Performance optimization in React is often misunderstood. Many developers reach for useMemo and useCallback prematurely, thinking they are silver bullets for performance. However, if used incorrectly, they can actually hurt performance.
The Cost of Memoization
Memoization comes with a cost. It requires memory to store the previous result and computation to compare dependencies. If the calculation being memoized is cheap, the overhead of memoization might be higher than the calculation itself.
When to Memoize?
You should generally only memoize when:
- The calculation is expensive (e.g., filtering a large array).
- The value is passed as a prop to a memoized component (React.memo).
- The value is used in the dependency array of another hook.