75 lines
2.2 KiB
TypeScript
75 lines
2.2 KiB
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 isTopVisible(el: Element | null): boolean {
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const scrollTop = getScrollPosition(el);
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const topPosition = el.offsetTop; // TODO: container内でのelの相対位置を取得できればより正確になる
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return scrollTop <= topPosition;
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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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if (isTopVisible(el)) {
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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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export function onScrollBottom(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 + el.clientHeight > el.scrollHeight - 1) {
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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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export function scroll(el: Element, top: number) {
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const container = getScrollContainer(el);
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if (container == null) {
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window.scroll({ top: top, behavior: 'instant' });
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} else {
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container.scrollTop = top;
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}
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}
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export function scrollToTop(el: Element) {
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scroll(el, 0);
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}
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export function scrollToBottom(el: Element) {
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scroll(el, 99999); // TODO: ちゃんと計算する
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}
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export function isBottom(el: Element, asobi = 0) {
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const container = getScrollContainer(el);
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const current = container
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? el.scrollTop + el.offsetHeight
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: window.scrollY + window.innerHeight;
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const max = container
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? el.scrollHeight
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: document.body.offsetHeight;
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return current >= (max - asobi);
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}
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