/**
 * Array deduplication function (High performance O(N) version).
 * @param arr The array to deduplicate.
 * @param iteratee The property name (keyof T) or mapping function ((item) => key).
 */
type KeyFn<T, K> = (item: T) => K;
export declare function uniqBy<T, K>(arr: readonly T[], iteratee: keyof T | KeyFn<T, K>): T[];
export {};