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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);

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);

• javascript
• node.js

Share Improve this question Follow edited Jan 30, 2017 at 3:40 Josh Crozier 241k5656 gold badges400400 silver badges313313 bronze badges asked Jan 30, 2017 at 0:28 CelaroCelaro 22622 gold badges88 silver badges1919 bronze badges

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1 Answer 1

Sorted by: Reset to default 4

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
  });
}

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