<tbody id="template">
            <tr>
                <td>
                    <select name="order[order_placed][][itemname]" id="order_place_id" class="form-control delete-comment" style="width: 300px">
                        <option value=""></option>
                        <% Item.all.each do |item| %>
                            <option value="<%= item.item_name %>">
                                <%= item.item_name %>
                            </option>
                            <% end %>
                    </select>
                </td>

                <td><input name="order[order_placed][][quantity]" type="text"  size='10' class="form-control" /></td>
                <td><input name="order[order_placed][][unitprice]" type="text"  size='10' class="form-control" /></td>
                <td><input name="order[order_placed][][tax]" type="text"  size='10' class="form-control"/></td>
                <td><input name="order[order_placed][][discount]" type="text"  size='10' class="form-control"/></td>
                <td><input name="order[order_placed][][itemtotalprice]" type="text" size='10' class="form-control" /></td>
                <td>
                    <button type="button" class="btn btn-default btn-sm sub" onClick="$(this).closest('tr').remove();">
                        <span class="glyphicon glyphicon-minus"></span>
                    </button>
                </td>
            </tr>
        </tbody>

$(document).on('change', 'select', function() {    //var url = $('.delete-comment').attr('data-url');
        $.ajax({
          url: "/items/getdata",
          type: 'get',
          data: {data_value: $(this).val()},
          dataType: 'json',
          success: function (data) {         $(this).closest('tr').next('td').next('td').next('td').find('input[name="order[order_placed][][unitprice]"]').val(data.unit_price);
             $('input[name="order[order_placed][][tax]"]').val(data.tax);
             $('input[name="order[order_placed][][discount]"]').val(data.discount);
 },        error: function () {
            alert('error');
          }
        });
      });