node.js - err empty response when trying to insert into mongodb using node -

i'm quite new mean stack , trying create application has 2 data collections, 'users' , 'courses'. users have used login-and registration example , works fine. courses have tried re-create same structure (so files named including same course has similar 1 named user) courses having trouble creating new course , adding database. err empty response cannot understand why , how correct it. below (compressed) code, let me know if more information needed. have excluded client-side code since know error on server-side. server.js called following command client-side:

function create(course) { return $http.post('/api/courses', course).then(handlesuccess, handleerror); } 

server.js

require('rootpath')(); var express = require('express'); var app = express(); var session = require('express-session'); var expressjwt = require('express-jwt'); var config = require('config.json'); var bodyparser = require('body-parser');  app.set('view engine', 'ejs'); app.set('views', __dirname + '/views'); app.use(bodyparser.urlencoded({ extended: false })); app.use(bodyparser.json()); app.use(session({ secret: config.secret, resave: false, saveuninitialized: true           }));  // use jwt auth secure api app.use('/api', expressjwt({ secret: config.secret }).unless({ path: ['/api/users/authenticate', '/api/users/register'] }));  // routes app.use('/login', require('./controllers/login.controller')); app.use('/register', require('./controllers/register.controller')); app.use('/app', require('./controllers/app.controller')); app.use('/api/users', require('./controllers/api/users.controller')); app.use('/api/courses', require('./controllers/api/courses.controller.js')); //app.use('/registercourse', require('./controllers/create.course.controller'));  // make '/app' default route app.get('/', function (req, res) {     return res.redirect('/app'); });  var ipaddress = process.env.openshift_nodejs_ip || "127.0.0.1"; var port      = process.env.openshift_nodejs_port || 3000;  // start server var server = app.listen(port, ipaddress); 

controllers/api/courses.controller

i don't think error in file since calls courseservice, wrong.

var config = require('config.json'); var express = require('express'); var router = express.router(); var courseservice = require('services/course.service');  router.post('/', createcourse);  module.exports = router;  function createcourse(req,res){ courseservice.create(req.body)     .then(function(){         res.sendstatus(200);     })     .catch(function(err) {         res.status(400).send(err);     }); } 

services/course.services think error in file since not behave same services/user.services do. in services/user.services, db.users becomes bold , connected db.bind('users') not work in file, db.courses looks db.courses. have tried introducing namespace, seems connect db.courses db.bind('course') still same error.

var config = require('config.json'); var _ = require('lodash'); var jwt = require('jsonwebtoken'); var bcrypt = require('bcryptjs'); var q = require('q'); var mongo = require('mongoskin');  var connectionstring = "mongodb://localhost:27017/mean-stack-registration-login-example"; if(process.env.openshift_mongodb_db_url){     connectionstring = process.env.openshift_mongodb_db_url + "studycontrol"; } var db = mongo.db(connectionstring, { native_parser: true });  db.bind('courses');  var service = {}; service.create = create; module.exports = service;  module.exports = service;  function create(courseparam) {     var deferred = q.defer();     //validation     db.courses.findone(         {coursename: courseparam.coursename}),         function (err, course) {             if (err) deferred.reject(err);             if (course) {                 deferred.reject('coursename "' + courseparam.coursename + '" taken');             } else {                 createcourse()             }         };      function createcourse() {         var course = courseparam         db.courses.insert(             course,             function (err, doc) {                 if (err) deferred.reject(err);                 deferred.resolve();             });     }      return deferred.promise;  }