minimum coroutine module (without error handling, dictionary). like https://github.com/visionmedia/co.

co.js

var co = function(fn){

  function is_gen(obj) {
    return obj && obj.constructor && 'GeneratorFunctionPrototype' == obj.constructor.name;
  }

  return function(done){
    var gen = fn;
    if(typeof gen == 'function')
      gen = gen();

    var check = function(thunk, next){
      // array
      if(Array.isArray(thunk)){
        var res = [];
        for(var i=0;i<thunk.length;i++){
          check(thunk[i], function(val){
            res.push(val);
            if(res.length == thunk.length)
              next(res);
          });
        }
        return;
      }
      // generator
      if(is_gen(thunk))
        thunk = co(thunk);
      // thunk
      if(typeof thunk == 'function')
        return thunk(next);
      // simple object
      next(thunk);
    }

    // next
    var next = function(val){
      var t = gen.next(val);
      var thunk = t.value;
      if(t.done){
        if(done)
          done(thunk);
      }else{
        check(thunk, next);
      }
    }

    // start
    next(undefined);
  }
};

// thunk
var child = function(name){
  return function(done){
    setTimeout(function(){done(name);}, 500);
  }
};

// nest generator
var parent = function*(name){
  var val = yield child(name + '1');
  console.log(" - ", val);
  val = yield child(name + '2');
  console.log(" - ", val);
  val = yield name + '3';
  console.log(" - ", val);
  return name
};

// test
co(function*(){

  // thunk
  var val = yield child('1');
  console.log(val);

  // nest
  var val = yield parent('2');
  console.log(val);

  // array
  var vals = yield [child('3'), child('4')];
  console.log(vals);

})();

node --harmony-generators co.js

output

1
 -  21
 -  22
 -  23
2
[ '3', '4' ]