title: how to detect whether file download successfully from client side in mean/angular js
body: <p>I have created a chat application in which I have kept file sending functionality over chat windows. Now I want to remove files from the server end when clients successfully download them.
  I'm using the MEAN stack.</p>
  
  <pre><code>router.post("/postChatFileSend",ensureAuthenticatedForPost,function(req,res) {
  
      if (req.body.fileName)
      {
          var filePath = __dirname + '/../public/ChatFile/'+req.body.fileName;
          fs.unlink(filePath, function (err) {
          })
      };
  
      return res.json({"status": true,"messages":"messages read sucessfully"});  
  })
  
  router.get('/downloadChatFile/:fileName',ensureAuthenticatedForPost, function(req, res) {
  
      var file = __dirname + '/../public/ChatFile/'+req.params.fileName;
      res.download(file); 
  });
  </code></pre>