title: How to get access to XHR in $http with Angular?
body: <p>Currently I am try to implement the upload function with Angular. At first I used XmlHttpRequest but later I changed it to $http. So I found that I could't get access to
  XmlHttpRequest to create a progress bar with $http. Below is my code. Any suggestions about create a progress bar when uploading images? Thanks.</p>
  
  <pre><code>    $http({
            method: 'POST',
            url: upload_url,
            data: fd, 
            headers: {'Content-Type': undefined}, 
            transformRequest: angular.identity
            })
  </code></pre>