node.js - Router.use() requires middleware function but got a Object at Function.use -

code contact.js :

var express = require('express'); var router = express.router(); var nodemailer= require('nodemailer'); var dateformat = require('dateformat'); var = new date();      // basic usage     dateformat(now, "dddd, mmmm ds, yyyy, h:mm:ss tt");  /* home page. */ router.get('/', function(req, res, next) {   res.render('contact', { title: 'contact' }); });     router.post('/send', function(req, res, next) {           verifyrecaptcha(req.body["g-recaptcha-response"], function(success) {                   if (success) {                           res.end("success!");                           // todo: registration using params in req.body                           var transporter = nodemailer.createtransport({                             service: 'gmail',                             auth: {                               user : 'email@gmail.com',                               pass : 'pass'                             }                           });                           var mailoptions = {                           from: 'thiyagaraj <email@gmail.com>',                           : 'email@gmail.com',                           subject : +req.body.from ,                           text : 'order placed '                            };                           transporter.sendmail(mailoptions, function(error, info){                             if(error){                               console.log(error);                               res.redirect('/');                             }else{                               console.log('message sent');                               res.redirect('/');                             }                           });                   } else {                           res.end("captcha failed, sorry.");                           // todo: take them previous page                           res.render('about', { title: 'about' });                   }           });   });  /* });  module.exports = router; */ 

this recaptcha verification ... there special dependency required ? or there mistake code ................................... ...................................

thanks in advance :)

last line of router needs uncommented.

module.exports = router; 

this code exposes router app. i'm guessing have requiring file somewhere , passing in app.use, file isn't exporting (because it's commented out) app.use expecting function getting undefined.