Trying to increment an integer in an Array

Good Evening, I am trying to increment an integer that I have index position of ‘0’ in my array, each time my function gets called. I have the variable added with .push, but then I just want to add one to that. I am trying to use indexof(), I have also tried findIndex(). Below is my code

  const addFunction = async () => {
    var storage_array = await AsyncStorage.getItem(ASYNC_STORAGE_KEY);
     try {
       if(storage_array) {
         storage_array = JSON.parse(storage_array);
         let flow_complete = 0;
     

 
         var foundIndex = storage_array.indexOf(flow_complete);
         console.log(foundIndex);
         storage_array[foundIndex] = flow_complete++;

        await AsyncStorage.setItem(ASYNC_STORAGE_KEY, JSON.stringify(storage_array));
         console.log('THIS IS THE ASYNCSTORAGE', storage_array);

       } else {
        flow_complete = 0;
        console.log('Storage array is empty')
       }
     } catch (error) {
       console.log(error);
     }
  }

Answer

Following the re-wording of the issue with your comment:

[…] the objective is to take the number ‘0’ that’s in the 0th position of the array and increment it by 1 each time the function runs

The first issue I see is that you may be misusing the indexOf function. That will not give you the index of an array, but instead the position of a particular value of an array.

Example:

const arr = [9, 2, 7, 14]
const index = arr.indexOf(9) // This will be 0, because the index of the number 9 in this array is 0 
const otherIndex = arr.indexOf(7) // This will be 2, because the index of the number 7 in this array is 2

So, for you to access the element in the 0th position, you will want to do arr[0]. So in your code you will want to do the following:

storage_array = JSON.parse(storage_array);
let flow_complete = 0;
     
// notice there is no need to get the `indexOf` 0 since you do want the position 0 
storage_array[0] = flow_complete++;

Now… This will have a second problem which is your usage of the incrementation operator ++. Although this will increment the flow_complete variable, it does not return it to set storage_array[0] as you intend to do so.

To fix this, all you have to do is increment flow_complete prior to assigning it to storage_array[0]. It will look something like this:

let flow_complete = 0;

flow_complete++;
storage_array[0] = flow_complete

However, if my interpretation of your comment above is correct, there is one more problem, which you are assigning flow_complete to storage_array[0] each time the function runs. flow_complete is set to 0 as you can see in your own block of code within the scope of your addFunction, so this means it will always go back to 0 every time it is run.

Going back to your original comment, you want to increment the value in the 0th index of storage_array, not flow_complete itself, correct? If this is the case, you can completely get rid of the flow_complete variable and instead increment storage_array[0]. This will make your if-block look as follows:

 if(storage_array) {
         storage_array = JSON.parse(storage_array);
     
         storage_array[0]++;

        await AsyncStorage.setItem(ASYNC_STORAGE_KEY, JSON.stringify(storage_array));
         console.log('THIS IS THE ASYNCSTORAGE', storage_array);

       }