Mongodb- Query to check if a field in the json array exists or not

I have a json in mongodb and I am trying to check if at least one of the items in the json doesnt contain a specific field.
{
"_id" : 12345,
"orderItems" : [
{
"itemId" : 45678,
"isAvailable" : true,
"isEligible" " false
},
{
"itemId" : 87653,
"isAvailable" : true
}
]
}

So in the above json, since the 2nd one under order items doesnt contain iseligible field, I need to get this _id.

I tried the below query so far, which didnt work:
db.getCollection(‘orders’).find({"orderItems.iseligible":{$exists:false})

>Solution :

You can use $elemMatch to evaluate the presence of the nested key. Once that’s accomplished, project out the _id value.

db.orders.find({
  orderItems: {
    $elemMatch: {
      "isEligible": {
        $exists: false
      }
    }
  }
},
{
  _id: 1
})

Here is a Mongo playground with the finished code, and a similar SO answer.