express.js

const fetch = require('node-fetch');
const http = require('http');

class Express {
  constructor(
    notFoundHandler = (req, res) => {
      res.statusCode = 404;
      res.write('not found');
      res.end()
    },
    errorHandler = (req, res, err = {}) => {
      if (res.headersSent) { res.end(); return; }
      res.statusCode = err.status || 500;
      res.write(err.message || 'error');
      res.end()
    }
  ) {
    this.stacks = [];

    this.server = http.createServer(async (req, res) => {
      try {
        for (const { method, path, handler } of this.stacks) {
          if (!method || method === req.method) {
            const m = req.url.match(path);
            if (m) {
              await handler(req, res, m);
            }
          }
        }
      } catch (err) {
        console.log('ERR', err);
        errorHandler(req, res, err);
      }
      if (!res.headersSent) {
        notFoundHandler(req, res);
      }
    });
  }

  use(path, handler) { this.stacks.push({ path, handler }) }
  get(path, handler) { this.stacks.push({ method: 'GET', path, handler }) }
  put(path, handler) { this.stacks.push({ method: 'PUT', path, handler }) }
  del(path, handler) { this.stacks.push({ method: 'DELETE', path, handler }) }
  post(path, handler) { this.stacks.push({ method: 'POST', path, handler }) }
  patch(path, handler) { this.stacks.push({ method: 'PATCH', path, handler }) }
  copy(path, handler) { this.stacks.push({ method: 'COPY', path, handler }) }


  listen(port) {
    return new Promise((resolve, reject) => this.server.listen(port, err => err ? reject(err) : resolve(this.server)));
  }
  close() {
    return this.server.close();
  }
}

(async () => {
  try {
    const app = new Express()
    app.use(/^\//, async (req, res) => {
      console.log('just logging stuff', req.url);
    });

    app.get(/^\/foo/, async (req, res) => {
      res.write('foo');
      res.end();
      throw new Error('7');
    });

    app.get(/^\/bar/, async (req, res) => {
      res.write('bar');
      res.end();
    });
    await app.listen(3000);

    const r = await fetch('http://localhost:3000/foo');
    console.log(1, r.status, await r.text());


    app.close();

  } catch (err) {
    console.error(err);
  }
})()