JSFiddle - React, Tailwind, and code Playground

HTML

<iframe id="iframeFromParser" srcdoc="From parser">

</iframe>

JavaScript

const child1 = document.getElementById("iframeFromParser");
const child2 = document.createElement("iframe");
document.body.insertBefore(child2, child1);
child2.contentWindow.requestAnimationFrame(() => {
  console.log("rAF for late-inserted but first-in-DOM iframe");
});
child1.contentWindow.requestAnimationFrame(() => {
  console.log("rAF for early-inserted but last-in-DOM iframe");
});