Bootstrap 4菜单下拉菜单和子菜单下拉菜单具有相同的高度

Question

我正在使用Bootstrap 4并尝试使菜单下拉菜单和子菜单下拉菜单具有相等的高度。

到目前为止，我设法使菜单下拉菜单的高度等于子菜单下拉菜单的高度，而不是使用jQuery的其他方式。我如何设法使其如下所示：

JSFiddle：https://jsfiddle.net/g9thp3j5/

HTML：

<div id="main-nav" class="justify-content-end">
  <ul id="menu-main-menu" class="navbar-nav">
    <li class="menu-item current-menu-item current_page_item menu-item-home active nav-item"><a href="#" class="nav-link">Main Menu 1</a>
    </li>
    <li class="menu-item menu-item-has-children dropdown nav-item"><a href="#" data-toggle="dropdown" class="dropdown-toggle nav-link">Main Menu 2</a>
      <ul class="dropdown-menu" role="menu">
        <li class="menu-item menu-item-has-children dropdown nav-item"><a href="#" class="dropdown-item">Menu 1</a>
          <ul class="dropdown-menu" role="menu">
            <li class="menu-item nav-item"><a href="#" class="dropdown-item">Sub Menu 1</a></li>
            <li class="menu-item nav-item"><a href="#" class="dropdown-item">Sub Menu 2</a></li>
            <li class="menu-item nav-item"><a href="#" class="dropdown-item">Sub Menu 3</a></li>
            <li class="menu-item nav-item"><a href="#" class="dropdown-item">Sub Menu 4</a></li>
            <li class="menu-item nav-item"><a href="#" class="dropdown-item">Sub Menu 5</a></li>
            <li class="menu-item nav-item"><a href="#" class="dropdown-item">Sub Menu 6</a></li>
          </ul>
        </li>
        <li class="menu-item menu-item-has-children dropdown nav-item"><a href="#" class="dropdown-item">Menu 2</a>
          <ul class="dropdown-menu" role="menu">
            <li class="menu-item nav-item"><a href="#" class="dropdown-item">Sub Menu 11</a></li>
            <li class="menu-item nav-item"><a href="#" class="dropdown-item">Sub Menu 12</a></li>
            <li class="menu-item nav-item"><a href="#" class="dropdown-item">Sub Menu 13</a></li>
            <li class="menu-item nav-item"><a href="#" class="dropdown-item">Sub Menu 14</a></li>
            <li class="menu-item nav-item"><a href="#" class="dropdown-item">Sub Menu 15</a></li>
            <li class="menu-item nav-item"><a href="#" class="dropdown-item">Sub Menu 16</a></li>
            <li class="menu-item nav-item"><a href="#" class="dropdown-item">Sub Menu 17</a></li>
          </ul>
        </li>
        <li class="menu-item nav-item"><a href="#" class="dropdown-item">Menu 3</a>
        </li>
      </ul>
    </li>
    <li class="menu-item nav-item"><a href="#" class="nav-link">Main Menu 3</a></li>
    <li class="menu-item nav-item"><a href="#" class="nav-link">Main Menu 4</a></li>
  </ul>
</div>

CSS：

.navbar-nav {
    -ms-flex-direction: row;
    flex-direction: row;
}
.navbar-nav .dropdown-menu {
    position: absolute;
}
.navbar-nav > li {
  margin: 0 15px;
}
.dropdown-menu .dropdown-toggle::after {
  border-bottom: 0.3em solid transparent;
  border-left: 0.3em solid;
  border-top: 0.3em solid transparent;
}
.dropdown-menu.show {
  border: 1px solid #999;
  background-color: #ffffff;
}
.dropdown.menu-item-has-children .dropdown.menu-item-has-children {
    position: relative;
}
.dropdown.menu-item-has-children .dropdown.menu-item-has-children>.dropdown-menu {
    top: 0;
    left: 100%;
    margin-top: -6px;
    margin-left: -1px;
    -webkit-border-radius: 4px;
    -moz-border-radius: 4px;
    border-radius: 4px;
    box-shadow: 0 1px 6px 0 rgba(0, 0, 0, 0.11);
    background-color: #ffffff;
    border: 1px solid #999;
}
.dropdown.menu-item-has-children .dropdown.menu-item-has-children:hover>.dropdown-menu {
    display: block;
}

.dropdown.menu-item-has-children .dropdown.menu-item-has-children>a:after {
    display: block;
    content: " ";
    float: right;
    width: 0;
    height: 0;
    border-color: transparent;
    border-style: solid;
    border-width: 5px 0 5px 5px;
    border-left-color: #ccc;
    margin-top: 5px;
    margin-right: -10px;
}

.dropdown.menu-item-has-children .dropdown.menu-item-has-children:hover>a:after {
    border-left-color: #fff;
}

.dropdown.menu-item-has-children .dropdown.menu-item-has-children.pull-left {
    float: none;
}

.dropdown.menu-item-has-children .dropdown.menu-item-has-children.pull-left>.dropdown-menu {
    left: -100%;
    margin-left: 10px;
    -webkit-border-radius: 6px 0 6px 6px;
    -moz-border-radius: 6px 0 6px 6px;
    border-radius: 6px 0 6px 6px;
}

JS：

$("#main-nav > ul > li").each(function(){
  var maxHeight = 0;
  var myUl=$("ul", $(this));

  myUl.each(function(){
    maxHeight = maxHeight > $(this).height() ? maxHeight : $(this).height();
  });

  myUl.height(maxHeight);
});