Frontend concepts that keep coming up in interviews, taken apart.

all · 14ready · 0under construction · 14

• 01under constructionClient-side cacheWhy does one screen fetch the same data five times, and what does staleTime actually change?
• 02under constructionRe-renders and memoizationWhich components re-render on a click, and does `useMemo` still matter with the Compiler?
• 03under constructionEvent loopIn what order do `setTimeout(0)`, `Promise.then` and the next paint run?
• 04under constructionDebounce vs throttleWhy does autocomplete fire 40 times when the user typed 8 letters?
• 05under constructionClosures and stale state in hooksWhy does the counter inside `setInterval` always show 0?
• 06under constructionAsync concurrency pool200 uploads, the server survives 4 at a time: how, without a library?
• 07under constructionCancellation and race conditionsYou typed "re", then "react": why do you see results for "re"?
• 08under constructionLong tasks and INPWhy does the click react after 400 ms although the code "works"?
• 09under constructionVirtualized lists and infinite scrollHow do you render 100,000 rows without killing the tab?
• 10under constructionEvent emitter and leaksWho is still listening when the component is gone?
• 11under constructionOptimistic updatesHow does a like appear instantly and roll back when the server says no?
• 12under constructionFailure isolation: boundaries and backoffChat dies: why does video keep playing, and why don't you DDoS your own API?
• 13under constructionReactivity graph (signals)Why does a spreadsheet recompute 3 cells while React re-renders the component?
• 14under constructionEvent propagation and delegationOne listener for 1,000 rows: how, and why?

Sources for each entry: the code itself, MDN, framework docs, and the newsletters I read.