使用multer NodeJs更改文件名

Question

我必须上传一个名称取决于发送的变量的文件到请求。所以我有一个声明的变量imageType，用于multer.diskStorage我还有另一个变量用于动态路径，imagePath它的工作方式与我使用的相同imageType，但我从undefined-logo.jpg获得imageType。这是代码：

var imagePath = '';
var imageType = '';
var storage = multer.diskStorage({
    destination: function (req, file, callback) {
        callback(null, imagePath);
    },
    filename: function (req, file, callback) {
        callback(null, (imageType + '-logo.jpg'));
    }
});

var upload = multer({ storage: storage }).single('file');

router.route('/representatives/:id/loginLogo')
    .post((req, res, next) => {
    /////SOME CODE BEFORE/////
    if (rows[0].client_directory == '') {
        imagePath = `${rows[0].subdomain_directory}`;
    } else {
        imagePath = `${rows[0].subdomain_directory}/${rows[0].client_directory}/`;
    }
    imageType = req.body.imageType;

upload(req, res, function (err) {
    if (err) {
       return next(err);
    }
    var sql = `UPDATE representatives SET login_logo = 'jpg' WHERE id = ${req.params.id}`;
    conn.query(sql, (err, rows, fields) => {
        if (err) {
            return next(err);
        }
        res.json({ message: 'Image uploaded!', representative: req.body.imageType}); //HERE RETURNS req.body.imageType OK
    })
  })
})

你可以帮帮我吗？谢谢！