What are Modules in Node.js?

In Node.js, any file with a .js extension is a module. Modules allow you to split your code into multiple files for better organization, reusability, and easier debugging.

Functions, classes, or objects defined in one module can be imported and reused in other files using require().

Every JavaScript file in Node.js is a module.

Let's create a file sum.js that exports a single function.

const add = require('./sum.js');

console.log("add(2,3) =", add(2, 3));
console.log("add(5,3) =", add(5, 3));

You can export multiple functions as an object from a module.

const calculator = require('./sum');

console.log("sum(2,3) =", calculator.sum(2, 3));
console.log("sub(5,3) =", calculator.sub(5, 3));

Instead of using dot notation, you can use destructuring to directly access exported functions.

const { sum, sub } = require('./sum');

console.log("sum(2,3) =", sum(2, 3));
console.log("sub(5,3) =", sub(5, 3));

Each function can be exported separately using module.exports.

const calculator = require('./sum');

console.log("sum(10,5) =", calculator.sum(10, 5));
console.log("sub(10,5) =", calculator.sub(10, 5));

You can also use the exports keyword instead of module.exports.

const calculator = require('./sum');

console.log("sum(20,10) =", calculator.sum(20, 10));
console.log("sub(20,10) =", calculator.sub(20, 10));

You can also organize modules inside directories.

For example, move sum.js inside a maths/ folder and require it with path.

const calculator = require('./maths/sum');

console.log("sum(4,6) =", calculator.sum(4, 6));
console.log("sub(9,4) =", calculator.sub(9, 4));