title: xmlHttpRequest.onerror handler use case
body: <p>What sort of situations could cause this handler to be called? I'm not finding any instance where this method throws an error.</p>
  
  <p>I tried with the device offline, I get <code>xmlHttpRequest.status = 0</code> but no error.</p>
  
  <p>Question is what sort of situations can I create in order to test functionality of this handler.</p>
  
  <pre><code>var xmlhttp = new XMLHttpRequest(),
    method = 'GET',
    url = 'https://developer.mozilla.org/';
  
  xmlhttp.open(method, url, true);
  xmlhttp.onerror = function () {
    console.log("** An error occurred during the transaction");
  };
  xmlhttp.send();
  </code></pre>
  
  <p>From: <a href="https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequestEventTarget/onerror" rel="noreferrer">https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequestEventTarget/onerror</a></p>