Regular Expression - Extract subdomain & domain

Question

Your regex doesn't seem correct. Try this regex:

/^(?:https?:\/\/)?(?:[^@\n]+@)?(?:www\.)?([^:\/\n?]+)/img

RegEx Demo

You are about the one millionth person to try to parse URLs in JavaScript. I'm a little bit surprised you didn't see any of the existing questions on SO dating back years. The last thing you want to do is write yet another broken regexp, with all due respect to those that provided answers to your question.

There are many well documented libraries and approaches to handling this. Google it. The simplest way is to create an a element in memory, assign it an href, and then access its hostname and other properties. See http://tutorialzine.com/2013/07/quick-tip-parse-urls/. If that does not float your boat, then use a library like uri.js.

If you really don't want to use a library, and insist on reinventing the wheel, then at least do something like the following:

function get_domain_from_url(url) {
    var a = document.createElement('a').
    a.setAttribute('href', url);
    return a.hostname;
}

Essentially, you are delegating the extraction of the subdomain/domain part of the URL to the browser's URL parsing logic, which is MUCH better than anything you will ever write.

Also see Parse URL with jquery/ javascript?, Parse URL with Javascript, How do I parse a URL into hostname and path in javascript?, or parse URL with JavaScript or jQuery. How did you miss those? Sorry, I have to vote to close this as a duplicate.

The same RegExp as in anubhava's answer, only added support for protocol-relative URLs like //google.com:

/^(?:https?:)?(?:\/\/)?(?:[^@\n]+@)?(?:www\.)?([^:\/\n]+)/im

RegEx Demo

Here's a solution ignoring everything before ://

.*\://?([^\/]+)

Incase you want to ignore www.

.*\://(?:www.)?([^\/]+)