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