在fs.mkdir您删除会话后，听起来很异国。（我发现了您的其他问题）

但是回到问题，这里有一些代码片段，您可以使用会话（redis）。

var express = require('express')
  , fs = require('fs')
  , http = require('http')
  , RedisStore = require('connect-redis')(express)
  , sessionStore = new RedisStore()
  , app = express()
  ;

app.configure(function(){
  app.set('port', 3000);
  app.use(express.bodyParser());
  app.use(express.methodOverride());
  app.use(express.cookieParser('secret'));
  app.use(express.session({
    store: sessionStore
  }));
  app.use(express.static(__dirname + '/public'));
  app.use(express.errorHandler({ dumpExceptions: true, showStack: true }));
});

app.get( '/', function(req, res){
  res.setHeader("Content-Type", "text/html");
  console.log( req.session );
  console.log( '------------------------' );
  res.end( 'root' );
});

app.get( '/dir/:id', function(req, res){
  console.log( req.session );
  console.log( '------------------------' );

  fs.mkdir( req.params.id );
  if ( req.session.dirs === undefined )
    req.session.dirs = [];
  req.session.dirs.push( req.params.id );

  console.log( req.session );
  console.log( '------------------------' );

  res.setHeader("Content-Type", "text/html");
  res.end( 'dir' );
});


server = http.createServer(app).listen(3000);

您应该阅读express的文档，并浏览express
的示例