使用JavaScript从URL提取域名

Question

I need a general script/pattern to extract the main domain name from URLs. I have the following attempt that failed.

Let use say I have this link1 and need to extract the main domain name (google.co.uk) without the sub-domain (mail). I made this script which worked fine with .co.uk but will fail with websites that has one top-level domain name like: .com and .com .

Is there a better way to extract main domain name from ANY URL? The URL is constructed as follows:

https://(optional sub-domain)*(domain name with two or three top-level domain name)(optional forward slash followed by text)*

The * refer to zero or more times.

var link1="https://mail.google.co.uk/link/link/link";
var url = new URL(link1);
var domain = url.hostname.split('.').slice(-3).join('.');
console.log("The domain name is: "+ domain);

In the above code, I expect: google.co.uk

It could work because the link has two parts in the top-level domain name ( .co.uk ) so -3 works. But I need the code to work with this link as well:

var link1="https://mail.google.com/link/link/link";

And I need the output to be: google.com

But the problem is that the code produces:

mail.google.com

And I only want the main domain name: google.com

EDIT: Some of the expected output examples are here:

1) In mail.google.co.uk it should be: google.co.uk

2) In mail.google.com it should be: google.com

3) In link.mail.google.com/link/link it should be: google.com

4) In link.link2.mail.google.com it should be: google.com

ie just the main domain name without sub-domains or links after the domain name. The top-level domain name can be in the fom of (.com, .net, .org, etc.) or in the form of (.co.uk, .co.us, etc). The top-level domain name should be captured either if it is one part or two parts (my code capture only two parts).

Answer 1

Sure if you wanted

"mail.google.co.uk"

you can just use

url.host

or if you wanted it with headers, use

url.origin

cheers!