问使Html表单输入字段在提交时保持不变

EN

    $('body').on("click",".addComment",function(){

        var element = $(this);
        var id = element.attr("id");

        $('#commentBox'+id).slideToggle(200);
        $('#comment'+id).focus();
        $('#comment'+id).val('');
        $('#comment'+id).attr("placeholder", "Write a message..");


    });



    $('body').on("click",".comBtn",function(){

        var element = $(this);
        var cid = element.attr("id");

         var ball=$('#ball').val();



        var comment=$('#comment').val();
        var datasend = 'com='+ comment + '&pid=' + cid +'&ball='+ball;


        if(comment==""){

            $('#comment'+cid).focus();
            $('#comment'+cid).attr("placeholder", "Enter the comment..");

        }else{

        $.ajax({

            type:"POST",
            url:"comment.php",
            data:datasend,
            cache:false,
            success:function(html){
                $('#loadcomment'+cid).append(html);
                $('#comment').val('');

                                 $('#ball').val('');


            }

        });

        }

        return false;

        });






<form action="" method="post">


<select name="ball" id="ball">
<option>none</option>
<option value="left">left</option>
<option value="right">right</option>
</select>

<input name="comment"  id="comment"  type="text">


<input id="comBtn"  type="submit"/>



</form>