Chaining call backs

//With asynchronous functions, you are not guranteed the order in which they will fun if two are palced on the event queue. The best way to resolve this is to implement callback chaining by having the callback from the asynchronous function call the function again until there is no more work to do. That way, the asynchronous function is never on the event queue more than once

function logCar(car, callback){
  console.log("Saw a %s", car);
  if(cars.length){
    process.nextTick(function(){
      callback();
    });
  }
}
function logCars(cars){
  var car = cars.pop();
  logCar(car, function(){
    logCars(cars);
  });
}
var cars = ["Ferrari", "Porsche", "Bugatti", "Lamborghini", "Aston Martin"];
logCars(cars);