Generate a row with empty cells and a filled select

I need to generate in JavaScript a new row on a table but with empty cell without a select who need to be the same as the other row and i want the function to work no matter where is the input in the row
here’s my function to add empty row and cells

// Insert new row in the table when clicking on the + button
// tableid: Id of the element to update
function AddRows(tableid){
    var table = document.getElementById(tableid);
    var rowCount = table.rows.length;
    var cellCount = table.rows[0].cells.length;
    var row = table.insertRow(rowCount);
     var editContent = !row.isContentEditable;
        row.contentEditable = editContent;
    row.setAttribute('onkeyup', "Disabled();");
    row.setAttribute('onclick', "SetSelectedRow(this)");
    row.setAttribute('id', 'Combo_row'+(row.rowIndex - 1)); //Set the id of the row
    row.setAttribute('class', 'default');


    for(var i =0; i < cellCount; i++){
        var cell = 'cell'+i;
        cell = row.insertCell(i);
        cell.id = 'Combo_cell' + i
    }

}

I also found this function but she copy the rows and keep the content of every cells not only the select

/* function to add row with a select */
    function addSelect(SelectTableId) {
  var T = document.getElementById(SelectTableId);

  var R = document.querySelectorAll('tbody .AddRowClass')[0];

  var C = R.cloneNode(true);

  T.appendChild(C);

    }