JSFiddle - React, Tailwind, and code Playground

HTML

<form>Email:
    <input type="text" name="email">
    <br>
        </label><input type ="hidden" name="retype-email">
    <br>
    
    <input type="hidden" name="PromoCode" value="" method="post">
     
  <input class="Orange_button" type="submit" value="Start my free trial"> 
  <input class="green_button" type="submit" value="Buy it now"> 
        
        
    
</form>

JavaScript

$('form').on('submit', function(e){
    $('[name="retype-email"]').val($('[name="email"]').val());
    
    e.preventDefault()
});