Node.js CommonJS vs ES Modules

What is CommonJS vs ES Modules in Node.js?

Node supports two module systems. CommonJS uses require and module.exports and is the historical default. ES modules use import and export, are the JavaScript standard, and are the recommended choice for new projects.

CommonJS vs ES Modules example

// CommonJS — math.js
function add(a, b) { return a + b; }
module.exports = { add };

const { add } = require('./math');

// ES modules — math.js
export function add(a, b) { return a + b; }
export default add;

import { add } from './math.js';   // extension required

Key points to remember

• Set "type": "module" in package.json to make .js files ES modules.
• ES modules can import CommonJS packages; the reverse needs a dynamic import().
• Local ES module imports must include the .js extension.
• Choose one style per project rather than mixing.

CommonJS vs ES modules

Common mistakes with CommonJS vs ES Modules

• ERR_REQUIRE_ESM — using require on an ES-module-only package.
• Omitting the file extension in an ES module import and getting ERR_MODULE_NOT_FOUND.
• Using top-level await in a CommonJS file.