yield from a list of generators created from an array

Answer 1

may be something like

var obj = [1, 2, 3, [4, 5, [6, 7, 8], 9], 10];

function* flat(x) {
    if (Array.isArray(x)) {
        yield x.map(v => {
            return [...flat(v)].join();
        });
    } else yield "foo" + x;
}

console.log([...flat(obj)]);