[JavaScript] Pick k items over size n array (nCk) - using Generator and flatMap

pick_2_items.js

const items = ['Foo', 'Bar', 'Dog', 'Cat', 'Tea'];
const indexes = [0, 1, 2, 3, 4];

console.log('');
console.log('-------------------');
console.log('Pick 2 items using flatMap');
const picked = indexes.flatMap(i =>
  indexes
    .slice(i + 1)
    .map(j => [items[i], items[j]])
);
console.log(picked);
console.log('-------------------');
console.log('');

console.log('');
console.log('-------------------');
console.log('Pick 2 items using Generator');
function* genPicker() {
  for (const i of indexes) {
    for (const j of indexes.slice(i + 1)) {
      yield [items[i], items[j]];
    }
  }
}
console.log([...genPicker()]);
console.log('-------------------');
console.log('');

pick_k_items.js

const items = ['Foo', 'Bar', 'Dog', 'Cat', 'Tea'];
const indexes = [0, 1, 2, 3, 4];

console.log('');
console.log('-------------------');
console.log('Pick k items using flatMap (default k is 3)');
function pickByFlatMap(k) {
  function pick(k, i = 0, v = []) {
    const sliced = indexes.slice(i);
    const concat = j => v.concat(items[j]);

    return (
      k === 1 ?
      sliced.map(j => concat(j)) :
      sliced.flatMap(j => pick(k - 1, j + 1, concat(j)))
    );
  }

  return pick(k);
}
console.log(pickByFlatMap(3));
console.log('-------------------');
console.log('');

console.log('');
console.log('-------------------');
console.log('Pick k items using Generator (default k is 3)');
function pickByGenerator(k) {
  function* pick(k, i = 0, v = []) {
    for (const j of indexes.slice(i)) {
      const v2 = v.concat(items[j]);

      if (k === 1) {
        yield v2;
      } else {
        yield* pick(k - 1, j + 1, v2);
      }
    }
  }

  return [...pick(k)];
}
console.log(pickByGenerator(3));
console.log('-------------------');
console.log('');