const order = { item: "Пенал" };
console.log("toString" in order, Object.hasOwn(order, "toString"), Object.hasOwn(order, "item"));

console.log({ a: 1 }.hasOwnProperty("a"));

const arr = [1];
console.log(arr.propertyIsEnumerable(0), arr.propertyIsEnumerable("length"));

console.log(Object.keys([1, 2]), Object.getOwnPropertyNames([1, 2]));

const id = Symbol("id");
const o = { [id]: 7, name: "Пенал" };
console.log(Object.keys(o), Object.getOwnPropertySymbols(o).length);

const defaults = { size: "M", sugar: 0 };
const order = Object.assign({}, defaults, { sugar: 2 });
console.log(order);

const catalog = [{ n: "Блокнот", c: "office" }, { n: "Стикер", c: "dessert" }, { n: "Пенал", c: "office" }];
console.log(Object.groupBy(catalog, (d) => d.c));