/**
 * Converts the first character of `string` to upper case.
 *
 * @since 5.5.1
 * @category String
 * @param str The string to convert.
 * @returns Returns the converted string.
 * @see camelCase, kebabCase, lowerCase, snakeCase, startCase, upperCase
 * @example
 *
 * ```js
 * upperFirst('fred')
 * // => 'Fred'
 *
 * upperFirst('FRED')
 * // => 'FRED'
 * ```
 */
export declare function upperFirst(str?: string): string;
export default upperFirst;