title: jQuery Ajax request async false
body: <p>I'd like to know why I get this error if I send a ajax request like: </p>
  
  <pre><code>$.ajax({
      url: "testOperation.php",
      async: false,
      data: compareHeure,
      success: function (data, statusRequest) {
  })
  </code></pre>
  
  <p>error: </p>
  
  <blockquote>
    <p><em>Synchronous XMLHttpRequest on the main thread is deprecated because of
    its detrimental effects to the end user's experience. For more help,
    check <a href="https://xhr.spec.whatwg.org" rel="nofollow">https://xhr.spec.whatwg.org</a></em>/.</p>
  </blockquote>
  
  <p>Is there a problem ?</p>
  
  <p>Thanks,</p>