demo_interface.ts

interface ShopModel {
  date: string;
}

class Shop extends ShopModel {
  constructor(shop: ShopModel){
    this.date = shop.date;
  }
	
  get formattedDate() {
    return moment(this.date).format("DD/MM/YYYY");
  }
}

const shop = new Shop({
  date: new Date()
});

console.log(shop.formattedDate);
// expected output: "c"