JSFiddle - React, Tailwind, and code Playground

HTML

<form id="sign" name="sign" method="post">
    <input type="text" name="username" placeholder="Username"><br>
    <input type="text" name="email" placeholder="Email"><br>
    <input type="password" name="password" placeholder="Password"><br>
    <input type="submit" name="submit" value="Signup" id="submit">
</form>

JavaScript

var form = document.getElementById('sign'),
    submit = document.getElementById('submit');

submit.onclick = function() {
	submit.value='Submitting ..';
  form.submit();
};