Empty array is returned outside mongoose function

Question

I'm trying to take some random values from Mongo using mongoose and push it to an array. But the array is empty outside the function:

exports.Run = (req, res) => {
    var response = {}
    var you = "you"
    response[you] = [];

    Model.estimatedDocumentCount().exec(function (err, count) {
        for (let i = 0; i < 8; i++) {
            let random = Math.floor(Math.random() * count)

            Model.findOne()
                .skip(random)
                .exec( function (err, result) {
                    response[you].push(result);
                    console.log(response); // Array is increased each iteration
                })
        }
    })
    console.log(response); // Array is empty here
    res.status(200).send(response);
};

Please, how to fix that?

Thanks in advance.

Does this answer your question? Node JS Asynchronous Database Calls — tbking
– tbking, Commented Jul 26, 2021 at 20:35
@tbking It doesn't work. I make a callback but it returns empty array. If I make another get request after the first I recieve the array — Anatoly
– Anatoly, Commented Jul 26, 2021 at 21:38

Dr. Selva Mary G · Accepted Answer · 2021-07-27 11:11:21Z

1

Check this way. Hope it should work

  exports.Run =async (req, res) => {
        var response = {}
        var you = "you"
        response[you] = [];
    
        var result = await Model.estimatedDocumentCount().exec(function (err, count) {
            for (let i = 0; i < 8; i++) {
                let random = Math.floor(Math.random() * count)
    
               await Model.findOne()
                    .skip(random)
                    .exec( function (err, result) {
                        response[you].push(result);
                        console.log(response); 
                    })
            }
    return response;
    
            })
           
    console.log(result); // Array is empty here
        res.status(200).send(result);
    };

edited Jul 27, 2021 at 11:11

answered Jul 27, 2021 at 3:59

Dr. Selva Mary G

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1 Comment

Anatoly Over a year ago

No, it doesn't work :( Moreover, I get warning "Void function return value is used" at var result = await Model.estimatedDocumentCount().exec( function (err, count)

Anatoly · Accepted Answer · 2021-07-27 16:49:47Z

0

I found the solution and it works for me:

exports.Run = (req, res) => {
    ex1( function(rp){
        console.log(rp);
        res.status(200).send(rp);
    });
}

function ex1(callback) {
    var response = {}
    var you = "you"
    response[you] = [];
    Model.estimatedDocumentCount().exec(async function (err, count) {
        for (let i = 0; i < 8; i++) {
            let random = Math.floor(Math.random() * count)
            var doc = await Model.findOne().skip(random).exec();
            response[you].push(doc);
        }
        callback(response);
    })

}

answered Jul 27, 2021 at 16:49

Anatoly

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