Node.js Modules - GeeksforGeeks (2024)

In Node.js, Modules are the blocks of encapsulated code that communicate with an external application on the basis of their related functionality. Modules can be a single file or a collection of multiple files/folders. The reason programmers are heavily reliant on modules is because of their reusability as well as the ability to break down a complex piece of code into manageable chunks.

We will discuss the different types of Node.js Modules:

Core Modules

Node.js has many built-in modules that are part of the platform and come with Node.js installation. These modules can be loaded into the program by using the required function.

Syntax:

const module = require('module_name');

The require() function will return a JavaScript type depending on what the particular module returns. The following example demonstrates how to use the Node.js http module to create a web server.

const http = require('http');http.createServer(function (req, res) { res.writeHead(200, { 'Content-Type': 'text/html' }); res.write('Welcome to this page!'); res.end();}).listen(3000);

In the above example, the require() function returns an object because the Http module returns its functionality as an object. The function http.createServer() method will be executed when someone tries to access the computer on port 3000. The res.writeHead() method is the status code where 200 means it is OK, while the second argument is an object containing the response headers. The following list contains some of the important core modules in Node.js:

Local Modules

Unlike built-in and external modules, local modules are created locally in your Node.js application. Let’s create a simple calculating module that calculates various operations. Create a calc.js file that has the following code:

// Filename: calc.jsexports.add = function (x, y) { return x + y;};exports.sub = function (x, y) { return x - y;};exports.mult = function (x, y) { return x * y;};exports.div = function (x, y) { return x / y;};

Since this file provides attributes to the outer world via exports, another file can use its exported functionality using the require() function.

// Filename: index.jsconst calculator = require('./calc');let x = 50, y = 10;console.log("Addition of 50 and 10 is " + calculator.add(x, y));console.log("Subtraction of 50 and 10 is " + calculator.sub(x, y));console.log("Multiplication of 50 and 10 is " + calculator.mult(x, y));console.log("Division of 50 and 10 is " + calculator.div(x, y));

Step to run this program: Run the index.js file using the following command:

node index.js

Output:

Addition of 50 and 10 is 60Subtraction of 50 and 10 is 40Multiplication of 50 and 10 is 500Division of 50 and 10 is 5

Note: This module also hides functionality that is not needed outside of the module.

Third-party modules

Third-party modules are modules that are available online using the Node Package Manager(NPM). These modules can be installed in the project folder or globally. Some of the popular third-party modules are Mongoose, express, angular, and React.

Example:

• npm install express
• npm install mongoose
• npm install -g @angular/cli

Example: Installing and Using Express

npm install express

Create a Simple Express Server:

const express = require('express');const app = express();const port = 3000;app.get('/', (req, res) => { res.send('Hello World!');});app.listen(port, () => { console.log(`Example app listening at http://localhost:${port}`);});

Run the Server:

node server.js

When you navigate to http://localhost:3000 in your browser, you should see Hello World!.