Functions

        
          // 1. FUNCTION DECLARATIONS (Hoisted)
function greet(name) {
  return `Hello, ${name}!`;
}

// Function declarations are hoisted (can be called before definition)
console.log(greet("Alice")); // ✅ Works: "Hello, Alice!"

// 2. FUNCTION EXPRESSIONS (Not hoisted)
const greetExpression = function(name) {
  return `Hello, ${name}!`;
};

// Anonymous function expression
const square = function(x) {
  return x * x;
};

// Named function expression (useful for debugging)
const factorial = function fact(n) {
  return n <= 1 ? 1 : n * fact(n - 1);
};

// 3. ARROW FUNCTIONS (ES6+)
const greetArrow = (name) => `Hello, ${name}!`;
const add = (a, b) => a + b;
const getUser = () => ({ name: "John", age: 30 }); // Return object

// Arrow functions don't have their own 'this'
const person = {
  name: "Alice",
  greet: function() {
    setTimeout(() => {
      console.log(`Hello, I'm ${this.name}`); // ✅ 'this' refers to person
    }, 1000);
  }
};

// 4. DEFAULT PARAMETERS
function createUser(name, role = "user", active = true) {
  return { name, role, active };
}

createUser("John");           // { name: "John", role: "user", active: true }
createUser("Jane", "admin");  // { name: "Jane", role: "admin", active: true }

// 5. REST PARAMETERS (...args)
function sum(...numbers) {
  return numbers.reduce((total, num) => total + num, 0);
}

sum(1, 2, 3);      // 6
sum(10, 20, 30, 40); // 100

function logArguments(first, second, ...others) {
  console.log(first, second, others);
}

logArguments(1, 2, 3, 4, 5); // 1, 2, [3, 4, 5]

// 6. IMMEDIATELY INVOKED FUNCTION EXPRESSIONS (IIFE)
(function() {
  const privateVar = "I'm private";
  console.log(privateVar);
})();

// IIFE with parameters
const result = (function(a, b) {
  return a + b;
})(5, 10);

// 7. HIGHER-ORDER FUNCTIONS
function calculator(operation, a, b) {
  return operation(a, b);
}

const multiply = (x, y) => x * y;
calculator(multiply, 4, 5); // 20

// 8. CLOSURES
function createCounter() {
  let count = 0;
  return function() {
    count++;
    return count;
  };
}

const counter = createCounter();
counter(); // 1
counter(); // 2

// 9. RECURSION
function fibonacci(n) {
  if (n <= 1) return n;
  return fibonacci(n - 1) + fibonacci(n - 2);
}

fibonacci(6); // 8

// 10. FUNCTION PROPERTIES
function greetUser(name) {
  greetUser.callCount = (greetUser.callCount || 0) + 1;
  return `Hello, ${name}! (Called ${greetUser.callCount} times)`;
}

greetUser("Alice"); // "Hello, Alice! (Called 1 times)"
greetUser("Bob");   // "Hello, Bob! (Called 2 times)"