JSFiddle - React, Tailwind, and code Playground

CSS

</style>
<!-- yup, that's how you can control <head> in jsfiddle, apparently -->
<meta http-equiv="content-security-policy" content="require-trusted-types-for 'script'">
<style>

JavaScript

trustedTypes.createPolicy('default', {
createHTML: (s) => 'default policy value',
});

// Select the node that will be observed for mutations
const f = document.createElement("iframe");
document.body.appendChild(f);

const config = { attributes: true };

// Callback function to execute when mutations are observed
const callback = (mutationList, observer) => {
  for (const mutation of mutationList) {
      console.log(mutation.attributeName, mutation.oldValue, mutation.target.getAttribute(mutation.attributeName));
  }
  observer.disconnect();
};

const observer = new MutationObserver(callback);

observer.observe(f, config);

f.setAttribute('srcdoc', 'raw value');