Frontend interviewpreparation
JavaScript, React and TypeScript: articles, in-browser problems and flashcards from real interviews.
Test task
Implement flattenArray function
function flattenArray(arr) {
return arr.reduce((acc, el) =>
Array.isArray(el) ?
acc.concat(flattenArray(el)) :
acc.concat(el)
, [])
}Check results
Knowledge base
Theory and practice write-ups from real interviews.
Online IDE
Write code in the browser and run tests at once.
Company problems
Problems from Yandex, Ozon, Sber, and other interviews.
Progress
See what is already done: problems, articles, cards.
Built by a developer for developers
How one person turned interview experience into a platform for thousands
Dastan Salmurzaev
I sat a lot of frontend interviews myself. I know what it is to assemble prep from tabs while working full-time.
That is why on 26 January 2025 I launched Hack Frontend: everything you need in one place.
Today the platform is used by 6300+ from CIS countries, and I still run it every day.
For the first year and a half the platform was entirely free. Built on enthusiasm, with no investors and no ads.
100% organic growth with no advertising budget
Why did I build this? Because I know what interview prep looks like next to a full-time job. Hack Frontend is the tool I wanted at the start of my career.
What users say
Over 6300 developers have already improved their skills
Senior Frontend Developer
Recently, I conducted an interview with a manager. I stumbled upon the platform and was surprised. Everything is gathered together. Not just a knowledge base, but a structured one with examples. I wish there was such a platform in my time!
Junior Developer
At the interview, 90% of the questions were about things I studied here. The documentation is written in clear language. I hope the knowledge base keeps growing!
Frontend Engineer
Hack Frontend fills a preparation gap: everything is structured, straight to the point, and without fluff. Theory is immediately backed by practice—you can solve problems right in a convenient IDE.
Elzar
I prepared with the platform and 70% of what I studied or solved appeared in interviews! The problems and quizzes are pure fire 🔥
Aleksandr Zheltov
A great place to prepare! Well-chosen theory and practice helped me feel much more confident at interviews. 100% recommended!
Baitemir
Thanks to this platform and the mock interviews I managed to get hired by a great company. Everything is sharp and structured. Wishing you success 🔥
Yerasyl
The platform pleasantly surprised me with how thoughtful and convenient it is. The visually pleasing interface makes studying the materials comfortable and inspiring.
Adilet
I used it as a checklist to see which topics I hadn’t touched during prep. The highly concentrated information helps to refresh the material fast.
Ilgiz
My current level is senior front-end. When I restarted my job search the platform helped me save time on preparation. The questions and answers are up to date 👍
Aktenir
As a beginner developer I can say the site is extremely useful. All the theory is collected in one place, plus practice and interview-focused questions.
Giokutela
A clear focus—you can tell the site is built for practice without any extra noise. Modern minimalist style, great readability, fast loading. Building such a platform is a huge achievement! 👏
Daniyar
A really cool platform with a solid knowledge base and real interview problems. Thank you!
Makka Akhrieva
I like the convenient navigation and how resources are broken down into subcategories. The knowledge base contains an up-to-date set of theory, and the problem base is just awesome!
LK
A good resource for quick interview prep. Easy to navigate and information is always within quick reach.
dashulinushka
Great product! I really like the platform that gathers all the main topics and sections you need to prepare for interviews!
Mari38
Thank you! Everything is done with great quality. Exactly what you need to prepare for interviews and level up your skills. Highly recommended 🔥
Developer
The platform turned out to be interesting and convenient for studying frontend. Advanced topics are explained simply and clearly, and the clean UI helps you focus faster.
NextTech
The platform is really awesome, and if the team keeps developing it like this it will become even cooler :)
Frontend Developer
I’m actively preparing for interviews right now. This platform is exactly what I was missing. You can tell it’s built with love and understanding of the community’s needs 💙
.px
Super high quality! I like everything: the convenient interface, lots of useful up-to-date info, and even a community 👍🏻
Developer
The platform makes it easy to find any topic you need. Convenient navigation and a clear UI. Every topic includes examples, which simplifies understanding and speeds up learning.
Frontend dev
A very valuable product for junior and middle devs. It has relevant problems from top companies (Yandex, Tinkoff, Sber) and all the frontend theory you need.
Developer
I stumbled upon it while looking for prep materials. A great find for refreshing knowledge before an interview!
Developer018
Such a great platform, thank you so much for the work! If there’s a chance to help with PRs or add questions, I’d be happy to participate.
Vladimir Kasperovich
An awesome project, thanks for all the materials!
Askhat Tassybayev
I happened to learn about Hack Frontend by chance and immediately bookmarked it. The resource turned out extremely useful and well structured. Pros: Structured content: topics are split into categories—JavaScript, CSS, HTML, React, Vue, and even Angular! That makes navigation much easier. Explanations: besides the answers you also get thorough explanations and documentation links, which helps you truly understand the topic. Relevance: the site is updated regularly and includes modern frameworks and approaches. All the useful things are gathered in one place so you can always refresh your knowledge. Big thanks to the author—I definitely recommend it!
Iuliia Iurkina
I really like this service. It’s convenient when you have a little free time—no need to start something big, but you also don’t want to waste the time. This resource is perfect! I open it, go through a few questions, and spend the time productively.
Natallia Astapenka
Thank you so much to the creators for this service! Before interviews I run through the questions. Everything is relevant and well explained. If I don’t understand something, I read it on Hack Frontend and everything becomes clear. It’s handy that each topic ends with a summary and key definitions. A real treasure! 🤩💔
Zhenya
While preparing for interviews I used to make my own notes, write down things to memorize, and keep comments on theory or common problems. A couple of months ago I discovered Hack Frontend and was pleasantly surprised that someone had already done all of this for me! I immediately shared the link with my company and in various frontend chats. What I love most is that the theory covers not only the basic questions every LinkedIn user reposts three times, but also deeper topics interviewers truly appreciate—or ones that simply help you understand the technology better. The problem base is just wow! Sometimes I drop in to solve a few tasks to make sure I haven’t lost the skill. Huge thanks for the work! Wishing the platform further growth, new technologies, questions, and problems.
Nursultan
I discovered Hack Frontend recently but instantly loved it. First, it helps you understand what questions appear in interviews and prepare for them. Second, it’s perfect for recalling tech details you may have long forgotten. I highly recommend it to both newcomers and experienced devs—you won’t regret it.
Erbol Nurmanbetov
I haven’t finished going through the platform yet, but I already like it a lot. Everything is thought out to the smallest detail, all the necessary frontend topics are there, and it’s great that everything is collected in one place (no need to hunt across different sources). Thanks for such a platform.
Davit Gasparyan
Hack Frontend is an excellent application for frontend developers. Everything is clear, to the point, with real examples and useful guides. It really helps structure knowledge and strengthen weak spots.
Senior Frontend Developer
Recently, I conducted an interview with a manager. I stumbled upon the platform and was surprised. Everything is gathered together. Not just a knowledge base, but a structured one with examples. I wish there was such a platform in my time!
Junior Developer
At the interview, 90% of the questions were about things I studied here. The documentation is written in clear language. I hope the knowledge base keeps growing!
Frontend Engineer
Hack Frontend fills a preparation gap: everything is structured, straight to the point, and without fluff. Theory is immediately backed by practice—you can solve problems right in a convenient IDE.
Elzar
I prepared with the platform and 70% of what I studied or solved appeared in interviews! The problems and quizzes are pure fire 🔥
Aleksandr Zheltov
A great place to prepare! Well-chosen theory and practice helped me feel much more confident at interviews. 100% recommended!
Baitemir
Thanks to this platform and the mock interviews I managed to get hired by a great company. Everything is sharp and structured. Wishing you success 🔥
Yerasyl
The platform pleasantly surprised me with how thoughtful and convenient it is. The visually pleasing interface makes studying the materials comfortable and inspiring.
Adilet
I used it as a checklist to see which topics I hadn’t touched during prep. The highly concentrated information helps to refresh the material fast.
Ilgiz
My current level is senior front-end. When I restarted my job search the platform helped me save time on preparation. The questions and answers are up to date 👍
Aktenir
As a beginner developer I can say the site is extremely useful. All the theory is collected in one place, plus practice and interview-focused questions.
Giokutela
A clear focus—you can tell the site is built for practice without any extra noise. Modern minimalist style, great readability, fast loading. Building such a platform is a huge achievement! 👏
Daniyar
A really cool platform with a solid knowledge base and real interview problems. Thank you!
Makka Akhrieva
I like the convenient navigation and how resources are broken down into subcategories. The knowledge base contains an up-to-date set of theory, and the problem base is just awesome!
LK
A good resource for quick interview prep. Easy to navigate and information is always within quick reach.
dashulinushka
Great product! I really like the platform that gathers all the main topics and sections you need to prepare for interviews!
Mari38
Thank you! Everything is done with great quality. Exactly what you need to prepare for interviews and level up your skills. Highly recommended 🔥
Developer
The platform turned out to be interesting and convenient for studying frontend. Advanced topics are explained simply and clearly, and the clean UI helps you focus faster.
NextTech
The platform is really awesome, and if the team keeps developing it like this it will become even cooler :)
Frontend Developer
I’m actively preparing for interviews right now. This platform is exactly what I was missing. You can tell it’s built with love and understanding of the community’s needs 💙
.px
Super high quality! I like everything: the convenient interface, lots of useful up-to-date info, and even a community 👍🏻
Developer
The platform makes it easy to find any topic you need. Convenient navigation and a clear UI. Every topic includes examples, which simplifies understanding and speeds up learning.
Frontend dev
A very valuable product for junior and middle devs. It has relevant problems from top companies (Yandex, Tinkoff, Sber) and all the frontend theory you need.
Developer
I stumbled upon it while looking for prep materials. A great find for refreshing knowledge before an interview!
Developer018
Such a great platform, thank you so much for the work! If there’s a chance to help with PRs or add questions, I’d be happy to participate.
Vladimir Kasperovich
An awesome project, thanks for all the materials!
Askhat Tassybayev
I happened to learn about Hack Frontend by chance and immediately bookmarked it. The resource turned out extremely useful and well structured. Pros: Structured content: topics are split into categories—JavaScript, CSS, HTML, React, Vue, and even Angular! That makes navigation much easier. Explanations: besides the answers you also get thorough explanations and documentation links, which helps you truly understand the topic. Relevance: the site is updated regularly and includes modern frameworks and approaches. All the useful things are gathered in one place so you can always refresh your knowledge. Big thanks to the author—I definitely recommend it!
Iuliia Iurkina
I really like this service. It’s convenient when you have a little free time—no need to start something big, but you also don’t want to waste the time. This resource is perfect! I open it, go through a few questions, and spend the time productively.
Natallia Astapenka
Thank you so much to the creators for this service! Before interviews I run through the questions. Everything is relevant and well explained. If I don’t understand something, I read it on Hack Frontend and everything becomes clear. It’s handy that each topic ends with a summary and key definitions. A real treasure! 🤩💔
Zhenya
While preparing for interviews I used to make my own notes, write down things to memorize, and keep comments on theory or common problems. A couple of months ago I discovered Hack Frontend and was pleasantly surprised that someone had already done all of this for me! I immediately shared the link with my company and in various frontend chats. What I love most is that the theory covers not only the basic questions every LinkedIn user reposts three times, but also deeper topics interviewers truly appreciate—or ones that simply help you understand the technology better. The problem base is just wow! Sometimes I drop in to solve a few tasks to make sure I haven’t lost the skill. Huge thanks for the work! Wishing the platform further growth, new technologies, questions, and problems.
Nursultan
I discovered Hack Frontend recently but instantly loved it. First, it helps you understand what questions appear in interviews and prepare for them. Second, it’s perfect for recalling tech details you may have long forgotten. I highly recommend it to both newcomers and experienced devs—you won’t regret it.
Erbol Nurmanbetov
I haven’t finished going through the platform yet, but I already like it a lot. Everything is thought out to the smallest detail, all the necessary frontend topics are there, and it’s great that everything is collected in one place (no need to hunt across different sources). Thanks for such a platform.
Davit Gasparyan
Hack Frontend is an excellent application for frontend developers. Everything is clear, to the point, with real examples and useful guides. It really helps structure knowledge and strengthen weak spots.
Senior Frontend Developer
Recently, I conducted an interview with a manager. I stumbled upon the platform and was surprised. Everything is gathered together. Not just a knowledge base, but a structured one with examples. I wish there was such a platform in my time!
Junior Developer
At the interview, 90% of the questions were about things I studied here. The documentation is written in clear language. I hope the knowledge base keeps growing!
Frontend Engineer
Hack Frontend fills a preparation gap: everything is structured, straight to the point, and without fluff. Theory is immediately backed by practice—you can solve problems right in a convenient IDE.
Elzar
I prepared with the platform and 70% of what I studied or solved appeared in interviews! The problems and quizzes are pure fire 🔥
Aleksandr Zheltov
A great place to prepare! Well-chosen theory and practice helped me feel much more confident at interviews. 100% recommended!
Baitemir
Thanks to this platform and the mock interviews I managed to get hired by a great company. Everything is sharp and structured. Wishing you success 🔥
Yerasyl
The platform pleasantly surprised me with how thoughtful and convenient it is. The visually pleasing interface makes studying the materials comfortable and inspiring.
Adilet
I used it as a checklist to see which topics I hadn’t touched during prep. The highly concentrated information helps to refresh the material fast.
Ilgiz
My current level is senior front-end. When I restarted my job search the platform helped me save time on preparation. The questions and answers are up to date 👍
Aktenir
As a beginner developer I can say the site is extremely useful. All the theory is collected in one place, plus practice and interview-focused questions.
Giokutela
A clear focus—you can tell the site is built for practice without any extra noise. Modern minimalist style, great readability, fast loading. Building such a platform is a huge achievement! 👏
Daniyar
A really cool platform with a solid knowledge base and real interview problems. Thank you!
Makka Akhrieva
I like the convenient navigation and how resources are broken down into subcategories. The knowledge base contains an up-to-date set of theory, and the problem base is just awesome!
LK
A good resource for quick interview prep. Easy to navigate and information is always within quick reach.
dashulinushka
Great product! I really like the platform that gathers all the main topics and sections you need to prepare for interviews!
Mari38
Thank you! Everything is done with great quality. Exactly what you need to prepare for interviews and level up your skills. Highly recommended 🔥
Developer
The platform turned out to be interesting and convenient for studying frontend. Advanced topics are explained simply and clearly, and the clean UI helps you focus faster.
NextTech
The platform is really awesome, and if the team keeps developing it like this it will become even cooler :)
Frontend Developer
I’m actively preparing for interviews right now. This platform is exactly what I was missing. You can tell it’s built with love and understanding of the community’s needs 💙
.px
Super high quality! I like everything: the convenient interface, lots of useful up-to-date info, and even a community 👍🏻
Developer
The platform makes it easy to find any topic you need. Convenient navigation and a clear UI. Every topic includes examples, which simplifies understanding and speeds up learning.
Frontend dev
A very valuable product for junior and middle devs. It has relevant problems from top companies (Yandex, Tinkoff, Sber) and all the frontend theory you need.
Developer
I stumbled upon it while looking for prep materials. A great find for refreshing knowledge before an interview!
Developer018
Such a great platform, thank you so much for the work! If there’s a chance to help with PRs or add questions, I’d be happy to participate.
Vladimir Kasperovich
An awesome project, thanks for all the materials!
Askhat Tassybayev
I happened to learn about Hack Frontend by chance and immediately bookmarked it. The resource turned out extremely useful and well structured. Pros: Structured content: topics are split into categories—JavaScript, CSS, HTML, React, Vue, and even Angular! That makes navigation much easier. Explanations: besides the answers you also get thorough explanations and documentation links, which helps you truly understand the topic. Relevance: the site is updated regularly and includes modern frameworks and approaches. All the useful things are gathered in one place so you can always refresh your knowledge. Big thanks to the author—I definitely recommend it!
Iuliia Iurkina
I really like this service. It’s convenient when you have a little free time—no need to start something big, but you also don’t want to waste the time. This resource is perfect! I open it, go through a few questions, and spend the time productively.
Natallia Astapenka
Thank you so much to the creators for this service! Before interviews I run through the questions. Everything is relevant and well explained. If I don’t understand something, I read it on Hack Frontend and everything becomes clear. It’s handy that each topic ends with a summary and key definitions. A real treasure! 🤩💔
Zhenya
While preparing for interviews I used to make my own notes, write down things to memorize, and keep comments on theory or common problems. A couple of months ago I discovered Hack Frontend and was pleasantly surprised that someone had already done all of this for me! I immediately shared the link with my company and in various frontend chats. What I love most is that the theory covers not only the basic questions every LinkedIn user reposts three times, but also deeper topics interviewers truly appreciate—or ones that simply help you understand the technology better. The problem base is just wow! Sometimes I drop in to solve a few tasks to make sure I haven’t lost the skill. Huge thanks for the work! Wishing the platform further growth, new technologies, questions, and problems.
Nursultan
I discovered Hack Frontend recently but instantly loved it. First, it helps you understand what questions appear in interviews and prepare for them. Second, it’s perfect for recalling tech details you may have long forgotten. I highly recommend it to both newcomers and experienced devs—you won’t regret it.
Erbol Nurmanbetov
I haven’t finished going through the platform yet, but I already like it a lot. Everything is thought out to the smallest detail, all the necessary frontend topics are there, and it’s great that everything is collected in one place (no need to hunt across different sources). Thanks for such a platform.
Davit Gasparyan
Hack Frontend is an excellent application for frontend developers. Everything is clear, to the point, with real examples and useful guides. It really helps structure knowledge and strengthen weak spots.
Senior Frontend Developer
Recently, I conducted an interview with a manager. I stumbled upon the platform and was surprised. Everything is gathered together. Not just a knowledge base, but a structured one with examples. I wish there was such a platform in my time!
Junior Developer
At the interview, 90% of the questions were about things I studied here. The documentation is written in clear language. I hope the knowledge base keeps growing!
Frontend Engineer
Hack Frontend fills a preparation gap: everything is structured, straight to the point, and without fluff. Theory is immediately backed by practice—you can solve problems right in a convenient IDE.
Elzar
I prepared with the platform and 70% of what I studied or solved appeared in interviews! The problems and quizzes are pure fire 🔥
Aleksandr Zheltov
A great place to prepare! Well-chosen theory and practice helped me feel much more confident at interviews. 100% recommended!
Baitemir
Thanks to this platform and the mock interviews I managed to get hired by a great company. Everything is sharp and structured. Wishing you success 🔥
Yerasyl
The platform pleasantly surprised me with how thoughtful and convenient it is. The visually pleasing interface makes studying the materials comfortable and inspiring.
Adilet
I used it as a checklist to see which topics I hadn’t touched during prep. The highly concentrated information helps to refresh the material fast.
Ilgiz
My current level is senior front-end. When I restarted my job search the platform helped me save time on preparation. The questions and answers are up to date 👍
Aktenir
As a beginner developer I can say the site is extremely useful. All the theory is collected in one place, plus practice and interview-focused questions.
Giokutela
A clear focus—you can tell the site is built for practice without any extra noise. Modern minimalist style, great readability, fast loading. Building such a platform is a huge achievement! 👏
Daniyar
A really cool platform with a solid knowledge base and real interview problems. Thank you!
Makka Akhrieva
I like the convenient navigation and how resources are broken down into subcategories. The knowledge base contains an up-to-date set of theory, and the problem base is just awesome!
LK
A good resource for quick interview prep. Easy to navigate and information is always within quick reach.
dashulinushka
Great product! I really like the platform that gathers all the main topics and sections you need to prepare for interviews!
Mari38
Thank you! Everything is done with great quality. Exactly what you need to prepare for interviews and level up your skills. Highly recommended 🔥
Developer
The platform turned out to be interesting and convenient for studying frontend. Advanced topics are explained simply and clearly, and the clean UI helps you focus faster.
NextTech
The platform is really awesome, and if the team keeps developing it like this it will become even cooler :)
Frontend Developer
I’m actively preparing for interviews right now. This platform is exactly what I was missing. You can tell it’s built with love and understanding of the community’s needs 💙
.px
Super high quality! I like everything: the convenient interface, lots of useful up-to-date info, and even a community 👍🏻
Developer
The platform makes it easy to find any topic you need. Convenient navigation and a clear UI. Every topic includes examples, which simplifies understanding and speeds up learning.
Frontend dev
A very valuable product for junior and middle devs. It has relevant problems from top companies (Yandex, Tinkoff, Sber) and all the frontend theory you need.
Developer
I stumbled upon it while looking for prep materials. A great find for refreshing knowledge before an interview!
Developer018
Such a great platform, thank you so much for the work! If there’s a chance to help with PRs or add questions, I’d be happy to participate.
Vladimir Kasperovich
An awesome project, thanks for all the materials!
Askhat Tassybayev
I happened to learn about Hack Frontend by chance and immediately bookmarked it. The resource turned out extremely useful and well structured. Pros: Structured content: topics are split into categories—JavaScript, CSS, HTML, React, Vue, and even Angular! That makes navigation much easier. Explanations: besides the answers you also get thorough explanations and documentation links, which helps you truly understand the topic. Relevance: the site is updated regularly and includes modern frameworks and approaches. All the useful things are gathered in one place so you can always refresh your knowledge. Big thanks to the author—I definitely recommend it!
Iuliia Iurkina
I really like this service. It’s convenient when you have a little free time—no need to start something big, but you also don’t want to waste the time. This resource is perfect! I open it, go through a few questions, and spend the time productively.
Natallia Astapenka
Thank you so much to the creators for this service! Before interviews I run through the questions. Everything is relevant and well explained. If I don’t understand something, I read it on Hack Frontend and everything becomes clear. It’s handy that each topic ends with a summary and key definitions. A real treasure! 🤩💔
Zhenya
While preparing for interviews I used to make my own notes, write down things to memorize, and keep comments on theory or common problems. A couple of months ago I discovered Hack Frontend and was pleasantly surprised that someone had already done all of this for me! I immediately shared the link with my company and in various frontend chats. What I love most is that the theory covers not only the basic questions every LinkedIn user reposts three times, but also deeper topics interviewers truly appreciate—or ones that simply help you understand the technology better. The problem base is just wow! Sometimes I drop in to solve a few tasks to make sure I haven’t lost the skill. Huge thanks for the work! Wishing the platform further growth, new technologies, questions, and problems.
Nursultan
I discovered Hack Frontend recently but instantly loved it. First, it helps you understand what questions appear in interviews and prepare for them. Second, it’s perfect for recalling tech details you may have long forgotten. I highly recommend it to both newcomers and experienced devs—you won’t regret it.
Erbol Nurmanbetov
I haven’t finished going through the platform yet, but I already like it a lot. Everything is thought out to the smallest detail, all the necessary frontend topics are there, and it’s great that everything is collected in one place (no need to hunt across different sources). Thanks for such a platform.
Davit Gasparyan
Hack Frontend is an excellent application for frontend developers. Everything is clear, to the point, with real examples and useful guides. It really helps structure knowledge and strengthen weak spots.
Frequently Asked Questions
Everything you need to know about Hack Frontend