What’s new
New topics, features and fixes in the trainer.
- Coding tasks: 18 classic JavaScript interview tasks (debounce, throttle, deepClone, Promise.all, EventEmitter, an LRU cache and more) at Junior, Middle and Senior levels. You write code right in the browser, tests check it instantly, and you can then compare with a reference solution and walkthrough. The editor, tests and solutions have syntax highlighting.
- Google sign-in now uses Google's official button: the sign-in window opens on behalf of the site, not a technical database domain.
- During a quiz, the question text, code and answer options can't be selected or copied.
- Security: the site now sends a Content-Security-Policy header - scripts and requests are allowed only from the site itself, Supabase and the support widget, and task code runs in an isolated worker with no network access.
- Spaced repetition for mistakes: a question you got wrong comes back after 1, 3 and 7 days once you answer it correctly, and only then counts as learned. Before, it left the list after the first correct answer.
- New “Review mistakes” page: everything due today from all topics and levels at once. The home page shows how many questions are due.
- Mistakes in the “Testing” and “Svelte” topics are now saved to your account.
- New topic “Svelte”: Svelte 5 and runes, snippets and attachments, async Svelte, SvelteKit with load, form actions, hooks, remote functions and the SvelteKit 3 changes - 75+ questions per level.
- New stack test “Svelte Developer”: JavaScript, TypeScript, Svelte and HTML & CSS - 75 questions.
- The quiz result screen now has a “Support the project” button.
- Fixed noun cases in Ukrainian, Polish and Russian page titles, and the “State Management” topic name is now capitalized like the others.
- New topic “Testing”: Jest and Vitest, React Testing Library, mocks and MSW, Playwright and Cypress, the test pyramid, flaky tests and strategy - 75+ questions for each of Junior, Middle and Senior.
- Testing is now part of the React developer and Next.js developer stack tests (8 questions each) and frontend architecture (10 questions).
- Tests by stack: React, Next.js, Angular and Vue developer plus frontend architecture - 75 questions from several topics at once, like an interview for a specific role. At the end you get a score for each topic and a link to practise the weak one. Mistakes go to “Review mistakes” in their original topics.
- Pressing Enter on the last question no longer triggers “Try again” on the results screen.
- Every question’s explanation now has a “Report a problem with this question” button: the topic, level and question number are filled in for you - just describe what’s wrong.
- “Try again” and “Start over” now let you choose the mode: a regular quiz or interview mode. The interview timer pauses while the window is open.
- Quiz, list and question pages now have clearer titles and descriptions in search results - a question’s description shows the correct answer right away.
- The guest mode notice moved above the home page header.
- Every question now has its own page with the correct answer, an explanation and links to the docs, and every level has a list of all its questions. The link is below the quiz.
- A new header on the home page.
- Interview mode: 60 seconds per question, no hints or correct answers along the way - mistakes are reviewed only at the end, like in a real interview.
- “Review mistakes” mode: questions you got wrong in any attempt are collected per level until you answer them correctly. The count is shown on the home page, and the list syncs across devices when you’re signed in.
- Share your quiz result on LinkedIn or Facebook, copy the link, or download a card with the topic, level and score.
- Each level now has 75 questions, and every quiz picks 50 at random, so no two attempts are the same.
- Added this page - “What’s new”.
- The privacy policy now has a section on visit statistics: they are collected without cookies and without identifying you.
- Added a privacy policy: what data is stored and how to delete it.
- When you're not signed in, the site shows that you're in guest mode and progress is saved only in this browser.
- Visitors from Ukraine can support the project via a monobank jar.
- New topics: Angular and Vue.
- The header now stays visible while you scroll.
- New topic: state management - from useState to Redux Toolkit, Zustand and TanStack Query.
- Feedback form: report a bug or suggest an idea.
- “Save quiz progress” setting: after closing the tab, the quiz resumes from the same question.
- The interface and questions are now available in Polish.
- The site is now available in Ukrainian and English.
- Sign in with GitHub or Google to keep your best scores across devices.
- New topics: design patterns and System Design.
- Dark theme.
- Launch: HTML & CSS, JavaScript, React, Next.js and TypeScript at three levels - Junior, Middle and Senior.