JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container1">
    <form name="reg-form" id="signup" action="" method="post">      
        <div class="sep"></div>
        <div class="inputs">
            <input type = "submit" id="submit" name="submitkey" value="GENERATE KEY" />
        </div>
        
    </form>         
</div>

JavaScript

document.getElementById('signup').onsubmit = function() {
    document.getElementById('submit').disabled = true;
};