React useMemo Patterns Guide

The useMemo hook memoizes expensive computations to avoid recalculating on every render. Here's when and how to use it effectively.

Best Practices#

When to Use:
✓ Expensive calculations
✓ Complex data transformations
✓ Stable object/array references
✓ Context provider values

Indicators:
✓ Sorting/filtering large arrays
✓ Recursive calculations
✓ Parsing/formatting operations
✓ Building derived data structures

Performance:
✓ Profile before optimizing
✓ Keep dependency arrays minimal
✓ Consider computation cost vs memory
✓ Test with realistic data sizes

Avoid:
✗ Trivial calculations
✗ Primitive values
✗ Constantly changing dependencies
✗ Premature optimization

useMemo memoizes expensive computations to avoid recalculating on every render. Use it for expensive operations like sorting large arrays, complex data transformations, or creating stable object references for memoized children. Avoid using it for cheap calculations where the memoization overhead exceeds the computation cost. Always profile first and optimize based on actual performance needs.

React useMemo Patterns Guide

Basic Usage#

Expensive Calculations#

Filtering and Sorting#

Derived State#

Object/Array Stability#

Complex Data Transformations#

Search Index#

Context Value Memoization#

Lazy Computation#

When NOT to Use useMemo#

Best Practices#

Conclusion#

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