While you should generally use CSS for transitions as much as possible, there are some effects that can’t be achieved without JavaScript, such as a typewriter effect:
App
function typewriter(node, { speed = 1 }) {
const valid = node.childNodes.length === 1 && node.childNodes[0].nodeType === Node.TEXT_NODE;
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 * 0.01);
return {
duration,
tick: (t) => {
const i = Math.trunc(text.length * t);
node.textContent = text.slice(0, i);
}
};
}previous next
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
<script>
let visible = $state(false);
function typewriter(node, { speed = 1 }) {const valid = node.childNodes.length === 1 && node.childNodes[0].nodeType === Node.TEXT_NODE;
if (!valid) {throw new Error(`This transition only works on elements with a single text node child`);
}
return {};}
</script>
<label>
<input type="checkbox" bind:checked={visible} />visible
</label>
{#if visible}<p transition:typewriter>
The quick brown fox jumps over the lazy dog
</p>
{/if}