Updated code to allow sidenav expand on click

app/assets/javascripts/sidenav.js

@@ -0,0 +1,42 @@
+document.addEventListener('DOMContentLoaded', () => {
+    const sidenavItems = document.querySelectorAll('.usa-sidenav__item > .parent-link');
+
+    sidenavItems.forEach((link) => {
+      const parentItem = link.parentElement;
+      const hasChildren = parentItem.querySelector('.usa-sidenav__sublist');
+      const currentUrl = window.location.pathname;
+
+      if (
+        link.getAttribute('href') === currentUrl ||
+        currentUrl.startsWith(link.getAttribute('href'))
+      ) {
+        parentItem.classList.add('open');
+        link.setAttribute('aria-expanded', 'true');
+      }
+
+      link.addEventListener('click', (event) => {
+        if (hasChildren) {
+          event.preventDefault();
+
+          const isOpen = parentItem.classList.contains('open');
+
+          document.querySelectorAll('.usa-sidenav__item.open').forEach((item) => {
+            if (item !== parentItem) {
+              item.classList.remove('open');
+              item.querySelector('.parent-link').setAttribute('aria-expanded', 'false');
+            }
+          });
+
+          if (!isOpen) {
+            parentItem.classList.add('open');
+            link.setAttribute('aria-expanded', 'true');
+          } else {
+            parentItem.classList.remove('open');
+            link.setAttribute('aria-expanded', 'false');
+          }
+
+          window.location.href = link.getAttribute('href');
+        }
+      });
+    });
+  });