What happened

I would expect the following code

Immutable.Range(0, 10).filter($ => true).slice(-2).toArray()

to return

[8, 9]

but instead it returns

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

i.e. the slice operation is ignored.

If you remove the filter operation, the slice works as expected.

If you slice with a positive begin value, it works as expected.

How to reproduce

Run the above code snippets in the Chrome debug console on the immutable-js.com website, which embeds the Immutable library.