anchor.diff:               <table class="table table-hover" style="border-color:red;">
                    <thead>
                   <tr>
  -                    <th>Período(meses)</th>
  +                    <th id="demo">Período(meses)</th>
                       <th>Prestação</th>
                       <th>Juros</th>
                       <th>Amortização</th>
  
positive.code:                 </div>
                  <div class="form-group  col-3">
                              <label for="selectPeriodo">Período da Taxa</label>
                              <select id="selectPeriodo" class="form-control" id="exampleSelect1">
                                  <option>Mensal</option>
                                  <option>Anual</option>
                              </select>
  
negative.code:     
  
      <%@include file="WEB-INF/jspf/footer.jspf" %>
      <script>
      function myFunction() {
          var x = document.getElementById("selectPeriodo").value;
          document.getElementById("demo").innerHTML = "Período("+x+")";
      }
      </script>
  
      </body>
  