Safari 12.0.1 will break most applications that has a 'Confirm' JS alert
I upgraded my MacBookAir to Mojave several weeks ago which includes Safari 12.0.1. I've also had been upgrading several internal rails applications to Rails 5.1.6 and new version of RailsFoundation with xy-grid.
I then started having problems with those applications. Mainly a CRUD delete link would not work consistantly. I spent several days trying to find the problem in my code, or was there a problem with rails-us or jQuery_ujs. Both seemed broke. At that time I could not find a reproducible sequence, seemed very intermittent. When I discovered that it worked in Chrome, I filed a bug on Webkit Bugzilla
They more or less ignored me until I could find a reproducible sequence. I finally found one that is documented in bugzilla. Also found a StackOverFlow post with someone having the same problem.
They passed to problem off to Apple on their Radr bug site confirming this was a Mac problem (IOS didn't have the problem). Or course I don't have access to the status since webkit submitted the bug and not me.
Short steps to reproduce
1. In a new Safari window/tab, click a delete link (or any link that has an event calls a JS confirm dialog) and click a confirm or cancel response and it should work.
2. Open another site using bookmark or URL on the same page/tab.
3. Use back arrow to go back to the page with the Confirm dialog.
3, Try clinking the delete link again,
The confirm link will not work, may get spinning beach ball. All open Web Inspector links in Develop menu will be grayed out. The window is toast. Close the window and open a new one and you will be ok.
I'm just posting this to prevent anyone else looking for a problem that is not theirs.
I also consider this a serious bug, but have no idea if Apple considers it serious. May someone have Apple connections and can relay the status on this site. Don't know how active or responsive this site it, but that is was better than filing a Rails bug that is not their bug.