สอบถามค่ะ หากเราอยากให้มีลำดับแถว ต้องเขียนเพิ่มเติมอย่างไรอะค่ะ [Simple add/delete table row with jQuery by PlaKriM]

//Created by Mr.Mongkon Kaenjan
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<script type="text/javascript">
$('document').ready(function(){
    $('#remove').hide();
    $('#addrow').click(function(){
        if(($('#tb tr').size()) > 1){
            $('#remove').show();
        }
        
        var no = parseInt($('#tb tr').length)+1;
         $('#tb tr:last').after(
            '<tr><td>'+no+'</td>'+
            '<td><input type="text" id="txt" name="txt[]"></td>'+
             '<td><select id="ddl" name="ddl[]">'+
                    '<option>--select one--</option>'+
                    '<option value="A">option A</option>'+
                    '<option value="B">option B</option>'+
                    '</select>'+
             '</td></tr>'
        );
    });
    
    $('#remove').click(function(){
        
        $('#tb tr:last').remove();
        if(($('#tb tr').size())==1){
            $('#remove').hide();
        }        
    });
});
</script>
<table id="tb">
    <tr>
        <td>1.</td>
        <td><input type="text" id="txt" name="txt[]"></td>
            <td>
                <select id="ddl" name="ddl[]">
                    <option>--select one--</option>
                    <option value="A">option A</option>
                    <option value="B">option B</option>
                </select>
             <button id="addrow">Add row</button><button id="remove">Remove</button></td>
   </tr>
</table>