gistfile1.txt

var breakfastSchema = new mongoose.Schema({
  steak: {
    type: String,
    required: true,
    enum: ['flank', 'ribeye'],
    validate: function(v) {
      // Woops! `this` is equal to the global object!
      if (this.eggs >= 4) {
        return v === 'flank';
      }
    }
  },
  eggs: {
    type: Number,
    required: true,
    min: 2
  }
});

var Breakfast = mongoose.model('breakfast', breakfastSchema, 'breakfasts');

var updates = { $set: { steak: 'ribeye', eggs: 4 } };
Breakfast.findOneAndUpdate({}, updates, { runValidators: true }, function(err) {
  // No err!
});