async function getReply(replyId){
    let db = await MongoClient.connect(MONGO_URI);
    let testDb = db.db("test");

    let reply = await testDb.collection('replies').findOne({'_id': replyId})

    if (typeof reply.replies !== 'undefined' && reply.replies.length > 0){
        let replyIds = reply.replies;

        let superArr = replyIds.map(
            async (replyId) => {
                console.log(replyId.toString());
                return await getReply(replyId)
            }
        )
        reply.replies = superArr;
        return reply
    } else {
        return reply
    }
}

getReply(ObjectID("5ee29a83b6f54879ebec9f45")).then(
    (reply)=>{
        console.log(reply)
    }
)