JSFiddle - React, Tailwind, and code Playground

HTML

<button id="button">Send Message</button>
<iframe id="frame" src="http://jsfiddle.net/mattography/a330qv87/show" style="width: 100%; height: 600px;"></iframe>

CSS

html, body {
    font-family:"Trebuchet MS", Verdana, sans-serif;
}

JavaScript

var el = document.getElementById('button');

 var getFontFamily = function () {

     for (var i = 0; i < document.styleSheets.length; i++) {
         for (var j = 0; j < document.styleSheets[i].rules && document.styleSheets[i].rules.length; j++) {

             if (document.styleSheets[i].rules[j].style.fontFamily) {
                 return document.styleSheets[i].rules[j].style.fontFamily;
             }
         }
     }

     return 'not-found';
 };