Securely Access Environment Variables in Node.js Applications

// In a production environment, environment variables are typically set
// through your hosting platform (e.g., Heroku, AWS, Netlify).
// For local development, you might use a package like 'dotenv'
// to load variables from a .env file, but the access method remains the same.

// server.js or app.js
const express = require('express');
const app = express();

// Securely access sensitive configuration data from environment variables
const DATABASE_URL = process.env.DATABASE_URL;
const API_KEY_SECRET = process.env.API_KEY_SECRET;
const PORT = process.env.PORT || 3000; // Provide a default for PORT

if (!DATABASE_URL) {
  console.error('Error: DATABASE_URL environment variable is not set.');
  process.exit(1); // Exit if critical variable is missing
}

if (!API_KEY_SECRET) {
  console.warn('Warning: API_KEY_SECRET environment variable is not set. Using a placeholder.');
  // In a real app, you might want to exit or handle this more strictly
  // For demonstration, we'll use a placeholder.
  // API_KEY_SECRET = 'a_default_secret_for_dev_only'; // NOT recommended for production
}

app.get('/', (req, res) => {
  // Avoid exposing sensitive variables directly in responses
  res.send(`App is running on port ${PORT}. Database URL is configured.`);
});

app.listen(PORT, () => {
  console.log(`Server listening on port ${PORT}`);
  // console.log(`Database URL: ${DATABASE_URL ? 'Configured' : 'Not Configured'}`);
  // console.log(`API Key Secret: ${API_KEY_SECRET ? 'Configured' : 'Not Configured'}`);
});

// To run this example locally for testing:
// 1. Set environment variables in your shell:
//    export DATABASE_URL="postgresql://user:pass@host:port/database"
//    export API_KEY_SECRET="your_very_secret_api_key"
// 2. Then run: node server.js
//
// For persistent local development, you'd typically use the `dotenv` package:
// require('dotenv').config(); // at the very top of your entry file
// But the access (`process.env.VARIABLE_NAME`) remains identical.