@nestjs/common

What is @nestjs/common?

The @nestjs/common package is a core part of the NestJS framework, which is a framework for building efficient, reliable and scalable server-side applications. This package provides a wide range of basic functionalities necessary for any NestJS application, including decorators, modules, middleware, filters, pipes, guards, and utilities for handling HTTP requests and responses.

What are @nestjs/common's main functionalities?

Decorators

Decorators are used to annotate classes and their members to define their roles within the application. For example, `@Injectable()` marks a class as a service that can be injected, and `@Controller()` defines a class as a controller with a specific route.

@Injectable()
class MyService {}

@Controller('my-route')
class MyController {
  constructor(private myService: MyService) {}
}

Modules

Modules are used to organize components by encapsulating them within bounded contexts. This code sample demonstrates how to define a module that includes controllers and providers.

@Module({
  imports: [],
  controllers: [MyController],
  providers: [MyService],
})
class MyModule {}

Middleware

Middleware are functions that execute during the request-response cycle. They can perform tasks like logging, request validation, etc. This code sample shows a basic middleware that logs a message on each request.

@Injectable()
class MyMiddleware implements NestMiddleware {
  use(req: Request, res: Response, next: NextFunction) {
    console.log('Request...');
    next();
  }
}

Exception Filters

Exception filters handle exceptions that occur during the processing of a request. This code sample demonstrates a filter that catches HTTP exceptions and formats the response.

@Catch(HttpException)
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,
        timestamp: new Date().toISOString(),
        path: ctx.getRequest<Request>().url,
      });
  }
}

Other packages similar to @nestjs/common

express

Express is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications. While it serves a similar purpose in building server-side applications, it is less opinionated than NestJS and does not provide the same level of structure and abstraction out of the box.

koa

Koa is a new web framework designed by the team behind Express, aiming to be a smaller, more expressive, and more robust foundation for web applications and APIs. Koa uses async functions, which allows for a simpler and more powerful way to handle asynchronous operations compared to Express. However, like Express, it is less opinionated than NestJS.

hapi

Hapi is a rich framework for building applications and services, allowing developers to focus on writing reusable application logic instead of spending time building infrastructure. It is designed to be more configurable and extensible than Express, offering a more comprehensive set of features out of the box. However, it still lacks the full-fledged module system and decorators provided by NestJS.

README

Modern, powerful web application framework for Node.js.

Description

Nest is a framework for building efficient, scalable Node.js web applications. It uses modern JavaScript, is built with TypeScript and combines elements of OOP (Object Oriented Progamming), FP (Functional Programming), and FRP (Functional Reactive Programming).

Under the hood, Nest makes use of Express, allowing for easy use of the myriad third-party plugins which are available.

Philosophy

In recent years, thanks to Node.js, JavaScript has become the “lingua franca” of the web for both front and backend applications, giving rise to awesome projects like Angular, React and Vue which improve developer productivity and enable the construction of fast, testable, extensible frontend applications. However, on the server-side, while there are a lot of superb libraries, helpers and tools for Node, none of them effectively solve the main problem - the architecture.

Nest aims to provide an application architecture out of the box which allows for effortless creation of highly testable, scalable, loosely coupled and easily maintainable applications.

Features

• Built with TypeScript
• Easy to learn - syntax similar to Angular
• Familiar - based on well-known libraries (Express / socket.io)
• Dependency Injection - built-in asynchronous IoC container with a hierarchical injector
• WebSockets module (based on socket.io, but you can bring your own library, by making use of WsAdapter)
• Modular - defines an easy to follow module definition pattern so you can split your system into reusable modules
• Reactive microservice support with message patterns (built-in transport via TCP / Redis, but other communication schemes can be implemented with CustomTransportStrategy)
• Exception layer - throwable web exceptions with status codes, exception filters
• Pipes - synchronous & asynchronous (e.g. validation purposes)
• Guards - attach additional logic in a declarative manner (e.g. role-based access control)
• Interceptors - built on top of RxJS
• Testing utilities (both e2e & unit tests)

Installation

Install the TypeScript Starter Project with Git:

$ git clone https://github.com/kamilmysliwiec/nest-typescript-starter.git project
$ cd project
$ npm install
$ npm run start

Start a New Project from Scratch with NPM:

$ npm i --save @nestjs/core @nestjs/common @nestjs/microservices @nestjs/websockets @nestjs/testing reflect-metadata rxjs

Documentation & Quick Start

Documentation & Tutorial

People

• Author - Kamil Myśliwiec
• Website - http://nestjs.com

Backers

I am on a mission to provide an architecture to create truly flexible, scalable and loosely coupled systems using the Node.js platform. It takes a lot of time, so if you want to support me, please become a backer / sponsor. I appreciate your help. Thanks!

License

MIT