Function joinArray

client/shared/utils/array-helper.ts:11–21

(arr: T[], separator: K)

 * @example joinArray([1, 2, 3], '5') => [1, '5', 2, '5', 3]
 */
export function joinArray<T, K>(arr: T[], separator: K): (T | K)[] {
  return _flatten(
    arr.map((item, i) => {
      if (i === 0) {
        return [item];
      } else {
        return [separator, item];
      }
    })
  );
}