Hi,

Apologies if I've missed something obvious, but is there any explicit 
specification of how this works in Mozilla:

xs = [1, 2, 3];
xs[1] = xs;
alert(xs.join()) // prints "1,,3"

It even works when the recursion is less direct, like this:

xs = [1, 2, 3];
ys = [1, xs, 3];
xs[1] = ys;
alert(xs.join()) // prints "1,1,,3,3"

Apparently Array.toString() returns empty string if it detects it is 
already inside an invocation of itself?

Best regards,

Michael

Apologies if I've missed something obvious, but is there any explicit specification of how this works in Mozilla:

```js
xs = [1, 2, 3];
xs[1] = xs;
alert(xs.join()) // prints "1,,3"
```

It even works when the recursion is less direct, like this:

```js
xs = [1, 2, 3];
ys = [1, xs, 3];
xs[1] = ys;
alert(xs.join()) // prints "1,1,,3,3"
```

Apparently `Array.toString()` returns empty string if it detects it is already inside an invocation of itself?