1 files changed, 24 insertions, 0 deletions
diff --git a/src/client/scripts/scroll.ts b/src/client/scripts/scroll.ts
index a915f2e9ef..be9ea22261 100644
--- a/src/client/scripts/scroll.ts
+++ b/src/client/scripts/scroll.ts
@@ -26,6 +26,19 @@ export function onScrollTop(el: Element, cb) {
 	container.addEventListener('scroll', onScroll, { passive: true });
 }
 
+export function onScrollBottom(el: Element, cb) {
+	const container = getScrollContainer(el) || window;
+	const onScroll = ev => {
+		if (!document.body.contains(el)) return;
+		const pos = getScrollPosition(el);
+		if (pos + el.clientHeight > el.scrollHeight - 1) {
+			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) {
@@ -34,3 +47,14 @@ export function scroll(el: Element, top: number) {
 		container.scrollTop = top;
 	}
 }
+
+export function isBottom(el: Element, asobi = 0) {
+	const container = getScrollContainer(el);
+	const current = container
+		? el.scrollTop + el.offsetHeight
+		: window.scrollY + window.innerHeight;
+	const max = container
+		? el.scrollHeight
+		: document.body.offsetHeight;
+	return current >= (max - asobi);
+}