[minor] Added missing JSDoc comments

lib/http-proxy/common.js

@@ -102,17 +102,36 @@ common.setupSocket = function(socket) {
  return socket;
 };
 
+/**
+ * Get the port number from the host. Or guess it based on the connection type.
+ *
+ * @param {Request} req Incoming HTTP request.
+ *
+ * @return {String} The port number.
+ *
+ * @api private
+ */
 common.getPort = function(req) {
- var res = req.headers.host ? req.headers.host.match(/:(\d+)/) : "";
+ var res = req.headers.host ? req.headers.host.match(/:(\d+)/) : '';
+
  return res ?
  res[1] :
- req.connection.pair ? '443' : '80' ;
+ req.connection.pair ? '443' : '80';
 };
 
-// OS-agnostic join (doesn't break on URLs like path.join does on Windows)
+/**
+ * OS-agnostic join (doesn't break on URLs like path.join does on Windows)>
+ *
+ * @return {String} The generated path.
+ *
+ * @api private
+ */
+
 common.urlJoin = function() {
  var args = Array.prototype.slice.call(arguments);
- // Join all strings, but remove empty strings so we don't get extra slashes from 
+ // Join all strings, but remove empty strings so we don't get extra slashes from
  // joining e.g. ['', 'am']
- return args.filter(function(a) { return !!a; }).join('/').replace(/\/+/g, '/');
+ return args.filter(function filter(a) {
+ return !!a;
+ }).join('/').replace(/\/+/g, '/');
 };