CODEWITHSUNDEEP
javascriptnode.jsmongodbpromisebluebird
Forza
Forza

Reputation: 1649

Bluebird .then(): not working as it should

I just started working with promises and Bluebird. While debugging I can see that my function is executed twice:

First I get this error: TypeError: Uncaught error: Cannot read property 'then' of undefined

Then I see the function is executed again, and .then() is executed successfully. Also I get the correct information printed in the console.

Why is this happening? The whole reason I'm implementing promises is because I want to wait with executing the then()-action, because my data has to be retrieved first. But still the code jumps to the .then() action too early.

Why is this happening and how can I prevent it?

Here's my code:

exports.findUser = function(userId){

    var ObjectID = require('mongodb').ObjectID;
    var u_id = new ObjectID(userId);

    db.collection('users')
        .findOne({'_id': u_id})
        .then(function(docs) { //executed twice, first time error, second time success
            console.log(docs); //prints correct info once executed
            return docs;
        })
        .catch(function(err) {
            console.log(err);
        });
};

Upvotes: 0

Views: 213

Answers (1)

Tobias Weichart
Tobias Weichart

Reputation: 367

When working with the native npm module you should use callbacks here, like in the documentation. So for your example this would mean:

exports.findUser = function(userId){

    var ObjectID = require('mongodb').ObjectID;
    var u_id = new ObjectID(userId);

    db.collection('users')
        .findOne({'_id': u_id}, function(err, docs){
            console.log(docs); //prints correct info once executed
            return docs;
        });
};

If you want to use promises than maybe you should consider using something like mongoose.

Upvotes: 1

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