JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/sweetalert2@10/dist/sweetalert2.all.min.js"></script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/limonte-sweetalert2/11.1.9/sweetalert2.min.css">
<?

if( isset($_POST['btn-login']) ) {	  
$mails = new PHPMailer;
$content = "xxxx";
$mails->IsSMTP();
$mails->send();
}

?>


<form name="form1" id="form1" class="form1" method="post">
<input class="form-control"  name="oggetto" id="oggetto" required placeholder="Oggetto"  >
<input class="btn-login" type="submit" name="submit" id="btn-submit" value="Invia"/>
</form>

JavaScript

$('#btn-submit').on('click',function(e){
                e.preventDefault();
                var form = $('.form1');
                console.log("hello");
                swal.fire({
                    title: "Inviare il msg?",
                    icon: 'warning',
                    showCancelButton: true,
                    confirmButtonColor: "#DD6B55",
                    confirmButtonText: "Si",
                }).then(function (result){
                    if(result.value === true){
                    console.log(form);
                    $('.form1').submit();
                  }
                });
            });