Keeping utility for accordion and observer for the future.

src/lib/util/accordion.ts

@@ -0,0 +1,27 @@
+export default function (node: HTMLElement) {
+	const setHeight = (detail: HTMLDetailsElement, open = false) => {
+		detail.open = open;
+		const rect = detail.getBoundingClientRect();
+		detail.dataset.width = `${rect.width}`;
+		detail.style.setProperty(open ? `--expanded` : `--collapsed`, `${rect.height}px`);
+	};
+	const RO = new ResizeObserver((entries) => {
+		return entries.forEach((entry) => {
+			const detail: HTMLDetailsElement = entry.target;
+			const width: number = parseInt(detail.dataset.width, 10);
+			if (width !== parseInt(entry.contentRect.width, 10)) {
+				detail.removeAttribute('style');
+				setHeight(detail);
+				setHeight(detail, true);
+				detail.open = false;
+			}
+		});
+	});
+	RO.observe(node);
+
+	return {
+		destroy() {
+			RO.unobserve(node);
+		}
+	};
+}