started by creating a middleware function to verify JSON Web Tokens (JWT), which are essential for user authentication. The middleware retrieves the token from the request headers, decodes it, and checks its validity. If the token is confirmed to be valid, the middleware allows the request to continue to the desired route; if not, it sends back an appropriate error message, such as "Unauthorized" or "Token expired."

This session was guided by a mentor-led code-along, which provided valuable insights into structuring and testing the middleware. Implementing this middleware required a solid understanding of the token lifecycle and addressing edge cases, including invalid tokens or missing authorization headers.

Adopting a test-driven development (TDD) approach, I created test cases to verify that the middleware function performed correctly in various situations. These tests examined scenarios like successfully authorizing valid tokens, rejecting invalid ones, and managing requests that lacked tokens in a user-friendly manner. Debugging these tests allowed me to enhance the middleware's robustness and efficiency.

Looking back on this milestone, I recognized the significance of having secure, reusable middleware functions in backend development. Completing this task deepened my understanding of JWT-based authentication and how middleware interacts with Express.js routes. As I move forward, I plan to implement this middleware throughout the application and further improve it with role-based access control to accommodate features like admin-specific permissions.