JavaScript获取已知结点的父结点方法

<script type="text/javascript">
 function change(event)
 {
  var curNode ;
  if(event == null)
  {
   curNode = window.event.srcElement ;
  }
  else
  {
   curNode = event.target ;
  }
  var parNode = curNode.parentNode ;
  parNode.action = "account/updateCart.action" ;
  parNode.submit() ;
  
 }
</script>
<s:iterator value="#items">
  <tr>
   <td><s:property value="bookName"/></td>
   <td>
    <s:text name="global.format.money"><s:param value="bookPrice"/></s:text>
   </td>
   <td>
    <form action="" >
  <input type="hidden" name="bookId" value="<s:property value="bookId"/>">
  <input type="text" name="quantity" size="2" value="<s:property value="quantity"/>" onchange="change();">
    </form>
   </td>
  </tr>
</s:iterator>