Das Node.js-Modulsystem erklärt

Organize Your Code with Modules

CommonJS: `require()` & `module.exports`

CommonJS: Exporting a Function

const add = (a, b) => a + b;
const subtract = (a, b) => a - b;

module.exports = add; // Only 'add' is exported

CommonJS: Importing and Using

const addFunction = require('./mathUtils.js');

console.log("Using the imported function:");
console.log(`5 + 3 = ${addFunction(5, 3)}`);
console.log(`10 + 2 = ${addFunction(10, 2)}`);

CommonJS: Exporting Multiple Items

const greet = (name) => `Hello, ${name}!`;
const farewell = (name) => `Goodbye, ${name}!`;

module.exports = {
  greetUser: greet,
  sayGoodbye: farewell
};

CommonJS: Importing Multiple Items

const { greetUser, sayGoodbye } = require('./utils.js');

console.log(greetUser('Alice'));
console.log(sayGoodbye('Bob'));

ES Modules: The Modern Standard

ESM: Named Exports & Imports

export const add = (a, b) => a + b;
export const multiply = (a, b) => a * b;

// app.mjs (main entry point)
// To run this: ensure package.json has "type": "module"
// and run with `node app.mjs`
import { add, multiply } from './calculator.mjs';

console.log(`2 + 4 = ${add(2, 4)}`);
console.log(`5 * 6 = ${multiply(5, 6)}`);

ESM: Default Exports

const logMessage = (msg) => console.log(`[LOG] ${msg}`);
export default logMessage;

// main.mjs (main entry point)
// To run this: ensure package.json has "type": "module"
// and run with `node main.mjs`
import myLogger from './logger.mjs';

myLogger('This is a default message.');
myLogger('Another important event.');

Quick Check: Module Systems

Recap: Node.js Modules