I was toggling a collection of nested HTML elements which was working fine in Firefox, but not in Safari. Even manipulating the display attribute using the console produced the same result. Even stranger, clicking outside of the element after a toggle made the element appear. After an hour or so trying to identify the issue, I left it to return later with a fresh mind. Before returning I had restarted my Mac. Yes, you guessed it. It was working. Have you come across this issue? Please let me know in the comments.