1 files changed, 14 insertions, 0 deletions

diff --git a/src/scripts/lib/toc.ts b/src/scripts/lib/toc.ts
new file mode 100644
index 0000000..958f209
--- /dev/null
+++ b/src/scripts/lib/toc.ts
@@ -0,0 +1,14 @@
+export function mountToc() {
+        const observer = new IntersectionObserver((entries) => {
+                for (const entry of entries) {
+                        const id = entry.target.getAttribute("id");
+                        document
+                                .querySelector(`.o-toc__item[href="#${id}"]`)
+                                ?.classList.toggle("is-selected", entry.intersectionRatio > 0);
+                }
+        });
+
+        document.querySelectorAll("section[id]").forEach((section) => {
+                observer.observe(section);
+        });
+}