Setting Up a NestJS Project

Introduction to NestJS

NestJS is an increasingly popular framework for building efficient, scalable Node.js server-side applications. It leverages TypeScript, which offers a type-safe development experience, and adopts the modular architecture of Angular, making it easier to organize your application code. In this guide, we will walk through the process of setting up a NestJS project step-by-step and create a simple REST API.

Prerequisites

Before we dive into the setup, make sure you have the following tools installed:

Node.js (version 14 or above): Ensure that Node.js is installed by running node -v in your terminal. If it’s not installed, download it from nodejs.org.
npm (Node Package Manager): npm is included with Node.js installation. You can verify its installation by running npm -v.
Nest CLI: We’ll use the NestJS command-line interface (CLI) to streamline our project setup. Install it globally using the following command:
```
npm install -g @nestjs/cli
```

Once you have these prerequisites in place, you’re ready to start your NestJS project!

Creating a New NestJS Project

Let’s create a new NestJS project using the Nest CLI. Open your terminal and type:

nest new my-nest-project

Replace my-nest-project with your desired project name. The CLI will prompt you to select a package manager; you can choose either npm or Yarn. After a few moments, you’ll see a new folder with your project structure set up!

Project Structure Overview

Navigate into your project directory:

cd my-nest-project

Let’s briefly discuss the essential folders and files created by the CLI:

src/: Contains the main application code, including modules, controllers, and services.
main.ts: The entry point of the application.
app.module.ts: The root module that connects various parts of the application.
app.controller.ts: The default controller created with the project.
app.service.ts: The default service that provides data for the controller.

Running Your NestJS Application

Now that you have your NestJS application set up, let's run it:

npm run start

Your server will start running on http://localhost:3000. You can verify it's working by navigating to that URL in your web browser. By default, you should see a message like “Hello World!”

Creating Your First Controller

To get a better understanding of NestJS, let’s create a new controller that returns a simple greeting. You can generate a new controller using the Nest CLI:

nest generate controller greeting

This command creates a greeting folder inside src/ with a default controller file named greeting.controller.ts.

Setting Up the Greeting Controller

Open the newly created controller file src/greeting/greeting.controller.ts. It should contain a basic structure like this:

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

@Controller('greeting')
export class GreetingController {
  @Get()
  getGreeting(): string {
    return 'Hello, welcome to NestJS!';
  }
}

@Controller('greeting'): This decorator defines a new controller with the route prefix greeting.
@Get(): This decorator maps HTTP GET requests to the getGreeting method, which returns a simple greeting message.

Registering the Greeting Controller in the Module

In order to use this controller, you need to register it in the application module located in src/app.module.ts. Update the AppModule like so:

import { Module } from '@nestjs/common';
import { AppController } from './app.controller';
import { AppService } from './app.service';
import { GreetingController } from './greeting/greeting.controller';

@Module({
  imports: [],
  controllers: [AppController, GreetingController],
  providers: [AppService],
})
export class AppModule {}

Testing Your New Route

Now that your greeting controller is set up and registered, you can test it. Make sure your NestJS application is running, and navigate to http://localhost:3000/greeting in your web browser or a tool like Postman.

You should see the message:

Hello, welcome to NestJS!

This confirms that your controller is functioning correctly!

Conclusion

Setting up a simple NestJS project is a straightforward process that sets the groundwork for building sophisticated backend applications. We've walked through creating a new project, running the server, and implementing your first controller, giving you a running start in backend development with NestJS. From here, you can explore more advanced features like services, middleware, and database integration to further elevate your backend skills.

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