i have this script in my website.

$(document).ready(function(){
        var comment = $('textarea[name=comment_text]').val();
        var vid = $('input[name=video_id]').val();
        $('#add_comment').on('click', function(){
            $.post('<?php echo site_url('comment/addcomments'); ?>', $('#comment-form').serialize(), function(data){
                data = JSON.parse(data);
                if(data.userdata){
                    var date = new Date(data.userdata.comment_create_time * 1000);
                    var picture = data.userdata.user_image.length > 0 ? 'fileupload/'+data.userdata.user_image:'images/no_pic.gif';
                    var newComment = '<div class="row">\
                        <div class="col-md-4">\
                            <img src="<?php echo base_url(); ?>'+picture+'" class="profile-pic margin-top-15" />\
                        </div>\
                        <div class="col-md-8 no-pade">\
                            <p id="comment-user" class="margin-top-15">'+data.userdata.user_firstname+' '+data.userdata.user_lastname+'</p>\
                            <p id="comment-time">'+date.getTime()+'</p>\
                        </div>\
                        <div class="clearfix"></div>\
                        <div class="col-md-12 margin-top-15" id="comment-text">'+data.userdata.comment_text +'</div>\
                        <div class="col-md-12">\
                            <div class="hr-grey margin-top-15"></div>\
                        </div>\
                    </div>';
                    $('#comment-scroll').append($(newComment));
                    $('#comment').modal('hide');
                }
            });
        });
    });

what i expect when a comment added to the DB and the PHP page give JSON response, the new comment will be added to the last line of $('#comment-scroll'). #comment-scroll is also have custom scroll bar by mcsCustomscrollbar.

the above script also hiding the modal dialog when comment saved and it's working fine which is mean data.userdata is not empty, but why the append() isnt?