页面选择radio单选选中的值

<script type="text/javascript">
function testFunc()
{
	var obj = document.all.finish;
	for (i = 0; i < obj.length; i++)
	{
		if (obj[i].checked)
		{
			alert(obj[i].value);
		}
	}
}
</script>
<input type=radio name=finish value=1>
<input type=radio name=finish value=2>
<input type=radio name=finish value=3>
<input type=button name=bu value=click onclick="testFunc();">