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 an .env file to define your environment variables. Use a simple 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

Note: By default, the application checks for an .env file. If you want to use different environment files for each environment, follow the steps below.

Step 3: Setting NODE_ENV in Different Operating Systems

Setting the NODE_ENV variable allows you to differentiate between environments. You can configure this in the application run scripts in your package.json file.

On Unix-based systems (Linux, macOS):

In your package.json, modify the scripts to set NODE_ENV:

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

On Windows:

There are two common methods to set environment variables on Windows:

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

Then, update your package.json scripts:

"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

Access the environment variables using process.env.<key>. By default, Node.js will search for an .env file. If you are using multiple .env files, configure dotenv as follows:

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';
import * as dotenv from 'dotenv';
dotenv.config({ path: process.cwd() + `/.env.${process.env.NODE_ENV}` });
//                                OR
// dotenv.config({ path: process.cwd() + `/${process.env.NODE_ENV}.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();

Security Tip: Ensure your .env files are added to .gitignore to prevent them from being committed to version control.

Additional Best Practices

1. Do Not Commit .env Files: Add your .env files to .gitignore to avoid exposing sensitive information.

# 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 all required environment variables are set and valid.

Conclusion

Setting up environment variables using the dotenv package in a NestJS application simplifies configuration management across various environments. By creating separate .env files for development, testing, and production, you ensure your application uses the correct settings and keeps sensitive information such as database credentials secure.

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