What Is Node.js and Why Should You Learn It?

What is Node.js?

Node.js is a runtime that lets you run JavaScript outside the browser — on a server or on your own machine. It's built on Google Chrome's V8 engine, which is why it's so fast.

Put simply: JavaScript used to live only in the browser. With Node.js, you can use it to build backends, CLI tools, and even desktop apps.

How does Node.js work?

The core idea behind Node.js is non-blocking I/O and the event loop.

Traditional servers open a separate thread for each request and wait for a file to be read or a database to respond. Node.js doesn't wait: it hands off the task, moves on to the next request, and comes back via a callback once the result is ready.

import { readFile } from 'node:fs/promises'

console.log('1. Started reading the file')

const data = await readFile('matn.txt', 'utf-8')
console.log('3. File read:', data.length, 'characters')

console.log('2. This line does not wait')

That's how Node.js can handle thousands of concurrent connections with very few resources.

Why Node.js?

One language — frontend and backend both in JavaScript (or TypeScript). Less context switching.
npm — the largest package ecosystem in the world. There's a ready-made library for almost anything.
Speed — a great fit for real-time apps (chat, notifications, online games).
Huge community — answers to your questions are easy to find.
Modern features — fetch, a built-in test runner (node:test), and --watch mode now ship with Node.js itself.

Where is it used?

REST and GraphQL APIs
Real-time apps (WebSocket, chat)
Telegram bots
CLI tools
The server side of fullstack frameworks like Next.js and Nuxt

Your first server

Download and install the LTS version from nodejs.org, then check it:

node -v
npm -v

Now create a server.js file:

import { createServer } from 'node:http'

const server = createServer((req, res) => {
  res.writeHead(200, { 'Content-Type': 'text/plain; charset=utf-8' })
  res.end('Hello, Node.js!')
})

server.listen(3000, () => {
  console.log('Server running: http://localhost:3000')
})

Run it:

node --watch server.js

Open http://localhost:3000 in your browser — congrats, your first server is live! The --watch flag automatically restarts the server whenever the file changes.

When is Node.js not a good fit?

Node.js isn't the best choice for heavy computation (video encoding, large-scale data processing, ML), because those tasks block the event loop. For that kind of work, worker_threads or another language (Go, Python, Rust) is a better fit.

Next steps

Get solid on JavaScript fundamentals, especially async/await and Promises.
Build a simple API with Express or Fastify.
Connect a database (PostgreSQL + Prisma or Drizzle).
Move to TypeScript.

Node.js is one of the easiest doors into the backend world. Start with a small project and grow from there. Good luck!