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Tutorials › React Modern Development › React Interview Prep

React Interview Prep

6 min read Quiz at the end
Key React interview topics: virtual DOM, reconciliation, Fiber, controlled vs uncontrolled inputs, why keys matter in lists, stale closures in useEffect, and the fundamental difference between state and props.

React Interview Topics

  • Virtual DOM — in-memory representation, diffed against real DOM
  • Reconciliation — how React decides what to update
  • Fiber — React's incremental rendering engine
  • Controlled vs Uncontrolled — state in React vs DOM
  • Keys — help React identify which items changed
  • useEffect cleanup — prevent memory leaks
  • Strict Mode — double-invokes functions to catch bugs
Topic Quiz · 5 questions

Test your understanding before moving on

1. What is React reconciliation?
💡 Reconciliation is React's algorithm for determining the minimum DOM updates needed.
2. What is a key prop for?
💡 Keys help React identify which list items changed, were added, or removed.
3. Controlled vs Uncontrolled input?
💡 Controlled inputs store value in React state; uncontrolled use DOM refs.
4. What is React Fiber?
💡 React Fiber is the internal reconciliation engine enabling incremental rendering.
5. What does React.StrictMode do?
💡 StrictMode intentionally double-invokes renders and effects in development to surface bugs.