JSFiddle - React, Tailwind, and code Playground

HTML

<div id="wrapper">
    <dl class="dropdown">
      <dt id="two-ddheader" onmouseover="ddMenu('one',1)" onmouseout="ddMenu('one',-1)" timer="8904">PS&amp;R Global Training</dt>
      <dd id="two-ddcontent" onmouseover="cancelHide('one')" onmouseout="ddMenu('one',-1)" timer="8905" maxh="224" style="filter: alpha(opacity=1.7857142857142858); display: block; height: 4px; opacity: 1.78571428571429e-02">
                 <ul>
            <li>
               <a class="underline" href="https://partners.dupont.com/sites/teams_PSR/LearningandDevelopment/psr_global_training/SitePages/Home.aspx">PS&R Upcoming Training</a></li>
            <li></li>
            <li>
               <a class="underline" href="https://partners.dupont.com/sites/teams_PSR/LearningandDevelopment/psr_global_training/Lists/Courses/calendar.aspx">Upcoming Training Calender View</a></li>
               <li>
               <a class="underline" href="https://partners.dupont.com/sites/teams_PSR/LearningandDevelopment/psr_global_training/SitePages/Training%20metrics%20by%20BU.aspx">Training Attendance Metrics by BU</a></li>
            <li>
            </li>
            <li>
            </li>
         </ul>
      </dd>
   </dl>
   <dl class="dropdown">
            <dt id="two-ddheader" onmouseover="ddMenu('two',1)" onmouseout="ddMenu('two',-1)" timer="8898">SharePoint Training</dt>
      <dd id="two-ddcontent" onmouseover="cancelHide('two')" onmouseout="ddMenu('two',-1)" timer="8901" maxh="136" style="filter: alpha(opacity=2.9411764705882355); display: block; height: 4px; opacity: 2.94117647058824e-02">
            <ul>
            <li>
              <a class="underline" href="ttps://partners.dupont.com/sites/teams_PSR/LearningandDevelopment/SPtraining_support/SitePages/Home.aspx">PS&R Training Presentations</a></li>
            <li>
               <a class="underline"...

CSS

#wrapper {
	width: 900px;
	padding: 25px;
	margin: 0 auto
}
.dropdown {float:left; padding-right:5px}
.dropdown dt {width:155px; border:2px solid #9ac1c9; padding:8px; font-weight:bold; cursor:pointer; background:https://partners.dupont.com/sites/teams_PSR/LearningandDevelopment/Shared%20Documents/header.gif}
.dropdown dt:hover {background:https://partners.dupont.com/sites/teams_PSR/LearningandDevelopment/Shared%20Documents/header_over.gif}
.dropdown dd {position:absolute; width:175px; display:none; background:#fff; z-index:200; opacity:0; padding:0; margin:0}
.dropdown ul {width:171px; border:2px solid #9ac1c9; list-style:none; border-top:none; padding:0; margin:0}
.dropdown li {padding:0; margin:0}
.dropdown a, .dropdown a:active, .dropdown a:visited {display:block; padding:5px; color:#333; text-decoration:none; background:#eaf0f2; width:161px}
.dropdown a:hover {background:#d9e1e4; color:#000}
.dropdown .underline {border-bottom:1px solid #b9d6dc}

JavaScript

var DDSPEED = 10;
var DDTIMER = 15;

// main function to handle the mouse events //
function ddMenu(id,d){
  var h = document.getElementById(id + '-ddheader');
  var c = document.getElementById(id + '-ddcontent');
  clearInterval(c.timer);
  if(d == 1){
    clearTimeout(h.timer);
    if(c.maxh && c.maxh <= c.offsetHeight){return}
    else if(!c.maxh){
      c.style.display = 'block';
      c.style.height = 'auto';
      c.maxh = c.offsetHeight;
      c.style.height = '0px';
    }
    c.timer = setInterval(function(){ddSlide(c,1)},DDTIMER);
  }else{
    h.timer = setTimeout(function(){ddCollapse(c)},50);
  }
}

// collapse the menu //
function ddCollapse(c){
  c.timer = setInterval(function(){ddSlide(c,-1)},DDTIMER);
}

// cancel the collapse if a user rolls over the dropdown //
function cancelHide(id){
  var h = document.getElementById(id + '-ddheader');
  var c = document.getElementById(id + '-ddcontent');
  clearTimeout(h.timer);
  clearInterval(c.timer);
  if(c.offsetHeight < c.maxh){
    c.timer = setInterval(function(){ddSlide(c,1)},DDTIMER);
  }
}

// incrementally expand/contract the dropdown and change the opacity //
function ddSlide(c,d){
  var currh = c.offsetHeight;
  var dist;
  if(d == 1){
    dist = (Math.round((c.maxh - currh) / DDSPEED));
  }else{
    dist = (Math.round(currh / DDSPEED));
  }
  if(dist <= 1 && d == 1){
    dist = 1;
  }
  c.style.height = currh + (dist * d) + 'px';
  c.style.opacity = currh / c.maxh;
  c.style.filter = 'alpha(opacity=' + (currh * 100 / c.maxh) + ')';
  if((currh < 2 && d != 1) || (currh > (c.maxh - 2) && d == 1)){
    clearInterval(c.timer);
  }
}