Optional chaining and nullish coalescing operator

optionalChaining.js

'use strict';

const weekDays = ['mon', 'tues', 'wed', 'thu', 'fri', 'sat', 'sun'];

const openingHours = {
  [weekDays[3]]: {
    open: 12,
    close: 22,
  },
  fri: {
    open: 11,
    close: 23,
  },
  sat: {
    open: 0, // Open 24 hours
    close: 24,
  },
};

const restaurant = {
  name: "Vini's Curry House",
  location: '123 Gora Way, Mumbai, India',
  categories: ['Punjabi', 'Bengali', 'Madras', 'Neplai'],
  starterMenu: ['Samosa', 'Pakora', 'Nan', 'Kebab'],
  mainMenu: ['Dosa', 'Chicken Madras', 'Tandoori Halibut'],

  // ES6 enhanced object literals
  openingHours,

  // new way of writing functions

  order(starterIndex, mainIndex) {
    return [this.starterMenu[starterIndex], this.mainMenu[mainIndex]];
  },

  orderDelivery({ starterIndex = 1, mainIndex = 0, time = '24.07', address }) {
    console.log(
      `Order received! ${this.starterMenu[starterIndex]} and ${this.mainMenu[mainIndex]} will be delivered ${address} at ${time}. `
    );
  },
};

const menu = [...restaurant.starterMenu, ...restaurant.mainMenu];

// for of loop

// for (const item of menu) console.log(item);

// destructuring arrays

for (const [i, el] of menu.entries()) {
  console.log(`${i + 1}: ${el}`);
}

// console.log([...menu.entries()]);

//  optional chaining

console.log(restaurant.openingHours?.mon?.open); // undefined
console.log(restaurant.openingHours.fri?.open); // opens at 11

// no monday prop
// if (restaurant.openingHours.mon)
// console.log(restaurant.openingHours.mon.open);

// fri prop
// if (restaurant.openingHours.fri)
// console.log(restaurant.openingHours.fri.open);

// use case of optional chaining and nullish coalescing operator

const days = ['mon', 'tues', 'wed', 'thu', 'fri', 'sat', 'sun'];

for (const day of days) {
  const open = openingHours[day]?.open ?? 'closed';
  console.log(`On ${day}, we open at ${open}`);
}

// optional chaining for methods

console.log(restaurant.order?.(0, 1) ?? 'method does not exist');
console.log(restaurant.orderPakora?.(0, 1) ?? 'method does not exist');

// optional chaining for arrays

const users = [{ name: 'Vini', email: 'vini@voice.com' }];

console.log(users[0]?.name ?? 'user array empty');