[Octane]

Изобретаем Deferred по новой

class Deferred {

    constructor(generator) {
        this.promise = new Promise((resolve, reject) => {
            Object.assign(this, {resolve, reject});
        });
        generator.next();
        let next = value => {
            let result = generator.next(value);
            if (!result.done) {
                value = result.value;
                if (value && value.next) {
                    new Deferred(value).done(next).fail(this.reject);
                } else {
                    next(value);
                }
            }
        };
        next(this);
    }

    done(onFulfilled) {
        this.promise.then(onFulfilled);
        return this;
    }
    
    fail(onRejected) {
        this.promise.catch(onRejected);
        return this;
    }

}

function * getFoo() {
    let deferred = yield;
    setTimeout(function() {
        deferred.resolve('foo');
    }, 100);
}

function * getBar() {
    let deferred = yield;
    let foo = yield getFoo();
    setTimeout(function() {
        deferred.resolve(foo + 'bar');
    }, 100);
}

new Deferred(getBar()).done(function(value) {
    console.log(value);
});

// в консоль выведется "foobar"