title: bifurcate tags: array,intermediate

Splits values into two groups. If an element in filter is truthy, the corresponding element in the collection belongs to the first group; otherwise, it belongs to the second group.

Use Array.prototype.reduce() and Array.prototype.push() to add elements to groups, based on filter.

const bifurcate = <T = any>(arr: T[], filter: boolean[]) =>
  arr.reduce(
    (acc, val, i) => {
      acc[filter[i] ? 0 : 1].push(val);
      return acc;
    },
    [[] as T[], [] as T[]]
  );

bifurcate(["beep", "boop", "foo", "bar"], [true, true, false, true]); // [ ['beep', 'boop', 'bar'], ['foo'] ]