title: Office-js Excel: Get filename of newly saved file
body: <p>How can I get filename of newly saved file?
  Normally, I can get the filename using:</p>
  
  <pre><code>Office.context.document.url
  </code></pre>
  
  <p>However, when the user opens a new workbook, it doesn't really have a filename, and oddly enough this line of code doesn't work even after they save it.
  Instead, they have to save it, close, and then re-open the file for that code to read their filename.</p>
  
  <p>Is there a way to refresh the Office context after a save, or another workaround for this?</p>