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NestJS Tutorial

Introduction​

NestJS is a powerful and scalable framework for building backend applications. It's built with TypeScript and is heavily inspired by Angular, making it a great choice for TypeScript developers.

Prerequisites​

Before we start, make sure you have the following installed:

  • Node.js (>= 14.0.0)
  • npm (>= 6.0.0) or Yarn (>= 1.22.0)
  • TypeScript (>= 4.0.0) – if not installed globally, it will be managed by NestJS CLI.

Installation​

Step 1: Install NestJS CLI​

First, install the NestJS CLI globally.

npm i -g @nestjs/cli

Step 2: Create a New Project​

You can create a new NestJS project with the following command:

nest new my-nest-app

This will generate a new NestJS project with a set of default files and folders.

Step 3: Install Dependencies​

Navigate to the project directory and install the required dependencies.

cd my-nest-app
npm install

Project Structure​

NestJS follows a modular architecture. The main elements in the project structure are:

  • src/: Contains all the source code for your application.
    • app.controller.ts: Basic controller for handling HTTP requests.
    • app.module.ts: The root module that ties everything together.
    • app.service.ts: Basic service for business logic.

Creating a Basic Controller​

  1. Generate a Controller To create a controller, use the NestJS CLI.
nest generate controller hello

This creates a hello.controller.ts file inside the src directory.

  1. Controller Code Inside hello.controller.ts, define a simple GET route.
import { Controller, Get } from '@nestjs/common';

@Controller('hello')
export class HelloController {
  @Get()
  getHello(): string {
    return 'Hello, NestJS!';
  }
}

Step 4: Running the Application​

To run the NestJS app, use the following command:

npm run start

Visit http://localhost:3000/hello in your browser, and you should see the message Hello, NestJS!.

Creating a Service​

  1. Generate a Service To generate a service, use the CLI:
nest generate service hello
  1. Service Code In hello.service.ts, add the logic:
import { Injectable } from '@nestjs/common';

@Injectable()
export class HelloService {
  getHello(): string {
    return 'Hello from the service!';
  }
}
  1. Injecting the Service into the Controller Update hello.controller.ts to use the HelloService:
import { Controller, Get } from '@nestjs/common';
import { HelloService } from './hello.service';

@Controller('hello')
export class HelloController {
  constructor(private readonly helloService: HelloService) {}

  @Get()
  getHello(): string {
    return this.helloService.getHello();
  }
}

Step 5: Running the Application Again​

Run the app again using:

npm run start

Now, when you visit http://localhost:3000/hello, you'll see the message Hello from the service!.

Conclusion​

You have successfully set up a basic NestJS application with a controller and service. NestJS offers powerful tools to build scalable and maintainable backend applications, with support for REST APIs, GraphQL, microservices, and more.

Further Learning​

Content Review​

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