JSFiddle - React, Tailwind, and code Playground

HTML

<ul class="sub-menu">
    <li id="menu-item-75"><a>a link</a></li>
</ul>

CSS

ul.sub-menu { margin-top:50px;}


ul.sub-menu li a {
    position: relative;
    text-decoration: none;
  }
ul.sub-menu li a:after {
    content: attr(data-tooltip);
    position: absolute;
    bottom: 130%;
    left: 20%;
    background: #ffcb66;
    padding: 5px 15px;
    color: black;
    -webkit-border-radius: 10px;
    -moz-border-radius   : 10px;
    border-radius        : 10px;
    white-space: nowrap;
    opacity: 0;
     /* At time of this creation, only Fx4 doing pseduo transitions */
    -webkit-transition: all 0.4s ease;
    -moz-transition   : all 0.4s ease;
  }
ul.sub-menu li a:before {
    content: "";
    position: absolute;
    width: 0;
    height: 0;
    border-top: 20px solid #ffcb66;
    border-left: 20px solid transparent;
    border-right: 20px solid transparent;
    /* At time of this creation, only Fx4 doing pseduo transitions */
    -webkit-transition: all 0.4s ease;
    -moz-transition   : all 0.4s ease;
    opacity: 0;
    left: 30%;
    bottom: 90%;
  }
ul.sub-menu li a:hover:after {
    bottom: 100%;
  }
ul.sub-menu li a:hover:before {
    bottom: 70%;
  }
ul.sub-menu li a:hover:after, ul.sub-menu li a:hover:before {
    opacity: 1;
  }

JavaScript

// set the tooltip content
jQuery('li#menu-item-75 a').attr('data-tooltip', 'w00t');