今天在做一个图片上传的功能，在用formidable的时候遇到一个问题，查了很多资料，但是渣渣的我还是找不到原因，求大神解答解答。

下面是我的报错的提示：

而我的代码如下：

入口文件 blog.js

var express=require('express'),
	mongoose=require('mongoose'),
	mongoStore=require('connect-mongo')(express),
	blog=module.export=express(),
	ejs=require('ejs'),
	dbUrl='mongodb://localhost/myblog',	
	SessionStore=require('session-mongoose')(express),
	db;	
mongoose.connect(dbUrl);
db=mongoose.connection;	
var store=new SessionStore({
	url:dbUrl,
	interval:120000
})	
blog.configure(function(){
	blog.set('views',__dirname+'/blog/views');
	blog.engine('.html',ejs.__express);
	blog.set('view engine','.html');
	blog.set("view options",{
		layout:false
	})
	blog.use(express.bodyParser());
	blog.use(express.methodOverride());
	blog.use(express.cookieParser());
	blog.use(express.cookieSession({
		key:'user',
		secret:'myblog',
		store:store,
		cookie:{maxAge:1200000}
	}));
	blog.use(express.static(__dirname+'/public'));
	
});
db.on('error',function(err){
	console.log("link to database error!");
})	
db.once('open',function(){
	require('./config/route')(blog);
})	
blog.listen(4000)

路由文件 route.js

		  var coverApi=require('../blog/controllers/cover');	  
		module.exports=function(blog){		  
		  blog.use(function(req,res,next){
			  var _user=req.session.user;
			  blog.locals.user=_user;
			  next();
		  })			  
		 blog.post('/manage/addCover.html',coverApi.addCover);	  
	  }

控制器文件 cover.js

	 var fs=require('fs'),
	path=require('path'),
	formidable=require('formidable'),
	Article=require('../models/article'),
	coverApi={},
	util = require('util');	
module.exports=coverApi;	
coverApi.addCover=function(req,res){ 

	var form = new formidable.IncomingForm({uploadDir:'./sources/'});
	form.parse(req, function(err, fields, files) {
		if(err) console.log(err);//这里报错了
	  res.writeHead(200, {'content-type': 'text/plain'});
	  res.write('received upload:\n\n');
	  res.end(util.inspect({fields: fields, files: files}));
	});
	
}	
coverApi.show=function(req,res){
	var id=req.params.id;
	res.render('cover',{
		id:id
	});	
}

视图文件 cover.html

	<div class="container">
		<h1>添加图片</h1>
		<form action="/manage/addCover.html" method='post' enctype="multipart/form-data">
			<div class="form-group">
				<input type="text" class='hidden' value="<%= id%>" name='id'>
				<label for="">图片</label>
				<input type="file"  name='cover'>
				<button type='submit' class='btn btn-lg btn-primary'>add</button>
			</div>
		</form>
	</div>

package.json 文件

项目目录结构

现在那个问题还是解决不了，求大神帮忙解答