/**
 * Check if `fn` is a function.
 *
 * @param {Function} fn
 * @return {Boolean}
 */
export declare const isCallback: (arg: any) => boolean;
/**
 * Check if `val` is a number.
 *
 * @param {Number} val
 * @return {Boolean}
 */
export declare const isNumber: (val: string) => boolean;