JSFiddle - React, Tailwind, and code Playground

HTML

<html>

<body>
  <p>
    This text should change once you've changed the dropdown below.
  </p>
  
  <p>
    Change font here:
  </p>

  <select id="fontToggle" onChange="changeFont()">
    <option value="0" selected="selected">None</option>
    <option value="courier">Courier</option>
    <option value="comic">Comic Sans</option>
    <option value="roman">Times New Roman</option>
  </select>
</body>

</html>

JavaScript

function changeFont(){
var drop = document.getElementById("fontToggle");
var fchoice = drop.options[drop.selectedIndex].value;
var family = "";

switch(fchoice){
	case "courier":
  	family = "Courier";
    break;
	case "comic":
  	family = "Comic Sans MS";
    break;
	case "roman":
  	family = "Times New Roman";
    break;
}

console.log(family);
document.body.style.fontFamily = family;
}