Bootstrap下拉框 Combobox

Bootstrap下拉框 Combobox显示效果如下：

源代码：

<select class="combobox">

  <option></option>

  <option value="PA">Pennsylvania</option>

  <option value="CT">Connecticut</option>

  <option value="NY">New York</option>

  <option value="MD">Maryland</option>

  <option value="VA">Virginia</option>

</select>

 

<script type="text/javascript">

  $(document).ready(function(){

    $('.combobox').combobox();

  });

</script>