NestJS

Getting Started with NestJS

Cover

Slug

getting-started-with-nestjs

Published

Date

Mar 5, 2023

Introduction

NestJS is a popular server-side framework for building Node.js web applications. It is built on top of Express, which is a minimal and flexible Node.js web application framework. NestJS provides a lot of features and abstractions that make it easy to build scalable and maintainable web applications. In this blog post, we will explore the basics of NestJS and how to get started with building web applications using this framework.

Installation and Setup

Before we can start building web applications with NestJS, we need to install the NestJS CLI and create a new project. To install the NestJS CLI, we can use the following command:


npm install -g @nestjs/cli

Once the NestJS CLI is installed, we can create a new project using the following command:


nest new my-app

This will create a new NestJS project in a directory called my-app. We can then navigate to this directory and start the development server using the following command:


cd my-app
npm run start:dev

This will start the development server at http://localhost:3000. We can then open this URL in a web browser to see the default NestJS welcome page.

Controllers and Routes

In NestJS, controllers are responsible for handling incoming HTTP requests and returning appropriate responses. We can create a new controller using the following command:


nest generate controller cats

This will create a new cats.controller.ts file in the src directory. We can then define a route handler method in this file as follows:


import { Controller, Get } from '@nestjs/common';

@Controller('cats')
export class CatsController {
  @Get()
  findAll(): string {
    return 'This action returns all cats';
  }
}

This controller defines a GET route at the /cats URL that returns a string response. We can then navigate to http://localhost:3000/cats in a web browser to see the response.

Services and Dependency Injection

In NestJS, services are used to encapsulate business logic and are usually injected into controllers using dependency injection. We can create a new service using the following command:


nest generate service cats

This will create a new cats.service.ts file in the src directory. We can then define a method in this file that returns a list of cats:


import { Injectable } from '@nestjs/common';

@Injectable()
export class CatsService {
  findAll(): string[] {
    return ['Persian', 'Siamese', 'Bengal'];
  }
}

We can then inject this service into our controller as follows:


import { Controller, Get } from '@nestjs/common';
import { CatsService } from './cats.service';

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

  @Get()
  findAll(): string[] {
    return this.catsService.findAll();
  }
}

This controller now returns a list of cats that is provided by the CatsService. We can then navigate to http://localhost:3000/cats in a web browser to see the list of cats.

Conclusion

NestJS is a powerful and flexible server-side framework that makes it easy to build scalable and maintainable web applications. In this blog post, we explored the basics of NestJS and how to get started with building web applications using this framework. We covered the installation and setup process, how to define controllers and routes, and how to use services and dependency injection. We hope that this blog post has given you a good introduction to NestJS and has inspired you to start building your own web applications using this framework.