JSFiddle - React, Tailwind, and code Playground

JavaScript

let iframe = document.createElement("iframe");
iframe.onload = () => {
  iframe.contentWindow.focus();
  let doc = iframe.contentDocument;
  doc.designMode = "on";
  doc.body.focus();
  //let editor = doc.getElementById("editor");
  //editor.focus();
  //doc.getSelection().collapse(editor, 0);
  iframe.style.display = "none";
  doc.execCommand("insertText", false, "foo");
  iframe.style.display = "block";
};
iframe.srcdoc = "<div id=\"editor\" contenteditable></div>";
document.body.appendChild(iframe);