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πŸ’» 40 JavaScript Interview Questions Every Frontend Developer Should Prepare in 2025 πŸ”₯

Hadil Ben Abdallah on May 09, 2025

Whether you're gearing up for your next big frontend role or just brushing up on your JS fundamentals, these 40 JavaScript interview questions will...
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nathan_tarbert profile image
Nathan Tarbert β€’

Nice list, but honestly after grinding so many of these questions, I still mess up the basics sometimes - you think doing tons of interview prep actually makes you better at the job or just better at passing interviews?

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hadil profile image
Hadil Ben Abdallah β€’

Totally feel you, you're definitely not alone in that. Messing up the basics even after lots of practice is more common than most people admit, and honestly, it just shows you're still actively learning and reflecting (which is a strength, not a weakness!).

As for prep vs. real job skills: I think intense interview prep sharpens specific muscles, like thinking aloud, recognizing patterns quickly, and handling pressure, which are super useful in interviews. But real job effectiveness often comes from solving messy, open-ended problems, collaborating with others, debugging in complex systems, and balancing trade-offs, things you usually don’t get in a coding interview.

That said, consistent prep does build habits like writing cleaner code, understanding fundamentals deeper, and learning how to explain your thinking, all of which carry over into the job. So while it might not mimic the day-to-day perfectly, it can still make you a more confident and competent developer overall.

Appreciate the honest comment. Keep at it, and don’t underestimate how far you've already come! πŸ’ͺ🏻πŸ”₯

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mahdijazini profile image
Mahdi Jazini β€’

This article was really practical and concise, especially for those who want to prepare for frontend interviews or need a quick review of JavaScript concepts.
Thanks for your clear explanations and helpful examples! πŸ‘
If you know any additional resources for practicing or testing these questions online, I’d love to hear your suggestions.

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hadil profile image
Hadil Ben Abdallah β€’

Thank you so much for your kind words Mahdi! πŸ™πŸ» It truly means a lot to know the article was helpful and clear, that kind of feedback keeps me motivated to keep sharing. I’m really glad it served as a practical and concise review for you!

As for practicing and testing your JavaScript knowledge, here are some excellent resources I highly recommend:

  • JavaScript.info: Comprehensive and beginner-friendly with practical tasks after each chapter.
  • Frontend Mentor: Hands-on challenges to apply JS in real UI/UX scenarios.
  • LeetCode: Great for sharpening problem-solving skills (look for the Frontend and JavaScript tags).
  • CodeWars: A wide range of JavaScript katas to practice and level up your thinking.
  • JavaScript30 by Wes Bos: 30 days of pure JavaScript projects to build confidence.
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mahdijazini profile image
Mahdi Jazini β€’

Thanks πŸ™

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hadil profile image
Hadil Ben Abdallah β€’

You're welcome πŸ™πŸ»πŸ™πŸ»

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miketalbot profile image
Mike Talbot ⭐ β€’

Good list!

I'd go with structuredClone as an essential option for 11.

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hadil profile image
Hadil Ben Abdallah β€’

Thank you so much! πŸ™πŸ»

Great catch, structuredClone() is definitely a modern and safer alternative for deep cloning, especially since it handles complex data types more reliably than JSON.parse(JSON.stringify()). It's also native and avoids the overhead of external libraries for many use cases.

I’ll consider adding it to that section as a recommended option. Thanks for the excellent suggestion! πŸ”₯

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Eric Walter β€’

Great list! These questions are super helpful for both interview prep and self-assessment. If you're a company looking to hire frontend developers, this is also a solid framework for evaluating real-world JS skills especially with concepts like closures, async/await, and the event loop. Thanks for putting this together!

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hadil profile image
Hadil Ben Abdallah β€’

Thank you so much! πŸ™πŸ»
That means a lot, especially coming from someone clearly thinking about both sides of the table, prepping and hiring.

You’re absolutely right: concepts like closures, the event loop, and async/await don’t just show up in interviews, they reflect real-world understanding of how JavaScript actually runs in the browser. If a candidate can reason through those, it says a lot about their ability to debug and build reliable apps.

Really appreciate your thoughtful take and kind words, glad this list could offer value from multiple angles!

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Nathan Tarbert β€’

been grinding through lists just like this for ages lol - makes me wonder though, you think its more about knowing all these inside out or just showing you can think on your feet when stuff gets weird in interviews

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hadil profile image
Hadil Ben Abdallah β€’

I totally feel that, the grind is real! πŸ˜…
Honestly, it's a bit of both. Knowing these concepts inside out gives you a solid foundation, but what really sets candidates apart is being able to stay calm, reason things through, and adapt when the interviewer throws a curveball.

Interviews often test how you think, not just what you know. So even if you don’t recall every detail, showing that you can break down a problem, ask good questions, and think on your feet goes a long way. Glad the list resonated with you, you’re clearly putting in the work, and that mindset pays off!

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yashu_yaswanth_ccfe5b41de profile image
yashu yaswanth β€’

Thanks so muchβ€”I’m really glad the breakdown was helpful! πŸ™πŸ»

Honestly, I’ve seen both approaches: some people dive deep into systematically drilling these questions, while others lean more on instinct and experience. That said, having a solid reference or structured guide (like the one you mentioned wishing for early on) can really make a difference. It helps turn β€œwinging it” into delivering confident, well-informed answers.

Really appreciate you stopping by and sharing your thoughtsβ€”always great to hear from others who’ve been through the process!
Digital Dopamine

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hadil profile image
Hadil Ben Abdallah β€’

Thank you so much! πŸ™πŸ»
Totally agree with you. Whether someone’s a seasoned dev or just starting out, having a clear and practical resource can really take the edge off the interview grind. It’s easy to overlook the fundamentals when we’re deep in frameworks and real-world projects, so revisiting core JS like this can be a game-changer, not just for interviews, but for writing better code overall.

I really appreciate your kind words and insight, comments like yours genuinely keep me motivated to create more content that’s helpful and grounded. πŸ™πŸ»

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nevodavid profile image
Nevo David β€’

so many of these trip me up way more than id like to admit - honestly, you think practicing a ton actually beats out just pure experience on the job?

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hadil profile image
Hadil Ben Abdallah β€’

Absolutely get where you're coming from, JavaScript can be deceptively tricky, and even experienced devs trip up on these sometimes. I really believe it's a mix: practice helps you recognize patterns and build confidence, but real-world experience teaches you how and when to apply them effectively.

In interviews, practice gives you clarity and speed. On the job, you get the kind of deep understanding that only comes from debugging real issues under real deadlines. Ideally, both feed into each other, practice sharpens your skills, and experience grounds them.

And, the fact that you're reflecting on this at all means you're already growing. πŸš€

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hanadi profile image
Ben Abdallah Hanadi β€’

Great list of JavaScript interview questions❀ Thank you so much for sharing πŸ™

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hadil profile image
Hadil Ben Abdallah β€’

You're welcome πŸ™πŸ»πŸ™πŸ» I'm glad you found it helpful

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isalahyt profile image
iSalah-YT β€’

Thanks πŸ™πŸ‘

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hadil profile image
Hadil Ben Abdallah β€’

You're welcome πŸ™πŸ»πŸ™πŸ»

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dotallio profile image
Dotallio β€’

Nice!

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hadil profile image
Hadil Ben Abdallah β€’

Thank you so much! πŸ™πŸ»

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larastewart_engdev profile image
Lara Stewart - DevOps Cloud Engineer β€’

Tip 38 question is something I've not seen in many places. Thank You for putting it all together. ❀️

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hadil profile image
Hadil Ben Abdallah β€’

You're welcome πŸ™πŸ» I'm so glad you found it helpful πŸ’™

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werliton profile image
Werliton Silva β€’

This was very helpful.

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hadil profile image
Hadil Ben Abdallah β€’

Thank you so much πŸ™πŸ» I'm so glad you found it helpful

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nadeem_zia_257af7e986ffc6 profile image
nadeem zia β€’

Interesting information provided

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hadil profile image
Hadil Ben Abdallah β€’

Thank you so much πŸ™πŸ» I'm so glad you found it interesting

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nathan_tarbert profile image
Nathan Tarbert β€’

Perfect breakdown for interview prep, tbh I wish I had this kinda thing when I was starting out. You think most people actually drill these or just wing it and hope for the best?

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hadil profile image
Hadil Ben Abdallah β€’

Thanks so much. I’m really glad you found the breakdown helpful! πŸ™πŸ»

Honestly, I’ve seen both: some folks go deep into drilling these questions, while others rely more on instinct and experience. But having a solid reference or structured guide (like the one you wished for starting out) definitely makes a difference, it helps turn β€œwinging it” into confident, well-informed answers.

Appreciate you dropping by and sharing your thoughts, always great to hear from others who've been through the process! πŸ”₯

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citronbrick profile image
CitronBrick β€’

Here's another:

What is the latest version of JavaScript ?
ECMAScript 2023 aka ES24 (not ES6)

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hadil profile image
Hadil Ben Abdallah β€’

Thank you for adding another solid question to the list! πŸ™πŸ»πŸ™πŸ»

You're absolutely right: "What’s the latest version of JavaScript?" is a practical one that trips up even experienced devs, especially with the ES6 vs ES2023 naming confusion.

I really appreciate you contributing to the conversation, it’s input like yours that makes the list even more valuable for everyone preparing. πŸ”₯
Feel free to share more if you think of any others!

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justcall profile image
JustCall β€’

Good job!

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hadil profile image
Hadil Ben Abdallah β€’

Thank you so much! πŸ™πŸ»πŸ™πŸ»

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jawad_ulhassan_44bdd87f7 profile image
Jawad ul Hassan β€’

πŸ”₯ Super useful listβ€”great prep for frontend interviews in 2025!
Also worth reviewing: event delegation, ES6 modules, and the JS runtime.
Practice beats just readingβ€”time to code! πŸ’»

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hadil profile image
Hadil Ben Abdallah β€’

Thank you so much! πŸ™πŸ» I'm glad you found it helpful

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Benjamin Vermeulen β€’

I recently launched two AI-powered Android apps β€” one is a voice-based emotional assistant, and the other is a GPT chatbot with image and voice input.

Evolve (Voice AI Companion): play.google.com/store/apps/details...

N3XG3N GPT Chatbot: play.google.com/store/apps/details...