// 1. What are Variables?

// 2. Var - The old way of declaring variables

// var name = "John";

// var age = 30;

// console.log(name);

// console.log(age);

// var score = 100;

// console.log(score);

// score = 150; // Re-assigning the value

// console.log(score);

// function test() {

// if (true) {

// var message = "Hello";

// }

// console.log(message); // This works! Prints "Hello"

// }

// test();

// console.log(greeting); // Undefined due to hoisting

// var greeting = "Hi";

// 3. Let - The new way of declaring variables (can be changed)

// let city = "New York";

// let population = 8000000;

// city = "Los Angeles"; // Re-assigning the value

// if(true){

// let localMessage = "Welcome!";

// console.log(localMessage); // This works! Prints "Welcome!"

// }

// console.log(localMessage); // Error: localMessage is not defined

// console.log(city); // Error: Cannot access 'city' before initialization

// let city = "New York";

// 4. Const - For constants values (cannot be changed)

// const country = "USA";

// const pi = 3.14;

// country = "Canada"; // Error: Assignment to constant variable

// const taxRate;

// const number = [1, 2, 3];

// number.push(4);

// console.log(number); // Prints [1, 2, 3, 4]

// 5. var vs let vs const

// - Avoid var in modern code.

// - Default to const.

// - Use let only when necessary.

// const userName = "Sarah"; // Won't change

// let score = 0; // Will increase during game

// const maxScore = 1000; // Fixed limit

// During game

// score = score + 50; // OK

// score = score + 30; // OK

// userName = "John"; // Would cause error

// maxScore = 2000; // Would cause error

// 6. Variable Naming Conventions

// let firstName = "Alice"; // camelCase

// let _private = "valid";

// let $dollar = "also valid";

// let user123 = "valid";

// const 123user = "invalid"; // Cannot start with a number

// const user-name = "invalid"; // Hyphens are not allowed

// const function = "invalid

// const MAX_ATTEMPTS = 5; // UPPER_SNAKE_CASE for constants