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React
Component-based UI. Understand the rendering model, hooks, and performance — not just the API.
Topics
Hooks
useState, useEffect, useCallback, useMemo, useRef, custom hooks.
Component Patterns
HOC, render props, compound components, controlled vs uncontrolled.
State Management
Context, Redux, Zustand — when to use each.
Performance
memo, lazy, Suspense, avoiding unnecessary re-renders.
◆ Mental Model
React re-renders a component whenever state or props change. The virtual DOM diffs the output and applies only the minimal DOM changes. Understand this before optimizing.
💡 Interview Tip
Know when NOT to use useCallback and useMemo — premature optimization with these hooks can actually hurt performance due to the overhead of memoization.