如何在提交前判断一组单选按钮是否被选择？

Question

<input name=radio1 type=radio>男
<input name=radio1 type=radio>女
<input name=button1 type=button value="检查" onclick=check()>
<script language=javascript>
    function  check()
    {
          var flag=false;
           var objs=document.getElementsByName("radio1")
           for(var i=0;i<objs.length;i++)
           {
                  if(objs[i].checked)
                  {
                              flag=true; 
                              break;                   
                   }
            }
           if(flag)
          {
                     alert("选了")
             }
          else
          {
                 alert("没选")
         }
     }
</script>

Answer 1

<script language="JavaScript">
function checkForm()
{
var rd=document.getElementsByName("rd");
var num=0;
for(i=0;i<rd.length;i++)
{
if(rd[i].checked)
{
num++;
break;
}
}
if(num>0)
return true;
else
{
alert("请选择");
return false;
}
}
</script>
<form name="myForm" action="test.htm" onsubmit="return checkForm();">
<input type="radio" name="rd">1
<input type="radio" name="rd">2
<input type="radio" name="rd">3
<input type="radio" name="rd">4
<input type="submit">
</form>