<script> let visible = 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`); } 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); } }; } </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}