SOKR

class Cupboard {
	constructor(props) {
		this._fromParent = { ...props };
    }

	delete() {
		console.log(this._fromParent);
    }

	refreshProps(props) {
		this._fromParent = { ...props }
    }

	//...
}

class Room {
	constructor() {
		this._number = 5;
		this._price = 500;
		this.cupboard = new Cupboard(this);
    }

	get number() {
		return this._number;
    }

	set number(value) {
		this._number = value;
		this.cupboard.refreshProps(this);
    }
}

const room = new Room();
room.cupboard.delete();
//{_number: 5, _price: 500}

room.number = 6
room.cupboard.delete()
//{_number: 6, _price: 500, cupboard: Cupboard}