009 - Array combinations recursively

function getCombos(arr) {
  if (arr.length === 1) {
    return [arr];
  }
  else {
    const subarr = getCombos(arr.slice(1));
    return [
      ...[[arr[0]]],
      ...subarr.map((e) => [arr[0], ...e]),
      ...subarr,
    ].sort((a, b) => a.length - b.length);
  }
}

console.info(JSON.stringify(getCombos(["a", "b", "c"])));
// Output: [["a"],["b"],["c"],["a","b"],["a","c"],["b","c"],["a","b","c"]]