NodeJS Introduction

NodeJS is a runtime environment for executing JavaScript outside the browser, built on the V8 JavaScript engine. It enables server-side development, supports asynchronous, event-driven programming, and efficiently handles scalable network applications.

Hello, World!” Program in NodeJS

A “Hello, World!” program is the simplest way to get started with NodeJS. Unlike the browser, where JavaScript runs inside the console, NodeJs executes JavaScript in a server environment or via the command line.

console.log("Hello, World!");

Output:

Key Features of NodeJS

• Server-Side JavaScript: NodeJS allows JavaScript to run outside the browser, enabling backend development.
• Asynchronous & Non-Blocking: Uses an event-driven architecture to handle multiple requests without waiting, improving performance.
• Single-Threaded Event Loop: Efficiently manages concurrent tasks using a single thread, avoiding thread overhead.
• V8 Chrome Engine: High performance, Open-Source Javascript web assembly engine developed by google and rewoned for compiling JS into native machine code to execute it with exceptional speed..
• Scalable & Lightweight: Ideal for building microservices and handling high-traffic applications efficiently.
• Rich NPM Ecosystem: Access to thousands of open-source libraries through Node Package Manager (NPM) for faster development.

How NodeJS Works?

NodeJS is a runtime environment that allows JavaScript to run outside the browser. It is asynchronous, event-driven, and built on the V8 JavaScript engine, making it ideal for scalable network applications.

Single-Threaded Event Loop Model

NodeJS operates on a single thread but efficiently handles multiple concurrent requests using an event loop.

• Client Sends a Request: The request can be for data retrieval, file access, or database queries.
• NodeJS Places the Request in the Event Loop: If the request is non-blocking (e.g., database fetch), it is sent to a worker thread without blocking execution.
• Asynchronous Operations Continue in Background: While waiting for a response, NodeJS processes other tasks.
• Callback Execution: Once the operation completes, the callback function executes, and the response is sent back to the client.

const fs = require('fs');

fs.readFile('file.txt', 'utf8', (err, data) => {
    if (err) throw err;
    console.log(data); 
});

console.log("Reading file..."); 

Components of NodeJS Architecture

• V8 Engine: Compiles JavaScript to machine code for fast execution.
• Event Loop: Manages asynchronous tasks without blocking the main thread.
• Libuv: Handles I/O operations, thread pool, and timers.
• Non-Blocking I/O: Executes tasks without waiting for previous ones to complete.

Where to Use NodeJS?

NodeJS is best suited for applications that require high performance, scalability, and real-time processing. Below are some common use cases:

• Web APIs and Backend Services : Ideal for building RESTful APIs and GraphQL APIs. It also Used in backend services for mobile apps and web applications.
• Real-Time Applications: Chat applications (e.g., WhatsApp, Slack). Live streaming services (e.g., Netflix, Twitch).
• Microservices Architecture: It helps in developing scalable and independent services. It also used in cloud-based applications.
• IoT (Internet of Things) Applications: Handles real-time data streaming from IoT devices. It is suitable for smart home automation and sensor-based systems.
• Serverless Computing: Works well with AWS Lambda, Azure Functions, and Google Cloud Functions. Runs lightweight serverless functions efficiently.
• Single-Page Applications (SPAs): It used in React, Angular, and Vue.js applications. It manages API requests efficiently in the backend.
• Data-Intensive Applications: It used for big data processing and real-time analytics. It works well with NoSQL databases like MongoDB and Firebase.