How to hide/show individual items in a document

I'm trying to hide all items in a document (and store each items original visibility state), iterate user pre-selected items and perform an export for each item in selection (I've got this part covered), and finally restore the visibility state of each item again (here's where the storing of original visibility state is needed).

I've found that I can iterate all items in the document using

app.activeDocument.pageItems

where i is the page item identified by the i-th index in the pageItems collection.

What is not clear, however, is how to get the visibility state of this page item. Indeed, there is a property visbilityVariable associated with page items, but when I try to "inspect" its content using an alert message, I get "undefined".

Are there better ways to iterate all items in a document? Ideally, I'd like to access all items regardless of wether they're path items, group items, text frame items or what have you. I need this collection to read/write the visibility state of each individual item. Thanks!