Express Middleware Type

  1. Built-in Middleware: Included with Express, performs common tasks, such as parsing request bodies, handling cookies, and serving static files.

  2. Third-Party Middleware: External modules providing additional functionality, integrated into Express applications using app.use(). Examples include body-parser for parsing request bodies and morgan for logging.

  3. Router Middleware: Allows modular route handling by creating separate routers using express.Router(). These routers can be mounted at specific paths, enhancing code organization.

  4. Error-Handling Middleware: Specialized middleware for handling errors in Express applications. Utilized through a function with four parameters (err, req, res, next).

  5. Custom Middleware: Application-specific middleware created using functions. Added to the request-response cycle using app.use(). Enables developers to inject custom logic at different points in the request processing pipeline.

  6. Application-Level Middleware: Bound to the app object and applied to every route in the application. Defined using app.use().

  7. Route-Level Middleware: Specific to particular routes, added using app.use() before defining the route. Useful for route-specific tasks.

  8. Error-Handling Middleware (app.use): Catches errors that occur in the application, irrespective of the route. Defined at the end of the middleware stack after all other route and middleware definitions.

  9. Built-in Express Middleware Examples:

  10. express.json(): Parses incoming JSON requests.
  11. express.urlencoded(): Parses incoming requests with URL-encoded payloads.
  12. express.static(): Serves static files.