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export function getScrollContainer(el: Element | null): Element | null {
if (el == null || el.tagName === 'BODY') return null;
const style = window.getComputedStyle(el);
if (style.getPropertyValue('overflow') === 'auto') {
return el;
} else {
return getScrollContainer(el.parentElement);
}
}
export function getScrollPosition(el: Element | null): number {
const container = getScrollContainer(el);
return container == null ? window.scrollY : container.scrollTop;
}
export function onScrollTop(el: Element, cb) {
const container = getScrollContainer(el) || window;
const onScroll = ev => {
if (!document.body.contains(el)) return;
const pos = getScrollPosition(el);
if (pos === 0) {
cb();
container.removeEventListener('scroll', onscroll);
}
};
container.addEventListener('scroll', onScroll, { passive: true });
}
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