split javascript file into multiple

scripts/ui/scroll.js

@@ -0,0 +1,48 @@
+// Scroll position restore across reloads (e.g. after switching language).
+
+function saveScroll() {
+    sessionStorage.setItem("scrollY", window.scrollY);
+}
+
+export function setupScrollRestoration() {
+    history.scrollRestoration = "manual";
+    window.addEventListener("beforeunload", saveScroll);
+}
+
+export function restoreScroll() {
+    const scrollY = sessionStorage.getItem("scrollY");
+    if (scrollY !== null) {
+
+        document.documentElement.style.scrollBehavior = "auto";
+
+        window.scrollTo(0, parseInt(scrollY));
+
+        document.documentElement.style.scrollBehavior = "smooth";
+    }
+}
+
+// Highlights the sidebar link of the section currently in view.
+export function setupScrollSpy() {
+    const sections = document.querySelectorAll("[data-nav]");
+    const navLinks = document.querySelectorAll(".nav-link");
+
+    const observer = new IntersectionObserver(entries => {
+        entries.forEach(entry => {
+            if (entry.isIntersecting) {
+
+                navLinks.forEach(link => {
+                    link.classList.toggle(
+                        "active",
+                        link.dataset.target === entry.target.id
+                    );
+                });
+
+            }
+        });
+    }, {
+        threshold: 0,
+        rootMargin: "-10% 0px -80% 0px"
+    });
+
+    sections.forEach(section => observer.observe(section));
+}