ARIA：group 角色

<div id="tree1" role="tree" tabindex="-1">
  <div
    id="animals"
    class="groupHeader"
    role="presentation"
    aria-owns="animalGroup"
    aria-expanded="true">
    <img role="presentation" tabindex="-1" src="images/treeExpanded.gif" />
    <span role="treeitem" tabindex="0">动物</span>
  </div>
  <div id="animalGroup" role="group">
    <div id="birds" role="treeitem">
      <span tabindex="-1">鸟</span>
    </div>
    <div
      id="cats"
      class="groupHeader"
      role="presentation"
      aria-owns="catGroup"
      aria-expanded="false">
      <img role="presentation" tabindex="-1" src="images/treeContracted.gif" />
      <span role="treeitem" tabindex="0">猫</span>
    </div>
    <div id="catGroup" role="group">
      <div id="siamese" role="treeitem">
        <span tabindex="-1">暹罗猫</span>
      </div>
      <div id="tabby" role="treeitem">
        <span tabindex="-1">虎斑猫</span>
      </div>
    </div>
  </div>
</div>

<div role="menu">
  <ul role="group">
    <li role="menuitem">收件箱</li>
    <li role="menuitem">归档</li>
    <li role="menuitem">已删除</li>
  </ul>
  <ul role="group">
    <li role="menuitem">自定义文件夹 1</li>
    <li role="menuitem">自定义文件夹 2</li>
    <li role="menuitem">自定义文件夹 3</li>
  </ul>
  <ul role="group">
    <li role="menuitem">创建文件夹</li>
  </ul>
</div>