mongodb node.js coping Id without ObjectId

Question

In my node.js code when I'm appending customer with an Id to my cart, but it is appending like this

"customer" : ObjectId("5755251e4e2210ce2f953407") is there a way to get like this

"customer" : "5755251e4e2210ce2f953407"


function login(req, res, next) {
    db.users.findOne({
            'email': req.body.email
        }, function(err, user) {
            if (err) return next(err);
            if (!user) {
                return res.status(401).send("user not found");
            }
            if (lib.getSaltedPassword(req.body.password) != user.password) {
                return res.status(401).send("wrong password");
            }
            req.session.user = user;
            if (req.session.cart) {
                req.session.cart.forEach(function(data) {
                    data.customer = user._id
                })
                db.carts.insert(req.session.cart, function(err, user_cart) {
                    if (err) return next(err);
                })
            }
        }
         res.send({
            message: 'logged in',
            user_id: user._id
        });
    });
}

Answer 1

simply add a .toString() as follows :

function login(req, res, next) {
    db.users.findOne({
            'email': req.body.email
        }, function(err, user) {
            if (err) return next(err);
            if (!user) {
                return res.status(401).send("user not found");
            }
            if (lib.getSaltedPassword(req.body.password) != user.password) {
                return res.status(401).send("wrong password");
            }
            req.session.user = user;
            if (req.session.cart) {
                req.session.cart.forEach(function(data) {
                    data.customer = user._id.toString();
                })
                db.carts.insert(req.session.cart, function(err, user_cart) {
                    if (err) return next(err);
                })
            }
        }
         res.send({
            message: 'logged in',
            user_id: user._id
        });
    });
}