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) {
 
   $('<input>').attr({
        type: 'hidden',
        name: 'extra data1',
        value: 'extra value 1'
    }).appendTo($(this));    
    data = $(this).serialize();
    console.log(data);
    
});