Experiment 1: Node.js

 Introduction to Node.js

Node.js is a runtime environment that allows us to run JavaScript outside the browser, mainly on  the server. 

With Node.js, developers can use the same language—JavaScript—for both the front end and back end, which makes development simpler and quicker.

Node.js is designed to handle many users at the same time without slowing down. It uses a non-blocking and event-driven model, meaning it does not wait for one task to finish before starting another. Instead, it responds to events as they happen. This makes Node.js perfect for applications that require quick responses and continuous communication.

Applications of Node.js

• Real-time chat applications

• Video streaming platforms

• Online gaming servers

• REST APIs and backend services

• Single-page applications (SPAs)

• IoT (Internet of Things) applications

• Collaborative tools like shared editors or dashboards

Architecture of Node.js

Node.js follows a single-threaded, event-driven architecture:

1. Single Thread

   • Node.js uses one main thread to execute JavaScript.

2. Non-blocking I/O

   • Tasks like reading files or database queries run in the background without stopping the main thread.

3. Event Loop

   • The event loop keeps checking for completed tasks and runs their callbacks.

4. V8 Engine

   • Converts JavaScript into fast machine code.

This design lets Node.js handle thousands of requests efficiently.

Logic of Node.js 

When a request comes in, Node.js does not stop and wait for long tasks. Instead, it quickly sends those tasks to the system to handle in the background. While those tasks run, Node.js continues handling other requests. When the background tasks finish, their results are sent back to the main program using callbacks or promises. This makes Node.js fast, lightweight, and good for real-time applications.

PROGRAMS

1. Write a program to show the workflow of JavaScript code executable by creating web server in Node.js.

// Import the http module

const http = require('http');

// Create a web server

const server = http.createServer((req, res) => {

    

    // 1. Client sends a request

    console.log("A request has been received!");

    // 2. Server processes JavaScript code

    const message = "Hello! This response is generated by JavaScript running on Node.js.";

    // 3. Server sends the response back to the client

    res.writeHead(200, { 'Content-Type': 'text/plain' });

    res.end(message);

});

// Start the server on port 3000

server.listen(3000, () => {

    console.log("Server is running at http://localhost:3000");

});

How the Workflow Happens

1. Start the Server

Run the file:

node server.js

2. Client Sends Request

Open browser and go to:

http://localhost:3000

3. Server Executes JavaScript Code

• Node.js receives the request

• Executes the callback function in createServer

• Runs the JavaScript logic

• Prepares the response

4. Response Sent to Client

You will see:

Hello! This response is generated by JavaScript running on Node.js.

2. Write a program to transfer data over http protocol using http module.

// Import http module

const http = require('http');

// Create HTTP server

const server = http.createServer((req, res) => {

    

    // Set response header

    res.writeHead(200, { 'Content-Type': 'text/plain' });

    // Data to transfer over HTTP

    const message = "Hello! This data is transferred over HTTP protocol.";

    // Send the data to the client

    res.write(message);

    // End the response

    res.end();

});

// Server listens on port 3000

server.listen(3000, () => {

    console.log("Server running at http://localhost:3000/");

});

3. Create a text file src.txt and add the following content to it. (HTML, CSS, Javascript, Typescript, MongoDB, Express.js, React.js, Node.js)

const fs = require('fs');

// Content to write in src.txt

const data = `

HTML

CSS

JavaScript

TypeScript

MongoDB

Express.js

React.js

Node.js

`;

// Create and write to src.txt

fs.writeFile('src.txt', data, (err) => {

    if (err) {

        console.log("Error writing file:", err);

    } else {

        console.log("src.txt file created successfully!");

    }

});

4. Write a program to parse an URL using URL module.

 // Import the URL module

const url = require('url');

// URL to parse

const address = "https://www.example.com/products?category=books&id=10";

// Parse the URL

const parsedURL = url.parse(address, true);

// Display parsed parts

console.log("Protocol:", parsedURL.protocol);

console.log("Host:", parsedURL.host);

console.log("Pathname:", parsedURL.pathname);

console.log("Search Query:", parsedURL.search);

console.log("Query Parameters:", parsedURL.query);

5.  Write a program to create an user-defined module and show the workflow of Modularization of application using Node.js

Create a file named mathModule.js

// mathModule.js

// A user-defined module that exports two functions

function add(a, b) {

    return a + b;

}

function multiply(a, b) {

    return a * b;

}

// Export the functions so other files can use them

module.exports = {

    add,

    multiply

};

Create another file: app.js

// app.js

// Import the user-defined module

const math = require('./mathModule');

// Use the functions from the module

console.log("Addition:", math.add(10, 20));

console.log("Multiplication:", math.multiply(5, 6));

// Show workflow

console.log("\nThis program demonstrates modularization in Node.js.");

console.log("1. mathModule.js contains reusable functions.");

console.log("2. app.js imports the module using require().");

console.log("3. app.js executes the imported functions.");