Secure Environment Variable Management with Dotenv in Node.js

// .env file content (create a file named .env in your project root):
// DB_HOST=localhost
// DB_USER=myuser
// DB_PASS=mysecurepassword
// API_KEY=supersecretapikey123
// NODE_ENV=development

// index.js (or main application file):
require('dotenv').config(); // Load environment variables from .env file

const express = require('express');
const app = express();

const dbHost = process.env.DB_HOST;
const dbUser = process.env.DB_USER;
const dbPass = process.env.DB_PASS;
const apiKey = process.env.API_KEY;
const nodeEnv = process.env.NODE_ENV || 'development';

if (!dbHost || !dbUser || !dbPass || !apiKey) {
  console.error('CRITICAL: Missing essential environment variables!');
  process.exit(1);
}

app.get('/config', (req, res) => {
  res.json({
    dbHost: dbHost,
    dbUser: dbUser,
    // NEVER expose sensitive passwords or keys directly in API responses
    // dbPass: dbPass, 
    // apiKey: apiKey,
    environment: nodeEnv,
    message: 'Configuration loaded securely.'
  });
});

const PORT = process.env.PORT || 3000;
app.listen(PORT, () => {
  console.log(`Server running on port ${PORT} in ${nodeEnv} mode.`);
  console.log('Database Host:', dbHost);
  // console.log('Database User:', dbUser); // For demo, usually not logged in production
  // console.log('API Key:', apiKey); // For demo, usually not logged in production
});