get value from RadioButtonList control in java script

How to get value from RadioButtonList control?

Here id is the name property of the RadioButtonList

function GetRadioButtonValue(id)

        {

            var radio = document.getElementsByName(id);

            for (var ii = 0; ii < radio.length; ii++)

            {

                if (radio[ii].checked)

                    alert(radio[ii].value);

            }

        }