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What is Node.js?

Node.jsJunior~1 min read
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More details in the official Node.js docs - About Node.js

Node.js is a JavaScript runtime outside the browser, built on Google Chrome's V8 engine. It lets you run JavaScript code on the server, not just in the browser.

Core characteristics

  1. Runtime Node.js is not a language or a framework, it is the environment in which JS code runs.
  2. The V8 engine Node.js is built on the V8 engine, written in C++, which compiles JavaScript into machine code for high execution speed.
  3. Single-threaded with non-blocking I/O Node.js runs in a single thread but efficiently handles thousands of requests at once thanks to asynchrony and the event loop.
  4. Modularity It uses the CommonJS module system (require, module.exports) and ES modules (import, export).
  5. The npm package manager Node.js ships with npm (Node Package Manager), the largest repository of JavaScript libraries.

Uses of Node.js

  • Building web servers (for example with Express.js, NestJS, Fastify)
  • Building REST APIs and GraphQL APIs
  • Building real-time applications (chats, online games, notifications)
  • CLI tools and automation scripts
  • SSR (Server-Side Rendering) for React, Next.js and others
  • Microservices and backend logic

A simple HTTP server in Node.js

javascript
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('Server running on http://localhost:3000'); });

Key advantages

  • High performance (V8 + non-blocking I/O)
  • Simple to work with JSON and REST
  • One language - JavaScript on the client and the server
  • A large npm package ecosystem
  • Support for microservice and event-driven architectures

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