function initTabGroup()

in styles/docfx.js [877:896]


    function initTabGroup(element) {
      var group = {
        independent: element.hasAttribute('data-tab-group-independent'),
        tabs: []
      };
      var li = element.firstElementChild.firstElementChild;
      while (li) {
        var a = li.firstElementChild;
        a.setAttribute(contentAttrs.name, 'tab');
        var dataTab = a.getAttribute('data-tab').replace(/\+/g, ' ');
        a.setAttribute('data-tab', dataTab);
        var section = element.querySelector("[id=\"" + a.getAttribute('aria-controls') + "\"]");
        var tab = new Tab(li, a, section);
        group.tabs.push(tab);
        li = li.nextElementSibling;
      }
      element.setAttribute(contentAttrs.name, 'tab-group');
      element.tabGroup = group;
      return group;
    }