If one of the javascript files fails to load in Web Access then the users gets no feedback of this. The page will just remain in its loading state until the user gives up. The only clue something has gone wrong is in the browser console, which most users probably don't know about. Detecting this can be done via the "error" event, and we actually already have a handler for this. However the event fires a bit differently for loading errors and we need to set up the listener with capture for it to work: https://developer.mozilla.org/en-US/docs/Web/API/GlobalEventHandlers/onerror A capture listener needs to be careful though as we probably don't want to trigger on stuff the javascript itself fails to load, e.g. images.
