Introduction to Node.js

What is Node.js?

Node.js is a JavaScript runtime built on Chrome's V8 JavaScript engine. It allows you to run JavaScript on the server-side, outside of a web browser. Before Node.js, JavaScript was primarily used for client-side scripting in browsers.

Node.js was created by Ryan Dahl in 2009 and has since become one of the most popular platforms for building web servers, APIs, real-time applications, and command-line tools.

Installing Node.js

Download and install Node.js from the official website or use a version manager like nvm.

# Install nvm (Node Version Manager)
curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.40.1/install.sh | bash

# Install the latest LTS version
nvm install --lts

# Use a specific version
nvm use 22

# Verify installation
node --version
npm --version

Your First Node.js Program

Create a file called hello.js and add the following code:

// hello.js
console.log('Hello, Node.js!');

// Node.js provides global objects
console.log('Current directory:', __dirname);
console.log('Current file:', __filename);

// Access command line arguments
console.log('Arguments:', process.argv);

// Environment information
console.log('Node version:', process.version);
console.log('Platform:', process.platform);

Run the program from your terminal:

node hello.js

Node.js vs Browser JavaScript

Global Objects in Node.js

Node.js provides several global objects that are available in all modules:

// __dirname - Directory path of current module
console.log(__dirname);

// __filename - File path of current module
console.log(__filename);

// process - Information about the current process
console.log(process.env.NODE_ENV);  // Environment variables
console.log(process.cwd());         // Current working directory
process.exit(0);                    // Exit the process

// global - The global namespace object (like window in browsers)
global.myVariable = 'Hello';

// Buffer - For handling binary data
const buf = Buffer.from('Hello');

// setTimeout, setInterval, setImmediate - Timers
setTimeout(() => console.log('Delayed'), 1000);