why does assigning a number to an array make the array object a nan?

Question

I have the following code:

function bytesToMb(arr)
{
    for(var i=0;i<arr.length;arr++)
    {
        var mbs= arr[i]/(1000*1000);

        arr[i]=mbs;
    }

    return arr;
}

after the line arr[i]=mbs executes, the value of arr (the array object itself) becomes NAN.
why is that????

Antti Haapala · Accepted Answer · 2013-07-30 23:25:58Z

3

You are incrementing arr, arr + 1 = NaN because array is NaN; you ought to do i++ in your for loop instead...

answered Jul 30, 2013 at 23:25

Antti Haapala

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Phylogenesis · Accepted Answer · 2013-07-30 23:26:00Z

1

You're using arr++ instead of i++ as the third clause in your for loop.

The type coercion from Array to Number leads to your NaN.

answered Jul 30, 2013 at 23:26

Phylogenesis

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zs2020 · Accepted Answer · 2013-07-30 23:29:55Z

1

Change arr++ to i++

function bytesToMb(arr) {
    for (var i = 0; i < arr.length; i++) {
        var mbs = arr[i] / (1024 * 1024); // you should use 1024*1024 here to make it more precise if you need to.
        arr[i] = mbs;
    }
    return arr;
}

answered Jul 30, 2013 at 23:29

zs2020

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