JSFiddle - React, Tailwind, and code Playground

HTML

<div id="window">Scale the window</div>

CSS

.t-entry-excerpt {
    font-size:2em;
}

JavaScript

document.getElementsByClassName('t-entry-excerpt').setScaledFont = function (f) {
   var s = this.offsetWidth,
       fs = s * f;
   this.style.fontSize = fs + '%';
   return this
   };

   document.getElementsByClassName('t-entry-excerpt').setScaledFont(0.35);
   window.onresize = function () {
   document.getElementsByClassName('t-entry-excerpt').setScaledFont(0.35);
   }