Node Intro

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:

1. We load the built-in fs module
2. We call readFile to read a file
3. Node.js continues to the next line while reading the file
4. 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.