Introduction to Node.js

🔷 1. What is Node.js?

Node.js is a runtime environment that lets you run JavaScript code outside the web browser, specifically on the server side.

• Traditionally, JavaScript was only used in the client-side (inside the browser).
• With Node.js, JavaScript can now run on the backend, similar to other server-side languages like PHP, Python, Java.

⚙️ Technical Definition:

Node.js is a runtime built on Google Chrome’s V8 JavaScript Engine, allowing fast execution of JavaScript code outside the browser.

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🔷 2. Core Features of Node.js

✅ Asynchronous and Event-Driven

• Node.js performs non-blocking I/O operations, allowing it to handle multiple requests simultaneously.
• Uses callbacks, promises, or async/await to handle asynchronous operations.

✅ Single-Threaded but Highly Scalable

• Unlike traditional multi-threaded servers (like Apache), Node.js handles concurrency using an event loop on a single thread.

✅ Extremely Fast

• Powered by V8 engine, written in C++ by Google, which compiles JavaScript to native machine code for high performance.

✅ NPM (Node Package Manager)

• Over 1.5 million packages in the npm registry.
• Simplifies dependency management for developers.

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🔷 3. Node.js Architecture (Event-Driven Model)

Diagram (Text Representation):

Client Request
     ↓
  Event Queue
     ↓
  Event Loop
     ├── Light Tasks (handled directly)
     └── Heavy Tasks → Thread Pool (via Libuv)
                          ↓
                    Callback Functions
                          ↓
                       Response Sent

Key Components:

• Event Loop: Heart of Node.js. Continuously checks for tasks to execute.
• Libuv: C library used for handling asynchronous I/O and the thread pool.
• Callback Queue: Stores callback functions to be executed once the task completes.

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🔷 4. Installing Node.js and Running First Script

📥 Steps to Install:

• Download from: https://nodejs.org
• After installation:

node -v    # to check Node version
npm -v     # to check npm version

💻 First Script: Hello World

// app.js
console.log("Hello, MCA Students! Welcome to Node.js");

Run:

node app.js

🧑‍💻 Creating a Web Server:

const http = require('http');

const server = http.createServer((req, res) => {
  res.writeHead(200, {"Content-Type": "text/plain"});
  res.end("Hello from Node.js server!");
});

server.listen(3000, () => {
  console.log("Server running at http://localhost:3000");
});

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🔷 5. Node.js Modules

🧱 Types of Modules:

• Core Modules (built-in): http, fs, path, url, events
• Local Modules: Your own custom modules.
• Third-party Modules: Installed via npm (e.g., express, lodash, mongoose)

📦 Example: Using fs module

const fs = require('fs');

fs.writeFile('hello.txt', 'Hello MCA!', (err) => {
  if (err) throw err;
  console.log('File created');
});

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🔷 6. NPM (Node Package Manager)

📌 What is npm?

• Comes bundled with Node.js.
• Helps in:
  • Installing libraries (packages)
  • Managing project dependencies
  • Running scripts (e.g., starting a server)

Example:

bashCopyEditnpm init       # initialize a project
npm install express   # install Express.js

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🔷 7. Express.js – The Framework on Node.js

🌟 Why Express?

• Minimal and flexible.
• Adds routing, middleware, and HTTP utilities.

🌐 Basic Express Server:

const express = require('express');
const app = express();

app.get('/', (req, res) => {
  res.send('Hello from Express!');
});

app.listen(3000, () => {
  console.log('Server started on port 3000');
});

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🔷 8. Real-World Applications Built with Node.js

Application Type	Example Platforms	How Node Helps
Chat Applications	WhatsApp Clone, Slack	Fast, event-driven real-time communication
Streaming Services	Netflix, YouTube	Streams large content efficiently
APIs & Microservices	REST APIs, GraphQL APIs	Lightweight and scalable
E-commerce Platforms	Flipkart, Amazon	Real-time updates, asynchronous processing
IoT Applications	Smart devices communication	Handles thousands of device connections

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🔷 9. Suggested Projects for MCA Students

Project Name	Description	Skills Covered
Student Management System	CRUD operations, database integration	Express, MongoDB
Chat Application	Real-time messaging with Socket.io	Event-driven architecture
Online Polling System	Voting, results in real-time	Routing, API, Frontend-Backend Sync
API for a Shopping App	REST API with authentication	JWT, Express, Middleware
Weather App using API	Fetch weather data from OpenWeather API	API calls, async/await, JSON handling

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🔷 10. Topics to Cover in Curriculum

Unit	Topics
Unit 1	Introduction to Node.js, installation, modules
Unit 2	Event Loop, EventEmitter, Streams
Unit 3	HTTP Module, File system, Routing
Unit 4	Express.js, Middleware, REST APIs
Unit 5	MongoDB Integration (with Mongoose), Authentication, Deployment

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🧠 Conclusion

Node.js is a powerful tool that every MCA student should learn for the following reasons:

• JavaScript dominance in both frontend and backend.
• High performance and scalability.
• Easy integration with modern frontend frameworks (React, Angular, Vue).
• Large job market for full-stack and backend developers.