JS-Q

Basics (1–10)
1️⃣ What is the difference between var, let, and const?
 2️⃣ What is hoisting in JavaScript?
 3️⃣ Explain lexical scope with an example.
 4️⃣ Difference between function declarations and function expressions?
 5️⃣ What are arrow functions and how are they different?
 6️⃣ What is the value of this in different contexts?
 7️⃣ What are call, apply, and bind?
 8️⃣ Difference between == and ===?
 9️⃣ What is event bubbling and event capturing?
 🔟 What is the DOM and how is it manipulated?

⚙️ Async & Scope (11–20)
1️⃣1️⃣ Synchronous vs. asynchronous code
 1️⃣2️⃣ What is the Event Loop?
 1️⃣3️⃣ Microtasks vs. macrotasks
 1️⃣4️⃣ What is a callback function?
 1️⃣5️⃣ What is callback hell and how to avoid it?
 1️⃣6️⃣ What is a Promise in JavaScript?
 1️⃣7️⃣ How does async/await work?
 1️⃣8️⃣ Shallow copy vs. deep copy
 1️⃣9️⃣ Difference between null, undefined, and NaN
 2️⃣0️⃣ What is a higher-order function?

🔥 Functional & Modern JS (21–30)
2️⃣1️⃣ What is a pure function?
 2️⃣2️⃣ What is immutability and how to achieve it?
 2️⃣3️⃣ What is the typeof operator?
 2️⃣4️⃣ What are template literals?
 2️⃣5️⃣ What is destructuring in JavaScript?
 2️⃣6️⃣ Spread syntax vs. rest parameters
 2️⃣7️⃣ for, for...in, and for...of — difference?
 2️⃣8️⃣ What is a closure?
 2️⃣9️⃣ What is currying in JavaScript?
 3️⃣0️⃣ What are default parameters?

🧠 Common Patterns (31–40)
3️⃣1️⃣ Difference between map(), forEach(), and filter()
 3️⃣2️⃣ Falsy vs. truthy values
 3️⃣3️⃣ What is optional chaining (?.)
 3️⃣4️⃣ What is nullish coalescing (??)
 3️⃣5️⃣ What is a memory leak? How to avoid it?
 3️⃣6️⃣ What are WeakMap and WeakSet?
 3️⃣7️⃣ Stack vs. heap memory
 3️⃣8️⃣ Difference between debounce and throttle
 3️⃣9️⃣ How setTimeout & setInterval really work
 4️⃣0️⃣ Purpose of Promise.all, Promise.any, Promise.race

🚀 Advanced Topics (41–50)
4️⃣1️⃣ Difference between Object.freeze() and Object.seal()
 4️⃣2️⃣ Object.keys(), Object.values(), Object.entries()
 4️⃣3️⃣ How do JS modules work? (import/export)
 4️⃣4️⃣ What is an IIFE?
 4️⃣5️⃣ What is event delegation?
 4️⃣6️⃣ Deep equality vs. strict equality
 4️⃣7️⃣ How does the JS engine work internally?
 4️⃣8️⃣ bind() vs. arrow function for this
 4️⃣9️⃣ How to handle errors (try/catch/finally)
 5️⃣0️⃣ How does garbage collection work in JS?