drop down menu header code example

Example 1: create a dropdown in html bootstrap

<div class="dropdown">
  <button class="btn btn-secondary dropdown-toggle" type="button" id="dropdownMenu2" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
    Dropdown
  </button>
  <div class="dropdown-menu" aria-labelledby="dropdownMenu2">
    <button class="dropdown-item" type="button">Action</button>
    <button class="dropdown-item" type="button">Another action</button>
    <button class="dropdown-item" type="button">Something else here</button>
  </div>
</div>

Example 2: dropdown navigation menu

li {
 display: block;
 transition-duration: 0.5s;
}

li:hover {
  cursor: pointer;
}

ul li ul {
  visibility: hidden;
  opacity: 0;
  position: absolute;
  transition: all 0.5s ease;
  margin-top: 1rem;
  left: 0;
  display: none;
}

ul li:hover > ul,
ul li ul:hover {
  visibility: visible;
  opacity: 1;
  display: block;
}

ul li ul li {
  clear: both;
  width: 100%;
}