Inspired by KOA

generator-demo.js

'use strict';

// middlewares: array of generator function
function compose(middlewares) {
  return function *() {
    var i = middlewares.length;
    var prev = function *(){};
    var current;
    while (i--) {
      current = middlewares[i];
      prev = current(prev);
    }
    yield *prev;
  };
}

function run(gen) {
  var result = gen.next();
  if (result.value)
    run(result.value);
  // if it return, gen has no next method
  if (!result.done)
    gen.next();
}

var middlewares = [
  function *(next) {
    console.log('enter first');
    yield next;
    console.log('leave firt');
  },
  function *(next) {
    console.log('enter second');
    yield next;
    console.log('leave second');
  },
  function *(next) {
    console.log('enter third');
    yield next;
    console.log('leave third');
  },
  function *(next) {
    console.log('end');
  }
];

run(compose(middlewares)());