Iterables

Any class that implements Iterator.<T>, IterableKeys.<T> or IterableValues.<T> may be iterated.

jet_proxy usage

class A implements IterableKeys.<Number>, IterableValues.<Number> {
    //
    jet_proxy function keys() {
        for (var i = 0; i < 10; i++) {
            yield i;
        }
    }

    //
    jet_proxy function values() {
        for (var i = 0; i < 10; i++) {
            yield i;
        }
    }
}