Error handling with Either

<!DOCTYPE html>
<html>

  <head>
    <link rel="stylesheet" href="style.css">
  </head>

  <body>
    <!-- // make console.log write to the page for better in-browser experience -->
    <script>
      (function () {
    var body = document.querySelector('body');
    body.style['fontFamily'] = 'monospace';
    body.style['fontSize'] = '2em';
    console.log = function (x) { body.innerText += x + '\n'; };
    }());
  </script>
  <script src="script.js"></script>
  </body>

</html>

// SETUP: fake fs
//==========
const fs = {
  readFileSync: name => {
    if(name === 'config.json') {
      return JSON.stringify({port: 8888})
    } else {
      throw('missing file!')
    }
  }
}

const Right = x =>
({
  chain: f => f(x),
  map: f => Right(f(x)),
  fold: (f, g) => g(x),
  inspect: () => `Right(${x})`
})

const Left = x =>
({
  chain: f => Left(x),
  map: f => Left(x),
  fold: (f, g) => f(x),
  inspect: () => `Left(${x})`
})

const fromNullable = x =>
  x != null ? Right(x) : Left(null)
  
const tryCatch = f => {
  try {
    return Right(f())
  } catch (e) {
    return Left(e)
  }
}

const getPort = () =>
  tryCatch(() => fs.readFileSync('config.json'))
  .chain(c => tryCatch(() => JSON.parse(c)))
  .fold(e => 3000, c => c.port)

const result = getPort()

console.log(result)