Radio button validation not working using javascript

var radioButtonlist = document.getElementById('<%=rbTransferType.ClientID%>');
 var opt = radioButtonlist.getElementsByTagName('input');
 for (var i = 0; i < opt.length; i++) {
                var rbref = opt[i];
                if (rbref.checked == true) {
                    if (rbref.value == "Third Party") {                      
                        break;
                    }
                    else if (rbref.value == "Inter IBS") {                       
                        break;
                    }
                }
      }