I see this question has come up a few times on here, but mine is a bit different. I'm new to JavaScript this is a basic program to show the problem.

```
var iterations = 0;

function someFunc(x, y, z) {

    for (var i=0; i<4; i++) {
        x[i] = x[i] * 2;
        y[i] = y[i] * 2;
        z[i] = z[i] * 2;
    }

    iterations++;

    if (iterations >= 10)
        return {done:true, x, y, z};
    else
        return {done:false, x, y, z};

}

function main() {

    var x = [0, 0, 0, 0];
    var y = [1, 1, 1, 1];
    var z = [2, 2, 2, 2];

    done = false;
    while (!done) {

        let {done, x, y, z} = someFunc(x, y, z);
        console.log(x, y, z);

        // Do some other stuff with x,y,z here,
        // like calling anotherFunc(x, y, z)

    }
}

main();

```

I get an error on the line with the call to someFunc. The error is "Exception Occurred: Reference error: x is not defined".

So what I'm doing is calling a function to update some arrays each time around a loop. I need to be able to get those arrays back out from the function called 'someFunc' so that I can pass them to another function to do some other work on them.

Then I need to feed them back into the first function again... and so on around and around the loop until I have finished.

I'm coming from Python where calls like 

```
a, b, c = someFunc(a, b, c) 

```

are fine.

But I have no idea how to proceed with JavaScript. Any help would be much appreciated. Happy to clarify if my question is not totally clear.