How do I execute Node.js programs online?

Write and execute Node.js scripts using our online Node.js compiler or locally using node filename.js.

What are the core built-in modules covered in Node.js?

Core modules include http, fs, path, os, events, crypto, and url.

How does Node.js handle asynchronous non-blocking I/O?

Node.js uses an event-driven single-threaded Event Loop backed by libuv.

NodeJS Programming Examples

Explore essential NodeJS programs covering fundamental concepts and syntax examples — HTTP servers, file system operations, streams, event emitters, promises, worker threads, and Express.js basics — with expected output to verify your code.

Node.js is an open-source, cross-platform JavaScript runtime environment built on V8 engine, designed for high-performance server-side web development. Ideal for backend engineers, bootcamp students, and API developers.

Last updated: September 2026 · 20 examples · Node.js v20/v22 Compatible

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Quick Start

Select a Node.js program from the sidebar or mobile navigation menu
Review the source code and expected console output
Test it in our Online NodeJS Compiler or locally using node script.js
Modify file operations, asynchronous promises, or API routes to experiment

Who is this for: Backend developers, JavaScript programmers, full-stack engineers, and students preparing for Node.js backend interview questions.

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Reading Environment Variables with process.env

Run Online

Shows how Node.js accesses system environment variables and fallback default values.

Program (Node.js)

const nodeEnv = process.env.NODE_ENV || "development";
const port = process.env.PORT || 8080;
const dbHost = process.env.DB_HOST || "localhost";

console.log("Environment Mode:", nodeEnv);
console.log("Server Port:", port);
console.log("Database Host:", dbHost);

Expected Output

Environment Mode: development
Server Port: 8080
Database Host: localhost

Frequently Asked Questions

You can write and execute Node.js scripts instantly using our Online Node.js Compiler. For local execution, install Node.js from nodejs.org and run node filename.js in your terminal.

Essential built-in modules include http (web servers), fs (file system), path (directory paths), os (system metadata), events (EventEmitter), crypto (hashing), and url (URL parsing).

Node.js operates on a single-threaded Event Loop backed by libuv. Heavy I/O tasks like reading files or database queries run in background worker threads, notifying the main thread via callbacks, Promises, or async/await.

Yes! Understanding Node.js core modules and async control flow is the foundation for building microservices, REST APIs, and full-stack applications with Express, NestJS, and Fastify.

Who Should Practice These Node.js Examples?

Target Audience: Programmers mastering backend JavaScript architecture:

Frontend Developers — transitioning to full-stack Node.js development
Backend Engineers — writing microservices, RESTful endpoints, and file processors
CS Students & Bootcamp Grads — building strong foundations in event loops, streams, and async programming
Interview Candidates — preparing for JavaScript and Node.js backend coding rounds

Node.js Developer Career Opportunities

Node.js is one of the most widely adopted server environments, utilized by Netflix, LinkedIn, Uber, and PayPal for real-time web applications.

Experience Level	Avg Salary (US)	Avg Salary (India)	Key Roles
Junior (0–2 yrs)	$80,000 - $100,000	₹5 - ₹9 LPA	Junior Node.js Developer, API Engineer
Mid-Level (3–5 yrs)	$110,000 - $145,000	₹13 - ₹22 LPA	Full-Stack Engineer, Node.js Backend Dev
Senior (6+ yrs)	$155,000 - $220,000+	₹25 - ₹45+ LPA	Backend Solutions Architect, Tech Lead