How to change name of input text, when adding more inputs

this is the form

<form action=""  method="POST">
  <input type="button" value="addmore" onClick="addRow('dataTable')" />
  <table id="dataTable" class="TFtable" border="1">
    <tr>
      <td><label>should be auto increment(like (name1, name2, name3 ...))</label>
        <input type="text" required="required" name="DONINID[]" value=""></td>
    </tr>
  </table>
  <input class="submit" type="submit" value="Confirm &raquo;" />
</form>

this is the script to add more => script.js:

function addRow(tableID) {
    var table = document.getElementById(tableID);
    var rowCount = table.rows.length;
    if(rowCount < 20){                          // limit the user from creating fields more than your limits
        var row = table.insertRow(rowCount);
        var colCount = table.rows[0].cells.length;
        for(var i=0; i<colCount; i++) {
            var newcell = row.insertCell(i);
            newcell.innerHTML = table.rows[0].cells[i].innerHTML;
        }
    }else{
         alert("Maximum Passenger per ticket is 20.");

    }
}

function deleteRow(tableID) {
    var table = document.getElementById(tableID);
    var rowCount = table.rows.length;
    for(var i=0; i<rowCount; i++) {
        var row = table.rows[i];
        var chkbox = row.cells[0].childNodes[0];
        if(null != chkbox && true == chkbox.checked) {
            if(rowCount <= 1) {                         // limit the user from removing all the fields
                alert("Cannot Remove all the Passenger.");
                break;
            }
            table.deleteRow(i);
            rowCount--;
            i--;
        }
    }
}

Now the idia is how to change the label name too as we add more input box it's should be auto increment like:

name1, name2, name3, name3 and when we add it should show us.

thanks in advance.