Question

I use this js code to match a hostname from a string:

url.match(/:\/\/(www\.)?(.[^/:]+)/);

This works when the url has protocol:// at the beginning. For example:

This works fine:

var url = "http://domain.com/page";
url.match(/:\/\/(www\.)?(.[^/:]+)/);

But this doesn’t:

var url = "domain.com/page";
url.match(/:\/\/(www\.)?(.[^/:]+)/);

I have tried:

url.match(/(:\/\/)?(www\.)?(.[^/:]+)/);

And that matches fine the hostname when it doesn’t contain protocol://, but when it does contains it it only returns the protocol and not the hostname.

How could I match the domain when it doesn’t contains it?

Answer 1

OK before you have a brain meltdown from @xanatos answer here is a simple regex for basic needs. The other answers are more complete and handle more cases than this regex :

(?:(?:(?:\bhttps?|ftp)://)|^)([-A-Z0-9.]+)/

Group 1 will have your host name. URL parsing is a fragile thing to do with regexes. You were on the right track. You had two regexes that worked partially. I simply combined them.

Edit : I was tired yesterday night. Here is the regex for jscript

if (subject.match(/(?:(?:(?:\bhttps?|ftp):\/\/)|^)([\-a-z0-9.]+)\//i)) {
    // Successful match
} else {
    // Match attempt failed
}