diff --git a/layouts/partials/toc.html b/layouts/partials/toc.html
index f7d0acf7..959347ac 100644
--- a/layouts/partials/toc.html
+++ b/layouts/partials/toc.html
@@ -19,47 +19,81 @@
   </div>
 </details>
 
-<script>
 {{ if .Site.Params.smartTOC }}
+<script>
   (function () {
-    var $toc = $('#TableOfContents');
-    if ($toc.length > 0) {
-      var $window = $(window);
+    'use strict'
 
-      function onScroll() {
-        var currentScroll = $window.scrollTop();
-        var h = $('.anchor');
-        var id = "";
-        h.each(function (i, e) {
-          e = $(e);
-          if (e.offset().top - $(window).height()/3 <= currentScroll) {
-            id = decodeURIComponent(e.attr('id'));
-          }
-        });
-        var active = $toc.find('a.active');      
-        if (active.length == 1 && active.eq(0).attr('href') == '#' + id) return true;
+    const SCROLL_OFFSET_RATIO = 0.33
+    const TOC_SELECTOR = '#TableOfContents'
+    const ANCHOR_SELECTOR = '.anchor'
+    const TOC_LINK_SELECTOR = 'a[href^="#"]'
+    const NESTED_LIST_SELECTOR = 'li ul'
+    const ACTIVE_CLASS = 'active'
 
-        active.each(function (i, e) {
-          {{ if .Site.Params.smartTOCHideUnfocusedChildren }} 
-            $(e).removeClass('active').siblings('ul').hide();
-          {{ else }}
-            $(e).removeClass('active');
-          {{ end }}
-        });
-        $toc.find('a[href="#' + id + '"]').addClass('active');
-        $toc.find('a[href="#' + id + '"]').parentsUntil('#TableOfContents').each(function (i, e) {
-          $(e).children('a').parents('ul').show();          
-        });
+    function getActiveAnchorId(anchors, offsetRatio) {
+      const threshold = window.scrollY + window.innerHeight * offsetRatio
+      for (let i = anchors.length - 1; i >= 0; i--) {
+        const top = anchors[i].getBoundingClientRect().top + window.scrollY
+        if (top <= threshold) return anchors[i].id
+      }
+      return anchors[0]?.id || ''
+    }
+
+    function updateTOC({ toc, anchors, links, scrollOffset, collapseInactive }) {
+      const activeId = getActiveAnchorId(anchors, scrollOffset)
+      if (!activeId) return
+
+      links.forEach(link => {
+        const isActive = link.getAttribute('href') === `#${activeId}`
+        link.classList.toggle(ACTIVE_CLASS, isActive)
+
+        if (collapseInactive) {
+          const ul = link.closest('li')?.querySelector('ul')
+          if (ul) ul.style.display = isActive ? '' : 'none'
+        }
+      })
+
+      if (collapseInactive) {
+        const activeLink = toc.querySelector(`a[href="#${CSS.escape(activeId)}"]`)
+        let el = activeLink
+        while (el && el !== toc) {
+          if (el.tagName === 'UL') el.style.display = ''
+          if (el.tagName === 'LI') el.querySelector('ul')?.style.setProperty('display', '')
+          el = el.parentElement
+        }
+      }
+    }
+
+    function initTOC() {
+      const toc = document.querySelector(TOC_SELECTOR)
+      if (!toc) return
+
+      const collapseInactive = {{ if site.Params.smartTOCHideUnfocusedChildren }}true{{ else }}false{{ end }}
+      const anchors = [...document.querySelectorAll(ANCHOR_SELECTOR)]
+      const links = [...toc.querySelectorAll(TOC_LINK_SELECTOR)]
+
+      if (collapseInactive) {
+        toc.querySelectorAll(NESTED_LIST_SELECTOR).forEach(ul => ul.style.display = 'none')
       }
 
-      $window.on('scroll', onScroll);
-      $(document).ready(function () {
-        {{ if .Site.Params.smartTOCHideUnfocusedChildren }} 
-          $toc.find('a').parent('li').find('ul').hide();
-        {{ end }}
-        onScroll();
-      });
+      const config = { 
+        toc, 
+        anchors, 
+        links, 
+        scrollOffset: SCROLL_OFFSET_RATIO, 
+        collapseInactive 
+      }
+
+      window.addEventListener('scroll', () => updateTOC(config), { passive: true })
+      window.addEventListener('hashchange', () => updateTOC(config), { passive: true })
+
+      updateTOC(config)
     }
-  })();
-{{ end }}
+
+    document.readyState === 'loading'
+      ? document.addEventListener('DOMContentLoaded', initTOC)
+      : initTOC()
+  })()
 </script>
+{{ end }}