title: JQuery JSONP randomly generated callback function
body: <p>I'm using JQuery to make JSONP requests and the documentation is quite confusing.</p>
  
  <p>I have several questions:</p>
  
  <ul>
  <li>A JSONP call is always async, is that correct? So the <code>async:false</code> would be simply ignored?</li>
  <li>If the <code>jsonpCallback</code> parameter is specified, this function will be executed when the data are retrieved. But right after, also the <code>success</code> callback will be executed. Jquery advices NOT to specify the <code>jsonpCallback</code> function(only for <em>caching</em>?). What is the role of this function in relation with the <code>success</code> function?</li>
  <li>If the <code>jsonpCallback</code> is not specified a random callback function will be created and attached to the <code>window</code> object. Something like <code>jQuery1360574548776335413_1776656584447</code>, what is its role? How does it work? Does it have any relation with the <code>success</code> function?</li>
  <li>Is the <code>error</code> callback never called?</li>
  </ul>
  
  <p>Here's my code:</p>
  
  <pre><code>(function($) {
      var url = "https://www.googleapis.com/books/v1/volumes/zyTCAlFPjgYC";
      $.ajax({
          type: 'GET',
          url: url,
          // JSONP always async?
          async: false,
          jsonp: "callback",
          jsonpCallback: 'jsonCallback',
          contentType: "application/json",
          dataType: 'jsonp',
          success: function(json) {
              console.dir(json);
          },
          // Error never called?
          error: function(e) {
              console.log(e.message);
          }
      });
  })(jQuery);
  
  function jsonCallback(json) {
      $(".test").html(json.volumeInfo.title);
  }
  </code></pre>