javascript - Calling helper function in node.js within callback? -

i'm new programming node.js , not quite sure why getting error. function looks set correctly, , don't believe have asynchronous problems b/c should account self variable put in place (i think). did try w/o too, using simple var consoleprint(...) anyways, code below , error log below that.

/* global __dirname */  var express = require('express'); var app = express(); var bodyparser = require('body-parser');  var self = this;  //calling helper function here var server = app.listen(8000, self.consoleprint(server));  app.use(bodyparser.urlencoded({ extended: true })); app.use(bodyparser.json()); app.use('/public', express.static(__dirname + '/public'));  app.get('/', function (req, res) {   res.sendfile(__dirname + '/public/views/index.html'); });   //---------------helper function(s)-------------------// self.consoleprint = function(servervar){   var host = servervar.address().address;   var port = servervar.address().port;   console.log('example app listening @ http://%s:%s', host, port); } 

and error:

c:\users\daniel\desktop\workspace\alarm_clock\index.js:17 var server = app.listen(8000, self.consoleprint(server));                                    ^ typeerror: undefined not function     @ object.<anonymous> (c:\users\daniel\desktop\workspace\alarm_clock\index.js:17:36)     @ module._compile (module.js:460:26)     @ object.module._extensions..js (module.js:478:10)     @ module.load (module.js:355:32)     @ function.module._load (module.js:310:12)     @ function.module.runmain (module.js:501:10)     @ startup (node.js:129:16)     @ node.js:814:3 12 may 01:01:36 - [nodemon] app crashed - waiting file changes before starting... 

this resolve problem:

var server = app.listen(8000, function(){self.consoleprint(server)});