function* range(start, end) {
  while (start < end) {
    yield start++;
  }
}

function* evens(iter) {
  for (const val of iter) {
    if (val % 2 === 0) yield val;
  }
}

function* take(n, iter) {
  let count = 0;
  for (const val of iter) {
    if (count++ >= n) return;
    yield val;
  }
}

function* pipeline() {
  yield* take(3, evens(range(1, 20)));
  yield* take(2, range(10, 15));
}

const result = [...pipeline()];
console.log(result);