# Interface TransitionStartFunction

interface TransitionStartFunction ((callback) => void)

- TransitionStartFunction(callback): void

- State updates caused inside the callback are allowed to be deferred.

  If some state update causes a component to suspend, that state update should be wrapped in a transition.

  #### Parameters

  - callback: TransitionFunction

    A synchronous function which causes state updates that can be deferred.

  #### Returns void

  - Defined in common/temp/node_modules/.pnpm/@types+react@18.3.3/node_modules/@types/react/index.d.ts:2088