svelte/test/runtime/samples/transition-js-dynamic-if-block-bidi/main.html

{#if visible}
	<div transition:foo>hello {name}!</div>
{/if}

<script>
	export default {
		transitions: {
			foo: function ( node, params ) {
				global.count += 1;
				return {
					duration: 100,
					tick: t => {
						node.foo = t;
					}
				};
			}
		}
	};
</script>