// Объявление генератора
function* numberGenerator() {
    yield 1;
    yield 2;
    yield 3;
    return 4;
}

const gen = numberGenerator();
console.log(gen.next()); // { value: 1, done: false }
console.log(gen.next()); // { value: 2, done: false }
console.log(gen.next()); // { value: 3, done: false }
console.log(gen.next()); // { value: 4, done: true }
console.log(gen.next()); // { value: undefined, done: true }