export declare type FilterCallback = (value: any, key: string, obj: object) => boolean;
export declare function map(obj: object, fn: (value: any, key: string, obj: object) => any): object;
export declare function filterBy(obj: object, keys: string[]): object;
export declare function filter(obj: object, fn: FilterCallback): object;
export declare function findKey(obj: object, fn: FilterCallback): string;
export declare function all(obj: object, fn: FilterCallback): boolean;
export declare function reduce<T = any>(obj: object, fn: (prev: T, value: any, key: string, obj: object) => T, start: T): T;