JSFiddle - React, Tailwind, and code Playground

HTML

<form action="index.html" method="post">
    <input type="submit" value="Submit me!" />
</form>

CSS

body {
    font-family: sans-serif;
    color: #fff;
    text-align: center;
}
input {
    border: none;
    padding: 20px;
    font-size: 20px;
    background: #036;
    color: #fff;
}

JavaScript

$('form').on('submit', function (e) {
    var form = this;
    $(this).find('input').css('background', 'green');
    setTimeout(function(){
        form.submit();        
    },2000);
    e.preventDefault();
});