Dropdown

<div id="myDropdown" class="dropdown">
  <button id="myTrigger" class="btn btn-default dropdown-toggle" type="button">
    Dropdown
    <span class="caret"></span>
  </button>
  <ul class="dropdown-menu">
    <li><a tabindex="-1" href="#">Action</a></li>
  </ul>
</div>

YUI().use(
  'aui-dropdown',
  function(Y) {
    new Y.Dropdown(
      {
        boundingBox: '#myDropdown',
        trigger: '#myTrigger'
      }
    ).render();
  }
);

Examples

Dropdown