token generator in node and express

Question

I trying create a function that generates a random token that doesn't exist in my database (Mongodb) and I use a unique property in my user schema. This is my function:

 var UniqueTokenGenerator = function () {



        var token = uuid.v4();

        UserModel.findOne({token : token} , (err , user)=> {



            if(err)

                res.status(500).send(err);

            else if(user){

                //1

            }else if(!user){

                 return token; //2

            }



        });



    };

My problems:

I want if token exist call UniqueTokenGenerator or whatever... like loop.

Token cannot be returned.

Anybody has a better idea?

I don't want to use any library like

jwt

.

Answer 1

Two answers:

First, you don't need to check the database to make sure your UUID is unique. UUIDs are so big that mathematically you won't run into a collision. See Are GUID collisions possible?

Second, to do what you're trying to do, you need to make your function asynchronous and deliver the result with a callback. E.g.

var generateUniqueToken = (callback) => {
    var token = uuid.v4();
    UserModel.findOne({ token: token }, (err, user) => {
        if(err) {
            // First parameter of the callback is an error.
            callback(err);
        } else if (user) {
            // Try again.
            generateUniqueToken(callback);
        } else if (!user) {
            // First parameter of the callback is an error. The second
            // parameter is the successful result.
            callback(null, token);
        }
    });
};

// Example usage:
generateUniqueToken((err, token) => {
    if (err) {
        res.status(500).send(err);
    } else {
        // Use the token here.
    }
});

token generator in node and express

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