Node.js Global Objects

What is Global Objects in Node.js?

Node provides globals that do not exist in browsers: process for environment and lifecycle, __dirname and __filename for paths in CommonJS, Buffer for binary data, and console for output.

Global Objects example

console.log(process.argv);        // command-line arguments
console.log(process.env.NODE_ENV); // environment variables
console.log(process.platform);     // 'linux' | 'darwin' | 'win32'
console.log(process.pid);

process.on('SIGINT', () => {
  console.log('Shutting down…');
  process.exit(0);
});

// CommonJS only
console.log(__dirname, __filename);

The ES module equivalent of __dirname

import { fileURLToPath } from 'node:url';
import { dirname } from 'node:path';

const __filename = fileURLToPath(import.meta.url);
const __dirname = dirname(__filename);

// Node 20.11+ offers a shorter form:
// import.meta.dirname

Key points to remember

• process.env holds environment variables and is how configuration reaches the app.
• __dirname and __filename are undefined in ES modules.
• process.exit(0) means success; any non-zero code signals failure.
• globalThis works in both Node and the browser.

Common mistakes with Global Objects

• Using __dirname in an ES module and getting a ReferenceError.
• Calling process.exit() before pending writes flush, truncating output.