I've been stuck at this error for a few days and still couldn't figure out what is wrong. Would be great if someone could just point me to the right direction of solving this issue.

Update:
I realise that error is gone when I commented addMessages(xml) in the updateMsg() function. How do I make it work then?

Error:
http://i.imgur.com/91HGTpl.png

Code:

$(document).ready(function () {

    var msg = $(#msg);

    var log = $(#log);

    var timestamp = 0;



    $(#name).focus();



    $(#login).click(function() {

        var name = $(#name).val();

        if (!name) {

            alert(Please enter a name!);

            return false;

        }



        var username = new RegExp('^[0-9a-zA-Z]+$');



        if (!username.test(name)){

            alert(Invalid user name! n Please do not use the following characters n `~!@#$^&*()=|{}':;',\[\].<>/?~@#);

            return false;

        }



        $.ajax({

            url: 'login.php',

            type: 'POST',

            dataType: 'json',

            data: {name: name},

            success: function() {

                $(.login).hide();

            }

        })

        return false;

    });



    $(#form).submit(function() {

        if (!msg.val()) {

            return false;

        }



        $.ajax({

            url: 'add_message.php',

            type: 'POST',

            dataType: 'json',

            data: {message: msg.val()},

        })



        msg.val();



        return false



    });



    window.setInterval(function () {

        updateMsg();

    }, 300);



    function updateMsg() {

        $.post('server.php', {datasize: '1024'}, function(xml) {

            addMessages(xml);

        });

    }



    function addMessages(xml) {



        var json = eval('('+xml+')');



        $.each(json, function(i, v) {



            tt = parseInt(v.time);



               if (tt > timestamp) {

                console.log(v.message);

                appendLog($(<div/>).text('[' + v.username + ']' + v.message));

                timestamp = tt

            }

        });

    }



    function appendLog(msg) {

        var d = log[0]

        var doScroll = d.scrollTop == d.scrollHeight - d.clientHeight;

        msg.appendTo(log)

        if (doScroll) {

            d.scrollTop = d.scrollHeight - d.clientHeight;

        }

    }

});