function generateTokenBehavior(data) {
    let username, password;
    // checks for authorisation headers
    if (_.has(data, 'headers.authorization')) {
      username = auth(data).name;
      password = auth(data).pass;
    } ...
    ... operations on username and password ...
    responseData.status = 200;
    responseData.data = {meta:{token}};
    return responseData;
}

function generateToken(req, res, next) {
    const responseData = generateTokenBehavior(req);
    return res.status(responseData.status).json(responseData.data);
}