Nestjs

NestJS

Progressive Node.js framework with TypeScript, decorators, and DI.

Quick Start

npm i -g @nestjs/cli && nest new my-api
cd my-api && npm run start:dev

Core Concepts

Modules

@Module({ imports: [UsersModule], controllers: [AppController], providers: [AppService] })
export class AppModule {}

Controllers

@Controller('users')
export class UsersController {
  @Get() findAll() { return this.usersService.findAll() }
  @Post() @Body() create(dto: CreateUserDto) { return this.usersService.create(dto) }
}

Providers (Services)

@Injectable()
export class UsersService {
  private users: User[] = []
  findAll() { return this.users }
  create(dto: CreateUserDto) { const user = { id: Date.now(), ...dto }; this.users.push(user); return user }
}

When to Use

• Enterprise TypeScript APIs
• Microservices with NATS/RabbitMQ
• GraphQL + REST hybrid APIs
• Projects needing strong structure

Step-by-Step

1. Init: nest new project
2. Generate: nest g module users, nest g controller users, nest g service users
3. Define entities and DTOs
4. Run: npm run start:dev

Examples

// Full module wired with DI: controller + provider + repository
import { Module } from '@nestjs/common';
import { TypeOrmModule } from '@nestjs/typeorm';
import { UsersController } from './users.controller';
import { UsersService } from './users.service';
import { User } from './user.entity';

@Module({
  imports: [TypeOrmModule.forFeature([User])],
  controllers: [UsersController],
  providers: [UsersService],
  exports: [UsersService],
})
export class UsersModule {}

// Validation DTO with class-validator
import { IsEmail, IsString, MinLength } from 'class-validator';

export class CreateUserDto {
  @IsEmail() email!: string;
  @IsString() @MinLength(2) name!: string;
}

# Generate a module with CRUD scaffold, then hit the endpoint
nest g resource users --no-spec
curl http://localhost:3000/users
curl -X POST http://localhost:3000/users -H "content-type: application/json" -d '{"email":"a@b.c","name":"Alice"}'

Validation

1. Server starts on port 3000
2. CRUD endpoints respond correctly
3. Dependency injection resolves providers