Getting parts of a URL (Regex)

I'm a few years late to the party, but I'm surprised no one has mentioned the Uniform Resource Identifier specification has a section on parsing URIs with a regular expression. The regular expression, written by Berners-Lee, et al., is:

^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\?([^#]*))?(#(.*))?
 12            3  4          5       6  7        8 9

The numbers in the second line above are only to assist readability; they indicate the reference points for each subexpression (i.e., each paired parenthesis). We refer to the value matched for subexpression as $. For example, matching the above expression to

http://www.ics.uci.edu/pub/ietf/uri/#Related

results in the following subexpression matches:

$1 = http:
$2 = http
$3 = //www.ics.uci.edu
$4 = www.ics.uci.edu
$5 = /pub/ietf/uri/
$6 = <undefined>
$7 = <undefined>
$8 = #Related
$9 = Related

For what it's worth, I found that I had to escape the forward slashes in JavaScript:

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

A single regex to parse and breakup a full URL including query parameters and anchors e.g.

https://www.google.com/dir/1/2/search.html?arg=0-a&arg1=1-b&arg3-c#hash

^((http[s]?|ftp):\/)?\/?([^:\/\s]+)((\/\w+)*\/)([\w\-\.]+[^#?\s]+)(.*)?(#[\w\-]+)?$

RexEx positions:

url: RegExp['$&'],

protocol:RegExp.$2,

host:RegExp.$3,

path:RegExp.$4,

file:RegExp.$6,

query:RegExp.$7,

hash:RegExp.$8

you could then further parse the host ('.' delimited) quite easily.

What I would do is use something like this:

/*
    ^(.*:)//([A-Za-z0-9\-\.]+)(:[0-9]+)?(.*)$
*/
proto $1
host $2
port $3
the-rest $4

the further parse 'the rest' to be as specific as possible. Doing it in one regex is, well, a bit crazy.

I realize I'm late to the party, but there is a simple way to let the browser parse a url for you without a regex:

var a = document.createElement('a');
a.href = 'http://www.example.com:123/foo/bar.html?fox=trot#foo';

['href','protocol','host','hostname','port','pathname','search','hash'].forEach(function(k) {
    console.log(k+':', a[k]);
});

/*//Output:
href: http://www.example.com:123/foo/bar.html?fox=trot#foo
protocol: http:
host: www.example.com:123
hostname: www.example.com
port: 123
pathname: /foo/bar.html
search: ?fox=trot
hash: #foo
*/