Modules and several files

Split a program into files with require / module.exports or import / export; no npm packages.

Runs in Zerethon IDE · Node.js 22 Official JavaScript documentation ↗

main.js

const { area } = require('./geometry');
const path = require('path');

console.log(area(3, 4));
console.log(path.extname('report.json'));

geometry.js

function area(width, height) {
  return width * height;
}

module.exports = { area };

Output

12
.json

Two files: main.js (the entry) and geometry.js. Local files start with ./.

A file that uses require() runs as CommonJS. A file that uses import / export runs as an ES module — Node.js 22 detects it; .mjs files always are. Do not mix both in one file.
With import, write the extension: import { area } from './geometry.js'.
Node's built-in modules work (fs, path, readline, crypto, util, …).
npm packages are not available: runs have no network and nothing is installed.

Official references