JavaScript 获取表单单选按钮值的方法

<form>
<tr bgcolor="#FFFFFF">
  <td width="84" height="23" rowspan="3" align="center" valign="middle"
  bordercolor="#999999"><span class="STYLE1">回退类型:</span></td>
  <td width="360" align="center" valign="middle" bordercolor="#999999"><input
  type="radio" name="returnTag" value="-1" checked="checked">
  申报部门</td>
</tr>
<tr bgcolor="#FFFFFF">
  <td align="center" valign="middle" bordercolor="#999999"><input
  type="radio" name="returnTag" value="1"> 省网招标中心</td>
</tr>
<tr bgcolor="#FFFFFF">
  <td align="center" valign="middle" bordercolor="#999999"><input
  type="radio" name="returnTag" value="2"> 国网招标中心</td>
</tr></form1>

function getValue()
{
//获取单选按钮值
  for(var i=0;i<form1.returnTag.length;i++)
  {
   if(form1.returnTag[i].checked)
   {
    var returnTagValue=form1.returnTag[i].value; //这里得到单选按钮值
    }
  }
}