import { Observable } from 'rxjs';
export declare type Diff<T, U> = T extends U ? never : T;
export declare const filterNil: <T>(source: Observable<T>) => Observable<Diff<T, null>>;
export declare function coerceArray<T>(value: T | T[]): T[];
export declare function isNil(v: any): boolean;
export declare function clone(value: any): any;
export declare function isValidDate(value: any): boolean;
export declare function isObject(val: any): boolean;
export declare function filterControlKeys(value: any): {};
export declare function isBrowser(): boolean;
export declare function mergeDeep(target: any, ...sources: any[]): any;