var garage = []; var Car = function (color, price){ this.color = color; this.price = price; return this; } // 伝えたいところはココ Car.prototype.isNew = function (){ this.isNew = true; return this; }; var old_car = new Car("red", 10000000); garage.push(old_car); var new_car = new Car("blue", 100000000).isNew(); garage.push(new_car); function searchNewCarsFromGarage (){ var new_cars = []; for ( car_num in garage ){ if (garage[car_num]. hasOwnProperty("isNew")){ new_cars.push(garage[car_num]); } return new_cars; }