> Yes... so concern here is that if animation is triggered when document is hidden, animation would never happen, right?

It's not about whether the animation happens, just whether the end state is reached. If you run `elem.animate({ height: 500 })` and the document is hidden, when the document becomes visible again, the element should have a height of 500. The no-op prevents that from happening; instead it should jump to the final state and invoke the callbacks.