get array if array contains id mongoose

Question

It is a tricky one. I thought I could use $in, but after querying, it wasn't where I was looking for.

This is my schema

var gameSchema = new mongoose.Schema({
    state: {
        type: String,
        default: "invited"
    },
    finished: {
        type: Boolean,
        default: false
    },
    players: {
        type: [{
            type: mongoose.Schema.Types.ObjectId,
            ref: 'users'
        }],
        required: true,
    },
    scores: [scoreSchema],
    chat : [chatSchema]
});

The request I'm trying to make is the following, I send a user Id, if the players array contains this Id, return the other id (the array will always have length 2) in the array.

The context is that you can lookup against whom you have played before.

This is what I had, but "players" should be an array and it's not games that I want to return, so

exports.getFriends = function(id, cb){
    gameSchema.find({ id: { "$in": "players"} }, function(err, games){
        if(err){
            return cb(err, null);
        }
        else{
            return cb(null, games);
        }
    });
};

Answer 1

Can you try this?

exports.getFriends = function(id, cb){
    gameSchema.find({ players: id }, function(err, games) {
        if (err) {
            return cb(err);
        }
        const players = games.map(game => game.players);
        const mergedPlayers = [].concat.apply([], players);
        const mappedPlayers = mergedPlayers.map(String); // convert ObjectIds to strings for comparisons.
        const idString = String(id);
        const filteredPlayers = mappedPlayers.filter(player => player !== idString);
        const uniquePlayers = filteredPlayers.filter((player, index, arr) => arr.indexOf(player) === index);
        return cb(null, uniquePlayers);
    });
};

I'm operating under the assumption that you want an array of the unique player ids that are not the player id you passed in. I kept the vars split apart instead of chaining all of the array methods, in an attempt to improve readability.