startTransitionint

startTransition is a React Hook that allows you to mark non-urgent state updates as transitions. This helps in keeping the UI responsive during these updates by prioritizing more urgent tasks like typing or clicking. When a transition is ongoing, React can interrupt it to handle more critical updates, preventing the application from feeling sluggish.

The hook is imported from the 'react' library. Its primary use is to wrap state updates that do not need immediate rendering. For example, filtering a large list of items based on user input might be a good candidate for a transition. If the user types quickly, a non-transitioned update would block the UI, making the typing experience jerky. By using startTransition, the filtering operation can be deferred, allowing the input to be rendered immediately.

startTransition takes a callback function as its argument. This function should contain the state update(s) that you want to mark as a transition. React will then handle the rendering of these updates in a non-blocking manner. It is important to note that startTransition does not guarantee that the update will be deferred; it only signals to React that the update is not urgent. React's scheduler will then decide how to best prioritize it. The hook returns a value, which is the callback function you passed to it.

There is also a related hook called `useDeferredValue`. While `startTransition` is used to mark state updates, `useDeferredValue` is used to defer the value itself. This can be useful when you want to render a stale, deferred version of a value while a more up-to-date version is being computed in a transition. Together, these tools provide developers with fine-grained control over rendering performance in React applications, especially for complex UIs with frequent updates.

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