JSFiddle - React, Tailwind, and code Playground

HTML

<div></div>

<div class="height">

</div>
<span></span>

CSS

div {
    height: 1vh;
    background: green;
}

.height {
  height: 3px;
  background: red;
}

JavaScript

$(document).ready( function() {
    var divH = $("div").height();
    var divH = $(".height").height();
    $("span").html( divH );
});