How to make these two similar blocks codes reusable?

I have two similar codes and I think it could be reusable but not sure where to start. If you can show me and example or link me to an article that would be fine.

I have this one block that updates a user info.

exports.updateUser = function(req, res, next) {
    User.findById(req.params.id, function(err, user) {
        if (err) {
            return next(err);
        }
        user.email = req.body.email || '';
        user.firstname = req.body.firstname || '';
        user.lastname = req.body.lastname || '';

        user.save(function(err) {
            if (err) {
                return next(err);
            }
            req.flash('success', {
                msg: 'User information updated.'
            });
            res.redirect('/users');
        });
    });
};

and this block that updates my user account info.

exports.updateAccount = function(req, res, next) {
    User.findById(req.user.id, function(err, user) {
        if (err) {
            return next(err);
        }
        user.email = req.body.email || '';
        user.firstname = req.body.firstname || '';
        user.lastname = req.body.lastname || '';

        user.save(function(err) {
            if (err) {
                return next(err);
            }
            req.flash('success', {
                msg: 'Profile information updated.'
            });
            res.redirect('/account');
        });
    });
};

How can I make a reusable update.