startTransition

startTransition(scope)

• Reference
  • startTransition(scope)
• Usage
  • Marking a state update as a non-blocking Transition

Reference

startTransition(scope)

The startTransition function lets you mark a state update as a Transition.

import { startTransition } from 'react';

function TabContainer() {
  const [tab, setTab] = useState('about');

  function selectTab(nextTab) {
    startTransition(() => {
      setTab(nextTab);
    });
  }
  // ...
}

See more examples below.

Parameters

• scope: A function that updates some state by calling one or more set functions. React immediately calls scope with no arguments and marks all state updates scheduled synchronously during the scope function call as Transitions. They will be non-blocking and will not display unwanted loading indicators.

Returns

startTransition does not return anything.

Caveats

• startTransition does not provide a way to track whether a Transition is pending. To show a pending indicator while the Transition is ongoing, you need useTransition instead.

• You can wrap an update into a Transition only if you have access to the set function of that state. If you want to start a Transition in response to some prop or a custom Hook return value, try useDeferredValue instead.

• The function you pass to startTransition must be synchronous. React immediately executes this function, marking all state updates that happen while it executes as Transitions. If you try to perform more state updates later (for example, in a timeout), they won’t be marked as Transitions.

• A state update marked as a Transition will be interrupted by other state updates. For example, if you update a chart component inside a Transition, but then start typing into an input while the chart is in the middle of a re-render, React will restart the rendering work on the chart component after handling the input state update.

• Transition updates can’t be used to control text inputs.

• If there are multiple ongoing Transitions, React currently batches them together. This is a limitation that will likely be removed in a future release.

Usage

Marking a state update as a non-blocking Transition

You can mark a state update as a Transition by wrapping it in a startTransition call:

import { startTransition } from 'react';

function TabContainer() {
  const [tab, setTab] = useState('about');

  function selectTab(nextTab) {
    startTransition(() => {
      setTab(nextTab);
    });
  }
  // ...
}

Transitions let you keep the user interface updates responsive even on slow devices.

With a Transition, your UI stays responsive in the middle of a re-render. For example, if the user clicks a tab but then change their mind and click another tab, they can do that without waiting for the first re-render to finish.