Mongodb. How to get boolean value representing existance of id in an array of ids?

Mongodb. How to get boolean value representing existance of id in an array
of ids?

I've got a model which have property
_idUserReadArr // array of users who have read an article
It it going to be a huge array.
And I want my API to return a boolean value
isRead
Which should be true if _idUserReadArr contains particular id and false in
other case.
So, instead of
_idUserArr = [1, 2, 3]
I want to get isRead = true or isRead = false and do NOT return or do some
manipulations directly with big _idUserReadArr array.
I'n working with node.js using mongoose.