nestjs-expert

NestJS dependency injection uses providers and modules to create clean module boundaries. Define services as providers, inject them into controllers, and organize related components into feature modules for scalable, testable architectures applicable to REST APIs and GraphQL services.

Use Data Transfer Objects (DTOs) with class-validator decorators to enforce input validation. NestJS automatically validates incoming requests against DTO schemas, catching errors before they reach your service logic and ensuring type safety across your API.

NestJS guards intercept requests and enforce authentication policies. Implement JWT guards to verify tokens and role-based guards to restrict endpoint access by user permission, protecting your controllers and services with declarative, reusable security middleware.

Both Prisma and TypeORM integrate seamlessly with NestJS through dependency injection. Inject your ORM client or repository into services, enabling type-safe database operations, migrations, and relationships while maintaining clean separation between data and business logic layers.

NestJS provides HTTP exceptions for standardized error responses. Use built-in exception classes to throw errors with specific status codes; NestJS automatically formats them into JSON responses, and you can create custom exception filters for centralized error handling across your application.

NestJS integrates with Swagger/OpenAPI to auto-generate API documentation from decorators. Annotate your controllers and DTOs with metadata, and NestJS produces interactive API docs automatically, reducing documentation drift and keeping specs in sync with implementation.