问题:

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.

回答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.

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

回答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();