How to export and import modules in Node.js

Short answer

In CommonJS, use module.exports to export and require() to import. In ES modules, use export or export default and import.

Steps

CommonJS: 1. Create a file math.js with module.exports.add = (a, b) => a + b;. 2. In another file, import it with const math = require('./math.js');. 3. Use the function with math.add(2, 3);.

ES Modules: 1. Create a file math.mjs with export const add = (a, b) => a + b;. 2. In another file, import it with import { add } from './math.mjs';. 3. Use the function directly with add(2, 3);.

Tips

• You can destructure CommonJS imports: const { add } = require('./math');.
• ES modules require the full file path including the extension unless you use a bundler.

Common issues

• Error: Cannot find module usually means the path is wrong or the file does not exist.
• Mixing CommonJS require with ES module import in the same file causes a syntax error.