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whippy-edition/app/javascript/mastodon/scroll.ts

49 lines
1.1 KiB
TypeScript

const easingOutQuint = (
x: number,
t: number,
b: number,
c: number,
d: number
) => c * ((t = t / d - 1) * t * t * t * t + 1) + b;
const scroll = (
node: Element,
key: 'scrollTop' | 'scrollLeft',
target: number
) => {
const startTime = Date.now();
const offset = node[key];
const gap = target - offset;
const duration = 1000;
let interrupt = false;
const step = () => {
const elapsed = Date.now() - startTime;
const percentage = elapsed / duration;
if (percentage > 1 || interrupt) {
return;
}
node[key] = easingOutQuint(0, elapsed, offset, gap, duration);
requestAnimationFrame(step);
};
step();
return () => {
interrupt = true;
};
};
const isScrollBehaviorSupported =
'scrollBehavior' in document.documentElement.style;
export const scrollRight = (node: Element, position: number) =>
isScrollBehaviorSupported
? node.scrollTo({ left: position, behavior: 'smooth' })
: scroll(node, 'scrollLeft', position);
export const scrollTop = (node: Element) =>
isScrollBehaviorSupported
? node.scrollTo({ top: 0, behavior: 'smooth' })
: scroll(node, 'scrollTop', 0);