/**
 * Converts a string to uppercase.
 *
 * @since 1.0.0
 *
 * @param {string} str - The string to convert.
 *
 * @returns {string} - The converted string in uppercase.
 *
 * @example
 *
 * toUpper('hello world') // 'HELLO WORLD'
 */
declare const toUpper: (str?: string) => string;
export default toUpper;