async-iterator.es7

class AsyncArray extends Array {
    [Symbol.iterator]() {
        let iter = super[Symbol.iterator]();
        return {
            next() {
                let elem = iter.next();
                let promise = new Promise(resolve => setTimeout(
                    () => resolve(elem.value), 1000)
                );
                return {done: elem.done, value: promise};
            }
        };
    }
}

async () => {
    for (let x of AsyncArray.of(1, 2, 3)) {
        let value = await x;
        console.log(value);
    }
}();