JSFiddle - React, Tailwind, and code Playground

HTML

<div class="first">Hello g World</div>
<div class="second">Hello g World</div>

CSS

div {
  background-color: rgba(255, 0, 0, 0.3);
  margin-top: 50px;
  vertical-align: text-bottom;
}

.first {
  font-size: 16px;
}

.second {
  font-size: 30px;
}

JavaScript

var d = document.getElementsByTagName('div');
for(var i = 0 ; i < d.length ; i++) {
  d[i].style.height= d[i].offsetHeight*0.8+'px';
}