powerset

Returns the powerset of a given array of numbers.

• Use Array.prototype.reduce() combined with Array.prototype.map() to iterate over elements and combine into an array containing all combinations.

const powerset = arr =>
  arr.reduce((a, v) => a.concat(a.map(r => [v].concat(r))), [[]]);

powerset([1, 2]); // [[], [1], [2], [2, 1]]