What is Node.js and How Does it Work?

What is Node.js?

Node.js is a runtime that lets you run JavaScript outside the browser — on servers, CLIs, and desktop apps. It's built on Chrome's V8 engine and uses a non-blocking, event-driven model that makes it excellent for I/O-heavy applications.

How Node.js Works

Node runs JavaScript on a single thread but handles thousands of concurrent connections using an event loop and asynchronous, non-blocking I/O. While one request waits on the database, Node serves others — it never sits idle.

Your First Server

const http = require("http");

const server = http.createServer((req, res) => {
  res.writeHead(200, { "Content-Type": "text/plain" });
  res.end("Hello from Node.js!");
});

server.listen(3000, () => console.log("Running on :3000"));

What Node.js is Great For

• REST & GraphQL APIs — fast, JSON-native.
• Real-time apps — chat, live dashboards (with WebSockets).
• Microservices — lightweight and quick to start.
• Tooling — bundlers, CLIs, build scripts.

What Node.js is NOT Ideal For

CPU-heavy work (video encoding, complex math) blocks the single thread. For that, use worker threads or a different language.

The npm Ecosystem

Node comes with npm, the world's largest package registry (2M+ packages). Install anything with npm install package-name.

FAQs

Is Node.js a programming language?

No — it's a runtime. The language is JavaScript.

Node.js vs Deno vs Bun?

All run JS server-side. Node is the mature standard; Bun is faster and newer; Deno is secure-by-default. More in our Node.js guides.