/**
 * Returns an array with unique elements.
 * Use `getId` to customize what uniquely identifies each array element.
 *
 * @param arr
 * @param getId
 */
export declare const unique: <TArrItem>(arr: TArrItem[], getId?: (item: TArrItem) => any) => TArrItem[];
/**
 * Flattens nested arrays into a single array.
 * `[1, [2, 3]]` becomes `[1, 2, 3]`.
 *
 * @param arrays
 */
export declare const flatten: <TArr extends Record<string, unknown>>(...arrays: TArr[][]) => TArr[];