+
+<script>
+ (function() {
+ // Get relevant elements and collections
+ const tabbed = document.querySelector('.tabbed');
+ const tablist = tabbed.querySelector('ul');
+ const tabs = tablist.querySelectorAll('a');
+ const panels = tabbed.querySelectorAll('[id^="section"]');
+
+ // The tab switching function
+ const switchTab = (oldTab, newTab) => {
+ newTab.focus();
+ // Make the active tab focusable by the user (Tab key)
+ newTab.removeAttribute('tabindex');
+ // Set the selected state
+ newTab.setAttribute('aria-selected', 'true');
+ newTab.classList.add('active');
+ oldTab.removeAttribute('aria-selected');
+ oldTab.setAttribute('tabindex', '-1');
+ oldTab.classList.remove('active');
+ // Get the indices of the new and old tabs to find the correct
+ // tab panels to show and hide
+ let index = Array.prototype.indexOf.call(tabs, newTab);
+ let oldIndex = Array.prototype.indexOf.call(tabs, oldTab);
+ panels[oldIndex].hidden = true;
+ panels[index].hidden = false;
+ }
+
+ // Add the tablist role to the first <ul> in the .tabbed container
+ tablist.setAttribute('role', 'tablist');
+
+ // Add semantics are remove user focusability for each tab
+ Array.prototype.forEach.call(tabs, (tab, i) => {
+ tab.setAttribute('role', 'tab');
+ tab.setAttribute('id', 'tab' + (i + 1));
+ tab.setAttribute('tabindex', '-1');
+ // tab.setAttribute('class', 'active');
+ tab.parentNode.setAttribute('role', 'presentation');
+
+ // Handle clicking of tabs for mouse users
+ tab.addEventListener('click', e => {
+ e.preventDefault();
+ let currentTab = tablist.querySelector('[aria-selected]');
+ if (e.currentTarget !== currentTab) {
+ switchTab(currentTab, e.currentTarget);
+ }
+ });
+
+ // Handle keydown events for keyboard users
+ tab.addEventListener('keydown', e => {
+ // Get the index of the current tab in the tabs node list
+ let index = Array.prototype.indexOf.call(tabs, e.currentTarget);
+ // Work out which key the user is pressing and
+ // Calculate the new tab's index where appropriate
+ let dir = e.which === 37 ? index - 1 : e.which === 39 ? index + 1 : e.which === 40 ? 'down' : null;
+ if (dir !== null) {
+ e.preventDefault();
+ // If the down key is pressed, move focus to the open panel,
+ // otherwise switch to the adjacent tab
+ dir === 'down' ? panels[i].focus() : tabs[dir] ? switchTab(e.currentTarget, tabs[dir]) : void 0;
+ }
+ });
+ });
+
+ // Add tab panel semantics and hide them all
+ Array.prototype.forEach.call(panels, (panel, i) => {
+ panel.setAttribute('role', 'tabpanel');
+ panel.setAttribute('tabindex', '-1');
+ let id = panel.getAttribute('id');
+ panel.setAttribute('aria-labelledby', tabs[i].id);
+ panel.hidden = true;
+ });
+
+ // Initially activate the first tab and reveal the first tab panel
+ tabs[0].removeAttribute('tabindex');
+ tabs[0].setAttribute('aria-selected', 'true');
+ tabs[0].setAttribute('class', 'active');
+ panels[0].hidden = false;
+ })();
+</script>