Exploring NestJS middleware: Benefits, use cases, and more

Middleware in NestJS is a function that operates before or after a route handler to perform tasks such as authentication, authorization, and logging, which can be applied globally or to specific routes. Middleware can be implemented as either functions or classes, using the @Injectable() decorator for class-based middleware. They help separate core application logic from ancillary tasks, offering benefits like reusability and modularity in complex applications. The article provides a detailed guide on creating and applying middleware in NestJS, with examples of common middleware tasks and their configurations, including CORS and Helmet for security enhancements. Despite their advantages, middleware can introduce performance bottlenecks and security vulnerabilities if not implemented correctly, as they might alter request and response objects or fail to complete the request-response cycle.