node.js怎么获取文件上传的进度

{ fields: { title: 'Hello World' }, files: { upload: { size: 1558, path: '/tmp/1c747974a27a6292743669e91f29350b', name: 'us-flag.png', type: 'image/png', lastModifiedDate: Tue, 21 Jun 2011 07:02:41 GMT, _writeStream: [Object], length: [Getter], filename: [Getter], mime: [Getter] } } }

这是请求的内容，请问一下，我怎么判断这个文件有没有上传完成到服务器，求大神教，纠结很久了，