Rename mobile.* files to mobilemenu.*.

assets/js/mobilemenu.js

@@ -0,0 +1,56 @@
+/**
+ * @file
+ * A JavaScript file for the mobile menu.
+ */
+
+(function () {
+  const nav = document.querySelector('.mobile-nav');
+  const sheet = document.querySelector('.mobile-nav__sheet');
+  const toggle = document.querySelector('.mobile-nav__toggle');
+
+  function navopen() {
+    nav.dataset.navopen = 'true';
+    sheet.setAttribute('aria-hidden', 'false');
+    toggle.setAttribute('aria-expanded', 'true');
+    document.body.addEventListener('keydown', closeonesc);
+  }
+
+  function navclose() {
+    delete nav.dataset.navopen;
+    sheet.setAttribute('aria-hidden', 'true');
+    toggle.setAttribute('aria-expanded', 'false');
+    document.body.removeEventListener('keydown', closeonesc);
+  }
+
+  // Close the nav sheet with "esc" key.
+  function closeonesc(e) {
+    if (e.key === 'Escape') {
+      navclose();
+    }
+  }
+
+  // Toggle the mobile nav sheet.
+  const toggles = document.querySelectorAll('.mobile-nav__cover, .mobile-nav__toggle');
+  toggles.forEach(function (toggle) {
+    toggle.addEventListener('click', function (e) {
+      e.preventDefault();
+      if (nav.dataset.navopen) {
+        navclose();
+      } else {
+        navopen();
+      }
+    });
+  });
+
+  // Close the nav sheet after click (needed for anchor links).
+  const links = document.querySelectorAll('.mobile-nav__sheet a');
+  links.forEach(function (link) {
+    link.addEventListener('click', () => navclose());
+  });
+
+  // Move focus back to button efter user tab out of last link.
+  if (links.length) {
+    const lastlink = [].slice.call(links).pop();
+    lastlink.addEventListener('blur', () => toggle.focus());
+  }
+})();