useMemo
useMemo is a React Hook that caches a calculated value between renders and recomputes it when specified dependencies change.
React in Depth
useMemo is a React hook that caches the result of a calculation between renders until its dependencies change.
- How it is used
- Uses useMemo to avoid repeated calculations and preserve prop identity during React rendering.
- How deep it goes
- Explains the calculation-and-dependency contract through implementations, but does not detail React’s cache internals.
- Examples
- Demonstrates employee filtering, cached to-do JSX, and a stable array prop for a memoized child.
- What you can do after
- Apply it via React’s useMemo hook to cache derived values or stabilize props, while weighing measured benefit against overhead.
React Quickly, Second Edition
useMemo is a React Hook that memoizes a calculated value and reuses it across renders until its dependencies change.
- How it is used
- Avoids recalculating values on repeated renders when their dependencies have not changed.
- How deep it goes
- Explains dependency-triggered recalculation and illustrates an empty dependency array with a generated ID.
- Examples
- Uses an expensive password hash and a gallery image's generated ID to demonstrate memoized values.
- What you can do after
- Apply useMemo to reuse a generated ID across renders or recalculate a value only when dependencies change.
React Hooks in Action: With Suspense and Concurrent Mode
useMemo is a React Hook that memoizes a calculated value and recomputes it when specified dependencies change.
- How it is used
- Uses memoization to reduce unnecessary expensive calculations during React rendering and protect interactive UI responsiveness.
- How deep it goes
- Explains calculation functions, dependency comparison, cache caveats, and a bookings-grid implementation, while stopping short of React internals.
- Examples
- Demonstrates expensive anagram generation and memoized booking-grid generation based on a selected bookable and week.
- What you can do after
- Apply useMemo to wrap an expensive calculation and regenerate it when named dependencies change.
Read how React Hooks in Action: With Suspense and Concurrent Mode explains useMemo →
Related concepts
- memoizationuses · Memoization is an optimization technique that stores computation results with their inputs so equivalent later evaluations can reuse them without recomputation.
- React hookkind of · A React Hook is a function-based API that enables function components to access state, effects, context, and other React capabilities.
- dependency arrayconfigured by · A dependency array is an array passed to a React effect or memoization Hook that specifies values whose changes trigger recomputation or rerunning.
- componentused by · A software component is a modular part of a larger system that provides related functionality and interacts with other parts through defined boundaries or interfaces.
- useCallbackequivalent to · useCallback is a React Hook that memoizes a function reference and reuses it across renders until its specified dependencies change.
- JSXuses · JSX is a JavaScript syntax extension for expressing user-interface elements with XML-like or HTML-like markup that is transformed into JavaScript.
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