JSFiddle - React, Tailwind, and code Playground

HTML

<div id="result"></div>

JavaScript

$(document).ready(function(){
  var xmlstr = '<test><val attr="&lt;popo" /></test>';
  var xmldoc = $(xmlstr);
  xmldoc.find('val').attr('pilou', '<toto>&');
  $("#result").text(xmldoc.html());
});