CODEWITHSUNDEEP
javascriptarraysforeach
Maxime Michel
Maxime Michel

Reputation: 615

How to write a function to be used in a forEach statement to add all numbers in an array?

I have an exercise where I have to write my own forEach function which takes an array and a 'callback' function to add all the elements in the array. So far I have this:

function forEachTest(arr, func){
    func(arr) // Simply apply the function to the array
}

However I don't know if this is the correct way a forEach call works.

Secondly, the said function to add the elements will therefore take the array and somehow add each element one by one till it reaches the end of the array and then console.log(result).

I tried using a variable to store the value but this doesn't work, I get NaN as a result.

function addEach(arr) {
    var sum;
    for(i = 0; i < arr.length; i++) {
        sum += arr[i];
    }
    console.log(sum);
}

The Nan happens when I call forEachTest(arr, addEach);

Note that arr is any array containing numbers.

Upvotes: 0

Views: 143

Answers (2)

A l w a y s S u n n y
A l w a y s S u n n y

Reputation: 38502

What about this with initialization of your sum variable with 0 because inside your function it is initially undefined. So inside your loop it is executing like this way undefined=undefined+1, undefined=undefined+2 and so on which is NaN for every number of your array. Also I guess you're missing the return before your func(arr);

function forEachTest(arr, func){
     return func(arr) // Simply apply the function to the array
}

function addEach(arr) {
    var sum=0;// see here
    for(i = 0; i < arr.length; i++) {
        sum += arr[i];
        //console.log(sum += arr[i]) //for debug purpose
    }
    //console.log(sum);
    return sum;
}

console.log(forEachTest([1,2,3,4,5],addEach))

Upvotes: 0

Ele
Ele

Reputation: 33726

Initialize the variable sum = 0.

function forEachTest(arr, func) {
  func(arr);
}

function addEach(arr) {
  var sum = 0;
  for (i = 0; i < arr.length; i++) {
    sum += arr[i];
  }
  console.log(sum);
}

forEachTest([1,2,3], addEach);

Upvotes: 2

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