JavaScript (Node.js)

1. Introduction & Use Cases

JavaScript is no longer just for browsers. With Node.js in Termux, you can build powerful server-side applications, automation scripts, and even sophisticated hacking tools directly on your mobile device.

• Backend Development: Creating REST APIs and web servers using Express.js.
• Tooling: Writing CLI tools and automation scripts.
• Networking: Building real-time applications with WebSockets.
• Security: Analyzing web traffic and creating security scanners.

2. Basic Syntax & Variables

JavaScript uses modern ES6+ syntax. To install Node.js in Termux, use pkg install nodejs.

// Modern variable declarations
const platform = "Termux";
let status = "learning";
const isAwesome = true;

console.log(`System: ${platform}`);
console.log(`Current Status: ${status}`);

3. Control Flow & Functions

Functional programming and logical control in JavaScript.

// Arrow function example
const greetUser = (name) => {
    return `Welcome back, ${name}!`;
};

const users = ["Alice", "Bob", "Charlie"];
users.forEach(user => {
    console.log(greetUser(user));
});

4. Core Commands Cheat-sheet

• node script.js - Run a JavaScript file.
• npm init - Initialize a new project.
• npm install [package] - Install a module.
• process.platform - Identify the OS platform.
• fs.readFileSync() - Read files from the system.

5. Popular Libraries & Frameworks

• Express.js: The most popular web framework for Node.js.
• Axios: Promise-based HTTP client for the browser and node.js.
• Puppeteer: Headless Chrome Node.js API for web scraping.
• Socket.io: Real-time bidirectional event-based communication.
• Lodash: A modern JavaScript utility library.

6. Advanced Practical Example: Calculator

A simple command-line calculator that takes arguments from the terminal.

// Simple CLI Calculator
const args = process.argv.slice(2);
const num1 = parseFloat(args[0]);
const operator = args[1];
const num2 = parseFloat(args[2]);

const calculate = (a, op, b) => {
    switch(op) {
        case '+': return a + b;
        case '-': return a - b;
        case '*': return a * b;
        case '/': return a / b;
        default: return "Invalid Operator";
    }
};

if (args.length === 3) {
    console.log(`Result: ${calculate(num1, operator, num2)}`);
} else {
    console.log("Usage: node calculator.js 5 + 10");
}