What is Node.js?

Introduction to Node.js

Node.js is a cross-platform, open-source runtime environment that enables the execution of JavaScript code outside a web browser. Developed by Ryan Dahl in 2009, Node.js revolutionized web development by enabling JavaScript previously confined to the browser to run on the server side. It uses the V8 JavaScript engine built by Google, which compiles JavaScript into native machine code for high performance. Node.js is renowned for its non-blocking, event-driven architecture, which allows it to handle multiple requests simultaneously. This makes it an ideal choice for building fast, scalable network applications like APIs, real-time chat servers, data streaming services, and single-page applications (SPAs). Its popularity has soared due to the simplicity it brings by allowing developers to write both client-side and server-side logic in JavaScript, streamlining the development process.

Key reasons for Node.js adoption include:

• High performance due to V8 engine
• Unified development language (JavaScript)
• Active community and rich ecosystem (npm)
• Support for modern web standards
• Scalable architecture for real-time applications

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Node.js Architecture

Node.js operates on a single-threaded, non-blocking architecture based on the event loop. Unlike traditional multi-threaded models, Node.js does not create a new thread for each request. Instead, it uses an event loop to manage concurrent operations efficiently.

Main architectural components:

• Event Loop: The core component that continuously checks the event queue and executes callback functions when events are ready.
• Callbacks and Promises: Used for asynchronous task handling.
• Libuv Library: Handles thread pooling and low-level OS operations.
• Worker Pool: Background threads for executing expensive or blocking operations.
• V8 Engine: Executes JavaScript code with high efficiency.

Node.js is particularly efficient at I/O-bound tasks such as reading/writing files, database operations, and API calls.

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Event-Driven Model

Node.js follows an event-driven, asynchronous model of programming. This allows it to perform non-blocking operations and continue executing other code while waiting for operations like file reads or API calls to complete.

EventEmitter is a built-in module in Node.js that facilitates this pattern. Developers can create custom events and listeners using it:

• const EventEmitter = require(‘events’);
• const emitter = new EventEmitter();
• emitter.on(‘data’, (data) => {
• console.log(‘Received:’, data);
• });
• emitter.emit(‘data’, ‘Hello, Node.js!’);

This event-driven nature is essential for creating highly responsive applications.

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Node.js vs Traditional Servers

Traditional web servers such as Apache or IIS use a multi-threaded model where each incoming request spawns a new thread. While effective, this model consumes significant system resources under heavy load.
Node.js uses a single-threaded model with a non-blocking event loop, enabling it to handle thousands of concurrent requests with minimal overhead.

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Setting Up Environment

To start developing with Node.js:

1. Download Node.js from https://nodejs.org
2. Install Node.js and verify with: node -v
3. npm -v
4. Create Project Folder:
   mkdir my-node-app && cd my-node-app
5. Initialize Project:
   npm init -y Create Entry File (index.js) and write a basic server:
   
   • const http = require(‘http’);
   • const server = http.createServer((req, res) => {
   • res.writeHead(200, { ‘Content-Type’: ‘text/plain’ });
   • res.end(‘Hello World from Node.js!’);
   • });
6. server.listen(3000);
   Run it with node index.js and navigate to http://localhost:3000.

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NPM and Packages

Node.js comes bundled with npm (Node Package Manager), which is used to manage dependencies and install packages.

Useful npm commands:

• npm install package-name – Install locally
• npm install -g package-name – Install globally
• npm uninstall package-name – Remove package
• npm update – Update all dependencies

Popular packages:

• Express – Web framework
• Mongoose – MongoDB ORM
• Dotenv – Environment variables
• Cors – Cross-origin resource sharing.

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Core Modules

Node.js includes several core modules that offer out-of-the-box functionality:

File System and Streams

Streams are abstract interfaces for working with streaming data in Node.js.

Types of streams:

• Readable – For reading data
• Writable – For writing data
• Duplex – Both read and write
• Transform – Modify data during read/write

Asynchronous Programming