Reconciliation Interview Questions

The key prop lets React match list elements across renders for efficient diffing. Using index as key is a common bug. Understand why and how to fix it.

Understand the heuristics React uses to compare virtual DOM trees efficiently and how keys enable correct list reconciliation.

Understand how React reconciles the virtual DOM with the real DOM, what triggers re-renders, and how the fiber architecture enables concurrent rendering.

Understand React as a UI library, how its declarative model and virtual DOM work, and why it became the dominant choice for frontend development.

Understand what the virtual DOM is, how it enables efficient updates, and what its real performance tradeoffs are.

React re-renders a component when its state changes, its props change, or its parent re-renders. The third trigger cascades through entire subtrees by default. Reconciliation limits DOM mutations. Memoization prevents component function calls. Profile before optimizing.