/**
 * Returns the number (integer) of DNS domain levels (number of dots) in the
 * hostname.
 *
 * Examples:
 *
 * ``` js
 * dnsDomainLevels("www")
 *   // returns 0.
 * dnsDomainLevels("www.netscape.com")
 *   // returns 2.
 * ```
 *
 * @param {String} host is the hostname from the URL.
 * @return {Number} number of domain levels
 */
export default function dnsDomainLevels(host: string): number;