Get random k numbers from an iterator of arbitrary N length array where N is unknown. (pseudo code)

k_from_n.js

function(iter, k) {
        var array = [];
        var count = 0;
        for (var val = iter(); val !== undefined; val = iter()) {
                count ++;
                if (array.length < k)
                        array.push_back(val);
                else {
                        var luck = rand() % count;
                        if (luck < k) {
                                array.unqueue_at(luck);
                                array.push_back(val);

                        }
                }
        }
}