JSFiddle - React, Tailwind, and code Playground

HTML

<div id="inline" class="various2">
      <div style="padding:20px; display: none;" id="my_first_div">
             This is the content of that shows inside the fancybox modal. CONTENT 1
       </div>
    <div style="padding:20px; display: none;" id="my_second_div">
             This is the content of that shows inside the fancybox modal. CONTENT 2
       </div>
</div>

JavaScript

var value1 = 'my_first_div';
var value2 = 'my_second_div';
var chosenValue = Math.random() < 0.5 ? value1 : value2;
var chosenDiv = document.getElementById(chosenValue);
chosenDiv.style.display = "block";