Frontend Developer Interview
Questions & Answers

Measure first with Lighthouse and Web Vitals (LCP, FID, CLS). Common culprits: unoptimised images, render-blocking scripts, large JavaScript bundles, layout shifts from dynamic content. Fix in order of impact: lazy-load images, code-split routes, defer non-critical JS, use CDN for static assets. Never optimise by instinct — profile first, then fix what the data shows.

Controlled: form input value is driven by React state — you own the data and can validate/transform on every keystroke. Uncontrolled: DOM owns the data, you access it via ref on submit. Controlled is preferred for validation, conditional logic, and integration with form libraries. Use uncontrolled when integrating with non-React code or when you genuinely do not need live value access.

Use Can I Use to check feature support before adopting. PostCSS/Autoprefixer handles vendor prefixes automatically. Test in Safari, Firefox, and Chrome — Safari is the most common divergence point. Avoid bleeding-edge CSS features in production without a polyfill or fallback. Document known divergences so the team does not rediscover them.

Interviewers want specifics: what the problem was (missing alt text, broken keyboard navigation, insufficient colour contrast), what tools you used to find it (axe, WAVE, screen reader testing), and what you changed. Show you understand WCAG 2.1 AA as the baseline standard, not an optional nice-to-have. Bonus if you mention testing with actual screen reader users.

Start with local component state, lift only when needed. Use Context for low-frequency global data (theme, auth). Reach for Zustand or Redux only when you have genuinely complex cross-component state with non-trivial update logic. The common mistake is centralising everything from day one — state complexity should grow with actual need, not anticipated need.

Structure your answer as a 60-second professional narrative: where you have been (your background), what you have done (your strongest achievement), and where you are going (why this role). Lead with your most relevant experience, not your entire career history. End with why you are excited about this specific opportunity.

Choose a genuine weakness that you have actively worked to improve. The structure is: name the weakness → show self-awareness of its impact → describe the concrete step you took to address it → show the improvement. Never say "I work too hard" — interviewers recognise this as evasion and it damages your credibility.

Use the STAR method (Situation, Task, Action, Result) but add a fifth element: what you learned. Choose a real failure, not a disguised success. Show you can take responsibility without making excuses, and demonstrate that the lesson changed your behaviour in a specific, verifiable way.

Be honest but constructive. Acceptable reasons: seeking greater scope, new challenge, skills you can not develop in the current role, or company-level changes (restructuring, direction shift). Never speak negatively about your current employer or manager — it signals you will do the same to the prospective employer in future conversations.

Describe the conflict specifically, show that you sought to understand the other person's perspective, and explain the resolution approach you took. Interviewers are assessing your emotional intelligence and whether you escalate or resolve. Avoid stories where you were right and they were wrong — choose a story where both parties grew.

Describe your specific prioritisation system: impact × urgency matrix, stakeholder alignment, or a specific tool or process you use. Then give an example where you applied it under real pressure. Show that your system is systematic rather than reactive, and that you communicate proactively when priorities change.

Choose an achievement that is specific, measurable, and relevant to the role. Lead with the result ("I reduced our error rate by 40% in 90 days"), then explain the context, challenge, and what you specifically did that drove the result. Show your ownership and impact, not just your team's work.

Be honest about your ambitions while showing that this role is a genuine step in that direction — not a stopgap. Hiring managers want to invest in people who will grow with the organisation. Show that your 5-year goal requires the specific skills and experience this role provides, making your ambition an asset for both sides.

Research before the interview and make the answer specific: cite their product, a recent company development, something about their culture or team, or a professional aspect of this particular role that matches your goals. Generic answers ("I love your values") signal you did not do the research. Specific answers signal genuine interest.

Always have 3–5 questions prepared. Ask about the biggest challenge in this role, what success looks like in the first 90 days, how the team operates, and the interviewer's own experience at the company. Never ask about salary, benefits, or holidays in a first interview. Questions show interest, strategic thinking, and that you care enough to have done research.