React re-renders can slow down applications. Here's how to optimize with memoization.
Understanding Re-renders
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React.memo Basics
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useCallback for Functions
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useMemo for Values
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Common Patterns
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Component Composition
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Virtualization
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Profiling Performance
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When NOT to Memoize
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Advanced Patterns
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Best Practices
When to Use:
✓ Expensive computations
✓ Components with many children
✓ Callbacks passed to memoized children
✓ Context values
✓ Virtualized lists
When to Skip:
✓ Simple/cheap operations
✓ Props that always change
✓ Components that rarely re-render
✓ Small component trees
Debugging:
✓ Use React DevTools Profiler
✓ Add console.logs to track renders
✓ Use why-did-you-render in development
✓ Measure before optimizing
Patterns:
✓ Move state down
✓ Lift content up
✓ Split contexts
✓ Use refs for callbacks
Conclusion
React.memo, useMemo, and useCallback prevent unnecessary re-renders when used correctly. Profile first to identify actual performance issues, then apply memoization strategically. Over-optimization adds complexity without benefits. Focus on component composition patterns and virtualization for the biggest performance gains.