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javascriptarraysdatasetaverage
anonsaicoder9
anonsaicoder9

Reputation: 115

Why is my JavaScript averaging function returning NaN?

I am trying to create a JavaScript (pure) function that averages an array of numbers. No error is returned, but it always returns NaN. What is wrong? Here is my code:

var arr = [1, 2, 3, 4, 5, 6, 7, 8];

function average(datasetArr) {
  var totalSum;
  var x;
  for (x in datasetArr) {
    totalSum = datasetArr[x] + totalSum;
  }
  var average = totalSum / datasetArr.length; //keeps returning NaN
  console.log(average); //In the console: returns: "NaN"
}
average(arr);

Does anyone have any working code snippets or improvements to my code?

Upvotes: 0

Views: 107

Answers (3)

Vivek Jain
Vivek Jain

Reputation: 2864

In your example you have not initialize the totalSum variable with 0.

You can use this way too.

var arr = [1, 2, 3, 4, 5, 6, 7, 8];

function average(datasetArr) {
  var average = datasetArr.reduce((result, current) => result += current, 0) / datasetArr.length;
  console.log(average);
}

average(arr);

Upvotes: 1

Jannes Carpentier
Jannes Carpentier

Reputation: 1898

You need to initialize totalSum to 0

If you don't initialize it, you are trying to add a number to undefined

for example 3 + undefined will evaluate to NaN

On a side note, you can use Array.prototype.reduce to sum an array

var array = [1, 2, 3, 4];
var sum = array.reduce((a, b) => a + b, 0);
console.log(sum); //10

Upvotes: 2

Arnold Gee
Arnold Gee

Reputation: 906

You have to set the totalSum variable to 0 first. If you don't set it to zero, you cannot add datasetArr[x] to totalSum inside the for loop.

Solution:

var arr = [1, 2, 3, 4, 5, 6, 7, 8];
function average(datasetArr) {
  let totalSum = 0;

  for (let x in datasetArr) {
    totalSum = datasetArr[x] + totalSum;
    console.log(totalSum)
  }
  var average = totalSum / datasetArr.length; 
  console.log(average); //In the console: returns: "NaN"
}
average(arr);

Upvotes: 0

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