ApiServer for Express - NodeJS

/************************** Info
    License: MIT license at bottom, nullifying any license stipulations of this platform

    Requirements: NodeJS with Express, Morgan packages
    This is a substitute for the /bin/www and server.js file generated when creating an Express App.
    This will not work out of the box, to make it work:
        - optional - add API_PORT to .env
        - remove reference to JsonParseCatch, hardcode it, or create the file
        - redefine ApiEndpoints and its usage in useRoutes, or create file at that path
        - remove references to routes, and add your own

        - Change npm start command in package.json, or run directly with "node ApiServer.js"
*/

/************************** JsonParseCatch.js
    Optional middleware, prevents Express from crashing when parsing JSON.
    Save in ./Middleware/JsonParseCatch.js, or elsewhere and modify reference
*/
const JsonParseCatch = (err, req, res, next) => {
    if(err instanceof SyntaxError && err.status === 400 && "body" in err){
            return res.status(400).send({status: 400, message: err.message});
    }
    next();
}

module.exports = {
    JsonParseCatch: JsonParseCatch,
    router: require("express").Router()
};

/************************** ApiServer.js */
require("dotenv").config();

class ApiServer {
    constructor() {
        this.ApiEndpoints = require("./Static/Shared/Config").ApiEndpoints;
        this.logger = require("morgan")("dev");
        this.port = this.normalizePort(process.env.API_PORT) || 3000;
        this.httpServer = (this.http = require("http")).createServer(this.app = (this.express = require("express"))());
    }

    run = () => {
        this.setConfig();
        this.setMiddleware();
        this.setRoutes();
        this.startListening();
    }

    setConfig = () => {
        this.app.use(this.logger);
        this.app.use(this.express.json());
    }

    setMiddleware = () => {
        this.app.use(require("./Middleware/JsonParseCatch").JsonParseCatch);
    }

    setRoutes = () => {
        let homeRouter = require("./Routes/HomeRouter");
        let productRouter = require("./Routes/ProductRouter");

        /*
            GET /products
            Returns:        Array of products
            Beschrijving:   Get all products
        */
        this.app.use(this.ApiEndpoints.Products, productRouter);

        /*
            GET /
            Returns:        Metric
            Beschrijving:   Get metrics
        */
        this.app.use(this.ApiEndpoints.Metrics, homeRouter);
    }

    startListening = () => {
        this.httpServer.listen(this.port);
        this.httpServer.on('error', this.onError);
        this.httpServer.on('listening', this.onListening);
    }

    normalizePort = (val) => {
        let port; return port = parseInt(val, 10), isNaN(port) ? val : port >= 0 ? port : false;
    }

    onError = (error) => {
        error.syscall !== "listen" ? (() => { throw error; }).call() : null;

        let bind = typeof this.port === 'string' ? 'Pipe ' + this.port : 'Port ' + this.port;

        switch (error.code) {
            case 'EACCES':
                console.error('[ApiServer - onError.EACCES] ' + bind + ' requires elevated privileges');
                process.exit(1);
                break;
            case 'EADDRINUSE':
                console.error('[ApiServer - onError.EADDRINUSE] ' + bind + ' is already in use');
                process.exit(1);
                break;
            default:
                throw error;
        }
    }

    onListening = () => {
        let addr = this.httpServer.address();
        let bind = typeof addr === 'string' ? 'pipe ' + addr : 'port ' + addr.port;
        console.log('[ApiServer - onListening] API server listening on ' + bind);
    }
}

const server = new ApiServer().run();

/* Author: Benjamin Van Renterghem
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */