JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://code.jquery.com/jquery-3.4.1.min.js" integrity="sha256-CSXorXvZcTkaix6Yvo6HppcZGetbYMGWSFlBw8HfCJo=" crossorigin="anonymous"></script>
   <div align="right">
     <button type="button" name="add" id="add" class="btn btn-info"><span class="glyphicon glyphicon-plus"></span></button>
    </div>
    <br />
    <div id="alert_message"></div>
<table id="user_data" class="table table-bordered table-striped">
    <thead>
     <tr>
      <th>Data</th>
      <th>Resp. de Turno</th>
      <th>Apoio</th>
      <th>Elementos ALA A</th>
      <th>Elementos ALA B</th>
      <th></th>
     </tr>
    </thead>
    <tbody>
    </tbody>
</table>

JavaScript

$(document).ready(function(){

 function fetch_data()
  {
   var dataTable = $('#user_data').DataTable({
    "processing" : true,
    "serverSide" : true,
	"oLanguage": {
    "sProcessing": "Aguarde enquanto os dados são carregados ...",
    "sLengthMenu": "Mostrar _MENU_ registros por pagina",
    "sZeroRecords": "Nenhum registro correspondente ao criterio encontrado",
    "sInfoEmtpy": "Exibindo 0 a 0 de 0 registros",
    "sInfo": "Exibindo de _START_ a _END_ de _TOTAL_ registros",
    "sInfoFiltered": "",
    "sSearch": "<span class='glyphicon glyphicon-search'></span>",
    "oPaginate": {
       "sFirst":    "<span class='glyphicon glyphicon-fast-backward'></span>",
       "sPrevious": "<span class='glyphicon glyphicon-backward'></span>",
       "sNext":     "<span class='glyphicon glyphicon-forward'></span>",
       "sLast":     "<span class='glyphicon glyphicon-fast-forward'></span>"
     }
    }, 
    "order" : [],
    "ajax" : {
     url:"./fetchmapa",
     type:"POST"
    }
   });
  }
  
  function novaData(d){
   var dia  = d.getDate().toString();
   dia = (dia.length == 1) ? '0'+dia : dia;
   var mes  = (d.getMonth()+1).toString();
   mes = (mes.length == 1) ? '0'+mes : mes;
   var ano = d.getFullYear();
   return dia+"-"+mes+"-"+ano;
}
 
  class CellDate {
    constructor(start_date) {
        this.date = start_date;
    }
    getNextDate() {
   //here the change for if condition     
   if ($('#user_data tbody tr') != null && $('#user_data tbody tr').length > 0) {
            var ultima_data = $("#user_data tbody tr:first td:first").text().trim().split("-");
            var ultimo_dia = +ultima_data[0];
            var ultimo_mes = +ultima_data[1];
            var ultimo_ano = +ultima_data[2];
            this.date.setDate(ultimo_dia);
            this.date.setMonth(ultimo_mes - 1);
            this.date.setYear(ultimo_ano);
            this.date.setDate(this.date.getDate() + 1);
            console.log('if', this.date);
        } else {
           ...