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29 lines
654 B
29 lines
654 B
6 years ago
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---
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title: Custom JS transitions
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---
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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:
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```js
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function typewriter(node, { speed = 50 }) {
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const valid = (
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node.childNodes.length === 1 &&
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node.childNodes[0].nodeType === 3
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);
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if (!valid) {
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throw new Error(`This transition only works on elements with a single text node child`);
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}
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const text = node.textContent;
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const duration = text.length * speed;
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return {
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duration,
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tick: t => {
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const i = ~~(text.length * t);
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node.textContent = text.slice(0, i);
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}
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};
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}
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```
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