Cant get the middleware work in express 4

I am just following the readme tutorial and encountered the problem of

Error: Unexpected field 
    at makeError (*\node_modules\multer\lib\make-error.js:12:13)

my code look like this:

var express = require('express');
var app = express();

var multer = require('multer');
var upload = multer({ dest: './uploads/'});

app.post('/image',upload.single('avatar'), function (req, res) {
    var image = req.body;
    res.status(204).end()
});

my client is angular from the tutorial :https://uncorkedstudios.com/blog/multipartformdata-file-upload-with-angularjs

I cant find the solution can you help me?

[LinusU]

What is the field name of the file uploaded? <input type="file" name="THISVALUE" />

The code you are using is expecting it to be avatar.

[rakeen]

Got it. I was using ng2-file-upload to send the XHR request. By default they set the name of all the fields to file.