How can I generate an ObjectId with mongoose?

Question

I'd like to generate a MongoDB ObjectId with Mongoose. Is there a way to access the ObjectId constructor from Mongoose?

• This question is about generating a new ObjectId from scratch. The generated ID is a brand new universally unique ID.

• Another question asks about creating an ObjectId from an existing string representation. In this case, you already have a string representation of an ID—it may or may not be universally unique—and you are parsing it into an ObjectId.

Zia

Answer 1

You can find the ObjectId constructor on require('mongoose').Types. Here is an example:

var mongoose = require('mongoose');
var id = mongoose.Types.ObjectId();

id is a newly generated ObjectId.

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Note: As Joshua Sherman points out, with Mongoose 6 you must prefix the call with new:

var id = new mongoose.Types.ObjectId();

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You can read more about the Types object at Mongoose#Types documentation.

Zia

how can you be sure that this is really unique? does mongoose any check before? – Trumpet

@Trumpet check out how these are generated (Google). There's no check but it's probabilistic – Zia

If you generate 16777216 within one second on the same machine, then you will probably get a duplicate. :) – Redpoll

Correction: If you generate 16777216 within one millisecond on the same machine, then you will probably get a duplicate. 😁 – Eusebioeusebius

@Redpoll what is this number 16777216 ? – Affluent

@SaahithyanVigneswaran it's 2^24, supposing you are using 24 bits for the random portion of the ID – Zia

How are MongoDB's ObjectIds generated? The local counter is three bytes, or six hex chars. We can calculate: 256 ** 3 === 16 ** 6 === 16777216 – Redpoll

looks like with mongoose 6 you have to add new new mongoose.Types.ObjectId() – Hersch

Answer 2

You can create a new MongoDB ObjectId like this using mongoose:

var mongoose = require('mongoose');
var newId = new mongoose.mongo.ObjectId('56cb91bdc3464f14678934ca');
// or leave the id string blank to generate an id with a new hex identifier
var newId2 = new mongoose.mongo.ObjectId();

Azikiwe

mongoose.mongo? – Baptiste

Answer 3

I needed to generate mongodb ids on client side.

After digging into the mongodb source code i found they generate ObjectIDs using npm bson lib.

If ever you need only to generate an ObjectID without installing the whole mongodb / mongoose package, you can import the lighter bson library :

const bson = require('bson');
new bson.ObjectId(); // 5cabe64dcf0d4447fa60f5e2

Note: There is also an npm project named bson-objectid being even lighter

Sacrum

The size of "unpacked" bson is almost as heavy as mongodb. – Tocsin

Answer 4

With ES6 syntax

import mongoose from "mongoose";

// Generate a new new ObjectId
const newId2 = new mongoose.Types.ObjectId();
// Convert string to ObjectId
const newId = new mongoose.Types.ObjectId('56cb91bdc3464f14678934ca');

Trek

what's the diff between mongoose.Type and mongoose.Schema.Types ? – Galeiform

mongoose.Schema.Types will be used to within your schema when you want to reference between collections. To create a single objectId within your code use simply mongoose.Types – Gelasias

@stefano, mongoose.Schema.Types.ObjectId and mongoose.Types.ObjectId, is the exactly same – Asyndeton

Answer 5

The import is mongo from mongoose, the node-mongodb-native driver. If you open the package you can verify !

import { mongo } from 'mongoose'
const newId = new mongo.ObjectId()

Eliaeliades

Answer 6

The code that worked for me in mongoose v8 (+ typescript) was this:

const id = new mongoose.Types.ObjectId().toString()

Orlosky

Answer 7

const mongoose = require('mongoose');
const objectId = new mongoose.Types.ObjectId();

console.log(objectId);

Tangled