Extract Root Domain from a URL

const url = "https://www.example.com/path/to/page?id=123";
const regex = /(?:https?:\/\/)?(?:www\.)?([a-zA-Z0-9.-]+\.[a-zA-Z]{2,})/; // Catches example.com
const match = url.match(regex);

if (match && match[1]) {
    console.log(match[1]); // "example.com"
} else {
    console.log("No domain found.");
}

How it works: This regex uses non-capturing groups `(?:...)` for optional `http(s)://` and `www.`. The key part is the capturing group `([a-zA-Z0-9.-]+\.[a-zA-Z]{2,})` which matches one or more alphanumeric characters, dots, or hyphens, followed by a dot and at least two letters for the top-level domain. This effectively isolates the root domain from the URL.