pop() is not a function - nodejs

Question

I am having a strange error with NodeJS when I call the function pop() on an array, it says TypeError: cars.pop is not a function... I am confused.

Any help? Below is the code. Thank you,

//callback chaining to avoid having multiple callbacks in the event queue
//only one callback calling others
function showCar(car, callback) {
  console.log('Saw a ' + car);
  if (car.length) {
    //register the function as asynchronous
    process.nextTick(function() {
      callback();
    })
  }
}

function logCars(cars) {
  var car = cars.pop();
  showCar(car, function() { //chaining of call backs
    logCars(car);
  });
}
var cars = ['ferrari', 'porsh', 'Hyundai', 'Peugeot'];
logCars(cars);

Answer 1

It's because you aren't passing an array to the logCars function on the second call. You are passing the popped string on the second recursive call.

In other words, logCars(car) should be logCars(cars) where you are nesting callbacks:

function logCars (cars){
  var car = cars.pop();
  showCar(car, function () {
    logCars(cars); // This should be `cars`, not `car` like you had
  });
}