JSFiddle - React, Tailwind, and code Playground

by espyMur

HTML

<form id="contact" action="" method="post">
    <input type="text" name="firstname" id="firstname">
    <input type="text" name="lastname" id="lastname">
    <input type="text" name="age" id="age">
     <input type="hidden" name="refer_page" id="refer_page" value="success.php">
    <input type="submit" value="submit">
</form>

JavaScript

let theForm =  document.getElementById("contact");
theForm.onsubmit = function(event) {
    event.preventDefault();
    
    let rawData = new FormData(theForm);
    let data = {};
    
   for(let pair of rawData.entries()) {
     data[pair[0]] = pair[1];
    }
    let contactData = JSON.stringify(data);
    console.warn(contactData);
};