Find the error in this JavaScript token refresh handler:

Find the error in this JavaScript token refresh handler:

async function refreshToken(req, res) {
  const refreshToken = req.body.refreshToken;
  if (!refreshToken) {
    res.status(400).json({ error: 'No refresh token provided' });
  }
  if (refreshToken === 'valid') {
    res.status(200).json({ accessToken: 'newAccessToken' });
  } else {
    res.status(401).json({ error: 'Invalid refresh token' });
  }
}