为什么给数组分配数字会使数组对象成为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????

Answer 1

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

Answer 2

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 .

Answer 3

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;
}