export declare function isDate(val: any): val is Date;
export declare function isObject(val: any): boolean;
export declare function isPlainObject(val: any): boolean;
export declare function isFormData(val: any): val is FormData;
export declare function isURLSearchParams(val: any): val is URLSearchParams;
export declare function isUndefined(val: any): boolean;
export declare function forEach(obj: any, fn: any): void;
export declare function merge(...argvs: any[]): any;
export declare function extend(a: any, b: any, thisArg?: any): any;