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NestJS 11 Best Practices
Quick Reference
| Topic | When to Use | Reference |
|---|---|---|
| Core Architecture | Modules, Providers, DI, forwardRef, custom decorators | core-architecture.md |
| Request Lifecycle | Middleware, Guards, Interceptors, Pipes, Filters | request-lifecycle.md |
| Validation & Pipes | DTOs, class-validator, ValidationPipe, transforms | validation-pipes.md |
| Authentication | JWT, Passport, Guards, Local/OAuth strategies, RBAC | authentication.md |
| Database | TypeORM, Prisma, Drizzle ORM, repository patterns | database-integration.md |
| Testing | Unit tests, E2E tests, mocking providers | testing.md |
| OpenAPI & GraphQL | Swagger decorators, resolvers, subscriptions | openapi-graphql.md |
| Microservices | TCP, Redis, NATS, Kafka patterns | microservices.md |
Essential Patterns
Module with Providers
typescript
@Module({
imports: [DatabaseModule],
controllers: [UsersController],
providers: [UsersService],
exports: [UsersService], // Export for other modules
})
export class UsersModule {}Controller with Validation
typescript
@Controller('users')
export class UsersController {
constructor(private readonly usersService: UsersService) {}
@Post()
create(@Body() createUserDto: CreateUserDto) {
return this.usersService.create(createUserDto);
}
@Get(':id')
findOne(@Param('id', ParseIntPipe) id: number) {
return this.usersService.findOne(id);
}
}DTO with Validation
typescript
import { IsEmail, IsString, MinLength, IsOptional } from 'class-validator';
export class CreateUserDto {
@IsEmail()
email: string;
@IsString()
@MinLength(8)
password: string;
@IsOptional()
@IsString()
name?: string;
}Exception Filter
typescript
@Catch(HttpException)
export class HttpExceptionFilter implements ExceptionFilter {
catch(exception: HttpException, host: ArgumentsHost) {
const ctx = host.switchToHttp();
const response = ctx.getResponse<Response>();
const status = exception.getStatus();
response.status(status).json({
statusCode: status,
message: exception.message,
timestamp: new Date().toISOString(),
});
}
}Guard with JWT
typescript
@Injectable()
export class JwtAuthGuard extends AuthGuard('jwt') {
canActivate(context: ExecutionContext) {
return super.canActivate(context);
}
}NestJS 11 Breaking Changes
- Express v5: Wildcards must be named (e.g.,
*splat), optional params use braces/:file{.:ext} - Node.js 20+: Minimum required version
- Fastify v5: Updated adapter for Fastify users
- Dynamic Modules: Same module with identical config imported multiple times = separate instances
Common Mistakes
- Not using `forwardRef()` for circular deps - Causes "cannot resolve dependency" errors; wrap in
forwardRef(() => ModuleName) - Throwing plain errors instead of HttpException - Loses status codes, breaks exception filters; use
throw new BadRequestException('message') - Missing `@Injectable()` decorator - Provider won't be injectable; always decorate services
- Global ValidationPipe without `whitelist: true` - Allows unexpected properties; set
whitelist: true, forbidNonWhitelisted: true - Importing modules instead of exporting providers - Use
exportsarray to share providers across modules - Async config without `ConfigModule.forRoot()` - ConfigService undefined; import ConfigModule in AppModule
- Testing without `overrideProvider()` - Uses real services in unit tests; mock dependencies with
overrideProvider(Service).useValue(mock) - E2E tests sharing database state - No isolation between tests; use transactions or truncate tables in beforeEach
