JSFiddle - React, Tailwind, and code Playground

HTML

<xml id="test"></xml>

JavaScript

/*
 * For jQuery < 1.4.2, this returns the element; 
 * for jQuery >= 1.4.2, it returns null.
 */
alert( $('#test').length );

// works fine if you pass in the element directly
alert( $(document.getElementById('test')).length );