Sums the items of an array

sumItems.js

function sumItems(array) {
  if (array.length === 0) {
    return 0;
  }else if (Array.isArray(array[0])) {
    return sumItems(array[0]) + sumItems(array.slice(1));
  } else {
    return array[0] + sumItems(array.slice(1));
  }
}

module.exports = sumItems;