按着github上的例子还是出错。

<form  id="addimgForm" method="post" enctype="multipart/form-data" action="/profile">  
    <input type='file' id='uploadedimg' name="file" accept='.jpg,.jpeg,.gif,.png,.bmp' ></input>
    <button  type="submit">上传</button>
  </form>

var  upload = multer({
    storage: multer.diskStorage({
        destination: function (req, file, cb) {
            cb(null, './uploads/')
        },
        filename: function (req, file, cb) {
            cb(null, file.originalname)
        }
    })
});

//var upload = multer({ dest: 'uploads/' })
app.post('/profile',upload.single('avatar'),function (req, res, next) {
  // req.file is the `avatar` file
  // req.body will hold the text fields, if there were any
  console.log(req.file);
})