Javascript Variable Clarification

Question

I came across this behavior while trying to write some tests for my code and was wondering if somebody could explain to me why this isn't performing as I expect it to.

I have the following code:

var arr = [];

for (i = 0; i < 5; i++) {
    console.log('pushing %s', i);
    arr.push(function() {
        console.log('logging %s - random %s', i, Math.random());
    });
}

for (ai in arr) {
    arr[ai]();
}

which outputs out something like this:

pushing 0
pushing 1
pushing 2
pushing 3
pushing 4
logging 5 - random 0.35618519759736955
logging 5 - random 0.4480402651242912
logging 5 - random 0.9252766149584204
logging 5 - random 0.4456857305485755
logging 5 - random 0.14507507369853556

though I was expecting it to output something like this:

pushing 0
pushing 1
pushing 2
pushing 3
pushing 4
logging 0 - random 0.35618519759736955
logging 1 - random 0.4480402651242912
logging 2 - random 0.9252766149584204
logging 3 - random 0.4456857305485755
logging 4 - random 0.14507507369853556

How is i changing after I've already pushed to the array? and why does i resolve to 5 in the logging ... lines even though it only reaches 4 in the pushing ... lines?