使用 express 中的multer上传文件， 上传的文件没有后缀名如何解决？

使用 express 中的multer上传文件， 上传的文件没有后缀名

var uploadZoneFile = upload.fields([{
                                        name: 'uploadLittleimg',
                                        maxCount: 1
                                    }, {
                                        name: 'uploadImg',
                                        maxCount: 1
                                    }, {
                                        name: 'uploadVoice',
                                        maxCount: 1
                                    }]);

router.post('/addZone', uploadZoneFile, function(req, res, next){


    console.log(req.files)

    var _uploadLittleimg = req.files.uploadLittleimg;
    var _uploadImg = req.files.uploadImg;
    var _uploadVoice = req.files.uploadVoice;

    if(_uploadLittleimg) req.body.littleimg = "/uploads/" + _uploadLittleimg[0].filename;
    if(_uploadImg) req.body.img = "/uploads/" + _uploadImg[0].filename;
    if(_uploadVoice) req.body.voice = "/uploads/" + _uploadVoice[0].filename;
    next();

}
...

其中有 filename 和 mimetype， 如何把文件后缀名加上去？
去官网看了没有参数做这种操作，
看源码我也很费力， 我还是新手， 求大神指点 谢谢

---

那你就不能再用upload.fields了，你得用diskStorage，代码类似：

var storage = multer.diskStorage({
  destination: function (req, file, cb) {
    cb(null, '/uploads');
  },
  filename: function (req, file, cb) {
    cb(null, file.fieldname + '.自己在这配置后缀名吧');
  }
})

var upload = multer({ storage: storage })

router.post('/addZone', upload, function(req, res, next){


    console.log(req.files)

    var _uploadLittleimg = req.files.uploadLittleimg;
    var _uploadImg = req.files.uploadImg;
    var _uploadVoice = req.files.uploadVoice;

    if(_uploadLittleimg) req.body.littleimg = "/uploads/" + _uploadLittleimg[0].filename;
    if(_uploadImg) req.body.img = "/uploads/" + _uploadImg[0].filename;
    if(_uploadVoice) req.body.voice = "/uploads/" + _uploadVoice[0].filename;
    next();

}