JSFiddle - React, Tailwind, and code Playground

HTML

<div class="header-wrapper" style="height:20px;">Head1</div>
<div class="header-wrapper" style="height:20px;">Head2</div>
<div id="top-bar" style="height:20px;">TOP</div>
<div id="new-showroom-header" style="height:20px;">SHOW ROOM</div>

JavaScript

$(function() {
  var hdr = 0;
  $('.header-wrapper, #top-bar, #new-showroom-header').each(function() {
    hdr += $(this).height();
  });
  alert(hdr);
});