Modules (ES Modules & CommonJS)

1// ===== ES Modules (ESM) =====
2
3// math.js — Named exports
4export const PI = 3.14159;
5export function add(a, b) { return a + b; }
6export function multiply(a, b) { return a * b; }
7
8// user.js — Default export
9export default class User {
10  constructor(name) { this.name = name; }
11}
12
13// app.js — Importing
14import User from "./user.js";                    // Default import
15import { add, multiply } from "./math.js";       // Named imports
16import { add as sum } from "./math.js";           // Renamed import
17import * as MathUtils from "./math.js";           // Namespace import
18
19// Re-exporting
20export { add, multiply } from "./math.js";
21export { default as User } from "./user.js";
22
23// Dynamic import (code splitting)
24async function loadChart() {
25  const { Chart } = await import("./chart.js");
26  return new Chart();
27}
28
29// ===== CommonJS (CJS) =====
30
31// math.js
32// module.exports = { add, multiply };
33// or
34// exports.add = (a, b) => a + b;
35
36// app.js
37// const { add, multiply } = require("./math");
38// const math = require("./math");