title: Express res.download() not actually downloading file
body: <p>I'm attempting to return generated files to the front end through Express' res.download function. I'm using chrome, but whenever I call that API that executes the following code all that is returned is the same values returned from the Express res.sendFile() function.</p>
  
  <p>I know that res.download uses res.sendFile, but I would like the download function to actually save to the file system instead of just returning the file in the body of the response. </p>
  
  <p>This is my code.</p>
  
  <pre><code>exports.download = function(req,res) {
      var filePath = //somefile that I want to download
      res.download(filePath, 'response.txt', function(err) {
          throw err;
      }
  }
  </code></pre>
  
  <p>I know that the above code at least partly works because I'm getting back, in the response, the contents of the file. However, I want it to be saved onto the file system.</p>
  
  <p>Am I misunderstanding what the download function is supposed to do? Do I just need to take the response data and write it to the file system manually?</p>