"Node.js is an open-source, cross-platform JavaScript runtime environment that allows developers to build server-side and networking applications using JavaScript. It's built on the V8 JavaScript engine, which is the same engine used by the Google Chrome browser."

Introduction to Node.js, its features, and use cases.

Features:

1. Asynchronous and Event-Driven: Non-blocking I/O model enables high concurrency.

2. JavaScript Everywhere: Enables full-stack JavaScript development.

3. NPM (Node Package Manager): Largest ecosystem of open-source libraries and tools.

4. Cross-Platform Compatibility: Runs on Windows, macOS, and Linux.

5. Scalability and Performance: Well-suited for real-time and high-traffic applications.

6. Rich Ecosystem: Abundance of frameworks, libraries, and tools.

Use Cases:

1. Web Servers and APIs: Fast and lightweight server-side applications.

2. Real-Time Applications: Chat applications, gaming platforms, and collaboration tools.

3. Microservices Architecture: Scalable, modular, and deployable microservices.

4. Command-Line Tools: Automation of build processes, testing, and deployment.

5. IoT (Internet of Things): Lightweight footprint for IoT applications.

6. Desktop Applications: Cross-platform desktop applications using web technologies.

01 Installation of Node.js and NPM.

• Download Node JS 🔗

• Git Bash - download and make it as default terminal in vs code

  

node - v

npm - v

03 Node.js Core Modules

• fs module for file system operations.

• http module for creating HTTP servers and clients.

• path module for handling file paths.

• events module for event-driven programming.

path module

const path = require("path");

let p1 = path.extname("./index.js");
p1 = path.basename("./index.js");
p1 = path.dirname("./index.js");
console.log(p1);

// Require the 'path' module, which provides utilities for working with file and directory paths
const path = require("path")
// Log the 'path' module object to the console
console.log(path);

// Set a variable 'x' to a file name
x = "indexes.html";
// Log the file extension of 'x' using the 'extname' method of the 'path' module
console.log("File extension:", path.extname(x)); // Output: .html

// Demonstrate path joining using the 'join' method of the 'path' module
// This will generate a file path by joining the provided arguments
console.log("a\b\c\d.js");
let y = path.join("a", "b", "c", "d.js")
console.log("Joined path:", y); // Output: a\b\c\d.js

// Log the directory path of the current module
console.log("Directory path:", __dirname); // Output: <current directory path>

// Log the file path of the current module
console.log("File path:", __filename); // Output: <current file path>

os module

const os = require('os');
console.log(os);
console.log(os.hostname());
console.log(os.platform());
console.log(os.freemem());
console.log(os.homedir());
console.log(os.networkInterfaces());
console.log(os.totalmem());
console.log(os.uptime());
console.log(os.userInfo());
console.log(os.version());

fs module

File Operation Methods :

writeFile method :

const fs = require('fs')

// fs.writeFile("./notes.txt", "enter text here...", () => {
fs.writeFile("./notes.txt", "enter text here...", (err) => {
    if (err) {
        // throw err;
        throw new Error("err");
    }
    console.log("File Created - using Async method")
});

fs.writeFileSync("./notes2.txt", "kuch bhi..")
console.log("File Created - Sync Method")

console.log("LEARNING FILE SYSTEM")

readFile Method :

// Build In Modules -----------------
const fs = require("fs") // fs means file system

// asynchronous funtion
fs.readFile("./notes.txt", "utf-8", (err, data) => {
    if (err) {
        throw err;
    }
    console.log(data)
})

// synchronous function
let data = fs.readFileSync("./notes.txt", "utf-8");
console.log(data)

// 🎯 shortcut of import- (don't need to write fs again & again) 🔽

const { readFileSync } = require("fs");
const data = readFileSync("./sample.txt", "utf-8");
console.log(data);

appendFile Method :

const fs = require("fs")

// asynchronous funtion
fs.appendFile("./notes.txt", " daaaataaa...", (err) => {
    if (err)
        throw err;

    console.log("Data appended - (Async)")
})

/* Synchronous version of append */
fs.appendFileSync("./notes.txt", "helloo");
console.log("appended")

unlink method - means delete

• NOTE: ⭐ Always keep fs sync method in try catch block

const fs = require('fs');

// Asynchronous Function
fs.unlink("./abc.txt", (err) => {
    if (err)
        throw err;
    console.log("File Deleted.")
})

// Synchronuos Function
fs.unlinkSync("./notes.txt");
console.log("File Deleted - using Sync method")

Directory Methods:

mkdir method :

const fs = require('fs')
const path = require('path')

// fs.mkdir('./a/assets', (err) => {  // 🚨💀
// Create 'assets' directory asynchronously
fs.mkdir('./assets', (err) => {
    if (err) throw err;
    console.log("Directory Created !")
})

// Create 'images' directory inside 'assets' synchronously
fs.mkdirSync('./assets/images');
console.log("Directory Created (Sync Method)");

// Write content to a file named 'style.css' inside the 'assets/images' directory
fs.writeFileSync(
    path.join(__dirname, "assets", "images", "style.css"), "Styling File"
);

readdir method :

const fs = require('fs'); // Import the fs module

// Synchronously read the contents of the "./assets" directory
const dirs = fs.readdirSync("./assets");
console.log(dirs); // Log the directory contents to the console

// Asynchronously read the contents of the "./assets" directory
fs.readdir("./assets", (err, files) => {
    if (err) throw err; // Handle any errors that occur during the operation
    console.log(files); // Log the directory contents to the console
});

rename method :

const fs = require('fs'); // Import the fs module

// Rename the directory "./assets" to "./newAssest" synchronously
fs.renameSync("./assets", "./newAssest");

// Rename the file "./x.txt" to "./newAssest/x.txt" synchronously
fs.renameSync("./x.txt", "./newAssest/x.txt");

rmdir method :

⭐ NOTE: before using fs.rmdir(), ensure ✔️ the directory is 🗑️ empty by 🧹 removing 📝 all files and 📂 subdirectories within it.

let fs = require('fs')

fs.rmdirSync("./assets/images")

Project: Generating HTML, CSS, and JS Boilerplate Files 📜

// Importing required modules
const fs = require('fs');
const path = require('path');
const os = require('os');

// Getting the user's home directory and desktop path
let home = os.homedir();
const desktopPath = path.join(os.homedir(), 'Desktop');

// Getting the current date for folder naming
const date = new Date();
const _suffix = `${date.getFullYear()}-${date.getMonth()}-${date.getDay()}`;
const folderPath = path.join(desktopPath, `BoilerPlate_${_suffix}`);

// Checking if the folder already exists, if not, create it
if (!fs.existsSync(folderPath)) {
    try {
        fs.mkdir(path.join(folderPath), (err) => {
            if (err) throw err;
            console.log(`"Website" - Folder Created`);
        });
    } catch (err) {
        console.log(err);
    }
}

// Writing HTML, CSS, and JS files to the folder
// Writing HTML file
fs.writeFile(path.join(folderPath, 'index.html'), htmlBoiler, (err) => {
    if (err) throw err;
    // console.log("Content Added to HTML File");
});

// Writing CSS file
fs.writeFile(path.join(folderPath, 'style.css'), cssBoiler, (err) => {
    if (err) throw err;
    // console.log("Content Added to CSS File");
});

// Writing JS file
fs.writeFile(path.join(folderPath, 'script.js'), jsBoiler, (err) => {
    if (err) throw err;
    // console.log("Content Added to JS File");
});

// Logging confirmation message with folder path
console.log("Your Boiler Plate is ready!");
console.log(`You can access the folder from ${folderPath}`);

const htmlBoiler = `<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <link rel="stylesheet" href="style.css">
</head>
<body>

    <script src="script.js"></script>
</body>
</html>`;

const cssBoiler = `*{
margin: 0;
padding: 0;
box-sizing: border-box;
}
html,body{
height: 100%;
width: 100%;
background-color: green;
}`;

const jsBoiler = `document.body.innerHTML = "Hello World for js";
console.log("Demo JS file")`;

import & export - creating and using a module

https://krayush1109.hashnode.dev/076-modules-in-javascript

// CREATING A MODULE
let a = 6450;
console.log(a);
console.log(a / 4);

console.log("Welcome to Node JS");

let b = {
    average: (m, n) => {
        console.log((m + n) / 2);
    },
    percent: (m, n) => {
        console.log((m / n) * 100);
    },
}

module.exports = a;
module.exports = b;

// USING A MODULE
const a = require("./index")

console.log("This is APP.JS FILE", a);

const b = require("./index")

b.average(25, 45);
b.percent(50,200)

Simple HTTP Server Setup

// Import the HTTP module
const http = require('http') 

// Create a server instance
const server = http.createServer() 

// Start the server listening on port 5000
server.listen(5000, () => { 
    console.log("Server is Listening...")
})