Svelte 自定义 JS 过渡

2023-02-22 13:55 更新

虽然通常应该尽可能多地使用CSS进行过渡,但是如果不借助JavaScript,有些效果是无法实现的,例如“逐字打印”效果:

function typewriter(node, { speed = 50 }) {
	const valid = (
		node.childNodes.length === 1 &&
		node.childNodes[0].nodeType === 3
	);

	if (!valid) {
		throw new Error(`This transition only works on elements with a single text node child`);
	}

	const text = node.textContent;
	const duration = text.length * speed;

	return {
		duration,
		tick: t => {
			const i = ~~(text.length * t);
			node.textContent = text.slice(0, i);
		}
	};
}

示例代码

  • App.svelte

<script>
	let visible = false;

	function typewriter(node, { speed = 50 }) {
		const valid = (
			node.childNodes.length === 1 &&
			node.childNodes[0].nodeType === 3
		);

		if (!valid) {
			throw new Error(`This transition only works on elements with a single text node child`);
		}

		const text = node.textContent;
		const duration = text.length * speed;

		return {
			duration,
			tick: t => {
				const i = ~~(text.length * t);
				node.textContent = text.slice(0, i);
			}
		};
	}
</script>

<label>
	<input type="checkbox" bind:checked={visible}>
	visible
</label>

{#if visible}
	<p in:typewriter>
		The quick brown fox jumps over the lazy dog
	</p>
{/if}


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