Return document count with mongoose in NodeJS

Question

How can I return the count of documents returned by a query? I have a routing file, which have the following code:

router.post('/facebookLogin', function(req, res, next){
    var User=require('../models/user');
    var a=User.facebookUserExist(req.body.id, req.body.email);
    console.log(a);
    res.end();
});

And here is the content of the User model file:

var User=function(data){
    this.data=data;
}
User.prototype.data={};
User.prototype.facebookUserExist=function(id, email){
    var output;
    db.collection('users').find({
        $or:[
            {
                facebookID:id
            },
            {
                email:email
            }
        ]
    }).count(function(err, numOfDocs){
        output=numOfDocs;
    });
    return output;
}
module.exports=new User;

I set the value of the output variable in the count method callback, but the function still return undefined.

1. you don't need to use find and count, you can use just count with the same filter. 2. you are using a callback method as an async method, that's why you get the undefined. — TomG
– TomG, Commented Oct 2, 2016 at 11:36

Arif Khan · Accepted Answer · 2016-10-02 12:26:50Z

1

We know that JavaScript is asynchronous and won't wait for result. So you may either use callback or Promise object, here is example of callback for your code

router.post('/facebookLogin', function(req, res, next){
    var User=require('../models/user');
    User.facebookUserExist(req.body.id, req.body.email, function(err, count)
        if(err)
            console.log('Error ', err);
        else
            console.log(count);
        res.end();
    });
});

and your User model take a callback as last argument

var User=function(data){
    this.data=data;
}
User.prototype.data={};
User.prototype.facebookUserExist=function(id, email, callback){
    var output;
    db.collection('users').find({
        $or:[
            {
                facebookID:id
            },
            {
                email:email
            }
        ]
    }).count(function(err, numOfDocs){
        callback(err, numOfDocs);
    });
    //return output;
}
module.exports=new User;

edited Oct 2, 2016 at 12:26

answered Oct 2, 2016 at 11:50

Arif Khan

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3 Comments

kukko Over a year ago

I can't make the code to wait for a functions return value?

kukko Over a year ago

When I try to use promise object, it is always in pending state and the then method not executing.

Arif Khan Over a year ago

@kukko return statement won't wait for you function completion. You may use either callback( as I explained in my answer) or Promise object

Arpit Yadav · Accepted Answer · 2017-09-21 21:15:22Z

1

.count() is required to get total docs in MongoDB. It might help.

USER.find(req.body.id, req.body.email).count(function(err, count) {
    console.log("Number of docs: ", count); });

answered Sep 21, 2017 at 21:15

Arpit Yadav

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