functional web framework

function listUsers (req, callback) {
  // use req as immutable input
  // standard node error-first callback API
  // success value of callback is a response-shaped object with properties: statusCode, headers, body
}

// I haven't built one of these, just riffing.
// Look at clojure and other functional languages for examples that might 
// have reasonable counterparts in "functional-light" JS
// Thinking more along the lines of react/redux reducer style

// Problems with express:
// - the res object being so stateful, harder to test
// - middleware dependencies are implicit instead of explicit
// - "next" connect middleware API is not just standard error-first callback pattern