CODEWITHSUNDEEP
node.jsmongodbpromise
Andrei Charnyshou
Andrei Charnyshou

Reputation: 74

NodeJS Promise.all for DB requests

how to make several requests to DB, wait for results from all requests and return results? I try with Promise.all, but all I get - [undefined] in console. 

MongoClient.connect(url, function (err, db) {
    if (err) throw err;
    var dbo = db.db("DBusers");
    var query = {};
    var U4 = dbo.collection("users");  
    const promises = [
        U4.find({}).count(function (err, result) { return result; }),
        U4.find({}).count(function (err, result) { return result; })
    ];

    Promise.all(promises).then(function (results) {
        console.log(results);
    }).catch(function (err) {
        console.log(err);
    });

    db.close();


});

Upvotes: 0

Views: 824

Answers (2)

Mahdi Hashemi
Mahdi Hashemi

Reputation: 127

you use a callback function to Promise.all array. it's correct way to use Promise.all:

const promises = [
    U4.find({}).count(),
    U4.find({}).count()
];

by default that returns a promise and you must be past array of promise to Promise.all.

Upvotes: 2

Andrei Charnyshou
Andrei Charnyshou

Reputation: 74

I think I found an answer, I had to change to: 

const promises = [
            U4.find({}).count(),
            U4.find({}).count()
];

Upvotes: 0

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