JSFiddle - React, Tailwind, and code Playground

JavaScript

function HTMLinXHR() {
  if (!window.XMLHttpRequest)
    return false;
  var req = new window.XMLHttpRequest();
  req.open('GET', window.location.href, false);
  try {
    req.responseType = 'document';
  } catch(e) {
    return true;
  }
  return false;
}

var msg = HTMLinXHR() ? "Your browser supports HTML in XHR, yay! \\o/" : "Your browser does not support HTML in XHR, booo! :-(";

alert(msg);