app.js

'use strict';

const http = require('http');
const path = require('path');
const fs = require('fs');

const hostname = '127.0.0.1';
const port = 3000;

const fileType = {
  '.html': 'text/html',
  '.css': 'text/css',
  '.js': 'text/javascript',
  '.json': 'application/json',
  '.ico': 'image/x-icon',
  '.png': 'image/png'
};

const server = http.createServer((req, res) => {
  if (req.url === '/') {
    res.statusCode = 302; //redirect
    res.setHeader('Location', '/matrices');
    res.end();
    return;
  }

  let page = req.url;
  let pathname;
  let ext = path.extname(req.url);

  if (req.url === '/matrices') {
    page = '/matrix.html';
    ext = '.html';
  }

  if (req.url === '/graphs') {
    page = '/graph.html';
    ext = '.html';
  }

  if (fileType[ext] === 'text/html') {
    pathname = path.join(__dirname, 'public', 'pages', page);
  } else if (fileType[ext] === 'text/css') {
    pathname = path.join(__dirname, 'public', page);
  } else if (fileType[ext] === 'text/javascript') {
    pathname = path.join(__dirname, 'public', page);
  }

  fs.exists(pathname, exist => {
    if (!exist) {
      res.statusCode = 404;
      res.end(`File ${pathname} not found!`);
    } else {
      fs.readFile(pathname, (err, data) => {
        if (err) {
          res.statusCode = 500;
          res.end(`Error getting the file: ${err}.`);
        } else {
          res.setHeader('Content-type', fileType[ext]);
          res.end(data);
        }
      });
    }
  });
});

server.listen(port, hostname, () => {
  console.log(`Starting on ${hostname}:${port}`);
});