Bootstrap按钮下拉大小

<div class = "btn-group">

   <button type = "button" class = "btn btn-default dropdown-toggle btn-lg" data-toggle = "dropdown">
      Default
      <span class = "caret"></span>
   </button>

   <ul class = "dropdown-menu" role = "menu">
      <li><a href = "#">Action</a></li>
      <li><a href = "#">Another action</a></li>
      <li><a href = "#">Something else here</a></li>

      <li class = "divider"></li>
      <li><a href = "#">Separated link</a></li>
   </ul>
</div>

<div class = "btn-group">
   <button type = "button" class = "btn btn-primary dropdown-toggle btn-sm" data-toggle = "dropdown">
      Primary
      <span class = "caret"></span>
   </button>

   <ul class = "dropdown-menu" role = "menu">
      <li><a href = "#">Action</a></li>
      <li><a href = "#">Another action</a></li>
      <li><a href = "#">Something else here</a></li>

      <li class = "divider"></li>
      <li><a href = "#">Separated link</a></li>
   </ul>
</div>

<div class = "btn-group">
   <button type = "button" class = "btn btn-success dropdown-toggle btn-xs" data-toggle = "dropdown">
      Success
      <span class = "caret"></span>
   </button>

   <ul class = "dropdown-menu" role = "menu">
      <li><a href = "#">Action</a></li>
      <li><a href = "#">Another action</a></li>
      <li><a href = "#">Something else here</a></li>

      <li class = "divider"></li>
      <li><a href = "#">Separated link</a></li>
   </ul>

</div>