它对于了解转换的开始和结束时间很有用。Svelte 调度事件，你可以像任何其他 DOM 事件一样监听：
¥It can be useful to know when transitions are beginning and ending. Svelte dispatches events that you can listen to like any other DOM event:
App
<p
transition:fly={{ y: 200, duration: 2000 }}
onintrostart={() => status = 'intro started'}
onoutrostart={() => status = 'outro started'}
onintroend={() => status = 'intro ended'}
onoutroend={() => status = 'outro ended'}
>
Flies in and out
</p>1
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<script>
import { fly } from 'svelte/transition';let visible = $state(true);
let status = $state('waiting...');</script>
<p>status: {status}</p><label>
<input type="checkbox" bind:checked={visible} />visible
</label>
{#if visible}<p
transition:fly={{ y: 200, duration: 2000 }}>
Flies in and out
</p>
{/if}