CODEWITHSUNDEEP
node.jsexpress
Thecave3
Thecave3

Reputation: 797

using express response into custom callbacks of Mongoose

I am using Mongoose and Firebase along with Express and since sometime I have to still go on with the same callback function of mongoose but with different parameters or after a firebase callback I was thinking of use a custom callback named function. My issue is that since I need to send a response in this function I need to use the res variable from the Express callback which is not available. So how can still use the Express res?

This snippet below generates a run time error of undefined variable res into userCallback (pseudocode). I wonder how can I use the same code twice in situations like this one?

function userCallback(err, user) {
    // some other processing
    res.json({});
}

router.get('/:username', function (req, res, next) {
    let idToken = req.header('idToken');
    admin.auth().verifyIdToken(idToken, true)
        .then(function (decodedToken) {
            let email = req.query.email;
            if (!email) {
                User.findOne({
                    username: req.params.username
                }, userCallback);
            } else {
                admin.auth().getUserByEmail(req.params.username).then((user_firebase) => {
                    User.findOne({
                        uid: user_firebase.uid
                    }, userCallback);
                }).catch((error) => {
                    res.json({
                        result: false,
                        error
                    });
                });
            }
        }).catch(function (error) {
            res.json({
                result: false,
                error
            });
        });
});

Upvotes: 0

Views: 91

Answers (1)

CodeCodey
CodeCodey

Reputation: 116

When you are using findOne(), you have to use its callback (not your customized callback) which is 

User.findOne({<search_params>}, (err, document)=>{ 
    // this callback is specific to mongoose API and you have to follow the parameters
    // err is the error occurred when running findOne()
    // document is returned document passed back to you by findOne()
    // when your customized callback uses res, it had no knowledge of it in its current scope
})

The reason why you are unable to return the res is because the res was not passed into your customized callback as a parameter. Thus your custom callback does not know res exists! I suggest you handle the response at function(decodeToken) level instead / you could try passing res into your callback as the last parameter see if it helps.

User.findOne({}, (err, document, res){} // Don't think this will work

Upvotes: 1

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