I've looked at Trent's solution and it's just what I'm looking for, but I just can't get it to work.
I've never understood why stuff like this is made so complicated.
I've managed to completely strip down Trent Richardson's page to the attached index.html example - and it works! - but when I try to implement this on my Bootstrap 3 page, also attached (add-event.php) with the code added that I've stripped from Trent's example it doesn't.
This will be, no doubt, be down to something conflicting with the code in Trent's example but I've tried every damn combination of removing stuff, retesting, adding it back, removing something else. Why doesn't this stuff just talk to each other and say "hey, you can't use that when you're using this" on a page?
Anyway - hoping someone can point out the obvious conflict. Thank you.