angularjs - router.post returns error "undefined is not a function" .Using mongo and express.js -

i'm trying buld app using files link .i found posting code breaks.has express js changed or syntax mistake ?

the router.post breaks once reaches maid.registermaid(new maid({... .i'm able make work using .save() explain why callback beaking ?

putting code below.. sorry, i'm beginner in m.e.a.n

api.js

var express = require('express'), router = express.router(), passport = require('passport'); user = require('../models/user.js'); maid = require('../models/maid.js');  router.post('/addmaid', function(req, res) {  console.log(req.body, req.body.firstname,req.body.lastname); maid.registermaid(new maid({ firstname: req.body.firstname }), ({lastname: req.body.lastname}), function(err, account) {     if (err) {         return res.status(500).json({err : err})     }     return res.status(200).json({status: 'registration successful!'}); }); 

});

services.js

angular.module('myapp').factory('authservice',['$q', '$timeout', '$http',     function ($q, $timeout, $http) {  var user = null; return ({   isloggedin: isloggedin,   getuserstatus: getuserstatus,   login: login,   logout: logout,   register: register,   registermaid: registermaid });   function registermaid(fname, lname) {      var deferred = $q.defer();      $http.post('/maid/addmaid', {         firstname : fname,         lastname : lname                     }).success(function(data, status) {          if (status === 200 && data.status) {             deferred.resolve();         } else {             deferred.reject();         }      }).error(function(data) {         debugger;         alert("error in services addmaid");         deferred.reject();     });     return deferred.promise; } }]);  

controllers.js

angular.module('myapp').controller('addmaidcontroller', ['$scope',        '$http','$location', 'authservice', function($scope, $http,$location,     authservice) {   console.log(authservice.getuserstatus());  $scope.register = function () {     $scope.error = false;     $scope.disabled = true;             authservice.registermaid($scope.registerform.firstname,$scope.registerform.lastname).then(function () {                     $scope.disabled = false;         $scope.registerform = {};      }).catch(function () {         $scope.error = true;         $scope.errormessage = "something went wrong!";     });         };}]); 

maid.js

var mongoose = require('mongoose'), schema = mongoose.schema;  var maid = new schema({ first_name: string, last_name: string });  module.exports = mongoose.model('maids', maid);  

first of globally defined ur user , maid modules, not practice. error occurs because maid module (maid model on server side, i.e. nodejs) doesnt have registermaid method. need use maid.create instead