CommonJS vs ES Modules

1. Definition

CommonJS and ES Modules are two module systems used in Node.js to organize and reuse code. CommonJS is the traditional module system, while ES Modules (ESM) is the modern standard introduced in JavaScript.

2. CommonJS

Uses require() to import modules
Uses module.exports to export
Synchronous loading
Default module system in Node.js

3. ES Modules (ESM)

Uses import to import modules
Uses export / export default
Asynchronous loading
Modern JavaScript standard

4. Key Differences

Syntax: require() vs import
Export: module.exports vs export
Loading: Sync vs Async
Usage: Older vs Modern

5. Example

👉 CommonJS

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

// app.js
const add = require("./math");
console.log(add(2, 3));

👉 ES Modules

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

// app.js
import { add } from "./math.js";
console.log(add(2, 3));

6. When to Use

Use CommonJS in older Node.js projects
Use ES Modules in modern applications
Prefer ES Modules for frontend and full-stack apps

7. Advantages

CommonJS is simple and widely supported
ES Modules provide cleaner syntax
Better compatibility with modern tools