editBackend.js

router.post('/updateUser', function(req, res, next) {
  var user = new User(req.body);

  User.update({_id : user.id}, user, function(err) {
    if (err) {
      console.log("not updated!");
      res.status(400);      
      res.send();
    }

    console.log("updated!");
    res.send({status: 'ok'});
  });
});