我自己处理悬停事件来添加一个三角形指针和一个水平对齐的子菜单栏。当单击顶部菜单时，它可以很好地显示和导航到子菜单。问题是在悬停期间，试图将鼠标移动到子菜单时，子菜单栏会消失。

TIA

代码：

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$("#menubar li.dropdown>a.nav-link").hover(function() {
    if ($("#menubar li.dropdown").filter(function() {
        return $(this).data("show")
      }).length === 0)
      $(this).closest("li").addClass("active show");
  },
  function() {
  /*when top menu is clicked, don't hide submenu*/
    if ($("#menubar li.dropdown").filter(function() {
        return $(this).data("show")
      }).length === 0)
      $(this).closest("li").removeClass("active show");
  });

$("#menubar li>a.nav-link").on("click", function(e) {
  e.stopPropagation();

  var $li = $(this).closest("li");

  if (!$li.hasClass("dropdown")) {
    $("#menubar li.dropdown").removeClass("active show");
    $("#menubar li.dropdown").data("show", false);
  } else {
    if ($li.data("show")) {
      $li.removeClass("active show");
      $li.data("show", false);
    } else {
      $("#menubar li.dropdown").removeClass("active show");
      $li.addClass("active show");
      $li.data("show", true);
    }
  }
});
$("#menubar ul.dropdown-menu>li>a").on("click", function(e) {
  $("#menubar li.dropdown").removeClass("active show");
  $("#menubar li.dropdown").data("show", false);
});

#menubar ul {
  height: 44px;
  padding-top: 5px;
}

#menubar .nav-link {
  font-size: 14px;
  padding: 8px 50px 0 0 !important;
  color: white !important;
}

#menubar .nav-link:focus,
#menubar .nav-link:hover,
#menubar .nav-link:visited {
  color: white !important;
}

#menubar .navbar {
  padding-left: 0 !important;
}

.navbar.navbar-dark {
  height: 44px;
  margin: 0 15%;
}

nav.navbar .navbar-nav li.nav-item.active:after {
  content: "";
  position: relative;
  margin-left: -31px;
  left: 50%;
  bottom: 15px;
  border-left: 6px solid transparent;
  border-right: 6px solid transparent;
  border-bottom: 6px solid white;
}


/*submenu*/

#menubar li.dropdown.show {
  position: static;
}

#menubar li.dropdown.show .dropdown-menu {
  display: table;
  width: 100%;
  text-align: center;
  left: 0;
  right: 0;
  margin: 0;
}

.dropdown-menu>li {
  display: table-cell;
  padding-top: 6px;
}

.dropdown-menu>li a {
  font-weight: 600;
}

.dropdown-menu>li a:hover {
  text-decoration: none;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">

<nav class="navbar navbar-expand-md navbar-dark ">
  <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#menubar">
                        <span class="navbar-toggler-icon"></span>
                    </button>
  <div class="navbar-collapse" id="menubar">
    <ul class="nav navbar-nav">
      <li class="nav-item ">
        <a class="nav-link" href="#">Menu1</a>
      </li>
      <li class="nav-item dropdown">
        <a class="nav-link" data-toggle="dropdown" href="#">Menu2</a>
        <ul class="dropdown-menu" role="menu">
          <li><a href="#">Submenu1</a></li>
          <li><a href="#">Submenu2</a></li>
          <li><a href="#">Submenu3</a></li>

        </ul>
      </li>

    </ul>
  </div>
</nav>

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