如何在javascript获得表单中单选按钮的值?

Question

<input type="radio" id="flag1" name="flag0" value="Y" ID=Radio1>
是
  <input type="radio" id="flag2" name="flag0" value="N" ID=Radio2>
否</td>
<script>
alert(document.all.flag1.value);
</script>

Answer 1

<input type="radio"  name="flag" value="Y" >
是
  <input type="radio"  name="flag" value="N" >
否</td>
<script>
alert(document.all.flag[0].value);
</script>

Answer 2

var radio=document.all.flag;
var value=null;
if(radio.length){
   for(var i=0;i<radio.length;i++){}
else if(radio.checked) {
  value=radio.value;
}

Answer 3

var radio=document.all.flag;
var value=null;
if(radio.length){
   for(var i=0;i<radio.length;i++){
      if(radio[i].checked) {value=radio[i].value;break;}
   }}
else if(radio.checked) {
  value=radio.value;
}

Answer 4

function Init()
{
  var obj=document.all.div1;
  for(var i=0;i<10;i++)
    {
      var sel=document.createElement("<SELECT NAME='mySel' id='selid0'><SELECT>");
      sel.add(new Option("--selected--","--selected--"));
      
    //  sel.name="mySel";
     addoption(obj,sel);
      
      sel.onchange=function()
      {