Calculate the sum of an array and then invoke a callback function from within another function

Question

Calculate the sum of an array and then invoke a callback function from within another function

I'm currently facing a challenge where I need to calculate the total sum of an array using the .reduce() method within a function. Instead of simply returning the sum, I am required to call a callback function and pass the sum as an argument.

Though I believe I am using the .reduce() method correctly, I keep receiving 'undefined' as a result. I'm struggling to understand how I can effectively invoke a function within another function.

Any assistance or explanations on this matter would be greatly welcomed!

Question: Can you sum all integers in the numbers array and then call a callback function with the sum as an argument?

Here is my code:

function sumArray(numbers, cb) {
  // Insert code here

  const result = numbers.reduce(function(sum, currentValue) {
    return sum + currentValue;
  }, 0);

  cb([1, 2, 3, 4, 5], result);
}

function addTwo(num) {
  const result = num + 2;
}

javascript arrays function methods callback

Answer 1

Answer №1

The query indicates

Instead of returning the total, call cb and input the total to it.

This simply translates to cb(sum), nothing complicated beyond that. This callback allows for additional functionality to be implemented.

For instance:

var numbers = [1, 2, 3, 4, 5];

function sumArray(numbers, cb) {
  var sum = numbers.reduce(function(sum, currentValue) {
    return sum + currentValue;
  }, 0);
  cb(sum);
}

function outputSum(sum) {
  console.log("The total is " + sum);
}

function addTwo(sum) {
  console.log(sum + 2);
}

sumArray(numbers, outputSum);
sumArray(numbers, addTwo);

Answer 2

The query indicates

Instead of returning the total, call cb and input the total to it.

This simply translates to cb(sum), nothing complicated beyond that. This callback allows for additional functionality to be implemented.

For instance:

var numbers = [1, 2, 3, 4, 5];

function sumArray(numbers, cb) {
  var sum = numbers.reduce(function(sum, currentValue) {
    return sum + currentValue;
  }, 0);
  cb(sum);
}

function outputSum(sum) {
  console.log("The total is " + sum);
}

function addTwo(sum) {
  console.log(sum + 2);
}

sumArray(numbers, outputSum);
sumArray(numbers, addTwo);

Answer 3

Answer №2

Your assignment requires some careful consideration, so I'll give you a nudge in the right direction without revealing too much.

Instead of simply calculating the sum with

numbers.reduce(function(sum, currentValue) {

, make sure to store it in a variable like var reduced = things.reduce(...).

It seems like cb is designed to accept only one argument (the sum), but you are currently passing an array and another variable result (which hasn't been declared yet). Make sure to adjust your approach accordingly.

Answer 4

Your assignment requires some careful consideration, so I'll give you a nudge in the right direction without revealing too much.

Instead of simply calculating the sum with

numbers.reduce(function(sum, currentValue) {

, make sure to store it in a variable like var reduced = things.reduce(...).

It seems like cb is designed to accept only one argument (the sum), but you are currently passing an array and another variable result (which hasn't been declared yet). Make sure to adjust your approach accordingly.

Answer 5

Answer №3

Below are the issues discovered:
1. It is necessary for your reduce() function to return its output to the result variable. Without either returning the output or defining the result variable, this functionality will not work correctly.
2. In case addTwo() is the callback function, it should operate with a single variable. Since there's no indication of where the cd callback is meant to go in the code snippet provided, it seems that it may have been omitted. Please ensure you include it as follows:

function sumArray(numbers, cb) {

 var result = numbers.reduce(function(sum, currentValue) {
    return sum + currentValue;
 }, 0);

 cb([1, 2, 3, 4, 5], result);

}

function addTwo(num) {
 const result = num + 2;
}

Answer 6

Below are the issues discovered:
1. It is necessary for your reduce() function to return its output to the result variable. Without either returning the output or defining the result variable, this functionality will not work correctly.
2. In case addTwo() is the callback function, it should operate with a single variable. Since there's no indication of where the cd callback is meant to go in the code snippet provided, it seems that it may have been omitted. Please ensure you include it as follows:

function sumArray(numbers, cb) {

 var result = numbers.reduce(function(sum, currentValue) {
    return sum + currentValue;
 }, 0);

 cb([1, 2, 3, 4, 5], result);

}

function addTwo(num) {
 const result = num + 2;
}

Answer 7

Answer №4

Looks like you're attempting to achieve something along these lines.

Make sure to save the reduced return value.
You should also return the callback function.

In order to access the internal callback, you need to return it.

function sumArray(numbers, cb) {
  // add your code here
  let result = numbers.reduce(function(sum, currentValue) {
    return sum + currentValue;
  }, 0);

  return cb([1, 2, 3, 4, 5], result);

}

function sumTwo(arr, num) {
return  Number(num + 2);
}

console.log(sumArray([1, 2, 3, 4, 5], sumTwo));

Answer 8

Looks like you're attempting to achieve something along these lines.

Make sure to save the reduced return value.
You should also return the callback function.

In order to access the internal callback, you need to return it.

function sumArray(numbers, cb) {
  // add your code here
  let result = numbers.reduce(function(sum, currentValue) {
    return sum + currentValue;
  }, 0);

  return cb([1, 2, 3, 4, 5], result);

}

function sumTwo(arr, num) {
return  Number(num + 2);
}

console.log(sumArray([1, 2, 3, 4, 5], sumTwo));

Calculate the sum of an array and then invoke a callback function from within another function

Answer №1

Answer №2

Answer №3

Answer №4

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