怎样用JavaScript校验多个Radiobutton中哪一个被选中?

Question

<input type="radio" name="a" value="a1">
<input type="radio" name="b" value="b1">
<input type="radio" name="c" value="c1">
<input type="radio" name="d" value="d1">
<script>
document.onclick=c;
function c(){
var o=event.srcElement;
if(o.tagName=="INPUT"){
if(o.type=="radio")alert(o.name+"被先中\r\n它的值是"+o.value)
}
}
</script>

Answer 1

<input type="radio" name="a" value="a1">
<input type="radio" name="b" value="b1">
<input type="radio" name="c" value="c1">
<input type="radio" name="d" value="d1">
<script>
var a = document.getElementsByTagName("input");
for (var i=0; i<a.length; i++){
if ((a[i].type == "radio")&&(a[i].checked))
alert(a[i].name+"被先中\r\n它的值是"+a[i].value);}
</script>

Answer 2

但我的radiobutton的name值全是一样的,这该怎样处理?

Answer 3

<input type="radio" name="a" value="a1">
<input type="radio" name="a" value="b1">
<input type="radio" name="a" value="c1">
<input type="radio" name="a" value="d1"><input type=submit onclick=c()>
<script>
function c(){
var a = document.all["a"];
for (var i=0; i<a.length; i++){
if (a[i].checked)
alert(a[i].name+"被先中\r\n它的值是"+a[i].value);}
}
</script>