title: Mootools XHR request: synchronous and/or chained?
body: <p>I have a couple of XHR requests, which are handled by the Mootools Request class. This class offers some options to time the requests appropriately. What I'm doing:</p>
  
  <ol>
  <li>XHR: Post form data</li>
  <li>XHR: Refresh main pane</li>
  <li>XHR: Refresh subpane</li>
  </ol>
  
  <p>Of course, requests 2 &amp; 3 must wait before 1 is finished. So these are triggered within the <code>onComplete</code> event handler. However, the Request class offers options for handling multiple XHR requests. My question is about these two:</p>
  
  <ol>
  <li><p>The option <code>link</code> can be set to <code>chain</code>, in order to 'chain' them, or, as the Moo docs state: </p>
  
  <blockquote>
    <p>Any calls made to start while the request is running will be chained up, and will take place as soon as the current request has finished, one after another.</p>
  </blockquote></li>
  <li><p>The option <code>async</code> can be set to <code>false</code>, to prevent later requests from executing. According to the Moo docs:</p>
  
  <blockquote>
    <p>If set to false, the requests will be synchronous and freeze the browser during request.</p>
  </blockquote></li>
  </ol>
  
  <p>Apart from the browser freezing part, what is exactly the difference? Which one should I use for request no. 1? Is it better to do it synchronously, so I'm sure nothing else executes in the meantime? And how about using both, does that make any sense?</p>