NestJS Skill

Expert assistance for building enterprise Node.js applications with NestJS.

Capabilities

• Design modular NestJS applications
• Implement dependency injection patterns
• Create guards, pipes, and interceptors
• Build microservices architectures
• Configure Swagger/OpenAPI documentation
• Set up testing with Jest

Usage

Invoke this skill when you need to:

• Build enterprise-grade APIs
• Implement microservices
• Create modular architecture
• Add authentication/authorization
• Generate API documentation

Inputs

Parameter	Type	Required	Description
moduleName	string	Yes	Module name
features	array	No	guards, pipes, interceptors
database	string	No	prisma, typeorm, mongoose
microservices	boolean	No	Enable microservices

Architecture Patterns

Module Structure

// src/users/users.module.ts
import { Module } from '@nestjs/common';
import { UsersController } from './users.controller';
import { UsersService } from './users.service';
import { PrismaModule } from '../prisma/prisma.module';

@Module({
  imports: [PrismaModule],
  controllers: [UsersController],
  providers: [UsersService],
  exports: [UsersService],
})
export class UsersModule {}

Controller with DTOs

// src/users/users.controller.ts
import {
  Controller,
  Get,
  Post,
  Put,
  Delete,
  Body,
  Param,
  Query,
  UseGuards,
  HttpCode,
  HttpStatus,
} from '@nestjs/common';
import { ApiTags, ApiOperation, ApiBearerAuth, ApiResponse } from '@nestjs/swagger';
import { UsersService } from './users.service';
import { CreateUserDto } from './dto/create-user.dto';
import { UpdateUserDto } from './dto/update-user.dto';
import { UserResponseDto } from './dto/user-response.dto';
import { PaginationDto } from '../common/dto/pagination.dto';
import { JwtAuthGuard } from '../auth/guards/jwt-auth.guard';
import { RolesGuard } from '../auth/guards/roles.guard';
import { Roles } from '../auth/decorators/roles.decorator';
import { CurrentUser } from '../auth/decorators/current-user.decorator';

@ApiTags('users')
@Controller('users')
@UseGuards(JwtAuthGuard, RolesGuard)
@ApiBearerAuth()
export class UsersController {
  constructor(private readonly usersService: UsersService) {}

  @Get()
  @ApiOperation({ summary: 'Get all users' })
  @ApiResponse({ status: 200, type: [UserResponseDto] })
  findAll(@Query() pagination: PaginationDto) {
    return this.usersService.findAll(pagination);
  }

  @Get(':id')
  @ApiOperation({ summary: 'Get user by ID' })
  @ApiResponse({ status: 200, type: UserResponseDto })
  findOne(@Param('id') id: string) {
    return this.usersService.findById(id);
  }

  @Post()
  @Roles('admin')
  @ApiOperation({ summary: 'Create user' })
  @ApiResponse({ status: 201, type: UserResponseDto })
  create(@Body() createUserDto: CreateUserDto) {
    return this.usersService.create(createUserDto);
  }

  @Put(':id')
  @ApiOperation({ summary: 'Update user' })
  update(@Param('id') id: string, @Body() updateUserDto: UpdateUserDto) {
    return this.usersService.update(id, updateUserDto);
  }

  @Delete(':id')
  @Roles('admin')
  @HttpCode(HttpStatus.NO_CONTENT)
  @ApiOperation({ summary: 'Delete user' })
  remove(@Param('id') id: string) {
    return this.usersService.delete(id);
  }
}

// src/users/dto/create-user.dto.ts
import { IsEmail, IsString, MinLength, IsOptional, IsEnum } from 'class-validator';
import { ApiProperty } from '@nestjs/swagger';

export class CreateUserDto {
  @ApiProperty({ example: 'John Doe' })
  @IsString()
  name: string;

  @ApiProperty({ example: 'john@example.com' })
  @IsEmail()
  email: string;

  @ApiProperty({ minLength: 8 })
  @IsString()
  @MinLength(8)
  password: string;

  @ApiProperty({ required: false, enum: ['user', 'admin'] })
  @IsOptional()
  @IsEnum(['user', 'admin'])
  role?: string;
}

Service with Dependency Injection

// src/users/users.service.ts
import { Injectable, NotFoundException, ConflictException } from '@nestjs/common';
import { PrismaService } from '../prisma/prisma.service';
import { CreateUserDto } from './dto/create-user.dto';
import { UpdateUserDto } from './dto/update-user.dto';
import { PaginationDto } from '../common/dto/pagination.dto';
import * as bcrypt from 'bcryptjs';

@Injectable()
export class UsersService {
  constructor(private readonly prisma: PrismaService) {}

  async findAll(pagination: PaginationDto) {
    const { page = 1, limit = 10, search } = pagination;
    const skip = (page - 1) * limit;

    const [users, total] = await Promise.all([
      this.prisma.user.findMany({
        where: search ? { name: { contains: search, mode: 'insensitive' } } : undefined,
        skip,
        take: limit,
        select: {
          id: true,
          name: true,
          email: true,
          role: true,
          createdAt: true,
        },
      }),
      this.prisma.user.count({
        where: search ? { name: { contains: search, mode: 'insensitive' } } : undefined,
      }),
    ]);

    return {
      data: users,
      meta: {
        total,
        page,
        limit,
        totalPages: Math.ceil(total / limit),
      },
    };
  }

  async findById(id: string) {
    const user = await this.prisma.user.findUnique({
      where: { id },
      select: {
        id: true,
        name: true,
        email: true,
        role: true,
        createdAt: true,
      },
    });

    if (!user) {
      throw new NotFoundException(`User with ID ${id} not found`);
    }

    return user;
  }

  async create(dto: CreateUserDto) {
    const existing = await this.prisma.user.findUnique({
      where: { email: dto.email },
    });

    if (existing) {
      throw new ConflictException('Email already in use');
    }

    const hashedPassword = await bcrypt.hash(dto.password, 10);

    return this.prisma.user.create({
      data: {
        ...dto,
        password: hashedPassword,
      },
      select: {
        id: true,
        name: true,
        email: true,
        role: true,
        createdAt: true,
      },
    });
  }

  async update(id: string, dto: UpdateUserDto) {
    await this.findById(id);

    if (dto.password) {
      dto.password = await bcrypt.hash(dto.password, 10);
    }

    return this.prisma.user.update({
      where: { id },
      data: dto,
      select: {
        id: true,
        name: true,
        email: true,
        role: true,
        createdAt: true,
      },
    });
  }

  async delete(id: string) {
    await this.findById(id);
    await this.prisma.user.delete({ where: { id } });
  }
}

Guards and Decorators

// src/auth/guards/jwt-auth.guard.ts
import { Injectable, ExecutionContext } from '@nestjs/common';
import { AuthGuard } from '@nestjs/passport';
import { Reflector } from '@nestjs/core';
import { IS_PUBLIC_KEY } from '../decorators/public.decorator';

@Injectable()
export class JwtAuthGuard extends AuthGuard('jwt') {
  constructor(private reflector: Reflector) {
    super();
  }

  canActivate(context: ExecutionContext) {
    const isPublic = this.reflector.getAllAndOverride<boolean>(IS_PUBLIC_KEY, [
      context.getHandler(),
      context.getClass(),
    ]);

    if (isPublic) {
      return true;
    }

    return super.canActivate(context);
  }
}

// src/auth/guards/roles.guard.ts
import { Injectable, CanActivate, ExecutionContext } from '@nestjs/common';
import { Reflector } from '@nestjs/core';
import { ROLES_KEY } from '../decorators/roles.decorator';

@Injectable()
export class RolesGuard implements CanActivate {
  constructor(private reflector: Reflector) {}

  canActivate(context: ExecutionContext): boolean {
    const requiredRoles = this.reflector.getAllAndOverride<string[]>(ROLES_KEY, [
      context.getHandler(),
      context.getClass(),
    ]);

    if (!requiredRoles) {
      return true;
    }

    const { user } = context.switchToHttp().getRequest();
    return requiredRoles.includes(user.role);
  }
}

// src/auth/decorators/roles.decorator.ts
import { SetMetadata } from '@nestjs/common';
export const ROLES_KEY = 'roles';
export const Roles = (...roles: string[]) => SetMetadata(ROLES_KEY, roles);

// src/auth/decorators/current-user.decorator.ts
import { createParamDecorator, ExecutionContext } from '@nestjs/common';

export const CurrentUser = createParamDecorator(
  (data: unknown, ctx: ExecutionContext) => {
    const request = ctx.switchToHttp().getRequest();
    return request.user;
  },
);

Interceptors

// src/common/interceptors/transform.interceptor.ts
import {
  Injectable,
  NestInterceptor,
  ExecutionContext,
  CallHandler,
} from '@nestjs/common';
import { Observable } from 'rxjs';
import { map } from 'rxjs/operators';

export interface Response<T> {
  data: T;
  meta?: Record<string, any>;
}

@Injectable()
export class TransformInterceptor<T> implements NestInterceptor<T, Response<T>> {
  intercept(context: ExecutionContext, next: CallHandler): Observable<Response<T>> {
    return next.handle().pipe(
      map((data) => {
        if (data?.data && data?.meta) {
          return data;
        }
        return { data };
      }),
    );
  }
}

Best Practices

• Use modules for feature encapsulation
• Leverage dependency injection
• Implement DTOs for validation
• Use guards for authorization
• Generate OpenAPI documentation

Target Processes

• enterprise-api-development
• microservices-architecture
• backend-development
• nestjs-application