Get the _id of inserted document in Mongo database in NodeJS

Question

Get the _id of inserted document in Mongo database in NodeJS

I use NodeJS to insert documents in MongoDB. Using collection.insert I can insert a document into database like in this code:

// ...
collection.insert(objectToInsert, function(err){
   if (err) return;
   // Object inserted successfully.
   var objectId; // = ???
});
// ...

How can I get the _id of inserted object?

Is there any way to get the _id without getting latest object inserted _id?

Supposing that in same time a lot of people access the database, I can't be sure that the latest id is the id of object inserted.

javascript
node.js
mongodb

Answer 1

There is a second parameter for the callback for collection.insert that will return the doc or docs inserted, which should have _ids.

Try:

collection.insert(objectToInsert, function(err,docsInserted){
    console.log(docsInserted);
});

and check the console to see what I mean.

you can also try it here: https://runnable.com/UTpPRysNM0MHAGAk/server.js

Answer 2

A shorter way than using second parameter for the callback of collection.insert would be using objectToInsert._id that returns the _id (inside of the callback function, supposing it was a successful operation).

The Mongo driver for NodeJS appends the _id field to the original object reference, so it's easy to get the inserted id using the original object:

collection.insert(objectToInsert, function(err){
   if (err) return;
   // Object inserted successfully.
   var objectId = objectToInsert._id; // this will return the id of object inserted
});

Answer 3

Mongo sends the complete document as a callbackobject so you can simply get it from there only.

for example

collection.save(function(err,room){
  var newRoomId = room._id;
  });

Answer 4

I actually did a console.log() for the second parameter in the callback function for insert. There is actually a lot of information returned apart from the inserted object itself. So the code below explains how you can access it's id.

collection.insert(objToInsert, function (err, result){
    if(err)console.log(err);
    else {
        console.log(result["ops"][0]["_id"]);
        // The above statement will output the id of the 
        // inserted object
       }
});