JSFiddle - React, Tailwind, and code Playground

HTML

<form id="my_form">
    <input type="text" name="foo" value="bar">
    <input type="submit">
</form>

JavaScript

$("#my_form").on("submit", function (e) {
 
   $('<input type="hidden" name="extra data1" value="extra value 1">').appendTo($(this));
    
    data = $(this).serialize();
    console.log(data);
    alert(data);
    
});