何度も似たようなの書いてるのでメモ。

regexp_url.js

// URL RegureExpression.
var regURL = /(https?:)\/\/([^\/]+)(([^?#]*\/)?([^#?]+)?)(\?[^#?]+)?(#.*)?/;
// if matched returns below
// 0: URL       ex) "http://example.com/path/to/index.html?foo=bar#baz"
// 1: Scheme    ex) "http:"
// 2: Domain    ex) "example.com"
// 3: Path      ex) "/path/to/index.html"
// 4: Directory ex) "/path/to/"
// 5: File      ex) "index.html"
// 6: Query     ex) "?foo=bar"
// 7: Hash      ex) "#baz"

regURL.exec("http://example.com");
["http://example.com", "http:", "example.com", "", undefined, undefined, undefined, undefined]

regURL.exec("http://example.com/");
["http://example.com/", "http:", "example.com", "/", "/", undefined, undefined, undefined]

regURL.exec("http://example.com/index.html");
["http://example.com/index.html", "http:", "example.com", "/index.html", "/", "index.html", undefined, undefined]

regURL.exec("http://example.com/path/to/index.html");
["http://example.com/path/to/index.html", "http:", "example.com", "/path/to/index.html", "/path/to/", "index.html", undefined, undefined]

regURL.exec("http://example.com/path/to/index.html?foo=bar");
["http://example.com/path/to/index.html?foo=bar", "http:", "example.com", "/path/to/index.html", "/path/to/", "index.html", "?foo=bar", undefined]

regURL.exec("http://example.com/path/to/index.html?foo=bar#baz");
["http://example.com/path/to/index.html?foo=bar#baz", "http:", "example.com", "/path/to/index.html", "/path/to/", "index.html", "?foo=bar", "#baz"]

regURL.exec("http://example.com/?foo=bar");
["http://example.com/?foo=bar", "http:", "example.com", "/", "/", undefined, "?foo=bar", undefined]

regURL.exec("http://example.com/#baz");
["http://example.com/#baz", "http:", "example.com", "/", "/", undefined, undefined, "#baz"]

regexp_url_2.js

// 以下のようにauth, port 等にも対応した版
// https://user:pass@example.com:8080/path/to/file.html?foo=bar&#baz
var regURL = /(https?:)\/\/(([^\/@]+)@)?(([^\/:@]+):?(\d+)?)(([^?#]*\/)?([^#?]+)?)(\?[^#?]+)?(#.*)?/;


regURL.exec("https://user:pass@example.com:8080/path/to/file.html?foo=bar&#baz")
["https://user:pass@example.com:8080/path/to/file.html?foo=bar&#baz",
  "https:",
  "user:pass@",
  "user:pass",
  "example.com:8080",
  "example.com",
  "8080",
  "/path/to/file.html",
  "/path/to/",
  "file.html",
  "?foo=bar&",
  "#baz"]

// TODO test case