JSFiddle - React, Tailwind, and code Playground

HTML

<div class="header">asdasdsadsad</div>
<div class="nav">nav</div>
<div class="myEle"></div>

CSS

.header { margin:10px 5px; padding:5px; border 2px solid #fff;  }
.nav { height:100px; margin:5px; padding: 2px 5px; border 1px solid #fff;  }

JavaScript

var myEleTop = $('.header').outerHeight(true) + $('.nav').outerHeight(true);

alert(myEleTop);