How To Configure And Use Environment Variables in NestJS?

Environment variables are an important part of application development, allowing developers to configure applications in different environments (development, staging, production) without hardcoding sensitive or environment-specific information into the application code.

In this article, we'll walk through how to configure and use environment variables in a NestJS application.

Prerequisites:

• NestJs
• Javascript
• env
• Node.js (version >= 16)
• npm

Steps to Configure and Use Environment Variables in NestJS:

Step 1: Create a New NestJS Project

If you haven't created a NestJS project, run the following command to set up a new one:

npx @nestjs/cli new nestjs-env-demo

Navigate to the project directory:

cd nestjs-env-demo

Step 2: Install @nestjs/config Package

Install the @nestjs/config package to manage environment variables easily in your NestJS project.

npm install @nestjs/config

Step 3: Create a .env File

In the root of your project, create a file called .env to store your environment variables:

PORT=3000
DATABASE_URL=mongodb://localhost:27017/mydb

Folder Structure

Dependencies

"dependencies": {
    "@nestjs/common": "^10.0.0",
    "@nestjs/config": "^3.2.3",
    "@nestjs/core": "^10.0.0",
    "@nestjs/platform-express": "^10.0.0",
    "reflect-metadata": "^0.2.0",
    "rxjs": "^7.8.1"
  }

Step 4: Modify AppModule to Use ConfigModule

To load environment variables, modify your src/app.module.ts file:

Example

// src/app.controller.ts

import { Controller, Get } from '@nestjs/common';
import { AppService } from './app.service';

@Controller() 
export class AppController {
    constructor(private readonly appService: AppService) { }

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

//app.module.ts

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

@Module({
    imports: [
        ConfigModule.forRoot({
            isGlobal: true, 
        }),
    ],
    controllers: [AppController],
    providers: [AppService],
})
export class AppModule { }

//app.service.ts

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

@Injectable()
export class AppService {
    constructor(private configService: ConfigService) { }

    getHello(): string {
        const dbUrl = this.configService.get<string>('DATABASE_URL');
        return `Hello! Your database is running at: ${dbUrl}`;
    }
}

//main.ts

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';
import { ConfigService } from '@nestjs/config';

async function bootstrap() {
    const app = await NestFactory.create(AppModule);
    const configService = app.get(ConfigService);

    const port = configService.get<number>('PORT') || 3000; \
    await app.listen(port);
    console.log(`Application is running on: http://localhost:${port}`);
}
bootstrap();

Step 5: Run the Application

Now, run the application:

npm run start

Step 6: Check the Output

When you open http://localhost:3000/ in your browser, you should see:

Hello! Your database is running at: mongodb://localhost:27017/mydb

Output