javascript - Mongoose promises documentation says queries are not promises?

Question

From the docs (Mongoose v5.4.1, latest version):

Mongoose async operations, like .save() and queries, return thenables. This means that you can do things like MyModel.findOne({}).then()

second parapraph from the docs states:

Mongoose queries are not promises. They have a .then() function for co and async/await as a convenience.

What Javascript MDN webpage states:

The then() method returns a Promise.

Does this mean that mongoose has another kind of implementation for async functions where they reserved the then keyword for the result of the async action?

In other words, they act like promises but are not JS promises?

Answer 1

From the documentation:

Mongoose queries are not promises. They have a .then() function for co and async/await as a convenience. However, unlike promises, calling a query's .then() can execute the query multiple times.

So unlike an actual promise, if you call then() multiple times on the query, you actually execute the query (or update) multiple times.

If you want an actual promise, call exec() on the query.

let promise = Test.findOne({}).exec();