JSFiddle - React, Tailwind, and code Playground

HTML

<form method="post" id="kontakt">
     <h3 class="title">Nur nicht sch&uuml;chtern !</h3>

    <input type="text" name="von" placeholder="Name" id="von">
    <input type="text" name="mail" placeholder="E-mail" id="mail">
    <textarea name="message" placeholder="Nachricht" id="nachricht"></textarea>
    <input id="submit" type="button" value="senden">
    </submit>
</form>
<div id="response"></div>

CSS

<?php

$data=$_POST['serialize'];
$von=$data['von'];
$mail=$data['mail'];  
$nachricht=$data['nachricht'];    

?>

JavaScript

$(document).ready(function () {
    $("#submit").click(function () {
        if ($("#von").val() == "" || $("#mail").val() == "" || $("#nachricht").val() == "") {
            $("#response").html("bitte fülle alle felder aus!");
        } else {
            $("#response").html("Lade...");
            $.ajax({
                type: "POST",
                data: $('#kontakt').serialize(),
                url: "/echo/json/",
                success: function (msg) {
                    alert(msg);
                    $("#response").html(msg);
                }

            });
        }

    });

});