JSFiddle - React, Tailwind, and code Playground

HTML

<form id="form" action="/" method="post" name="form" target="_blank">
     <h3><span>Subscribe to Newsletter</span></h3>

    <p class="email_first">
        <label for="email">Your Email</label>
        <input id="EMAIL" class="email" type="email" name="EMAIL"
        value="Your Email Address:" size="30" />
    </p>
    <p class="submit">
        <button type="submit">Send</button>
    </p>
</form>

JavaScript

window.onload = function () {
    var bindEvent = function(element, type, handler) {
        if (element.addEventListener) {
            element.addEventListener(type, handler, false);
        } else {
            element.attachEvent('on' + type, handler);
        }
    };
    var popUp = function () {
        var popup = document.createElement('div');
        popup.className = 'popup';
        popup.id = 'test';
        var cancel = document.createElement('div');
        cancel.className = 'cancel';
        cancel.innerHTML = 'close';
        cancel.onclick = function (e) {
            popup.parentNode.removeChild(popup)
        };
        var message = document.createElement('span');
        message.innerHTML = "This is a test message";
        popup.appendChild(message);
        popup.appendChild(cancel);
        document.body.appendChild(popup);
    };
    bindEvent(document.getElementById("form"), "submit", popUp);
}