JSFiddle - React, Tailwind, and code Playground
HTML
<script src="http://getfirebug.com/firebug-lite-debug.js"></script>
<xml id="test"></xml>JavaScript
/*
* For jQuery < 1.4.2, this returns the element;
* for jQuery >= 1.4.2, it returns null.
*/
console.log( $('#test').length );
// works fine if you pass in the element directly
console.log( $(document.getElementById('test')).length );