javascript – Get the _id of inserted document in Mongo database in NodeJS-ThrowExceptions

Exception or error:

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.

How to solve:

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.

###

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
});

###

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.

###

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
       }
});

###

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;
  });

###

Now you can use insertOne method and in promise’s result.insertedId

###

@JSideris, sample code for getting insertedId.

db.collection(COLLECTION).insertOne(data, (err, result) => {
    if (err) 
      return err;
    else 
      return result.insertedId;
  });

###

if you want to take “_id” use simpley

result.insertedId.toString() 

// toString will convert from hex

###

You could use async functions to get _id field automatically without manipulating data object:

async function save() {
  const data = {
    name: "John"
  }

  await db.collection('users', data )

  return data
}

Returns data:

{
  _id: '5dbff150b407cc129ab571ca',
  name: 'John'
}

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