jQuery AJAX表单未提交

I'm trying to submit a form through AJAX but not submit when click button. The HTML is just a standard form with method="post" and my jQuery code is as follows:

$('#form-submit').on('submit', function(e) {
  e.preventDefault();
  var formData = new FormData(this);
  $.ajax({
    type: 'POST',
    url: $('#form-submit').attr('action'),
    data: formData,
    cache: false,
    contentType: false,
    processData: false,
    success: function(result) {
      $('#server-results').html(result);
    }
  });
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<form id="form-submit" role="form" method="post" action="mailer.php" enctype="multipart/form-data">
  <div class="form-group"><input type="text" id="nome" name="nome" placeholder="Name" required /></div>
  <div class="form-group"><input type="text" id="cognome" name="cognome" placeholder="Nachname" /></div>
  <div class="form-group"><input type="email" id="email" name="email" placeholder="Email" required /></div>
  <div class="form-group"><input type="tel" id="telefono" name="telefono" placeholder="Telefonnummer" /></div>
  <div class="form-group"><textarea name="richiesta" id="richiesta" placeholder="Nachricht"></textarea></div>
  <div class="form-check-inline">
    <input type="checkbox" name="check" class="form-check-input" id="exampleCheck1" required>
    <label class="form-check-label" for="exampleCheck1">Ich bin mit der Verarbeitung personenbezogener Daten einverstanden, wie in den <a style="color: rgba(164,131,81,1)" href="datenschutzerklarung.php" target="_blank" title="datenschutzerkl&auml;rung">Datenschutzerkl&auml;rung</a> der Website angegeben</label>
  </div>
  <div class="form-group"><input id="invia" type="submit" name="invia" value="SENDEN" /></div>
</form>
<div id="server-results"></div>

</div>