refactoring-nodejs-extract-logic.js

router.get("/some-file", function (req, res) {
  const url = "./data/some-file.ext";

  function handleError (err) {
    res.writeHead(404);
    res.end();
  }

  function handleSuccess (file) {
    res.writeHead(200, { "Content-Type": "application/octet-stream" });
    res.write(file);
    res.end();
  }

  readFile(url, function (err, file) {
    if (err) {
      handleError(err);
    } else {
      handleSuccess(file);
    }
  });
});