When a reactive value changes in React, it triggers a re-render of all components in the React data flow that depend on that value. This means that React will re-run the entire body of these components everytime it re-renders. This includes the component where the state or prop is defined, as well as any child components that use that state or prop.
In such case, the
useMemo() hook provides the benefit of optimizing performance of components by memoizing/caching values (such as calculations, functions, arrays, objects, and even components) between re-renders. This way, the cached values are not re-computed until any of the dependencies change (as specified in the
useMemo() dependency array). This can be particularly useful in the following situations:
- Calculating expensive calculations;
- Passing a value as a prop to a memoized component;
- Passing a value to the dependency array of some hook.
For this reason, you can use the
useMemo() hook to optimize the performance issues caused by re-renders. It works by caching the result of values in a previous render, so they don't need to be computed again unnecessarily. However, memoizing too many values can actually degrade performance, as it adds an overhead to the rendering process.
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