Node.js Environment Variables — Configuration Management

Using dotenv

npm install dotenv

// At the top of your entry file
require('dotenv').config();

// .env file
PORT=3000
DATABASE_URL=mongodb://localhost:27017/myapp
JWT_SECRET=your-secret-key
NODE_ENV=development

// Access variables
const port = process.env.PORT || 3000;
const dbUrl = process.env.DATABASE_URL;

Validating Environment Variables

const required = ['DATABASE_URL', 'JWT_SECRET', 'PORT'];

for (const key of required) {
  if (!process.env[key]) {
    throw new Error(`Missing required environment variable: ${key}`);
  }
}

// Or use envalid
const { cleanEnv, str, port } = require('envalid');

module.exports = cleanEnv(process.env, {
  DATABASE_URL: str(),
  JWT_SECRET: str(),
  PORT: port({ default: 3000 }),
  NODE_ENV: str({ choices: ['development', 'production', 'test'] })
});

Best Practices

• Never commit .env files to git
• Use .env.example to document required variables
• Provide defaults for non-critical variables
• Use different .env files per environment