/**
 * Filters duplicate items in an `array` using the keys extracted from each item by a function `keyFn`.
 * @note When keys are equal, the last item is kept.
 * @param array Array to filter.
 * @param keyFn Optional function that extracts a key from each item. Default: `identity()`.
 * @example
 * const array = [{ id: 4 }, { id: 1 }, { id: 4, last: true }];
 * unique(array, x => x.id);
 * // [{ id: 1 }, { id: 4, last: true }]
 */
export declare function unique<T>(array: T[], keyFn?: KeyFn<T>): T[];
/**
 * Returns a function that
 * filters duplicate items in an `array` using the keys extracted from each item by a function `keyFn`.
 * @note When keys are equal, the last item is kept.
 * @param keyFn Optional function that extracts a key from each item. Default: `identity()`.
 * @example
 * const array = [{ id: 4 }, { id: 1 }, { id: 4, last: true }];
 * const uniqId = unique(x => x.id);
 * uniqId(array);
 * // [{ id: 1 }, { id: 4, last: true }]
 */
export declare function unique<T>(keyFn?: KeyFn<T>): typeof deferred;
/**
 * Filters duplicate items in an `array` using the keys extracted
 * from each item by a previously specified function `keyFn`.
 * @note When keys are equal, the last item is kept.
 * @param array Array to filter.
 */
declare function deferred<T>(array: T[]): T[];
declare type KeyFn<T> = (item: T, index: number) => any;
export {};