Node.js static file server.

server.js

/* eslint-env node */

const http = require('http');
const fs = require('fs');
const path = require('path');
const url = require('url');
const { exec } = require('child_process');
const { promisify } = require('util');

const readFile = promisify(fs.readFile);

const hostname = '127.0.0.1';
const port = 3030;
const staticDir = path.join(__dirname, 'static');
const staticFileExtensions = ['.html', '.css', '.js'];

async function readStaticFile(fileName) {
  const filePath = path.join(staticDir, fileName);
  const buffer = await readFile(filePath);
  return buffer;
}

function getMimeType(fileExtension) {
  switch (fileExtension) {
    case '.html':
      return 'text/html';
    case '.css':
      return 'text/css';
    case '.js':
      return 'text/javascript';
    default:
      return 'text/plain';
  }
}

/**
 * @param {http.IncomingMessage} req
 * @param {http.ServerResponse} res
 */
async function handler(req, res) {
  if (req.method !== 'GET') {
    res.statusCode = 403;
    res.setHeader('Content-Type', 'text/plain');
    res.end('forbidden');
    return;
  }

  const { pathname } = url.parse(req.url);

  if (pathname === '/' || pathname === '/index.html') {
    const buffer = await readStaticFile('index.html');
    res.statusCode = 200;
    res.setHeader('Content-Type', 'text/html');
    res.end(buffer);
    return;
  }

  const fileExtension = path.extname(pathname);

  if (staticFileExtensions.includes(fileExtension)) {
    const buffer = await readStaticFile(pathname);
    const mimeType = getMimeType(fileExtension);
    res.statusCode = 200;
    res.setHeader('Content-Type', mimeType);
    res.end(buffer);
    return;
  }

  res.statusCode = 404;
  res.setHeader('Content-Type', 'text/plain');
  res.end('not found');
}

const server = http.createServer(async (req, res) => {
  try {
    await handler(req, res);
  } catch (err) {
    console.error(err);
    res.statusCode = 500; // eslint-disable-line require-atomic-updates
    res.setHeader('Content-Type', 'text/plain');
    res.end('internal server error');
  }
});

server.listen(port, hostname, () => {
  const url = `http://${hostname}:${port}`;
  console.log(`Server running at ${url}`);

  if (process.platform === 'darwin') {
    exec(`open ${url}`, err => {
      if (err) {
        console.error(err.message);
      }
    });
  } else {
    exec(`xdg-open ${url}`, err => {
      if (err) {
        console.error(err.message);
      }
    });
  }
});