failed uploading file using Express4 and multer

I am trying to do the image ajax upload using Express4 and multer, but it doesn't work

here is my request screenshot

and here is the server script

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

router.route('/upload')
  .post(upload.single('file'), function(req, res) {
    console.log(req.file);
    //req.file is undefined
});

updated client code:

import Ember from 'ember';

export default Ember.TextField.extend({
  type: 'file',
  change: function(e) {
    var inputFiles = e.target.files;
    var inputFile = inputFiles[0];
    var formData = new FormData();
    formData.append('file', inputFile);
    Ember.$.ajax({
      type: 'POST',
      url: '/upload',
      data: formData,
      cache: false,
      contentType: false,
      processData: false,
      success: function(data) {
        console.log(data);
      },
      error: function(err) {
        console.error(err)
      }
    })
  }
});