Need Help with Single RadioButton JS Problem

JavaScript
1

What I am trying to do is make a single radiobutton works link a checkbox, click on, click off. But after many test, it looks like I have to have a line of code, such as alert(), in order to make it happen, any idea why? ( I don’t want alert() pupops up ). Thanks in advance~!


<script type="text/javascript">
function on_off(id)
{  

    if(document.getElementById(id).checked == false)
    {
        alert("Select VIP"); // function works with this line
        document.getElementById(id).checked = true;
    }
    else if(document.getElementById(id).checked == true)
    {
        alert("unSelect VIP");  // function works with this line
        document.getElementById(id).checked = false;
    }
      

}
</script>



<input name="x_checker" id="x_checker" value="yes" checked="checked"  onfocus="on_off('x_checker')"  type="radio">
2 

//Fixed. I think I got a logic wrong. Here is what i got finally:


    var flag = false;
    function on_off(id) {
                //alert(flag == true);
        if (flag == true) {
            document.getElementById('x_checker').checked = false;
            flag = false;
        }
        else {
            document.getElementById('x_checker').checked = true;
            flag = true;
        }
    }