title: Input type file - how to access files property?
body: <p>I've started to rewrite some of my Javascript code in Typescript to learn how Typescript works. However I'm at a point where the Type annotations make some trouble.</p>
  
  <p>I try to get a file from an input field, in Javascript I do</p>
  
  <pre><code>var file = document.getElementById('upload_files').files[0];
  </code></pre>
  
  <p>what I now try to write in typescript but I can't figure out, how I've to cast to access the <code>.files</code> property in Typescript.</p>