How to check WHEN localstorage is empty?

Hi redditors.

Here is my question: is there a blockUI analogue for localstorage? JsFiddle

Problem is that the indexes of new list items are given before localstorage is clean (that's why I'd like to lock UI until localstorage is empty) and that causes wrong indexes to be given to new list items. The result is null list items when the page is refreshed.

Thanks!