Introduction to Node.js

What is Node.js?

Node.js is a runtime environment that allows you to run JavaScript on the server-side. Built on Chrome's V8 engine, it enables full-stack JavaScript development.

Event-Driven Architecture

Node.js uses an event loop for non-blocking I/O operations. This asynchronous nature allows handling many concurrent connections without threads.

const fs = require('fs');
  fs.readFile('file.txt', 'utf8', (err, data) => {
    if (err) throw err;
    console.log(data);
  });
  console.log('Reading file...'); // This executes first

Modules and NPM

Node.js uses CommonJS modules. Create modules by exporting functions and require them in other files:

// math.js
  module.exports = { add: (a, b) => a + b };

  // app.js
  const math = require('./math');
  console.log(math.add(2, 3)); // 5

NPM (Node Package Manager) handles dependencies. Use npm init to create a package.json file and npm install to add packages.

Building a Simple Server

Create an HTTP server with the built-in http module:

const http = require('http');
  const server = http.createServer((req, res) => {
    res.writeHead(200, { 'Content-Type': 'text/plain' });
    res.end('Hello World!');
  });
  server.listen(3000);

Use Cases

• APIs and microservices
• Real-time applications (chat, gaming)
• CLI tools and build systems
• IoT applications

Node.js has revolutionized server-side development by bringing JavaScript to the backend. Its ecosystem of packages and active community make it a powerful choice for modern applications.