export declare function firstLetter(str: string, option?: {
    case?: 'upper' | 'lower';
    include?: boolean;
}): string;
export declare function lastLetter(str: string, option?: {
    case?: 'upper' | 'lower';
    include?: boolean;
}): string;
declare const _default: {
    firstLetter: typeof firstLetter;
    lastLetter: typeof lastLetter;
};
export default _default;