User blog comment:DaNASCAT/Technical Update: May 6, 2015/@comment-24473195-20150506193215/@comment-452-20150508171027

More notifications is definitely an interesting idea, many are already possible by adding categories to MediaWiki error messages so that email notifications are sent when the error is displayed. I haven't encountered the "node counts exceeded" in a while, so I forget the exact text of that message, and can't currently find it.

Script errors are nigh on impossible to automatically detect, and I don't think it's possible to write a script to actively inform you that an error has been logged in your javascript console.

In the case of actively informing about entries on SpecialPages and maintenance categories, I've written a MaintenanceReport script, which you can see in action here. It would be possible to have it run on every page and display a notification about an issue, but since it makes a number of API calls, I would advise using a localStorage variable to record when it was last run, and only run it once hour. Or just use it as I do and just check Special:Maintenance to get a report of all pages instead of having to visit each page individually.