示例:下拉菜单3
<div class="btn-group">
  <button class="btn btn-info btn-sm dropdown-toggle" type="button" data-toggle="dropdown" aria-expanded="false">
    Statistics
  </button>
<div class="dropdown-menu">
    <a class="dropdown-item" href="#">动作更新: <span class="recent-action-count"/></a>
    <a class="dropdown-item" href="#">今日访问: <span class="today-hit-times"></span></a>
    <a class="dropdown-item" href="#">总访问量:<span class="hit-times"></span></a>
    <div class="dropdown-divider"></div>
    <a class="dropdown-item" href="#">点赞数:<span class="badge badge-danger"><span class="action-likes"></span></span></a>
  </div>
</div>