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Frontend Interviews in the Agent Era

Prepare for the Questions Interviewers Ask in the AI Era

Frontend Interviews in the Agent Era
This book is 100% completeLast updated on 2026-10-29
Sandeep Kumar Patel

The frontend interview questions you will be asked, with the answer to say in 30 seconds, the deeper answer for the follow-up, and what the interviewer is testing. Includes a full part on agents: streaming chat, tool calls, approvals, safety and cost.

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About

About

About the Book

Frontend interviews now cover the web platform, JavaScript and algorithms, and the work of building products on top of AI models. This book prepares you for all three.

It has 1,048 questions in 61 chapters. Each one is laid out the same way: how it is usually asked, what the interviewer is testing, a 30-second answer you can say aloud, a deeper answer for the follow-ups, and the red flags that cost candidates points. Chapters end with a timed mock interview and a summary.

The traditional rounds are covered in depth: HTML and accessibility, CSS, JavaScript functions, objects, values and asynchronous code, TypeScript, the DOM and rendering, networking, security, performance, state and data fetching, polyfills and small libraries, UI machine coding, algorithm patterns, and frontend system design.

A part of its own covers agentic frontends: how models behave from the interface's point of view, streaming and chat state, tools and generated UI, sandboxed surfaces, approvals and agent state, tool design and failure modes, browser agents, safety, evaluation and cost, working with AI coding agents, and agentic system design interviews.

The code is real. Listings come from tested files, outputs are captured from real runs, and the diagrams are drawn in one style. A reading path for junior, mid, senior and agentic roles, and study plans for two, six and twelve weeks, are in the appendices.

Who it is for
  • Frontend engineers preparing for interviews at any level
  • Engineers moving into roles that build AI products
  • Interviewers who want a shared list of questions and red flags

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Author

About the Author

Sandeep Kumar Patel

Sandeep Kumar Patel is a senior web developer with more than 17 years of experience building web applications in object-oriented JavaScript and JSON. In 2012 he founded tutorialsavvy, a programming blog that developers have been reading ever since.

He is GATE-2005 Information Technology (IT) qualified and holds a Master's degree from VIT University, Vellore.

Contents

Table of Contents

Part I: How interviews work now
  • Chapter 1. The modern frontend loop
  • Chapter 2. How interviewers evaluate
Part II: Core web
  • Chapter 3. HTML and accessibility
  • Chapter 4. CSS
  • Chapter 5. Functions, scope and this
  • Chapter 6. Objects, prototypes and patterns
  • Chapter 7. Values, coercion and modern syntax
  • Chapter 8. Async JavaScript
  • Chapter 9. TypeScript
Part III: Browser and platform
  • Chapter 10. The DOM, events and rendering
  • Chapter 11. Web Components
  • Chapter 12. Networking and caching
  • Chapter 13. Security
  • Chapter 14. Performance
Part IV: Frameworks and architecture
  • Chapter 15. Rendering models
  • Chapter 16. State and reactivity
  • Chapter 17. Data fetching and routing
  • Chapter 18. Components, design systems, testing and tooling
Part V: Coding rounds: JavaScript patterns
  • Chapter 19. How to attack any coding question
  • Chapter 20. Polyfills
  • Chapter 21. Memoization and caching
  • Chapter 22. Rate limiting and scheduling
  • Chapter 23. Currying, composition and function helpers
  • Chapter 24. Async utilities and event emitters
  • Chapter 25. Build your own Promise
  • Chapter 26. Data shaping
  • Chapter 27. Recursion and nested data
  • Chapter 28. Build your own mini libraries
  • Chapter 29. UI machine coding
Part VI: Algorithm patterns
  • Chapter 30. Hashing and counting
  • Chapter 31. Two pointers and sliding window
  • Chapter 32. Prefix sums, running state and greedy
  • Chapter 33. Sorted data and binary search
  • Chapter 34. Stacks, heaps and scheduling
  • Chapter 35. Linked lists
  • Chapter 36. Trees
  • Chapter 37. Tries and prefix search
  • Chapter 38. Graphs
  • Chapter 39. Grids and matrices
  • Chapter 40. Intervals
  • Chapter 41. Backtracking
  • Chapter 42. Dynamic programming
  • Chapter 43. Bit manipulation
Part VII: Frontend system design
  • Chapter 44. A system-design method
  • Chapter 45. How system design is evaluated
  • Chapter 46. Designing UI components
  • Chapter 47. Designing applications: feeds, media and communication
  • Chapter 48. Designing applications: collaboration, commerce and tools
  • Chapter 49. Cross-cutting design topics
Part VIII: Agentic frontend
  • Chapter 50. Models for UI developers
  • Chapter 51. Streaming and chat UI
  • Chapter 52. The chat data model and conversation state
  • Chapter 53. Tools and generative UI
  • Chapter 54. Sandboxed surfaces: artifacts, canvases and MCP Apps
  • Chapter 55. Agent UX and state
  • Chapter 56. Tool design, permissions and failure modes
  • Chapter 57. Agents that operate the web: browser agents and agent-friendly pages
  • Chapter 58. Safety, evaluation and economics
  • Chapter 59. Building frontends with AI coding agents
  • Chapter 60. Agentic system design interviews
Part IX: Career
  • Chapter 61. Behavioural, leadership and the offer

Appendix A. Quick-reference sheets

Appendix B. Study plans

Appendix C. Full mock interviews

Appendix D. Companion code index

Appendix E. Warm-up problems (junior tier, compact)

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