title: How to listen for Request complete event? Or how to get response object back
body: <p>I am totally new to firefox extensions and javascript. I have something like this: </p>
  
  <pre><code>var json = JSON.parse(links);
  for (var i = 0; i &lt; json.length; i++) {
      var link = json[i];
      Request({
          url: link.url,
          onComplete: function (response) {
              console.log(response.status);
          }
      }).get();
  }
  </code></pre>
  
  <p>Now I need to do something based on a status of a response object. But I would like to continue in my for loop because I need that link object...</p>
  
  <p>On documentation page of Request <a href="https://developer.mozilla.org/en-US/Add-ons/SDK/High-Level_APIs/request" rel="nofollow">https://developer.mozilla.org/en-US/Add-ons/SDK/High-Level_APIs/request</a> is mentioned 'complete' event which is emitted after response being returned but I really don't know how to listen for events like this. </p>
  
  <p>I really don't know how to approach this but this is result I need: </p>
  
  <pre><code>var json = JSON.parse(links);
  for (var i = 0; i &lt; json.length; i++) {
      var link = json[i];
      Request({
          url: link.url,
          onComplete: function (response) {
              // something
          }
      }).get();
      // I need RESPONSE object here
      if(response.status == 404) {
           // do something with link object
      }
  }
  </code></pre>