Finding by Id is not working in Nodejs MongoDB

Question

db.collection('test').find({"title":"I like cake"}/*,{projection:{_id:true}}*/).toArray(function(err, results){
            if(err) throw err;

            id = "5b7fb08f823d6137e08a7d8a";
        });

        db.collection('test').findOne({_id: new ObjectId(id)}, function(err, results){
            if(err) throw err;  
            console.log(results);
        });

it' not work. (return null) following example is work.

db.collection('test').find({"title":"I like cake"}/*,{projection:{_id:true}}*/).toArray(function(err, results){
            if(err) throw err;

        });

        db.collection('test').findOne({_id: new ObjectId("5b7fb08f823d6137e08a7d8a")}, function(err, results){
            if(err) throw err;  
            console.log(results);
        });

What's the difference? How do i fix it?

score 1 · Accepted Answer · answered Aug 24 '18 at 09:24

1

The real issue is that you are setting the ID in a callback function which is asynchronous. Thus, when the findOne query executes, the ID is not yet set.

You might want to move the second query inside the callback function itself:

db.collection("test")
  .find({ title: "I like cake" } /*,{projection:{_id:true}}*/)
  .toArray(function(err, results) {
    if (err) throw err;

    var id = "5b7fb08f823d6137e08a7d8a";

    db.collection("test").findOne({ _id: new ObjectId(id) }, function(err,results) {
      if (err) throw err;
      console.log(results);
    });
  });

answered Aug 24 '18 at 09:24

Anand Undavia

3,493
5
19
33

thanks for answer. when i user this code, occur this error "MongoError: Topology was destroyed" – 김동환 Aug 24 '18 at 09:41
That seems more of a connection issue. Read: https://stackoverflow.com/questions/30909492/mongoerror-topology-was-destroyed – Anand Undavia Aug 24 '18 at 09:48
thanks! i called close() out of callback – 김동환 Aug 24 '18 at 10:50
Happy to help ! – Anand Undavia Aug 24 '18 at 10:51
@김동환 Hey Thanks for accepting the answer, If you could also upvote, that would help :) – Anand Undavia Aug 24 '18 at 10:54
I wanna do that. but i don't know how can i get reputations, so i'm searching that! :) – 김동환 Aug 26 '18 at 10:48

Prashant Gupta · Answer 2 · 2018-08-24T09:42:18.890

1

Try this code

 db.collection("test").find({}).toArray(function(err, result) {
   db.collection("test").find({
     _id:new ObjectID('5b7fb08f823d6137e08a7d8a')
     }).toArray(function(err, result) {
     if (err) throw err;
     console.log(JSON.stringify(result,undefined,2));
     //db.close();
   });
 });

edited Aug 24 '18 at 09:42

answered Aug 24 '18 at 09:37

Prashant Gupta

788
8
26

thanks for answer. when i user this code, occur this error "MongoError: Topology was destroyed" – 김동환 Aug 24 '18 at 09:41
i updated the code – Prashant Gupta Aug 24 '18 at 09:42

Finding by Id is not working in Nodejs MongoDB

2 Answers2