JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8/themes/dot-luv/jquery-ui.css">
<div id="panel">Click me</div>

JavaScript

function Load(el, script)
{
    el.addEventListener('click',
        function (e)
        {
            this.test = "testing";
            script.apply(this, arguments);
        }, false);
};

Load(document.getElementById("panel"),
    function (e)
    {
        alert(this.test); // test is undefined
    });