Tipado de variables de entorno y configuración

const port = process.env.PORT; // string | undefined
// server.listen(port); // could be undefined!

declare global {
  namespace NodeJS {
    interface ProcessEnv {
      PORT: string;
      DATABASE_URL: string;
      NODE_ENV: 'development' | 'staging' | 'production';
    }
  }
}

function requireEnv(key: string): string {
  const val = process.env[key];
  if (!val) throw new Error(`Missing env var: ${key}`);
  return val;
}
export const config = {
  port: parseInt(requireEnv('PORT')),
  dbUrl: requireEnv('DATABASE_URL'),
};

import { z } from 'zod';
const envSchema = z.object({
  PORT: z.string().transform(Number),
  DATABASE_URL: z.string().url(),
  NODE_ENV: z.enum(['development', 'production']),
});
export const env = envSchema.parse(process.env);

import 'dotenv/config';
// Or:
import dotenv from 'dotenv';
dotenv.config();

const envFile = `.env.${process.env.NODE_ENV ?? 'development'}`;
dotenv.config({ path: envFile });

console.log({ ...config, dbPassword: '***', apiKey: '***' });

const flags = {
  enableBeta: process.env.ENABLE_BETA === 'true',
  logLevel: (process.env.LOG_LEVEL ?? 'info') as 'debug' | 'info' | 'warn',
};

// tests/setup.ts
process.env.DATABASE_URL = 'sqlite:///:memory:';
process.env.NODE_ENV = 'test';