This is an example of a backend application built with Node.js that uses PostgreSQL for the database and implements JWT (JSON Web Token) authentication. The application includes a User class, which holds basic user information and two methods, Login and Register. These methods allow users to perform login and registration actions.

To store database connection details securely, the application uses a .env file. Additionally, there are three routes available:

1. Login: This route enables users to log in by verifying their credentials using JWT authentication.
2. Register: This route allows new users to sign up and stores their basic information in the database.
3. Example Endpoint: This route represents an endpoint that can only be accessed by users with valid JWT authentication. It's designed to test the functionality of JWT authentication.

You can clone this basic example, customize it with your own database information, and modify the User class to meet your specific requirements. You can also create additional classes as needed to extend the functionality of your project.