<!DOCTYPE html>
<html>
<head>
<script>
function TotalElements() {
var el = document.getElementsByName("rb");
document.getElementById("pid").innerHTML = el.length;
}
</script>
</head>
<body>
A: <input name="rb" type="radio" value="A">
B: <input name="rb" type="radio" value="B">
C: <input name="rb" type="radio" value="C">
<br /><br />
<input type="button" onclick="TotalElements()" value="Total Elements">
<p id="pid"></p>
</body>
</html>