nodejs如何提供本地文件的http访问路径？

Question

一个上传图片返回url的nodejs程序，返回

{

  "name": "name",

  "url": "/uploader/upload"

}

怎么才能将本地路径转化成http路径呢，比如 example.com/upload/a.jpg

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

    if (req.busboy) {

        var name = ''

        req.busboy.on('file', function (fieldname, file, fileName, encoding, mimeType) {

            name = fileName

            var stream = fs.createWriteStream(path.join(__dirname, '../', uploadPath, fileName))

            file.pipe(stream)

            console.log('uploading %s -> %s', fileName, stream.path)

        }).on('finish', function () {

            res.send({

                name: 'name',

                url: path.join(uploadPath, name)

            })

        })

        req.pipe(req.busboy)

    } else {

        console.log('uploadFile - busboy undefined.')

        res.status(502)

    }

})