url: add a got host pattern in url.js

Add a hostPattern variable for readable purposes

PR-URL: https://github.com/nodejs/node/pull/9653
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Brian White <mscdex@mscdex.net>

lib/url.js

@@ -38,6 +38,7 @@ function Url() {
 // compiled once on the first module load.
 const protocolPattern = /^([a-z0-9.+-]+:)/i;
 const portPattern = /:[0-9]*$/;
+const hostPattern = /^\/\/[^@/]+@[^@/]+/;
 
 // Special case for a simple path URL
 const simplePathPattern = /^(\/\/?(?!\/)[^\?\s]*)(\?[^\s]*)?$/;
@@ -200,7 +201,7 @@ Url.prototype.parse = function(url, parseQueryString, slashesDenoteHost) {
   // user@server is *always* interpreted as a hostname, and url
   // resolution will treat //foo/bar as host=foo,path=bar because that's
   // how the browser resolves relative URLs.
-  if (slashesDenoteHost || proto || /^\/\/[^@/]+@[^@/]+/.test(rest)) {
+  if (slashesDenoteHost || proto || hostPattern.test(rest)) {
     var slashes = rest.charCodeAt(0) === 47/*/*/ &&
                   rest.charCodeAt(1) === 47/*/*/;
     if (slashes && !(proto && hostlessProtocol[proto])) {