我正在使用nodejs/Express js，我试图使用“API”上传图像，图像正在上传，但“图像名称”中缺少扩展名，我如何解决这个问题？这是我当前的代码

var storage =   multer.diskStorage({
  destination: function (req, file, callback) {
    callback(null, './uploads');
  },
  filename: function (req, file, callback) {
      console.log('data is'+ file.ext);
    callback(null, file.ext + '-' + Date.now());
  }
});

 var upload = multer({ storage: storage }).any('userPhoto');
 const uploadavatar = function (req, res) {
    upload(req,res,function(err) {
        if(err) {
            return res.end("Error uploading file." + err);
        }
        res.end("File is uploaded");
    });
};