title: Javascript save data to file system (with user prompt)
body: <p>What is the best way to achieve the below in latest latest browsers (with html5 support). I mainly target Google Chrome.</p>
  
  <p>In my application, data is manipulated through javascript and needs to write output to the file system with a browser prompt (save as dialog). I am not sure about the security restrictions to write to file system, but I am not planning anonymous write (but user is prompted, and selects the location). </p>
  
  <p>I see <a href="http://updates.html5rocks.com/2011/08/Saving-generated-files-on-the-client-side" rel="noreferrer">saveAs</a> not natively supported yet. With my research, I see few options.</p>
  
  <ol>
  <li><a href="https://github.com/eligrey/FileSaver.js" rel="noreferrer">https://github.com/eligrey/FileSaver.js</a></li>
  <li>a.download (<a href="http://html5-demos.appspot.com/static/a.download.html" rel="noreferrer">http://html5-demos.appspot.com/static/a.download.html</a>)</li>
  <li>web filesystem</li>
  <li>object URLs</li>
  </ol>
  
  <p>FileServer falls back to 2,3,4 if no native support and I may use it. But, I don't find a way to open a Save As dialog. It just save a file in default location (downloads folder in mac).</p>
  
  <p>Which option would you use to get a good support in latest browsers? 
  How can get open the Save As dialog and let the user name the file.</p>
  
  <p>Thanks.</p>