node process.nextTick()

next-tick.js

function doInner(i) {
  console.log(i, 'doInner');
  process.nextTick(function() {
    // runs after everything else is done
    console.log(i, 'nextTick');
  });
}

function doOuter(i) {
  console.log(i, 'doOuter before inner');  
  doInner(i);
  console.log(i, 'doOuter after inner');  
}

for (var i = 0; i < 5; i++) {
  doOuter(i);
}

All the functions in a given call tree will run before nextTick runs. Similarly, you should use process.nextTick to call callbacks, because if you call them directly, they aren't truly asynchronous (see example over here: http://howtonode.org/understanding-process-next-tick)