Frontend Developer Interview Questions

What is Frontend Development?

Frontend development (or client-side development) involves building the visual and interactive parts of a website or web application that users see and interact with directly. It includes:

  • Structure: HTML (HyperText Markup Language) defines the content and layout.

  • Styling: CSS (Cascading Style Sheets) controls the appearance and design.

  • Behavior: JavaScript (JS) adds interactivity, dynamic content, and logic.

Modern frontend development also includes frameworks (React, Angular, Vue), state management, performance optimization, accessibility, and responsive design.

Learning Platforms

  1. MDN Web Docs: developer.mozilla.org
  2. freeCodeCamp: freecodecamp.org
  3. Scrimba: scrimba.com
  4. Frontend Mentor: frontendmentor.io
  5. JavaScript30: javascript30.com

YouTube Channels

  1. Traversy Media: youtube.com/c/TraversyMedia
  2. Web Dev Simplified: youtube.com/c/WebDevSimplified
  3. Fireship: youtube.com/c/Fireship
  4. Kevin Powell (CSS): youtube.com/kepowob

Code Snippets & Inspiration

  1. FreeFrontend: freefrontend.com
  2. CodePen: codepen.io
  3. CSS-Tricks: css-tricks.com

Interview Prep

  1. Frontend Interview Handbook: frontendinterviewhandbook.com
  2. GreatFrontEnd: greatfrontend.com
  3. BFE.dev: bigfrontend.dev

Tools & Utilities

  1. CSS Gradient Generator: cssgradient.io
  2. Can I Use: caniuse.com
  3. Google Fonts: fonts.google.com
  4. Font Awesome: fontawesome.com
  5. Unsplash (Free Images): unsplash.com

HTML Fundamentals

  1. What is HTML and what is its purpose?
  2. Explain the basic structure of an HTML document.
  3. What are HTML tags and attributes?
  4. What is the difference between <div> and <span>?
  5. What are semantic HTML elements? Provide examples.
  6. Explain the difference between <ul>, <ol>, and <dl>.
  7. What is the purpose of the alt attribute in images?
  8. How do you create a hyperlink in HTML?
  9. What is the difference between id and class attributes?
  10. How do you embed audio and video in HTML5?
  11. What are data attributes and how do you use them?
  12. Explain the difference between <script>, <script async>, and <script defer>.
  13. What is the purpose of the meta tag?
  14. How do you create a responsive image in HTML?
  15. What are HTML entities and when would you use them?
  16. Explain the difference between GET and POST methods in forms.
  17. How do you create a table in HTML?
  18. What is the purpose of the iframe element?
  19. How do you implement drag and drop in HTML5?
  20. What are web components and how do they work?

CSS and Styling

  1. What is CSS and how does it work with HTML?
  2. What are the different ways to include CSS in a webpage?
  3. Explain the CSS box model.
  4. What is the difference between margin and padding?
  5. How do you center a div horizontally and vertically?
  6. What are CSS selectors? Explain different types.
  7. What is the difference between display: none and visibility: hidden?
  8. How does CSS specificity work?
  9. What are pseudo-classes and pseudo-elements?
  10. Explain the difference between em and rem units.
  11. What is Flexbox and how does it work?
  12. Explain CSS Grid layout.
  13. What are CSS variables and how do you use them?
  14. How do you create responsive designs with CSS?
  15. What are media queries and how do you use them?
  16. Explain the difference between position: relative, absolute, fixed, and sticky.
  17. How do you implement CSS animations?
  18. What is BEM methodology in CSS?
  19. How do you handle CSS for print media?
  20. What are CSS preprocessors and why use them?
  21. Explain CSS stacking context.
  22. What are CSS blend modes?
  23. How do you implement dark mode in CSS?
  24. What is the difference between will-change and transform properties?
  25. How do you optimize CSS for performance?
  26. What are CSS containment properties?
  27. Explain CSS feature queries (@supports).
  28. What are CSS methodologies (OOCSS, SMACSS, ITCSS)?
  29. How do you implement responsive typography?

JavaScript Core Concepts

  1. What is JavaScript and how does it work in browsers?
  2. Explain data types in JavaScript.
  3. What is the difference between let, const, and var?
  4. Explain hoisting in JavaScript.
  5. What are closures and how do they work?
  6. Explain the this keyword in JavaScript.
  7. What are promises in JavaScript?
  8. How does event delegation work?
  9. Explain the difference between == and ===.
  10. What are arrow functions and how do they differ from regular functions?
  11. What is the event loop in JavaScript?
  12. Explain async/await in JavaScript.
  13. What are higher-order functions?
  14. How does prototypal inheritance work?
  15. What are generators in JavaScript?
  16. Explain the module system in JavaScript (ES6 modules).
  17. What is the difference between null and undefined?
  18. How do you deep clone an object in JavaScript?
  19. What are Web APIs in the context of JavaScript?
  20. Explain the difference between call, apply, and bind.
  21. What is the JavaScript execution context?
  22. Explain memory management in JavaScript.
  23. What are service workers and how do they work?
  24. How does WebSockets differ from HTTP?
  25. What are Web Workers and when would you use them?
  26. Explain the Proxy and Reflect API in JavaScript.
  27. What are decorators in JavaScript?
  28. How does JavaScript handle concurrency?
  29. Explain the Temporal API in JavaScript.
  30. What are tagged template literals?

Complete JavaScript Interview Questions

DOM Manipulation

  1. What is the DOM?
  2. How do you select elements in the DOM?
  3. What is the difference between innerHTML and textContent?
  4. How do you create and add elements to the DOM?
  5. What is event bubbling and capturing?
  6. How do you prevent default behavior in event handlers?
  7. What is the difference between stopPropagation and stopImmediatePropagation?
  8. How do you implement drag and drop with JavaScript?
  9. What is the Shadow DOM?
  10. How do you implement virtual scrolling?

React (or Framework of Choice)

  1. What is React and how does it work?
  2. Explain the difference between class and functional components.
  3. What are props in React?
  4. What is state in React and how do you manage it?
  5. Explain the component lifecycle in React.
  6. What are React hooks and why were they introduced?
  7. Explain the useState and useEffect hooks.
  8. What is JSX and how does it differ from HTML?
  9. How do you handle events in React?
  10. What are keys in React and why are they important?
  11. What is the virtual DOM and how does it work?
  12. Explain React context API.
  13. What are higher-order components in React?
  14. How do you optimize React performance?
  15. What is React Router and how does it work?
  16. Explain error boundaries in React.
  17. What are controlled vs uncontrolled components?
  18. How do you implement forms in React?
  19. What is Redux and when would you use it?
  20. Explain the difference between React.memo, useMemo, and useCallback.
  21. What is React Fiber?
  22. Explain server-side rendering in React.
  23. What are React portals?
  24. How does code splitting work in React?
  25. What is suspense in React?
  26. Explain concurrent mode in React.
  27. How do you implement animations in React?
  28. What are React hooks rules and why do they exist?
  29. How do you test React components?
  30. What are React server components?

Complete React Interview Questions

Performance Optimization

  1. How do you optimize website loading performance?
  2. What are critical rendering path optimizations?
  3. Explain lazy loading and how to implement it.
  4. What are webpack code splitting techniques?
  5. How do you reduce time to first byte (TTFB)?
  6. What are some techniques to reduce JavaScript bundle size?
  7. How do you optimize images for the web?
  8. What are service workers and how do they improve performance?
  9. Explain the importance of caching strategies.
  10. How do you measure and improve web performance?

Testing

  1. What are the different types of frontend testing?
  2. Explain unit testing vs integration testing.
  3. What testing frameworks are you familiar with?
  4. How do you test React components?
  5. What is end-to-end testing and how is it different?
  6. Explain mocking in testing.
  7. What are snapshot tests?
  8. How do you test asynchronous code?
  9. What is test-driven development (TDD)?
  10. How do you measure test coverage?

Accessibility

  1. What is web accessibility and why is it important?
  2. What are ARIA attributes and when would you use them?
  3. How do you make a website keyboard navigable?
  4. What are some common accessibility pitfalls to avoid?
  5. How do you test for accessibility issues?
  6. What is WCAG and what are its different levels?
  7. How do you make images accessible?
  8. What are skip links and why are they important?
  9. How do you ensure proper color contrast?
  10. What are accessible forms best practices?

Security

  1. What are common frontend security vulnerabilities?
  2. How do you prevent XSS attacks?
  3. What is CSRF and how do you prevent it?
  4. How do you securely store sensitive data in the browser?
  5. What is CORS and how does it work?
  6. How do you implement content security policy (CSP)?
  7. What are same-origin policy and cross-origin requests?
  8. How do you secure frontend API calls?
  9. What are JWT tokens and how do they work?
  10. How do you prevent clickjacking attacks?

Tooling & Build

  1. What is package.json and what information does it contain?
  2. Explain npm vs yarn.
  3. What is webpack and how does it work?
  4. What are Babel and polyfills?
  5. How do you set up a frontend build pipeline?
  6. What are source maps and why are they useful?
  7. Explain tree shaking in JavaScript.
  8. What are module bundlers and why use them?
  9. How do you set up linting in a project?
  10. What are pre-commit hooks and how do you use them?

Version Control

  1. What is Git and how does it work?
  2. Explain the difference between Git merge and rebase.
  3. What is a Git conflict and how do you resolve it?
  4. How do you squash commits in Git?
  5. What are Git hooks?
  6. Explain Git branching strategies.
  7. How do you revert a Git commit?
  8. What is the difference between git pull and git fetch?
  9. How do you stash changes in Git?
  10. What is .gitignore file used for?

Design & Architecture

  1. What are design patterns you've used in frontend development?
  2. Explain MVC, MVVM, and other architectural patterns.
  3. How do you structure a large-scale frontend application?
  4. What is component-driven development?
  5. How do you manage state in a complex application?
  6. What are micro frontends and when would you use them?
  7. How do you ensure code reusability in frontend development?
  8. What are atomic design principles?
  9. How do you implement feature flags in frontend?
  10. What is domain-driven design in frontend?

Behavioral & Soft Skills

  1. Tell me about a challenging project you worked on.
  2. How do you handle disagreements with designers or backend developers?
  3. Describe your debugging process when something isn't working.
  4. How do you stay updated with frontend technologies?
  5. Tell me about a time you improved performance in an application.
  6. How do you approach learning a new technology or framework?
  7. Describe your ideal development workflow.
  8. How do you handle tight deadlines or scope changes?
  9. Tell me about a time you mentored someone or helped a teammate.
  10. What are you looking for in your next role?

System Design Questions

  1. How would you design a responsive image gallery?
  2. Design a real-time chat application frontend.
  3. How would you implement an infinite scroll feature?
  4. Design a frontend architecture for a large e-commerce site.
  5. How would you implement a dark/light mode toggle?
  6. Design a dashboard with multiple data visualizations.
  7. How would you implement offline capabilities in a web app?
  8. Design a collaborative text editor frontend.
  9. How would you implement a search-as-you-type feature?
  10. Design a frontend for a video streaming platform.

Complete System Design Interview Questions

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