Browser-platform depth, framework reasoning, and the frontend-specific design round that full-stack candidates are least prepared for.
14 published across 9 topics.
Frontend fundamentals57 short answers on one page, for revising rather than studying.Closures, the event loop, prototypes, coercion, and the async semantics in every frontend screen.
`this` is decided by how a function is called, not where it is written: a method call binds the receiver, `new` binds the fresh object, `call`/`apply`/`bind` bind explicitly, and a plain call gives `undefined` in strict mode or the global object in sloppy mode. Extracting a method into a callback drops the receiver.
A closure is a function plus the scope it was created in, held by reference rather than copied. It leaks when something long-lived keeps the function alive, because everything the captured scope can reach stays reachable with it.
Structural typing, generics, narrowing, utility types, and typing component contracts.
Model the component's legal states as a discriminated union so contradictory prop combinations do not typecheck, use a type parameter to tie related props like items and renderItem together, and keep any out of the public surface because one any erases the narrowing everything else depends on.
Types are erased before the code runs, so anything crossing a boundary is unverified. The checker also has deliberate unsound spots - assertions, index access, bivariant method parameters, array covariance - so the answer is a validating parse per boundary plus knowing which flag closes which hole.
Reconciliation, hook rules and dependency correctness, server components, and state management.
memo does a shallow comparison of props, so any prop recreated during the parent's render - an object literal, an inline callback, JSX passed as children - fails it every time. Context updates and state owned inside the component bypass the comparison entirely.
In development, Strict Mode deliberately runs one extra setup-cleanup-setup cycle for every effect so that missing cleanup becomes visible; it does not happen in production builds, and the fix is to write the cleanup the effect was missing rather than to guard the effect or remove Strict Mode.
Change detection, reactivity models, DI and modules, and framework-specific lifecycle questions.
Each must decide what to re-render when data changes, how derived values stay correct, and how a component gets a dependency it did not create. Angular answers with dirty checking now moving to signals plus a hierarchical injector, Vue with proxy-based per-property tracking, React with convention plus memoisation.
The critical rendering path, reflow and repaint, event delegation, and storage and cookie mechanics.
The browser parses HTML into the DOM and CSS into the CSSOM, combines them into a layout tree, then runs style, layout, paint and composite. Reading a geometry property after a write forces the browser to flush layout early, so a loop that interleaves reads and writes pays for a full layout every iteration.
Core Web Vitals, bundle splitting, image strategy, and measuring rather than guessing.
Split the LCP into TTFB, resource load delay, resource load time and render delay, use field attribution rather than a single lab run to see which part dominates, then fix that part specifically - prioritise the hero image, stop lazy-loading it, and remove render-blocking work.
Split the interaction into input delay, processing time and presentation delay, then attribute a real interaction from the field rather than guessing. Most of the budget is usually spent before your handler runs or after it returns, so yielding and cutting rendering cost beats optimising the handler.
The cascade and specificity, flexbox and grid, stacking contexts, and responsive strategy.
Flexbox distributes items along one axis and lets content decide the sizes; grid defines tracks up front and places items into them, aligning in both axes. z-index looks broken because it only orders siblings inside one stacking context, and ordinary properties like transform and opacity create new ones.
Semantics, keyboard interaction, ARIA use and misuse, and WCAG criteria raised in review.
Colour is not a signal on its own, so each error needs text, and that text must be programmatically tied to the field with aria-describedby and marked with aria-invalid. On submit, move focus to a summary or the first invalid field rather than hoping a live region is announced.
Build it from the nearest native element so role, focusability and key handling come free, decide the keyboard model before the visuals, move and restore focus deliberately, and add ARIA only for state the markup cannot express - it changes what assistive technology announces but adds no behaviour.
Component architecture, data-fetching and caching layers, and designing autocomplete or a feed client-side.
Stream a server-rendered shell, virtualise the dense views and draw high-density charts to canvas, keep server cache separate from UI and URL state, coalesce socket messages into one commit per frame, give every widget its own empty, error and stale states, and enforce a byte budget per pull request.