how to query inside array in mongoose code example

Example 1: Find document with array that contains a specific value

As favouriteFoods is a simple array of strings, you can just query that field directly:

PersonModel.find({ favouriteFoods: "sushi" }, ...);

model:
person = {
    name : String,
    favoriteFoods : Array
}

Example 2: how to query array of object in mongoos

User.findOne({'local.rooms': {$elemMatch: {name: req.body.username}}}, function (err, user) {

        if (err){
            return done(err);
        }    

        if (user) {
            console.log("ROOM NAME FOUND");
            req.roomNameAlreadyInUse = true;
            next();

        } else {
            req.roomNameAlreadyInUse = false;
            console.log("ROOM NAME NOT FOUND");
            next();

        }

    });