Building Non-Blocking UIs with useTransition and useActionState
Explore how to maintain responsive user interfaces in Next.js applications by using React 19 hooks useTransition and useActionState. Learn to defer non-urgent UI updates and handle asynchronous data mutations effectively, improving app interactivity and user experience through practical examples like search filtering and form submissions.
So far in this chapter, we’ve managed client-side state and data fetching. However, handling state updates that depend on heavy computation or asynchronous processes can introduce additional complexity. If not managed correctly, these updates can block the main thread, leaving the application unresponsive.
React 19 provides specialized hooks, useTransition and useActionState, to handle these async state transitions natively, removing the need for manual “loading” booleans or complex effect chains.
Deferring UI updates with useTransition
Imagine typing into a search box that filters a long list of items. With every keystroke, the app has to rerender the list. If the list is large, the UI can become sluggish and lag behind the typing. This is a classic example of a high-priority update (the input text changing) conflicting with a low-priority update (the list rerendering).
The useTransition hook lets us tell React that a certain state update is not urgent. This update can be interrupted if something more important (like another keystroke) comes in. It prevents the UI from blocking.
The hook returns two values:
isPending: It is a boolean that istruewhen the transition is active.startTransition: It is a function we use to wrap the non-urgent ...