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About the Book

This book is your complete roadmap to crushing React.js 19 interviews and rising above the competition.

Based on 350+ real-world front-end interviews, it delivers the most relevant technical questions asked by top companies—along with clear, practical answers that help you build confidence, deepen your React.js knowledge, and prove your skills where it matters most.

What’s Inside

• Core React Concepts – JSX, Virtual DOM, props, state, and component structure (React.js v19)
• Hooks Deep Dive – useState, useEffect, useReducer, useRef, useMemo, and more (React.js v19)
• Performance Optimization – Avoid re-renders, lazy loading, memoization, and profiling (React.js v19)
• Component Design & Reusability – HOCs, render props, children, and Fragments (React.js v19)
• Forms & Event Handling – Controlled/uncontrolled components, validation, synthetic events (React.js v19)
• Styling Techniques – CSS Modules, Tailwind CSS (v4.0), clsx (v2.1), and scalable styling strategies
• Routing – Nested routes, useParams, useSearchParams, and route protection (React Router v7.4)
• Error Handling – Error boundaries, debugging practices, graceful fallbacks (React.js v19)
• Global State Management – Context API (React 19), Redux Toolkit (v2.6), Zustand (v5.0), and best practices

Who This Book Is For ?

• Beginner Developers – If you're new to React.js, this book will build a strong foundation, helping you understand the core concepts and prepare for entry-level technical interviews.
• Intermediate Developers – If you already have experience with React.js, this book will deepen your knowledge, reinforce best practices, and prepare you for mid-level interviews.

What Makes This Book Different?

• Real Insights from a Technical Lead – Gain first-hand knowledge from a Front-end expert who has conducted 350+ React.js interviews.
• Hands-On Learning – Work through practical coding exercises and real-world scenarios to apply what you learn.
• Common Interview Pitfalls & Best Practices – Learn the mistakes that trip up candidates and how to stand out in interviews.
• Up-to-Date with React 19 & Latest Tools – Covers React.js 19, React Router v7.4, Redux Toolkit v2.6, Tailwind CSS v4.0, Zustand v5.0, and more.

What’s Inside Each Question?

Every question follows a structured format designed to maximize your understanding and retention:

• Detailed Answer – A clear and in-depth explanation of the concept.
• Short Answer – A quick summary for rapid review.
• Code Examples – Practical TypeScript-based examples demonstrating real-world usage.
• Common Pitfalls & Best Practices – Learn what mistakes to avoid and how to write optimal code.
• Fun Facts – Insightful historical or technical trivia related to React.js.
• Resources for Further Learning – Links to official documentation, articles, and other trusted sources to dive deeper.

About the Author

Kristiyan Velkov

@krisvelkov

Kristiyan Velkov is software developer, technical leader, tech book author, tech blogger, mentor, speaker, and educator with over a 10+ years of expertise in Front-end and open-source technologies.

His comprehensive skill set spans:

• JavaScript and TypeScript
• React.js, Angular, and Next.js
• DevOps, Web Accessibility, and Security
• Over 350 Front-End Technical Interviews: Expertise in assessing and mentoring developers, ensuring alignment with industry standards.

As a lifelong learner, Kristiyan has earned more than 100+ certifications from prestigious organizations and institutions, including:

• AWS Cloud Solutions Architect – Amazon Web Services (AWS)
• Advance React.js Developer – Meta
• Developing Cloud Apps with Node.js and React – IBM
• Cybersecurity for Everyone – University of Maryland
• Foundations of Cybersecurity – Google
• Leadership and Influence – University of Michigan

With extensive experience working at some of the world’s top IT organizations, Kristiyan excels as a technical lead, driving innovation, mentoring teams, and fostering a culture of growth and excellence. His passion for technology, leadership, and mentorship has positioned him as a thought leader in the field.

Kristiyan has conducted more than 350 technical interviews, bringing a wealth of insights into what top companies look for in candidates. He has also participated in several conferences, sharing his expertise on mastering tech interviews and advancing as a front-end developer.

Kristiyan’s influence extends beyond his projects. He has built a significant following with:

• 30,000 LinkedIn connections
• 6,500 Medium subscribers
• 100,000+ monthly readers

Through his blogs and articles, Kristiyan shares valuable insights on advanced coding techniques, best practices, productivity hacks, and leadership strategies. His content inspires and empowers a global audience of developers, making complex topics accessible and actionable.

Kristiyan is also the author of:

• "Mastering React.js Interviews – From Zero to Hero", a complete interview preparation guide based on real-world scenarios, designed to help developers confidently navigate React.js interviews at junior and intermediate levels.
• "Mastering TypeScript Core Utility Types", a comprehensive guide that demystifies TypeScript utility types, helping developers unlock their full potential in building scalable and maintainable applications.

Follow Kristiyan Velkov:

• Medium Blog
• LinkedIn
• X (Twitter)