dwib,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.0/jquery.min.js"></script>
<script>
$(function(){
var chec = $('.vis [name="vir"]');
if(!chec.is(":checked")) chec.eq(0).prop("checked",true)
})
</script>
</head>
<body>
<form action="http://" class="vis">
<input name="vir" type="radio">
<input name="vir" type="radio">
<input name="vir" type="radio">
</form>
</body>
</html>