In a hole in the ground there lived a hobbit. Not a nasty, dirty, wet hole, filled with the ends of worms and an oozy smell, nor yet a dry, bare, sandy hole with nothing in it to sit down on or to eat: it was a hobbit-hole, and that means comfort.
Notice how slice does not trigger an update in the observable array and thus no message is shown when you click on it. That makes perfectly sense since slice does not modify the original array. It just makes a shallow copy of its contents and returns it.