NodeJS Introduction (original) (raw)

Last Updated : 17 Sep, 2025

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

Nodejs

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.

JavaScript `

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

`

**Output:

Hello, World! in NodeJS

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. JavaScript `

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.

Introduction to Node JS | Web Development