{#each things as thing, i}
	<span out:foo="{delay: i * 50}">{thing}</span>
{/each}

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