1 files changed, 41 insertions, 0 deletions
diff --git a/layouts/_partials/scripts/toc-js.html b/layouts/_partials/scripts/toc-js.html
new file mode 100644
index 00000000..110f2357
--- /dev/null
+++ b/layouts/_partials/scripts/toc-js.html
@@ -0,0 +1,41 @@
+{{ if .Params.toc }}
+<script>
+document.addEventListener('DOMContentLoaded', () => {
+  const toc = document.getElementById('toc');
+  if (!toc) return;
+
+  const headings = document.querySelectorAll('h2, h3');
+  const observer = new IntersectionObserver(entries => {
+    entries.forEach(entry => {
+      if (!entry.isIntersecting) return;
+
+      const id = entry.target.id;
+      const tocLink = toc.querySelector(`a[href="#${id}"]`);
+      if (!tocLink) return;
+
+      const listItem = tocLink.parentElement;
+      const isH2 = entry.target.tagName === 'H2';
+
+      // Clear all active states when a new H2 is encountered
+      if (isH2) {
+        toc.querySelectorAll('li.active').forEach(el => el.classList.remove('active'));
+      }
+
+      // Set current item as active
+      listItem.classList.add('active');
+
+      // If this is an H3, find and activate its parent H2
+      if (!isH2) {
+        const parentH2Item = listItem.closest('ul').previousElementSibling?.closest('li');
+        if (parentH2Item) parentH2Item.classList.add('active');
+      }
+    });
+  }, {
+    rootMargin: '0px 0px -50% 0px',
+    threshold: 0.5
+  });
+
+  headings.forEach(heading => observer.observe(heading));
+});
+</script>
+{{ end }}