radion 번트 값 받아오기

<script type="text/javascript">

function radiovalue(form)
{
 var mylen = form.rvinfo.length;
 
 alert("라디오 버튼 갯수:" + mylen);
 
 if (mylen == "undefined") //조회된 갯수가 1개일경우
 {
  mylen = 1;
 }
 
 for ( var i  = 0;i < mylen; i++)
 {
  if (form.rvinfo[i].checked == true)
  {
   alert("선택한 값:" + form.rvinfo[i].value);
   break;
  }
 
 }
 
 if (i == mylen)
 {
  alert("선택하세요!");
  return;
 }
}
</script>

 

<form name="rvForm">
 <input type="radio" name="rvinfo" value="1">일<br />
 <input type="radio" name="rvinfo" value="2">이<br />
 <input type="radio" name="rvinfo" value="3">삼<br />
 <input type="button" value="test" onclick="radiovalue(this.form)">
</form>