how to print a default selected radio button value if there is a single radio button ?

Here is My Code:-

please help me out in this
I am unable to get the output here

<html>
<head>
<script type="text/javascript">

function get_radio_value()
{

for (var i=0; i < document.orderform.music.length; i++)
{
if (document.orderform.music[i].checked)
{
var rad_val = document.orderform.music[i].value;
alert("hai"+rad_val);
}
}
}

</script>
<form name="orderform">
Which one is your favorite?<br>
<input type="radio" name="music" value="Rock" checked="checked"> Rock<br>
<input type="submit" onclick="get_radio_value()">
</form>
</body>

</head>
</html>

When you post code, please you code tags.

Answer can be found on this old post: http://www.coderanch.com/t/115796/HTML-CSS-JavaScript/inconsistency-radiobutton

Eric