Replace jekyll-tabs plugin with custom code

[rnaseq-cwl-training.git] / assets / js / tabs.js

diff --git a/assets/js/tabs.js b/assets/js/tabs.js
index 0148f3255c1339ccb102164bc935fb65d48d5642..0e5b795e4f2483755373a1c29122d4e7024a4f08 100644 (file)
--- a/assets/js/tabs.js
+++ b/assets/js/tabs.js
@@ -1,43 +1,77 @@
-const removeActiveClasses = function (ulElement) {
-    const lis = ulElement.querySelectorAll('li');
-    Array.prototype.forEach.call(lis, function(li) {
-        li.classList.remove('active');
-    });
-  }
+window.addEventListener('load', 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"]');
 
-  const getChildPosition = function (element) {
-        var parent = element.parentNode;
-        var i = 0;
-        for (var i = 0; i < parent.children.length; i++) {
-            if (parent.children[i] === element) {
-                return i;
-            }
-        }
+  // 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;
+  }
 
-        throw new Error('No parent found');
-    }
+  // Add the tablist role to the first <ul> in the .tabbed container
+  tablist.setAttribute('role', 'tablist');
 
-window.addEventListener('load', function () {
-    const tabLinks = document.querySelectorAll('ul.tab li a');
+  // 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');
 
-    Array.prototype.forEach.call(tabLinks, function(link) {
-      link.addEventListener('click', function (event) {
-        event.preventDefault();
+    // 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);
+      }
+    });
 
-        liTab = link.parentNode;
-        ulTab = liTab.parentNode;
-        position = getChildPosition(liTab);
-        if (liTab.className.includes('active')) {
-          return;
-        }
+    // 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;
+      }
+    });
+  });
 
-        removeActiveClasses(ulTab);
-        tabContentId = ulTab.getAttribute('data-tab');
-        tabContentElement = document.getElementById(tabContentId);
-        removeActiveClasses(tabContentElement);
+  // 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;
+  });
 
-        tabContentElement.querySelectorAll('li')[position].classList.add('active');
-        liTab.classList.add('active');
-      }, false);
-    });
+  // 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;
 });