/**
 * null check
 * @param value
 * @returns {boolean}
 */
export declare function isNull(value: unknown): boolean;
/**
 * object check
 * @param value
 * @returns {boolean}
 */
export declare function isObject(value: unknown): boolean;
/**
 * function check
 * @param value
 * @returns {*|boolean}
 */
export declare function isFunction(value: unknown): boolean;
/**
 * string check
 * @param value
 * @return {boolean}
 */
export declare function isString(value: unknown): boolean;
/**
 * number check
 * @param value
 * @return {boolean}
 */
export declare function isNumber(value: unknown): boolean;
/**
 * boolean check
 * @param value
 * @return {boolean}
 */
export declare function isBoolean(value: unknown): boolean;
/**
 * array check
 * @param value
 * @returns {arg is Array<unknown>}
 */
export declare function isArray(value: unknown): boolean;
/**
 * undefined check
 * @param value
 * @returns {boolean}
 */
export declare function isUndefined(value: unknown): value is undefined;
export declare function isValidUrl(url: string): boolean;
export declare function isValidISOCode(code: string): boolean;