为什么Enter键不能与selectpicker配合使用

Question

我正在寻找创建一个表单，在其中按Enter键可使焦点移至页面上的“下一个”表单元素。那是我的代码，但在引导程序中无法与“ selectpicker”一起使用 HTML代码

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div class="col-md-6 pdr0 ">
    <div class="col-md-12 pdl0 pdt5">DOB</div>
    <div class="col-md-12 pdl0 pdb0 pdt0">
        <asp:TextBox ID="DOB" runat="server" TabIndex="7" CssClass="TextBox validate[required] " />
        <span class="required"></span>
    </div>
</div>
<div class="col-md-6 pdr0 ">
    <div class="col-md-12 pdl0 pdt5">Level</div>
    <div class="col-md-12 pdl0 pdb0 pdt0">
        <asp:DropDownList ID="Level" TabIndex="8" runat="server" CssClass="selectpicker  validate[required]" />
        <span class="required"></span>
    </div>
</div>
<script>
  $('body').on('keydown', 'input,button, a, select, textarea', function (e) {
    var self = $(this), form = self.parents('form:eq(0)'), focusable, next;
    if (e.keyCode == 13) {
      focusable = form.find('input,button,a,select,textarea').filter(':visible:not([readonly]):enabled');
      next = focusable.eq(focusable.index(this) + 1);
      if (next.length) { next.focus(); } else { form.submit(); }
        return false;
      }
      else if (e.keyCode === 113) {
        $(".cmsbtupdate").click();
      }
    });
</script>