node.js - CORS enabled - ajax response failure -

i trying make ajax 'post' request backbone client node.js server. have enabled cors on server seems successful not getting 'allow-cross-origin' errors in console' , server receiving posted data - posting username / password client , searching match in user database - server responds username found receiving ajax error on client. can soemone please - has been killing me days

here client user model:

app.userauth = backbone.model.extend({     defaults : {     username : '',     password : '' }, initialize : function(){     this.testreq() }, testreq : function(){     $.ajax({         url : "http://localhost:8080/api/authenticate",         method : "post",         datatype : "json",         xhrfields : {             withcredentials : true         },         data : {             username:"bottles24",             password:"yoyo1234"         },         success : function(data){             console.log(data);         },         error : function(thrownerror){             console.log(thrownerror)         }     }); } }); 

and here server.js file being run on different port client:

var express = require('express'), app     = express(), bodyparser = require('body-parser'), morgan     = require('morgan'), mongoose = require('mongoose'), uriutil = require('mongodb-uri'), jwt      = require('jsonwebtoken'), config = require('./config'), user = require('./models/user');  // enable cors var allowcrossdomain = function(req, res, next) { res.header('access-control-allow-origin', 'http://localhost:4000'); res.header('access-control-allow-methods', 'get,put,post,delete,options'); res.header('access-control-allow-headers', 'content-type, authorization,     content-length, x-requested-with'); res.header('access-control-allow-credentials', 'true');  // intercept options method if ('options' == req.method) {   res.send(200); } else {   next(); } };   var port = process.env.port || 8080;   var mongodburi = config.database; var mongooseuri = uriutil.formatmongoose(mongodburi); mongoose.connect(mongooseuri);  app.set('supersecret', config.secret);  app.use(bodyparser.urlencoded({ extended : false })); app.use(bodyparser.json());  app.use(morgan('dev'));  // instance of router api routes var apiroutes = express.router();  apiroutes.post('/authenticate', function(req, res){  console.log(req.body) // find user user.findone({     username : req.body.username }, function(err, user){     if (err) throw err;      if(!user){         res.json({ success: false, message : 'authentication failed'})     }     else if(user){          // check password         if (user.password != req.body.password){             res.json({success : false, message : 'authentication failed. wrong password'})         }         else{               // if user found , password right             // create token             var token = jwt.sign(user, app.get('supersecret'), {                 expiresinminutes : 1440 // expires in 24 hours             });              // return info including token json             res.json({                 success : true,                 message : 'enjoy token',                 token : token             });             console.log('user found')         }     } }) });  // apply routes application prefix /api app.use('/api', apiroutes);   // start server app.listen(port); console.log('listening @ port: '+ port) 

when initialize ajax request - server logs 'user found' reason don't receive client - when test server code using 'postman' works fine i'm assuming on front-end... can see issue is? appreciated. thanks

edited: have got working, reason ajax request still fails when url 'localhost:4000' (which domain specified in access-control-allow-origin) - when url 'localhost:4000/?#' request succesful - know why might be?