Setting Up Environment Variables and Configurations in NestJS

When developing a NestJS application, managing configuration and environment variables efficiently is crucial, especially when dealing with sensitive data. This guide will show you how to set up environment variables using the .env file, and how to manage different configurations for various environments like development and production.

The env helps in keeping sensitive data like database credentials and API keys secure and separate from your source code.

Prerequisites

Before we begin, ensure you have the following installed on your machine:

• Node.js (version >= 16)
• NPM
• MySQL server
• A basic NestJS application (refer to our article “Getting Started with NestJS” if needed)

Setup and access env file

Step 1: Create Environment Files

In the root directory of your application, create a .env file to define your environment variables. The basic notation is a key-value pair format, as shown below:

APPNAME='NestJS-Application'
APPVERSION='v1.0'
APP_PORT=4000

HOST='localhost'
DB_PORT=3306
USERNAME='root'
PASSWORD='root'
DATABASE='nestjs'

For different environments, you can manually create multiple .env files, such as:

• .env.development or development.env
• .env.production or production.env

Step 2: Install dotenv Package

To access these environment variables within your application, install the dotenv package:

$ npm install --save dotenv

To use different environments files we have to config the .env in main file.

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';
import * as dotenv from 'dotenv';

dotenv.config({ path: process.cwd() + `/.env.${process.env.NODE_ENV}` }); 

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  await app.listen(process.env.APP_PORT);
  console.log(`This application is running on: ${await app.getUrl()}`);
}

bootstrap();

• The cmd method will return the current working directory of the Node.js process.
• .env.development is a file which i am using for storing environmental variables.
• If you are using normal .envfile. The above import and config steps are not required, you can directly use variables in application.

Step 3: Setting NODE_ENV in Different Operating Systems

This step is used to access the different env file in different environment. This NODE_ENV can be used to differentiate different application environment. we will use this value in future development of application and it is set in application run scripts which are in package.json file:

On Unix-based systems (Linux, macOS):

You can set the NODE_ENV variable, In start script of application. For example, to start the application in production mode.

"scripts": {
  "start:dev" : "NODE_ENV=development nest start --watch",
  "start:prod": "NODE_ENV=production node dist/main"  // replace the existing script
}

On Windows:

On Windows, setting environment variables can be slightly different. Here are a few ways to do it:

Using set command:

"scripts": {
  "start:dev" : "set NODE_ENV=development && nest start --watch",
  "start:prod": "set NODE_ENV=production && node dist/main" // replace the existing script
}

Using cross-env package:

1. The cross-env package allows you to set environment variables across platforms. First, install the package:

$ npm install --save-dev cross-env

2. Then, modify your package.json scripts to use cross-env:

"scripts": {
  "start:dev" : "cross-env NODE_ENV=development nest start --watch",
  "start:prod": "cross-env NODE_ENV=production node dist/main" // replace the existing script
}

Now, you can run your application with:

$ npm run start:prod

Step 4: Config and Access Environment Variables in Your Application

You can access the environment variables using process.env.<key>. By default the the “Node.process” will search for .env file.

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';
import * as dotenv from 'dotenv';

dotenv.config({ path: process.cwd() + `/.env.${process.env.NODE_ENV}` }); 
// the cmd method will return the current working directory of the Node.js process.
// .env.development is a file which i am using to storing environmental variables.
// if you are using normal .env file, the above import and config steps are not required.

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  await app.listen(process.env.APP_PORT);
  console.log(`This application is running on: ${await app.getUrl()}`);
}

bootstrap();

Ensure your .env files are added to .gitignore to prevent them from being included in version control.

Additional Best Practices

1. Do Not Commit .env Files: Ensure your .env files are added to .gitignore to avoid committing sensitive information to version control.

# dotenv environment variable files
.env
development.env
.env.development.local
.env.test.local
production.env
.env.production.local
.env.local
*.env.*

2. Validate Environment Variables: Use a validation library like joi to ensure that all required environment variables are set and valid.

Conclusion

Setting up environment variables using the dotenv package in a NestJS application helps in managing different configurations for various environments. By creating separate .env files for each environment and loading them appropriately, you can ensure that your application uses the correct settings in development, testing, and production.

This method not only simplifies the configuration management but also enhances the security by keeping sensitive information such as database credentials out of the source code.

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