Extracting top-level and second-level domain from a URL using regex

Question

How can I extract only top-level and second-level domain from a URL using regex? I want to skip all lower level domains. Any ideas?

Answer 1

For anyone using JavaScript and wanting a simple way to extract the top and second level domains, I ended up doing this:

'example.aus.com'.match(/\.\w{2,3}\b/g).join('')

This matches anything with a period followed by two or three characters and then a word boundary.

Here's some example outputs:

'example.aus.com'       // .aus.com
'example.austin.com'    // .austin.com
'example.aus.com/howdy' // .aus.com
'example.co.uk/howdy'   // .co.uk

Some people might need something a bit cleverer, but this was enough for me with my particular dataset.

Edit

I've realised there are actually quite a few second-level domains which are longer than 3 characters (and allowed). So, again for simplicity, I just removed the character counting element of my regex:

'example.aus.com'.match(/\.\w*\b/g).join('')