Intro:
JavaScript is everywhere — frontend, backend (Node.js), and even full-stack interviews.
In 2025, these 10 classic but tricky questions still dominate coding interviews.
🔹 1. Difference between var, let, and const
Scope, hoisting, and re-declaration rules.
🔹 2. What is a Closure?
Function + lexical environment.
Interview tip: Write a quick code example.
🔹 3. Explain == vs ===
Type coercion vs strict equality.
🔹 4. What are Promises and Async/Await?
Handling asynchronous code.
🔹 5. Event Loop in JavaScript
Call stack, callback queue, microtasks.
🔹 6. Difference between null and undefined
A simple but tricky favorite.
🔹 7. What is Hoisting?
Variables and functions behavior before execution.
🔹 8. Explain Prototypal Inheritance
Key to understanding OOP in JavaScript.
🔹 9. What is the difference between map(), forEach(), filter(), and reduce()?
Practical array method comparisons.
🔹 10. Explain Debouncing and Throttling
Critical for frontend performance optimization.
✅ Final Thoughts
If you can explain these 10 concepts clearly (with examples), you’ll ace JavaScript interview rounds in 2025.
👉 Call to Action:
I’ve created JavaScript interview cheat sheets, example code, and practice problems here:
FullStackPrep.dev – JavaScript Interview Prep Guide
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Top comments (2)
As someone who regularly interviews JS developers, these are topics I would expect an experienced developer to know. Good post.
Thanks @tracygjg