Tukukkk

$(document).on("click",".Change_Nodes",function(){



  cmd_name = $(this).attr("id");



  if(confirm("Sure to Update ""+cmd_name+"" Command Executable Nodes?"))

  {

    $('#custom_script_modal').modal('show');

  }

  else

  { return false; }

}

); //update: removed extra curly brace

<link href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css" rel="stylesheet"/>

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>



<div class="modal fade" id="custom_script_modal" tabindex="-1" role="dialog" aria-hidden="true">

    <div class="modal-dialog modal-dialog-centered">

        <div class="modal-content">

            <div class="modal-header">

                <h4 class="modal-title text-center" id="custom_script_data_modal">Update Custom Script Executable Nodes</h4>

            </div>

            <div class="modal-body">

                <form method="POST" id="custom_script_modal">

                    <label class="control-label col-sm-4" for="cmd">List of Nodes</label>

                    <div class="col-sm-8 tab-pan fade in active">

                        <select size="3" name="popup_hostlist" id="popup_hostlist" class="dis_tab" multiple>

                            <?php    

                                //-----------Database                                                                           echo "<option value='". $row['NodeName'] . "'>". $row['NodeName'] ."</option>";           

                            ?>

                        </select>

                    </div>



                    <div class="form-group">

                        <button type="submit" class="btn btn-info form-control">Update</button>

                    </div>

                </form>

            </div>

            <div class="modal-footer">

                <button type="button" class="btn btn-danger" data-dismiss="modal">Close</button>

            </div>

        </div>

    </div>

</div>