Node.js Fundamentals

Chapter 12: Environment Variables

12.1 Using process.env

Environment variables store configuration that varies between environments. Access them via process.env.

// Access environment variables
const port = process.env.PORT || 3000;
const dbUrl = process.env.DATABASE_URL;
const nodeEnv = process.env.NODE_ENV || 'development';

// Use in application
const server = http.createServer((req, res) => {
    res.end('Hello World');
});

server.listen(port, () => {
    console.log(`Server running on port ${port}`);
});

Common Environment Variables:

• NODE_ENV: Environment (development, production, test)
• PORT: Server port number
• DATABASE_URL: Database connection string
• API_KEY: External API keys
• JWT_SECRET: Secret for JWT tokens

Setting Environment Variables:

// Windows
set PORT=3000
set NODE_ENV=production

// Linux/Mac
export PORT=3000
export NODE_ENV=production

// Or inline
PORT=3000 NODE_ENV=production node app.js

12.2 .env Files

Use dotenv package to load environment variables from .env files.

// Install dotenv
// npm install dotenv

// Load at start of application
require('dotenv').config();

// Now access variables
const dbUrl = process.env.DATABASE_URL;
const apiKey = process.env.API_KEY;

.env File Format:

# .env file
PORT=3000
NODE_ENV=development
DATABASE_URL=mysql://user:pass@localhost:3306/mydb
API_KEY=your-api-key-here
JWT_SECRET=your-secret-key

Security Best Practices:

• Never commit .env files to version control
• Add .env to .gitignore
• Use .env.example as template
• Don't store secrets in code
• Use different .env files for different environments

12.3 Environment Configuration

Organize configuration based on environment.

// config.js
const config = {
    development: {
        port: 3000,
        dbUrl: 'mongodb://localhost:27017/devdb'
    },
    production: {
        port: process.env.PORT,
        dbUrl: process.env.DATABASE_URL
    }
};

const env = process.env.NODE_ENV || 'development';
module.exports = config[env];

12.4 Environment Variable Best Practices

Follow best practices for environment variables.

• Use descriptive variable names
• Document required variables
• Provide default values when appropriate
• Validate required variables on startup
• Use different values per environment
• Keep sensitive data in environment variables