jquery动态增添表格行 移动行

html：

<table id="tbl">
   <tr>
     <td>111</td>
     <td>张三</td>
     <td>
      <input type="button" value="up" onclick="move(this,'up')" /> 
      <input type="button" value="down" onclick="move(this,'down')" /> 
      <input type="button" value="addTr" onclick="addTR()" /> 
     </td>
   </tr>
   <tr>
     <td>222</td>
     <td>李四</td>
     <td>
      <input type="button" value="up" onclick="move(this,'up')" /> 
      <input type="button" value="down" onclick="move(this,'down')" />
      <input type="button" value="addTr" onclick="addTR()" />  
      </td>
   </tr>
   <tr>
     <td>333</td>
     <td>王五</td>
     <td>
      <input type="button" value="up" onclick="move(this,'up')" /> 
      <input type="button" value="down" onclick="move(this,'down')" /> 
      <input type="button" value="addTr" onclick="addTR()" /> 
      </td>
   </tr>
   <tr>
     <td>444</td>
     <td>赵六</td>
     <td>
      <input type="button" value="up" onclick="move(this,'up')" /> 
      <input type="button" value="down" onclick="move(this,'down')" /> 
      <input type="button" value="addTr" onclick="addTR()" /> 
     </td>
   </tr>
 </table>

javascript：

  function move(obj,der){
    var $pre = $(obj).parent().parent().prev();
    var $next = $(obj).parent().parent().next();
    var $src = $(obj).parent().parent();
    
    switch(der){
      case 'up':
      if($pre){
         $src.insertBefore($pre);
       }
       break;
      case 'down':
      if( $next){
          $src.insertAfter($next);
       }
       break;
     }
   }
   
   function addTR(){
     var $tr = $('#tbl tr:last').clone(true);
     $tr.appendTo($('#tbl'));
    }