Svelte自定义JS过渡

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}