Frontend Developer interview questions & mock practice
A Frontend Developer interview in 2026 runs across 4 rounds — javascript / dom round, framework round, machine coding, css & accessibility. Below are the most-asked Frontend Developer interview questions and a focused prep plan. Rehearse every answer with OnJob's free AI mock interview and get instant, specific feedback before the real one.
The Frontend Developer interview process
JavaScript, React, CSS and browser fundamentals — the front-of-house engineering interview for product and services companies.
JavaScript / DOM round
Core JS, closures, async, event loop and DOM manipulation.
Framework round
React (hooks, state, rendering) or Angular/Vue depending on the stack.
Machine coding
Build a small UI component live — a counter, autocomplete or modal.
CSS & accessibility
Layout, flexbox/grid, responsiveness and accessibility basics.
Most-asked Frontend Developer interview questions
12 of the questions Frontend Developer candidates are asked most often in India. Practise answering each one out loud in your AI mock interview.
- 1. Explain the difference between let, const and var.
- 2. What is a closure in JavaScript? Give a practical use.
- 3. Explain the event loop and how async/await works under the hood.
- 4. What is the difference between == and === in JavaScript?
- 5. Explain the difference between == null and === null, and what hoisting is.
- 6. What are React hooks? Explain useState and useEffect.
- 7. What is the virtual DOM and how does React's reconciliation work?
- 8. Explain the difference between props and state in React.
- 9. What is the difference between flexbox and CSS grid, and when do you use each?
- 10. What is event delegation and why is it useful?
- 11. Explain debouncing vs throttling with an example.
- 12. What is the box model in CSS?
How to prepare for your Frontend Developer interview
Be fluent in JS fundamentals: closures, the event loop, promises, this-binding, and prototypal inheritance.
Build 2–3 small machine-coding components from scratch (autocomplete, infinite scroll, star rating) without a framework.
Know React deeply: hooks rules, dependency arrays, memoisation (useMemo/useCallback) and why re-renders happen.
Be ready to write semantic, accessible HTML and responsive CSS live — interviewers watch your CSS instincts.
Prepare to discuss performance: bundle size, lazy loading, Core Web Vitals, and reducing re-renders.
Practise other roles
- Software Engineer
- Backend Developer
- Full Stack Developer
- Data Analyst
- Data Scientist
- Product Manager
- DevOps Engineer
- Java Developer
- Python Developer
- UI/UX Designer
- Sales / Business Development
- Digital Marketing
- HR / Recruiter
- Accountant
- Customer Support
- Data Engineer
- Machine Learning Engineer
- QA / Test Engineer
- Android Developer
- iOS Developer
- Business Analyst
- Project Manager
- Scrum Master
- SQL Developer
- React Developer
- Node.js Developer
- Cloud Engineer (AWS)
- Cybersecurity Analyst
- Network Engineer
- Database Administrator
- SEO Specialist
- Content Writer
- Graphic Designer
- Sales Executive
- Business Development Manager
- Operations Manager
- Financial Analyst
- Chartered Accountant
- Customer Success Manager
- Technical Support Engineer
- Civil Engineer
Frontend Developer interview — FAQs
What questions are asked in a Frontend Developer interview?
Common Frontend Developer interview questions include: Explain the difference between let, const and var. What is a closure in JavaScript? Give a practical use. Explain the event loop and how async/await works under the hood. What is the difference between == and === in JavaScript? Interviews usually run across 4 rounds — JavaScript / DOM round, Framework round, Machine coding, CSS & accessibility. Practice all of them with instant AI feedback using OnJob's free mock interview.
How many rounds are in a Frontend Developer interview?
A typical Frontend Developer interview has 4 rounds: JavaScript / DOM round (Core JS, closures, async, event loop and DOM manipulation.); Framework round (React (hooks, state, rendering) or Angular/Vue depending on the stack.); Machine coding (Build a small UI component live — a counter, autocomplete or modal.); CSS & accessibility (Layout, flexbox/grid, responsiveness and accessibility basics.).
How do I prepare for a Frontend Developer interview?
To prepare for a Frontend Developer interview: Be fluent in JS fundamentals: closures, the event loop, promises, this-binding, and prototypal inheritance. Build 2–3 small machine-coding components from scratch (autocomplete, infinite scroll, star rating) without a framework. Know React deeply: hooks rules, dependency arrays, memoisation (useMemo/useCallback) and why re-renders happen. Then run a full AI mock interview on OnJob to rehearse out loud and get instant, specific feedback before the real thing.
What skills do I need for a Frontend Developer role?
Core Frontend Developer skills tested in interviews include JavaScript, React, HTML, CSS, TypeScript, Web Performance, Accessibility. OnJob shows you exactly which of these skills stand between you and a 100% match on every live Frontend Developer job.
Is OnJob's Frontend Developer mock interview free?
Yes. OnJob's AI mock interview is free to start (₹0) and gives you instant feedback on your answers. Pro (₹99/month) adds unlimited interview-prep AI alongside recruiter tracking and unlimited applications.
Ace your Frontend Developer interview
Rehearse every Frontend Developer question out loud with OnJob's AI mock interview and get instant, specific feedback. Then apply to AI-matched jobs in one click — free to start.
Everything about Frontend Developer on OnJob
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