Environment & Config

Node.js · Reference cheat sheet

📋 Overview

Configure Node apps with environment variables, optionally loaded from .env files via dotenv or platform secrets. Validate required keys at startup.

🔧 Core concepts

💡 Examples

Fail-fast config:

function required(name) {
  const v = process.env[name];
  if (!v) throw new Error(`Missing env: ${name}`);
  return v;
}

export const config = {
  port: Number(process.env.PORT || 9000),
  databaseUrl: required("DATABASE_URL"),
};

dotenv (dev):

import "dotenv/config";

.env.example:

PORT=9000
DATABASE_URL=postgres://user:pass@localhost:5432/app

⚠️ Pitfalls

• process.env values are strings — PORT needs Number(...).
• Loading .env in production can accidentally override platform secrets if misordered.
• Never log raw env objects — they often contain credentials.

🔗 Related

• getting_started.md
• error_handling.md
• packaging.md
• Next.js/env.md