function greet(name, callback) {
    console.log("Hello " + name);
    callback();
}

function done() {
    console.log("Completed");
}

• greet("Deepak", done);

Output:

• Hello Deepak

• Completed

🚀 14. Higher Order Functions

Higher Order Functions -> functions that:

• Accept functions as arguments

• Return functions

Example:

function operation(callback) {
    callback();
}

• operation(() => {

console.log("Executed");

});

⚡ 15. Closures

Closures -> one of the most important interview topics.

A closure -> allows a function to remember variables from its outer scope.

Example:

function counter() {
    let count = 0;
    return function() {
        count++;
        console.log(count);
    };
}

const increment = counter();

• increment();

• increment();

Output:

• 1

• 2

🎯 16. Recursive Functions

Recursive -> a function calling itself.

Example:

function countdown(n) {
    if(n === 0) {
        return;
    }
    console.log(n);
    countdown(n - 1);
}

• countdown(5);

Output:

• 5

• 4

• 3

• 2

• 1

🧮 17. Practical Example — Sum of Array

function sumArray(arr) {
    return arr.reduce((sum, num) => sum + num, 0);
}

console.log(sumArray([1, 2, 3]));

Output:

• 6

⭐ Important Interview Topics

Focus heavily on:

• 🔥 Function Declaration

• 🔥 Function Expression

• 🔥 Arrow Functions

• 🔥 Scope

• 🔥 Closures

• 🔥 Callback Functions

• 🔥 Higher Order Functions

• 🔥 Recursion

• 🔥 Hoisting

📝 Mini Practice Questions

Easy

• ✅ Create calculator function

• ✅ Find maximum of two numbers

• ✅ Check even or odd

Medium

• ✅ Reverse string

• ✅ Find factorial

• ✅ Check palindrome

Advanced

• ✅ Implement debounce

• ✅ Implement throttle

• ✅ Create custom map() function

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