combinations.ts

combinations.ts

/**
 * Returns an array of all combinations of elements from all arrays.
 *
 * @examples
 *   combinations([1], [2, 3], [4, 5, 6])
 *   => "[[1,2,4],[1,2,5],[1,2,6],[1,3,4],[1,3,5],[1,3,6]]"
 */
export const combinations = <T extends unknown>(...arrays: T[][]): T[] => {
  const result: T[] = []
  const _combinations = (n: number, current: T[]) => {
    if (n === arrays.length) {
      result.push(current as T)
    } else {
      arrays[n].forEach((item) => _combinations(n + 1, current.concat(item)))
    }
  }
  _combinations(0, [])
  return result
}