JSFiddle - React, Tailwind, and code Playground

HTML

<form id="f1" action="action1.html">
form1 <button id="btn1" onclick="testaction(this); return false;" >test form 1</button>
</form>

JavaScript

function testaction(element) {
    var e = $(element);
    var form = e.parent('form').get(0);

    alert(form.id); // undefined!!
    alert(form.action); // undefined!!
    alert(document.forms[0].action); //http://localhost/action1.html
}