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export function getScrollContainer(el: Element | null): Element | null {
if (el == null || el.tagName === 'BODY') return null;
const overflow = window.getComputedStyle(el).getPropertyValue('overflow');
if (overflow.endsWith('auto')) { // xとyを個別に指定している場合、hidden auto みたいな値になる
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 });
}
export function scroll(el: Element, top: number) {
const container = getScrollContainer(el);
if (container == null) {
window.scroll({ top: top, behavior: 'instant' });
} else {
container.scrollTop = top;
}
}
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