While building a product landing page, the layout looked misaligned across browsers.

Ensure each component’s dimensions and spacing were consistent.

Described the box model—content, padding, border, margin—and showed how adjusting padding and margin changes spacing without altering content size. Demonstrated using box-sizing:border-box to include padding/border in width calculations.

The layout rendered consistently, reducing cross‑browser bugs and speeding up the QA cycle.

A design required a navigation menu where items needed to sit side‑by‑side but also respect width constraints.

Choose the appropriate display type for each element.

Explained that block elements start on a new line and take full width, inline elements flow within text without width/height control, and inline‑block combines inline flow with block‑level box properties, allowing width/height settings while staying on the same line.

Implemented the menu using inline‑block, achieving the desired layout without extra floats.

A dynamic list of items was being added and removed frequently, each requiring a click handler.

Implement click handling efficiently without attaching listeners to every new element.

Described event delegation: attaching a single listener to a common ancestor, using event.target to identify the actual clicked element, and leveraging bubbling. Highlighted benefits like reduced memory usage and automatic handling of future elements.

Reduced the number of listeners from dozens to one, improving performance and simplifying code maintenance.

Refactoring legacy code to modern standards required updating variable declarations.

Explain scope, hoisting, and mutability differences to the team.

Outlined that var is function‑scoped and hoisted with initialization to undefined, let and const are block‑scoped, let is mutable while const creates a read‑only binding. Mentioned temporal dead zone for let/const and that const objects can still have mutable properties.

Team adopted let/const appropriately, eliminating accidental global leaks and improving code readability.

A component needed to fetch data after mounting and update state, but it kept re‑rendering endlessly.

Implement data fetching with useEffect without causing an infinite loop.

Explained that useEffect runs after render and can depend on a dependency array. Showed that omitting the array or including a state variable that is updated inside the effect creates a loop. Recommended providing an empty array for one‑time fetch or listing only stable dependencies, and using cleanup functions when needed.

Data fetched once on mount, UI rendered correctly, and performance issues were resolved.

A dashboard displayed a table with thousands of rows, causing UI lag during scrolling.

Improve rendering performance while preserving functionality.

Recommended using windowing libraries like react-window or react-virtualized to render only visible rows, memoizing row components with React.memo, and ensuring stable keys. Also suggested avoiding inline functions/objects in props and leveraging useCallback for event handlers.

Scrolling became smooth, render time dropped dramatically, and the app remained responsive on low‑end devices.

A marketing site had a high bounce rate due to slow initial load.

Identify and implement performance improvements.

Discussed critical rendering path optimization: minify and bundle assets, use code‑splitting with dynamic import, defer non‑critical CSS, lazy‑load images with srcset, enable HTTP/2, and leverage browser caching. Also mentioned measuring with Lighthouse and monitoring with Web Vitals.

First Contentful Paint dropped from 4.2 s to 1.8 s, improving user engagement and SEO scores.

A single‑page app needed to be usable by screen‑reader users.

Integrate ARIA attributes to convey UI semantics.

Defined ARIA (Accessible Rich Internet Applications) as a set of attributes that expose UI component roles, states, and properties to assistive technologies. Gave examples: role="button" for div acting as button, aria‑expanded for collapsible sections, aria‑live for dynamic content. Emphasized using native HTML elements first and adding ARIA only when necessary.

Screen‑reader testing showed correct navigation and state announcements, achieving WCAG AA compliance.

During a sprint review, the product manager pointed out that my component’s color contrast didn’t meet accessibility standards.

Address the feedback, improve the component, and prevent future issues.

Acknowledged the concern, consulted the design system for approved contrast ratios, updated the CSS, added automated contrast testing with axe-core in the CI pipeline, and documented the change in the component library’s README.

The component passed the next accessibility audit, and the team adopted the new testing step, reducing similar issues by 70%.

The design team delivered a high‑fidelity animation for the homepage hero that required heavy SVG filters and large video assets.

Deliver a visually appealing experience without exceeding the 2 MB initial load budget.

Collaborated with designers to simplify the animation, replaced the video with a lightweight Lottie JSON animation, used CSS will‑change and transform for smoother GPU rendering, and implemented lazy loading for the hero assets. Conducted performance testing to ensure the load time stayed under the target.

The final hero loaded in 1.6 s, retained the intended visual impact, and received positive stakeholder feedback while staying within performance budgets.