A great React developer is an architect of the user experience, deeply understanding state management, performance optimization, and the modern JavaScript ecosystem. They make critical decisions that determine if an application is scalable and maintainable or brittle and slow.
Industry Finding: The cost of a bad technical hire can exceed $250,000 in lost time, salary, and recruitment fees. Vetting for the right skills upfront is paramount.
Phase 1: The Vetting Framework
1.1 Portfolio & GitHub Analysis
A candidate's code is their resume. Before an interview, a thorough review of their public work can reveal more than any conversation.
- Project Structure: Is the code organized logically? Look for a clear separation of components, services, hooks, and utilities. A messy codebase is a major red flag.
- Commit History: Review their commit messages on GitHub. Are they clear and descriptive? Frequent, small commits show a methodical and professional workflow.
- Custom Hooks: Have they created their own custom hooks (`useSomething`)? This demonstrates a deeper understanding of React's composition model and code reusability.
Phase 2: The Technical Interview
Go beyond basic definitions and ask questions that probe their problem-solving process.
2.1 Core Concepts: React Hooks & Lifecycle
- Explain the purpose of the dependency array in `useEffect`. What happens if you omit it? What happens if it's empty?
- You have a component that re-renders frequently, causing a child component to re-render as well, even though its props haven't changed. How would you prevent this? (Tests knowledge of `React.memo`).
2.2 Application State & Data Flow
- Describe a situation where you had to manage complex, shared state. What solution (Context, Zustand, Redux) did you choose and why?
- What is "prop drilling" and how can you avoid it?
Phase 3: The Coding Challenge
A good take-home or live coding challenge should mirror a real-world task, not an abstract algorithm.
Challenge Prompt: "Using a public API of your choice, build a simple React application that allows a user to search for something and display a list of results. The application should handle loading and error states. Focus on clean code, component structure, and state management."
This single task allows you to assess their ability to handle API calls, manage state, structure components, and create a good user experience—all core skills for a React developer.