middleware pattern practice.

middleware.js

function requestIDMiddleware(next, params) {
  var requestID = 'hogehoge';

  if(next) next({
    requestID: requestID
  });
}

function sessionMiddleware(next, params) {
  var session = {
    user_id: 123
  };

  var params = Object.assign(
      params,
      {session: session}
    );

  if(next) next(params);
}

function renderer(params) {
  console.log(
    'Hello, World.',
    'Your Sesssion is ', params.session,
    'Your RequestID is ', params.requestID
    );
}

class Middleware {
  constructor() {
    this.queue = [];
  }

  register(middleware) {
    this.queue.push(middleware);
  }

  run() {
    this.queue.reverse().reduce((memo, fn) => {
      if(!memo) return fn;
      return fn.bind(this, memo);
    })({});
  }
}

var middleware = new Middleware();
middleware.register(requestIDMiddleware);
middleware.register(sessionMiddleware);
middleware.register(renderer);

middleware.run();