如何在节点js中插入注册数据

Question

exports.signup = function (req, res) {
  // For security measurement we remove the roles from the req.body object
  delete req.body.roles;

  // Init user and add missing fields
  var user = new User(req.body);
  user.provider = 'local';
  user.displayName = user.firstName + ' ' + user.lastName;

  // Then save the user
  user.save(function (err) {
    if (err) {
      return res.status(400).send({
        message: errorHandler.getErrorMessage(err)
      });
    } else {
      // Remove sensitive data before login
      user.password = undefined;
      user.salt = undefined;

      req.login(user, function (err) {
        if (err) {
          res.status(400).send(err);
        } else {
          res.json(user);
        }
      });
    }
  });
};

我的代码中没有理解下面两行的含义     1）删除req.body.roles;     2）req.login（user，function（err）{

任何人请给我有效的解释