Tell me about a small frontend feature you built. What was your approach and what did you learn?

I can't recall any specific feature I built.I built something by copying code, but I’m not sure why it worked.I implemented it with guidance and fixed a couple of issues along the way.I broke it into steps, implemented, tested, and explained trade-offs clearly.I considered UX, edge cases, accessibility, and validated behavior with tests.I owned the feature end-to-end, communicated well, and improved code quality/performance.

What’s the difference between HTML, CSS, and JavaScript in a web page?

They’re basically the same thing.HTML is styles, CSS is logic, JavaScript is structure.HTML is structure, CSS is styles, JavaScript is behavior.HTML is semantic structure, CSS controls layout/presentation, JS handles interactivity/data.Plus: HTML aids accessibility/SEO, CSS supports responsive design, JS integrates APIs/state.Not sure, I usually just use frameworks for everything.

How would you debug a UI issue where a button looks clickable but doesn’t respond?

I would refresh and hope it fixes itself.I would randomly change code until it works.I would check the console for errors and confirm the click handler exists.I would inspect the DOM, check overlaying elements, pointer-events, z-index, and handlers.I would reproduce, isolate, inspect event listeners, and verify state/props flow systematically.I would ask someone else to debug it for me.

Explain `const`, `let`, and `var` in JavaScript.

They are identical.`var` is best because it works everywhere.`let` and `const` are block-scoped; `var` is function-scoped.`const` means you can’t change the value at all.`const` prevents reassignment (object properties can still change); prefer `const` by default.`let` is for variables that change; avoid `var` due to hoisting and scope surprises.

What is a REST API? How do you fetch data from it in a frontend app?

It’s a database you can directly query from the browser.It’s any URL that returns JSON.An API exposes endpoints; in frontend you can use `fetch`/Axios to call them.REST uses HTTP methods; I fetch with proper headers, handle errors/loading states.I also consider caching, aborting requests, retries, and mapping data into UI state safely.I usually just console.log the response and move on.

What is React state, and when would you use state vs props?

State and props are the same thing.Props are internal data; state is passed from parent.Props come from parent; state is internal to a component.Use props for inputs/config; use state for UI data that changes over time.Lift state up when multiple components need it; keep state minimal and derived where possible.I store everything in state to be safe.

How do you make a layout responsive?

I don’t; users can zoom if needed.I set everything to fixed pixel widths.I use flexible units and media queries / responsive utilities (e.g., Tailwind breakpoints).I use flex/grid, responsive images, and test on multiple viewport sizes.I only test on desktop because most users are on desktop.I use a CSS framework and hope it handles it.

What does accessibility (a11y) mean for a frontend developer? Give examples.

It’s mostly about adding alt text to images.Accessibility isn’t important for most apps.It means the UI works for keyboard and screen readers; use semantic HTML and labels.Examples: focus states, ARIA where needed, color contrast, and proper form labels.I add ARIA to everything to be safe.I only follow a11y when QA reports an issue.

How do you prevent common performance issues in frontend apps?

Performance is only a backend problem.I don’t think about performance unless users complain.I optimize images and avoid unnecessary re-renders.I use code-splitting, memoization when appropriate, and keep bundles small.I measure with Lighthouse/DevTools, optimize critical rendering, caching, and expensive components.I add more loaders/spinners to hide slow performance.

How do you handle errors and edge cases when rendering data from an API?

I assume the API always returns perfect data.I show a spinner forever if something goes wrong.I add loading/error states and check for null/undefined fields.I validate/sanitize data, handle empty states, and log/report errors responsibly.I wrap everything in try/catch and ignore the error.I only handle errors in the console.

What is Git, and how do you typically work with branches and pull requests?

Git is a file storage system; I usually just upload files.I commit everything directly to main to keep it simple.I create a branch, commit logical changes, and open a PR for review.I keep commits small, write clear messages, respond to review feedback, and rebase/merge safely.I only use Git when someone tells me exactly what to run.I use branches sometimes, but I’m not sure why.

How do you collaborate with designers and backend developers to ship a feature?

I just implement whatever I think looks right.I wait for perfect specs and block until I get them.I clarify requirements early and align on API contracts and UI states.I communicate assumptions, propose alternatives, and ensure UX/a11y/error states are covered.I only talk to others when something breaks.I ask questions occasionally but mostly work independently.

Mock Interview - Junior Frontend Developer