This is a simple dropdown-menu core functions, To create a dropdown menu add the following HTML code:

<div class="dropdown-menu">
    <div class="btn-content btn">
      Dropdown menu
      <img
        src="./dropdown-arrow.svg"
        class="dropdown-icon"
        width="15px"
        height="15px"
      />
    </div>
    <ul class="dropdown-content hidden">
      <li class="btn">
        <a href="/blanck.html" rel="noopener noreferrer"># first button</a>
      </li>
      <li class="btn">
        <a href="#" rel="noopener noreferrer"># second button</a>
      </li>
      <li class="btn">
        <a href="#" rel="noopener noreferrer"># third button</a>
      </li>
    </ul>
  </div>