/**
 * Truncates string if it's longer than the given maximum string length.
 * The last characters of the truncated string are replaced with the omission
 * string which defaults to "...".
 *
 * @param string - The string to truncate
 * @param options - The options object
 * @returns The truncated string
 *
 * @example
 * ```ts
 * truncate('hi-diddly-ho there, neighborino');
 * // => 'hi-diddly-ho there, neighbo...'
 *
 * truncate('hi-diddly-ho there, neighborino', {
 *   length: 24,
 *   omission: ' [...]'
 * });
 * // => 'hi-diddly-ho there [...]'
 *
 * truncate('hi-diddly-ho there, neighborino', {
 *   length: 24,
 *   omission: ' [...]',
 *   separator: ' '
 * });
 * // => 'hi-diddly-ho there [...]'
 *
 * truncate('hi-diddly-ho there, neighborino', {
 *   length: 24,
 *   omission: ' [...]',
 *   separator: /,? +/
 * });
 * // => 'hi-diddly-ho there [...]'
 * ```
 */
export declare function truncate(string: string, options?: {
    length?: number;
    omission?: string;
    separator?: string | RegExp;
}): string;