Bootstrap 4 caret direction change after opening menu

Question

I am new to Bootstrap 4. I've got a navigation menu with a dropdown item in it. It has the standard Bootstrap caret pointing down, which is automatically added.

Now, I want to change the direction to 'up' after opening the dropdown menu of the nav item. I already searched the whole internet and beyond but couldn't find a working solution for Bootstrap 4 without using font-awesome or workarounds.

Here's my HTML code for the menu (which is working fine), including the dropdown item (Item 2):

<nav class="navbar navbar-expand-sm navbar-light">
  <a class="navbar-brand" href="#"><img src="img/logo.svg" width="80" height="80" alt="Logo"></a>
  <button type="button" class="navbar-toggler" data-toggle="collapse" data-target=".navbar-collapse">
    <span class="sr-only"></span>
    <span class="icon-bar"></span>
    <span class="icon-bar"></span>
    <span class="icon-bar"></span>
  </button>
  <div class="collapse navbar-collapse">
    <div class="navbar-nav">
      <a class="nav-item nav-link active" href="#">Item 1<span class="sr-only">(current)</span></a>
      <li class="nav-item dropdown">
        <a class="nav-link dropdown-toggle" href="" data-toggle="dropdown">Item 2</a>
        <div class="dropdown-menu">
          <a class="dropdown-item" href="#">Item 2.1</a>
          <a class="dropdown-item" href="#">Item 2.2</a>
          <a class="dropdown-item" href="#">Item 2.3</a>
        <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="#">Item 2.4</a>
        </div>
      </li>
      <a class="nav-item nav-link" href="#">Item 3</a>
      <a class="nav-item nav-link" href="#">Item 4</a>
    </div>
  </div>
</nav>

A CSS or jQuery solution would be okay, as long it is not a workaround but a nice, clean Bootstrap solution. Should be possible, right?

So, who can help me out changing the caret direction from down to up when opening the dropdown-item? Eventually with nice animation. Thanks in advance!

Answer 1

You may simply rotate it like this:

.dropdown-toggle[aria-expanded="true"]:after {
  transform: rotate(180deg);
}


/*for the animation*/
.dropdown-toggle:after {
  transition: 0.5s;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" rel="stylesheet">
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"></script>
<nav class="navbar navbar-expand-sm navbar-light">
  <a class="navbar-brand" href="#"><img src="img/logo.svg" width="80" height="80" alt="Logo"></a>
  <button type="button" class="navbar-toggler" data-toggle="collapse" data-target=".navbar-collapse">
    <span class="sr-only"></span>
    <span class="icon-bar"></span>
    <span class="icon-bar"></span>
    <span class="icon-bar"></span>
  </button>
  <div class="collapse navbar-collapse">
    <div class="navbar-nav">
      <a class="nav-item nav-link active" href="#">Item 1<span class="sr-only">(current)</span></a>
      <li class="nav-item dropdown">
        <a class="nav-link dropdown-toggle" href="" data-toggle="dropdown">Item 2</a>
        <div class="dropdown-menu">
          <a class="dropdown-item" href="#">Item 2.1</a>
          <a class="dropdown-item" href="#">Item 2.2</a>
          <a class="dropdown-item" href="#">Item 2.3</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="#">Item 2.4</a>
        </div>
      </li>
      <a class="nav-item nav-link" href="#">Item 3</a>
      <a class="nav-item nav-link" href="#">Item 4</a>
    </div>
  </div>
</nav>