async.js

function asynchronousIterator(limit, f1) {
  var sum = 0;
  var limit = 3;

  fAsync(limit, function(res) {
    console.log("Intermediate result", res);
    sum += res;
    limit--;
      if(limit === 0){
        f1(sum);
      }

  })
}

function fAsync(x, f2) {
  var result = x * x;
  setTimeout(function(){
    f2(result);
  }, Math.random() * 100);
  x--;
  if(x > 0){
    fAsync(x,f2);
  }
}

asynchronousIterator(5, function(a){
  console.log(a);
});

output.txt

➜  i3bitrix-test git:(master) ✗ node synh_vs_an.js
Intermediate result 4
Intermediate result 9
Intermediate result 1
14
➜  i3bitrix-test git:(master) ✗ node synh_vs_an.js
Intermediate result 1
Intermediate result 4
Intermediate result 9
14
➜  i3bitrix-test git:(master) ✗ node synh_vs_an.js
Intermediate result 9
Intermediate result 1
Intermediate result 4
14