JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
        <title>Untitled Document</title>

        <script type="text/javascript">
            function demande_jeu(w) {
                var demande_j=confirm("Voulez-vous jouer contre "+w+" ?");
                if (demande_j==true) {
                    alert('confirm passé');
                    var xhr_conf = null;
                    var URL4 = "ajout_dem.php";
                    if(window.XMLHttpRequest)
                        xhr_conf = new XMLHttpRequest();
                    else if(window.ActiveXObject)
                        xhr_conf = new ActiveXObject("Microsoft.XMLHTTP");
                    else
                    {
                        alert("Votre navigateur ne supporte pas l'affichage de cette page (Javascript AJAX)");
                        return;
                    }
                    URL4 = URL4 + "?dest="+w;
                    xhr_conf.open("GET",URL4, false);
                    
                    xhr_conf.onreadystatechange = function()
                    {
                        if(xhr_conf.readyState == 4)
                        {
                            /*rien*/
                        }
                    }
                    
                    xhr_conf.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
                    
                    xhr_conf.send(null);
                }
                else return 0;
            }
            demande_jeu('ok');
        </script>

    
    </head>

    <body>
        
    </body>
</html>