const restaurant = {
  name: 'Chicken Republic',
  openingHours: {
    thurs: {
      open: 12,
      close: 22,
    },
  },
};
const newRestaurant = JSON.parse(JSON.stringify(restaurant));
newRestaurant.name = 'Mega Chicken';
newRestaurant.openingHours.thurs.open = 8;
console.log(restaurant); //{ name: 'Chicken Republic',openingHours: { thurs: { open: 12, close: 22 } } }

console.log(newRestaurant);//{ name: 'Mega Chicken', openingHours: { thurs: { open: 8, close: 22 } } }