Svelte 自定义 JS 过渡
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}