018 - Array combos using bitmasking

function getCombos(array) {
  return new Array(2 ** array.length).fill()
    .map((_empty_, i) => {

    return array.filter((_item_, j) => {
      return i & (1 << j);
    });
  });
}

getCombos(["a", "b", "c"]);

// Output
// [[],["a"],["b"], ["a","b"],["c"],["a","c"], ["b","c"],["a","b","c"]]