Node.js

Server-side JavaScript Runtime Environment

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Node.js

Node.js is an open-source, cross-platform JavaScript runtime environment that executes JavaScript code outside of a web browser. It allows developers to use JavaScript to write command line tools and for server-side scripting.

1. Installation

To install Node.js, visit the official website (nodejs.org) and download the installer for your operating system. Follow the installation instructions provided.

2. Hello World in Node.js

Create a file named app.js with the following content:

console.log('Hello, World!');

Run the script using the command: node app.js

3. Built-in Modules

Node.js comes with several built-in modules. Here's an example using the fs (File System) module:

const fs = require('fs');

fs.writeFile('example.txt', 'Hello, Node.js!', (err) => {
if (err) throw err;
console.log('File has been saved!');
});

4. Creating a Web Server

Node.js can be used to create a simple web server:

const http = require('http');

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

server.listen(3000, () => {
console.log('Server running on http://localhost:3000/');
});

5. NPM (Node Package Manager)

NPM is the package manager for Node.js. It allows you to install and manage third-party packages. Here's how to initialize a new Node.js project:

npm init

To install a package:

npm install package-name

6. Asynchronous Programming

Node.js is designed to be non-blocking and asynchronous. Here's an example using Promises:

const fs = require('fs').promises;

async function readFile() {
try {
const data = await fs.readFile('example.txt', 'utf8');
console.log(data);
} catch (error) {
console.error('Error reading file:', error);
}
}

readFile();

7. Event-Driven Programming

Node.js uses an event-driven programming model. Here's an example:

const EventEmitter = require('events');

class MyEmitter extends EventEmitter {}

const myEmitter = new MyEmitter();

myEmitter.on('event', () => {
console.log('An event occurred!');
});

myEmitter.emit('event');

These examples demonstrate some of the core concepts and features of Node.js. As you continue to explore Node.js, you'll discover its vast ecosystem and powerful capabilities for building scalable, high-performance applications.