JSFiddle - React, Tailwind, and code Playground
by Kai
HTML
<span rel="kai">Kai</span>
<span rel="khary">Khary</span>
JavaScript
// IE
var elements = document.querySelectorAll('*[rel]') || document.evaluate("//*[@rel]", document, null, XPathResult.ORDERED_NODE_SNAPSHOT_TYPE, null) ||
oXmlDom.documentElement.selectNodes("[@rel]");
alert(elements.length);