Function cross

src/cross.js:17–33

(...values)

}

export default function cross(...values) {
  const reduce = typeof values[values.length - 1] === "function" && reducer(values.pop());
  values = values.map(arrayify);
  const lengths = values.map(length);
  const j = values.length - 1;
  const index = new Array(j + 1).fill(0);
  const product = [];
  if (j < 0 || lengths.some(empty)) return product;
  while (true) {
    product.push(index.map((j, i) => values[i][j]));
    let i = j;
    while (++index[i] === lengths[i]) {
      if (i === 0) return reduce ? product.map(reduce) : product;
      index[i--] = 0;
    }
  }
}