// SAVE A REVIEW TO DATABASE
router.post('/', function(req, res, next) {
var decoded = jwt.decode(req.query.token);
User.findById(decoded.user._id, function(err, doc) {
    if (err) {
        return res.status(404).json({
            title: 'An error occurred',
            error: err
        });
    }
    var review = new Review({
        content: req.body.content,
        rating: req.body.rating,
        app: req.body.appId,
        user: doc
    })
Application.findById(req.body.appId, function(err, doc) {
    if (err) {
        return res.status(404).json({
            title: 'An error occurred',
            error: err
        });
    }
    review.save(function(err, result) {
        if (err) {
            return res.status(404).json({
                title: 'An error occurred',
                error: err
            });
        }
    review.update(function(err, result) {
        if (err) {
            return res.status(404).json({
                title: 'An error occurred',
                error: err
            });
        }
        doc.reviews.push(result);
        doc.save();
        res.status(201).json({
            message: 'Saved review',
            obj: result
        });
    });
});
});

Review Model:

var schema = new Schema({
    content: {type: String, required: true},
    rating: {type: Number},
    dateCreated: {type: String},
    app: {type: Schema.Types.ObjectId, ref: 'Application'},
    user: {type: Schema.Types.ObjectId, ref: 'User'}
});

Application Model:

var schema = new Schema({
    name: {type: String, required: true},
    description: {type: String},
    reviews: [{type: Schema.Types.ObjectId, ref: 'Review'}],
})

User Model:

var schema = new Schema({
    firstName: {type: String, required: true},
    lastName: {type: String, required: true},
    password: {type: String, required: true},
    passwordConfirm: {type: String, required: true},
    email: {type: String, required: true, unique: true},
    reviews: [{type: Schema.Types.ObjectId, ref: 'Review'}]
});