'use strict';

const cities = new Set([

{ name: 'Beijing' },

{ name: 'Kiev' },

{ name: 'London' },

{ name: 'Baghdad' },

]);

const list = new WeakSet();

for (const city of cities) {

console.log('Add city', city, 'to WeakSet');

list.add(city);

}

console.dir({ cities, list });

const iterator = cities.values();

const beijing = iterator.next().value;

console.log('select', beijing);

iterator.next();

const london = iterator.next().value;

console.log('select', london);

cities.delete(london);

console.log('remove', london, 'from Set');

list.delete(beijing);

console.log('remove', beijing, 'from WeakSet');

for (const city of cities) {

console.log('City', city, 'in WeakSet', list.has(city));

}