Node.js Introduction — Node.js interactive lesson

What You'll Learn

In this tutorial, you'll learn:

How to install and run Node.js
Core concepts like modules and the event loop
How to build web servers and APIs
Working with databases and files
Deploying Node.js applications

What is Node.js?

Node.js is a free, open-source JavaScript runtime that runs on Windows, Mac, Linux, and more.

It lets you execute JavaScript code outside of a web browser, enabling server-side development with JavaScript.

Built on Chrome's V8 JavaScript engine, Node.js is designed for building scalable network applications efficiently.

Example: Print a Message

console.log('Hello from Node.js!');

Why Node.js?

Node.js excels at handling many simultaneous connections with minimal overhead, making it perfect for:

Real-time applications (chats, gaming, collaboration tools)
APIs and microservices
Data streaming applications
Command-line tools
Server-side web applications

Its non-blocking, event-driven architecture makes it highly efficient for I/O-heavy workloads.

Asynchronous Programming

Node.js uses asynchronous (non-blocking) programming.

This means it can keep working while waiting for tasks like reading files or talking to a database.

With asynchronous code, Node.js can handle many things at once-making it fast and efficient.

Example: Read a File Asynchronously

// Load the filesystem module
const fs = require('fs');
// Read file asynchronously
fs.readFile('myfile.txt', 'utf8', (err, data) => {
 if (err) {
 console.error('Error reading file: ' + err);
 return;
 }
 console.log('File content: ' + data);
});
console.log('Reading file... (this runs first!)');

In this example

We load the built-in fs module
We call readFile to read a file
Node.js continues to the next line while reading the file
When the file is read, our callback function runs

This non-blocking behavior lets Node.js handle many requests efficiently.

What Can Node.js Do?

Web Servers : Create fast, scalable network applications
File Operations : Read, write, and manage files on the server
Database Interaction : Work with databases like MongoDB, MySQL, and more
APIs : Build RESTful services and GraphQL APIs
Real-time : Handle WebSockets for live applications
CLI Tools : Create command-line applications

Example: Simple Web Server

const http = require('http');
http.createServer((req, res) => {
 res.writeHead(200, {'Content-Type': 'text/plain'});
 res.end('Hello World!');
}).listen(8080);

What is a Node.js File?

Node.js files contain code that runs on the server. They usually have the .js extension and can be started with the node command.

Node.js files run tasks when certain events happen (like a web request)
They must be started on the server to have any effect
They use JavaScript syntax

Example: Running a Node.js File

node app.js

Node.js Versions & LTS:

Node.js releases a new major version every six months.

For stability, use an LTS (Long Term Support) version for production projects.