JSFiddle - React, Tailwind, and code Playground

HTML

one
<script>alert(run());</script>
two

JavaScript

function run()
{
    var $mark = $('<mark>');
    $mark.appendTo('body');
    var bg = $mark.css('backgroundColor');
    if (/rgb\(255\, 255\, 0\)/.test(bg)) return true;
    else return false;
}