startTransition

startTransition(action)

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

Reference

startTransition(action)

ThestartTransition function lets you mark a state update as a Transition.

import{startTransition}from'react';

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

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

See more examples below.

Parameters

• action: A function that updates some state by calling one or moreset functions. React callsaction immediately with no parameters and marks all state updates scheduled synchronously during theaction function call as Transitions. Any async calls awaited in theaction will be included in the transition, but currently require wrapping anyset functions after theawait in an additionalstartTransition (seeTroubleshooting). State updates marked as Transitions will benon-blocking andwill 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 needuseTransition instead.

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

• The function you pass tostartTransition is called immediately, marking all state updates that happen while it executes as Transitions. If you try to perform state updates in asetTimeout, for example, they won’t be marked as Transitions.

• You must wrap any state updates after any async requests in anotherstartTransition to mark them as Transitions. This is a known limitation that we will fix in the future (seeTroubleshooting).

• 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 may be removed in a future release.

Usage

Marking a state update as a non-blocking Transition

You can mark a state update as aTransition by wrapping it in astartTransition call:

import{startTransition}from'react';

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

functionselectTab(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.