SOURCE

function one() {
    setTimeout(() => {
        console.log(1111);
        iterator.next();
    }, 1000);
}
function two() {
    setTimeout(() => {
        console.log(2222);
        iterator.next();
    }, 2000);

}
function three() {
    setTimeout(() => {
        console.log(3333);
        iterator.next();
    }, 3000);

}
function* gen() {
    yield one();
    yield two();
    yield three();
}

let iterator = gen();
// console.log(iterator.next());
iterator.next();