AJAX RADIOBUTTON Not working

I have 3 radio buttons.

<input type="radio" name="length" value="1">
<input type="radio" name="length" value="2">
<input type="radio" name="length" value="3">

and im passing this values using like this. name,bay,pall,dest working fine. but length output as "undefined". please help me to fine this error.. thanks..

this is my ajax codE:

    $(document).ready(function()

{



    $("#bcode").focus();
    //prevents autocomplete in some browsers
    $("#bcode").attr('autocomplete', 'off').keyup(function(event)
    {

                var name = $("#bcode").val();
                var bay  = $("#select").val();
                var pall = $("#select2").val();
                var dest = $("#select4").val();
                var length = $("#length").val();


            $("#status").empty();
            if(name.length > 17 )
            {
                selectAll();

                $("#status").html('<img align="absmiddle" src="images/loading.gif" /> Checking availability...').show();




     $.ajax({
                    type: "POST",
                    url: "namecheck.php",
                    data : "bcode=" + name + "&select=" + bay+ "&select2=" + pall+ "&select4=" + dest+ "&length=" + length,
                    success: function(msg)
                    {
                        $("#status").html(msg).show();
                    }
                    });

        }
        else
        {
            $("#status").html('').addClass('err').s开发者_Python百科how();
        }
    });
    });

---

I think this is wrong: var length = $("#length").val(); it should be

var length = $("input[name=length]:checked").val();