Glossary

What Is Node.js?

Node.js Runtime

Node.js is a JavaScript runtime that lets you run JavaScript outside the browser — on servers, command lines, and IoT devices. Built on Chrome's V8 engine, it uses a non-blocking, event-driven architecture that excels at I/O-heavy applications like APIs, real-time servers, and build tools.

How Node.js Works

Node.js unified frontend and backend development under one language — JavaScript. This means one team can build the entire stack, share code between client and server, and use the same package manager (npm) everywhere.

Node.js is not for CPU-intensive tasks (use Go or Rust instead). It excels at I/O-bound work: API servers, real-time chat, streaming, file processing, and microservices. Express, Fastify, and Hono are popular Node.js web frameworks.

The Node.js ecosystem (npm) has 2M+ packages — the largest package registry in any language. Alternatives like Bun and Deno provide faster performance and modern features while maintaining Node.js compatibility.

Why Developers Use Node.js

Node.js powers the backends of Netflix, LinkedIn, PayPal, Uber, and countless startups. It's the most popular server-side JavaScript runtime and the foundation of the modern web development toolchain (webpack, Vite, ESLint all run on Node).

Key Concepts

  • Event Loop — Node.js processes I/O operations asynchronously — handles thousands of connections without blocking on any single one
  • npm — Node Package Manager — the world's largest software registry with 2M+ packages
  • Express — The most popular Node.js web framework — minimal, flexible, and middleware-based
  • Streams — Process data in chunks without loading everything into memory — essential for file processing and HTTP responses
  • Worker Threads — Run CPU-intensive code in parallel without blocking the main event loop
  • CommonJS vs ESM — Two module systems — require() (legacy) and import/export (modern standard)

Node.js HTTP Server

javascript
const http = require('http');

const server = http.createServer((req, res) => {
  if (req.url === '/api/hello') {
    res.writeHead(200, { 'Content-Type': 'application/json' });
    res.end(JSON.stringify({ message: 'Hello from Node.js!' }));
  } else {
    res.writeHead(404);
    res.end('Not Found');
  }
});

server.listen(3000, () => console.log('Server running on port 3000'));

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Frequently Asked Questions

Is Node.js a programming language?

No. Node.js is a runtime environment that executes JavaScript code. JavaScript is the language; Node.js is the platform that lets it run on servers.

Node.js vs Bun vs Deno?

Node.js has the largest ecosystem and most production deployments. Bun is the fastest and includes a bundler/test runner. Deno has better security defaults and native TypeScript. For production, Node.js is safest; for new projects, try Bun.

Is Node.js good for large applications?

Yes, with proper architecture. Companies like Netflix and PayPal run massive Node.js deployments. Use TypeScript, follow microservices patterns, and choose a framework (Fastify, NestJS) that provides structure.

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Related Terms

JavaScriptExpress.jsnpmTypeScriptBun

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