船长gridfs验证和表达响应问题

Question

我在express.js应用程序中使用skipper-gridfs模块将图像上传到mongoDb。我的上传代码如下

        upload: function  (req, res) {
                req.file('avatar')
                    .upload({
                        adapter: require('skipper-gridfs'),
                        uri: 'mongodb://localhost:27017/test.images'
                    }, function (err, uploadedFiles) {
                        if (err) return res.negotiate(err);
                        else return res.ok({
                            files: uploadedFiles,
                            });
                    });
            }


    I get the following response from this...

    {
        "files": [
            {
                "fd": "2d8910a0-8ca2-4df1-9930-6ddd721a0416.jpg",
                "size": 172883,
                "type": "image/jpeg",
                "filename": "Photo on 12-20-14 at 9.53 PM.jpg",
                "status": "bufferingOrWriting",
                "field": "avatar",
                "extra": {
                    "fileId": "54aee6ced4a0e88f0dc9025f",
                    "fd": "2d8910a0-8ca2-4df1-9930-6ddd721a0416.jpg",
                    "dirname": "."
                }
            }
        ]
    }

I am sending the image in a post request using google chrome rest client, and My question is need to check the file size and type before uploading the file in db  , what shall I do ?

有人可以帮我这个吗？提前谢谢。