Environment-based configuration in NestJS - Mini Project: Build & Apply

Environment-based configuration in NestJS

📖 Scenario: You are building a simple NestJS application that needs to read configuration values from environment variables. This is common when you want to change settings like the app port or database URL without changing the code.

🎯 Goal: Learn how to set up environment-based configuration in NestJS using the ConfigModule. You will create a configuration file, load environment variables, and access them in a service.

📋 What You'll Learn

Create a configuration file that exports a function returning an object with app settings

Import and configure the ConfigModule to load environment variables

Inject ConfigService into a service to read configuration values

Use the configuration values in the service logic

💡 Why This Matters

🌍 Real World

Many real-world NestJS apps need to change settings like ports, database URLs, or API keys without changing code. Environment-based configuration makes this easy and safe.

💼 Career

Understanding environment-based configuration is essential for backend developers working with NestJS, as it helps build flexible and secure applications that adapt to different deployment environments.

1

Create a configuration file

Create a file named app.config.ts that exports a default function returning an object with these exact properties: port set to 3000 and databaseUrl set to "mongodb://localhost:27017/myapp".

NestJS

// Create and export default function returning { port: 3000, databaseUrl: 'mongodb://localhost:27017/myapp' }
// Your code here

Need a hint?

This file returns an object with your app settings. Use export default () => ({ ... }).

2

Import ConfigModule with your config

In app.module.ts, import ConfigModule from @nestjs/config and configure it with ConfigModule.forRoot({ load: [appConfig] }). Also, import your app.config.ts as appConfig.

NestJS

import { Module } from '@nestjs/common';
import { ConfigModule } from '@nestjs/config';
import appConfig from './app.config';

@Module({
  imports: [
    // Configure ConfigModule here
  ],
})
export class AppModule {}

// Your code here

Need a hint?

Use ConfigModule.forRoot with the load option to load your config function.

3

Inject ConfigService in a service

Create a service named AppService that injects ConfigService from @nestjs/config in its constructor. Store it in a private readonly property named configService.

NestJS

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

@Injectable()
export class AppService {
  constructor(
    // Inject ConfigService here
  ) {}
}

// Your code here

Need a hint?

Use constructor injection with private readonly configService: ConfigService.

4

Use configuration values in the service

Add a method getPort() in AppService that returns the port value from configService.get<number>('port'). Also add a method getDatabaseUrl() that returns the databaseUrl string from configService.get<string>('databaseUrl').

NestJS

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

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

  // Add getPort() and getDatabaseUrl() methods here

  // Your code here
}

Need a hint?

Use configService.get<type>('key') to read config values.