Javascript/Regex for finding just the root domain name without sub domains

Question

I had a search and found lot's of similar regex examples, but not quite what I need.

I want to be able to pass in the following urls and return the results:

• www.google.com returns google.com

• sub.domains.are.cool.google.com returns google.com

• doesntmatterhowlongasubdomainis.idont.wantit.google.com returns google.com

• sub.domain.google.com/no/thanks returns google.com

Hope that makes sense :) Thanks in advance!-James

Answer 1

I've not done a lot of testing on this, but if I understand what you're asking for, this should be a decent starting point...

([A-Za-z0-9-]+\.([A-Za-z]{3,}|[A-Za-z]{2}\.[A-Za-z]{2}|[A-za-z]{2}))\b

EDIT:

To clarify, it's looking for:

one or more alpha-numeric characters or dashes, followed by a literal dot

and then one of three things...

1. three or more alpha characters (i.e. com/net/mil/coop, etc.)
2. two alpha characters, followed by a literal dot, followed by two more alphas (i.e. co.uk)
3. two alpha characters (i.e. us/uk/to, etc)

and at the end of that, a word boundary (\b) meaning the end of the string, a space, or a non-word character (in regex word characters are typically alpha-numerics, and underscore).

As I say, I didn't do much testing, but it seemed a reasonable jumping off point. You'd likely need to try it and tune it some, and even then, it's unlikely that you'll get 100% for all test cases. There are considerations like Unicode domain names and all sorts of technically-valid-but-you'll-likely-not-encounter-in-the-wild things that'll trip up a simple regex like this, but this'll probably get you 90%+ of the way there.