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.

Solution 1:

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
});

Solution 2:

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.

Solution 3:

As ktretyak said, to get inserted document's ID best way is to use insertedId property on result object. In my case result._id didn't work so I had to use following:

db.collection("collection-name")
  .insertOne(document)
  .then(result => {
    console.log(result.insertedId);
  })
  .catch(err => {
    // handle error
  });

It's the same thing if you use callbacks.