Hard JavaScript Interview Questions

This section contains advanced JavaScript interview questions. Click on each question to see its detailed answer.

1. What is the difference between map(), filter(), and reduce() methods? ✅
2. What is the purpose of the async and await keywords? ✅
3. Explain the working of the Event Loop. ✅
4. How can you remove duplicates from an array in JavaScript?
5. What is memoization in JavaScript? ✅
6. What is the difference between innerHTML and innerText? ✅
7. Explain how localStorage, sessionStorage, and cookies differ. ✅
8. What is destructuring in JavaScript, and how does it work? ✅
9. How can we handle callback hell situations? ✅
10. Explain Default and Named Exports. ✅
11. What is currying in JavaScript, and how is it used? ✅
12. What is the purpose of the Proxy object in JavaScript?
13. What is a WeakMap, and how is it different from a Map?
14. What are generators in JavaScript, and how do they work?
15. Explain how to debounce and throttle functions in JavaScript. ✅
16. What is the purpose of the Symbol data type in JavaScript? ✅
17. How does garbage collection work in JavaScript?
18. What are Service Workers, and how are they used in JavaScript?
19. Explain the concept of Web Workers in JavaScript.
20. What is the difference between mutable and immutable objects in JavaScript? ✅
21. Explain the difference between Map, Set, WeakMap, and WeakSet in JavaScript. ✅
22. How does CORS (Cross-Origin Resource Sharing) work in JavaScript? ✅