如果没有选择的话，返回的值为 undefined
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html
xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta
http-equiv="Content-Type" content="text/html; charset=gb2312"
/>
<title>xxx</title>
<script>
/**
*state 的值为单选中 value
的值
*/
function test(form){
var i =
form.ok.length;
var state;
for(var j=0; j<i; j++){
if(form.ok[j].checked){
state = form.ok[j].value;
}
}
if(state == undefined){
alert("你没有选择！");
return false;
}
alert(state);
return
false;
}
</script>
</head>
<body>
<table
border="1" width="150">
<form name="myform" id="myform"
method="post" action="test.php">
<input type="radio" name="ok"
value="1" />aaaa<br />
<input type="radio" name="ok" value="2"
/>bbbb<br />
<input type="radio" name="ok" value="3"
/>cccc<br />
<button name="sub" onclick="return
test(myform)">Button</button>
</form>
</table>
</body>
</html>