Is there a better way to structure the express entry point? - node.js

Question

I'm relatively new programmer. What I'm currently trying to do is to create a good code base, from which I can then develop the API I need. The requirements for that are, that I want to use NodeJS with Express and TypeScript. So I've created a new express bootstrapped project with the express-generator and started to convert the code into a TypeScript conform structure.
My question starts here:
I moved and renamed the "root/bin/www" file into "src/bin/index.ts". My tslint is set to "recommended" and therefore the "no-shadowed-variable" is true. So I got a "no-shadowed-variable" error in my index.ts, because the variable port is defined twice. Once in the outer function, as well as in the "onListening" function. So I started to separate the "onListening" and the "onError" function into a new module called "expressHandlers.ts", and the "normalizePort" function into "normalizePort.ts".
You can see the full project structure on: https://github.com/owme/server-template/tree/master/src/bin
It's currently working right now, but would you please let me know if you think this approach to rename and modularize the bin/www is reasonable?
Btw. I had to rewrite parts of the "onListening" function, because addr can be of type AddressInfo | string | null. And null is not a valid entry of the variable.
So my index.ts now exports the two variables { port, server } to be available for normalizePort. What is left, in the index.ts is the following:
index.ts:
#!/usr/bin/env node
'use strict';
/**
* Module dependencies.
* #private
*/
import { createServer } from 'http';
import app, { set } from '../app';
import { onError, onListening } from './expressHandlers';
import { normalizePort } from './normalizePort';
/**
* Get port from environment and store in Express.
*/
const port = normalizePort(process.env.PORT || '3000');
set('port', port);
/**
* Create HTTP server.
*/
const server = createServer(app);
/**
* Listen on provided port, on all network interfaces.
*/
server.listen(port);
server.on('error', onError);
server.on('listening', onListening);
/**
* Module exports.
* #public
*/
export {
port,
server
};
normalizePort.ts:
'use strict';
/**
* Normalize a port into a number, string, or false.
*/
function normalizePort(val: number|string): number|string|boolean {
const port: number = (typeof val === 'string') ? parseInt(val, 10) : val;
if (isNaN(port)) {
// named pipe
return val;
}
if (port >= 0) {
// port number
return port;
}
return false;
}
/**
* Module exports.
* #public
*/
export {
normalizePort
};
expressHandler:
'use strict';
/**
* Module dependencies.
* #private
*/
import debug from 'debug';
debug('server:server');
import {
port,
server
} from './index';
/**
* Event listener for HTTP server "error" event.
*/
function onError(error: NodeJS.ErrnoException) {
if (error.syscall !== 'listen') {
throw error;
}
const bind = (typeof port === 'string') ? `Pipe ${port}` : `Port ${port}`;
// handle specific listen errors with friendly messages
switch (error.code) {
case 'EACCES':
debug(`${bind} requires elevated privileges`);
process.exit(1);
break;
case 'EADDRINUSE':
debug(`${bind} is already in use`);
process.exit(1);
break;
default:
throw error;
}
}
/**
* Event listener for HTTP server "listening" event.
*/
function onListening() {
const addr = server.address();
let bind = null;
if (addr !== null) {
if (typeof addr === 'string') {
bind = `pipe ${addr}`;
} else {
bind = `port ${addr.port}`;
}
} else {
throw new Error('The Host-Address is null');
}
debug(`Listening on ${bind}`);
}
/**
* Module exports.
* #public
*/
export {
onError,
onListening
};