Node.js - Nest.js framework

Nest.js framework

• Currently, it supports two libraries — Express and Fastify
• it forces developers to use a specific architecture by introducing Angular-like modules, services, and controllers, ensuring the application is scalable, highly testable, and loosely coupled
• A controller is a class annotated with the @Controller decorator and it checks what request comes in and calls the appropriate service’s method. They don’t care about what’s going on between the request and the response.
• A service is a class annotated with the @Injectable decorator. It contains domain (business) logic. By separating the access layer (controllers) and logic layer (services), we have a clear separation of concerns.
• Dependency injection is one of the most important aspects of Nest. By providing the support out of the box, Nest allows us to write loosely coupled code, which, in turn, is also easily testable.
• By using dependency injection, it is very easy to mock out the modules we are not currently testing thanks to Nest’s custom providers feature.
• Nest stays on top of the new trends and makes it very easy to write an application based on the microservices architecture.
• Nest is used for building REST APIs but also the architecture can be used to create a GraphQL API as well.

Sample Controller

Sample 1

@Controller('cats')
export class CatsController {
  @Post()
  create(@Body() createCatDto: CreateCatDto) {
    return 'This action adds a new cat';
  }

  @Get()
  findAll(@Query() query: ListAllEntities) {
    return `This action returns all cats (limit: ${query.limit} items)`;
  }

  @Get(':id')
  findOne(@Param('id') id: string) {
    return `This action returns a #${id} cat`;
  }

  @Put(':id')
  update(@Param('id') id: string, @Body() updateCatDto: UpdateCatDto) {
    return `This action updates a #${id} cat`;
  }

  @Delete(':id')
  remove(@Param('id') id: string) {
    return `This action removes a #${id} cat`;
  }
}

Sample 2

@Controller('cats')
export class CatsController {
  constructor(private readonly catsService: CatsService) {}

  @Post()
  async create(@Body() createCatDto: CreateCatDto) {
    this.catsService.create(createCatDto);
  }

  @Get()
  async findAll(): Promise<Cat[]> {
    return this.catsService.findAll();
  }
}

Sample Service

@Injectable()
export class CatsService {
  private readonly cats: Cat[] = [];

  create(cat: Cat) {
    this.cats.push(cat);
  }

  findAll(): Cat[] {
    return this.cats;
  }
}

Sources

• Take your Node backend to the next level with NestJS