export declare function isPlainObject(value: any): boolean;
export declare function isBoolString(value?: string): boolean;
export declare function isBlank(value: any): boolean;
export declare function isNumeric(value: any): boolean;
export declare function isLetter(value: any): boolean;
export declare function isAlpha(value: any): boolean;
export declare function hasWhitespace(text: string): boolean;
export declare function isPromise(value?: any): boolean;
export declare function isJson(value?: any): boolean;
export declare function isIsoDate(value?: string): boolean;
export declare function isEmail(value?: string): boolean;