表单提交时如何使用JavaScript判断哪个radio按钮被选中了

表单提交时通过JavaScript判断哪个radio按钮被选中了

<script type="text/javascript">
function findButton() {
var myForm = document.forms.animalForm;
var i;
for(i=0;i<myForm.marsupial.length; i++) {
   if(myForm.marsupial[i].checked) {
      break;
   }
}
alert("You selected \""+myForm.marsupial[i].value+"\".");
}
</script>
<form name="animalForm">
<input type="radio" name="marsupial" value="kangaroo" />75271.com
<br /><input type="radio" name="marsupial" value="Opossum" />Opossum
<br /><input type="radio" name="marsupial" value="Tasmanian Tiger" />Tasmanian Tiger
<br />
<input type="button" name="GO" value="GO" onclick="findButton()" />
</form>