[fix] Optimize fix for x-forwarded-for-port.

Author: indexzero

Diff for: lib/node-http-proxy/http-proxy.js

@@ -30,6 +30,13 @@ var events = require('events'),
     url = require('url'),
     httpProxy = require('../node-http-proxy');
 
+//
+// @private {RegExp} extractPort
+// Reusable regular expression for getting the
+// port from a host string.
+//
+var extractPort = /:(\d+)$/;
+
 //
 // ### function HttpProxy (options)
 // #### @options {Object} Options for this instance.
@@ -957,14 +964,12 @@ HttpProxy.prototype._forwardRequest = function (req) {
 };
 
 function getPortFromHostHeader(req) {
-  var portMatch = req.headers.host.match(/:(\d+)$/);
-
-  if(portMatch) {
-    return parseInt(portMatch[1]);
-  }
-  else {
-    return getProto(req) === 'https' ? 443 : 80;
+  var match;
+  if ((match = extractPort.exec(req.headers.host))) {
+    return parseInt(match[1]);
   }
+
+  return getProto(req) === 'https' ? 443 : 80;
 }
 
 function getProto(req) {