const factorial = function calc(n) {
    if (n <= 1) return 1;
    return n * calc(n - 1);
};

console.log(factorial(5));
console.log(typeof calc);

const arr = [1, 2, , 4, [5, , 7]];
console.log(arr.flat());

const [a, ...[b, _, ...c]] = [1, 2, 3, 4, 5];
console.log(a, b, c);

const order = {
  stage: 'processing',
  client: {
    name: 'Bob',
    age: 30,
  },
};
const updatedOrder = { ...order };

updatedOrder.client.age = 25;
updatedOrder.stage = 'completed';

console.log(order.client.age);
console.log(order.stage);

type A = string | never;
type B = string & never;

const arr = [NaN, NaN, NaN];
console.log(arr.every(el => el === NaN));