why is createServer() considered not a function?

Question

I installed express globally and npm installed my express app, yet neither the intellisence or the app is working ( I am using visual studio code on mac OS Yosemite).

here is a sample code:

/// <reference path="typings/node/node.d.ts" />
/// <reference path="typings/express/express.d.ts" />

var express = require('express');
var app = express.createServer();
app.get('/', function (req, res) {
    res.send('hi');
})

app.listen(8000);

and here are the errors I am getting:

Abeds-MacBook-Pro:myNode AZ$ node twitter.js 
/Users/AZ/Desktop/myNode/twitter.js:5
var app = express.createServer();
                  ^

TypeError: express.createServer is not a function
    at Object.<anonymous> (/Users/AZ/Desktop/myNode/twitter.js:5:19)
    at Module._compile (module.js:397:26)
    at Object.Module._extensions..js (module.js:404:10)
    at Module.load (module.js:343:32)
    at Function.Module._load (module.js:300:12)
    at Function.Module.runMain (module.js:429:10)
    at startup (node.js:139:18)
    at node.js:999:3

I researched a bit and found that createServer() has been deprecated. I read that I need to change the version somewhere in my application.

Note: I did another application using purely Node.js, and createServer() did work without any error along with the intellisence.

EDIT: in my other application I used require('net') instead.

I modified my code to the following:

var express = require('express')
  , http = require('http');

    var app = express(); 
    var server = http.createServer(app);
    console.log('Listening on port 8000')
    app.get('/', function (req, res) {
        res.send('hi');
    })

    app.listen(8000)

The problem I have now is that res.send('hi'); has not been reached, aka, I cannot send to the client.

EDIT 2:

I tried the following code provided in one of the answers:

const express = require('express');
const http = require('http');

const app = express();
const server = http.createServer(app).listen(8080, function(err) {
  if (err) {
    console.log(err);
  } else {
    const host = server.address().address;
    const port = server.address().port;
    console.log(`Server listening on ${host}:${port}`);
  }
});
app.get('/', function (req, res) {
    res.send('hi');
})

res.send('hi'); still does not work, neither does it provide an error.

Answer 1

createServer is a function of http so it should be:

const express = require('express');
const http = require('http');

const app = express();
app.get('/', function (req, res) {
  res.send('hi');
});

const server = http.createServer(app).listen(8080, function(err) {
  if (err) {
    console.log(err);
  } else {
    const host = server.address().address;
    const port = server.address().port;
    console.log(`Server listening on ${host}:${port}`);
  }
});

P.S. Installing express globally is a bad idea