Modules

Modules

A module is a file that exports functions, objects or values so that other files can import them. This is how you organize code into small, reusable pieces.

ES Modules (modern standard)

// math.js
export function add(a, b) {
  return a + b;
}
export const PI = 3.14159;

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

There is also the default export:

// greeting.js
export default function (name) {
  return `Hello, ${name}`;
}

// app.js
import greeting from "./greeting.js";

CommonJS (classic Node style)

Before ES Modules, Node used require and module.exports:

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

// app.js
const { add } = require("./math.js");

Today it is recommended to use ES Modules (import/export), which are the standard both in the browser and in modern Node.

Examples

A 'module' as an exported object

const math = {
  add: (a, b) => a + b,
  subtract: (a, b) => a - b,
};
console.log(math.add(10, 5));
console.log(math.subtract(10, 5));