JavaScript callback function return undefined

September 13, 2022

I am trying to write two functions. One contains elements of array with forEach method and another is a callback function that access elements of array from the first function and log their length. The second function is not working and throws Uncaught ReferenceError. I wonder why I get this error.

const fruits = ["Banana", "Mango", "Apple"];
fruits.forEach(listFruits);

function listFruits(allFruits) {
  console.log(allFruits);
}

function countFruits(callback) {
  callback(allFruits);
  console.log(allFruits.length);

}

countFruits(listFruits);

how can i fix this error? and access the length of elements in my callback function , any help will be appreciated

>Solution :

You’re trying to call a function using an array as prop

const fruits = ["Banana", "Mango", "Apple"];
fruits.forEach(listFruits);

function listFruits(allFruits) {
  console.log(allFruits);
}

function countFruits(callback) {
  // the following line is the problem, "allFruits" are not defined.
  // if you change the prop to the array "fruits" the error is solved
  callback(fruits); 
  console.log(fruits.length);

}


countFruits(listFruits);