TypeError：Router.use()需要中间件功能,但有一个Object

我的app.js代码

var express = require('express');
var path = require('path');
var favicon = require('serve-favicon');
var logger = require('morgan');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');
 
var routes = require('./routes/index');
var users = require('./routes/users');
 
var app = express();
 
// view engine setup
app.set('views',path.join(__dirname,'views'));
app.set('view engine','ejs');
 
// uncomment after placing your favicon in /public
//app.use(favicon(__dirname + '/public/favicon.ico'));
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname,'public')));
 
app.use('/',routes);
app.use('/users',users);
 
 
 
/// catch 404 and forwarding to error handler
app.use(function(req,res,next) {
    var err = new Error('Not Found');
    err.status = 404;
    next(err);
});
 
/// error handlers
 
// development error handler
// will print stacktrace
if (app.get('env') === 'development') {
    app.use(function(err,req,next) {
        res.status(err.status || 500);
        res.render('error',{
            message: err.message,error: err
        });
    });
}
 
// production error handler
// no stacktraces leaked to user
app.use(function(err,next) {
    res.status(err.status || 500);
    res.render('error',{
        message: err.message,error: {}
    });
});
 
module.exports = app;

我的index.js代码

var express = require('express');
var router = express.Router();
 
/* GET home page. */
router.get('/',function(req,res) {
    res.render('index',{ title: 'Express' });
});
 
/* GET Hello World page. */
router.get('/helloworld',res) {
    res.render('helloworld',{ title: 'Hello,World!' })
});
 
module.exports = router;

我刚刚使用Node和express.我不明白我哪里错了.任何人都可以看到我的问题是什么？