Real life scenario for a context: A two instances of a JS library, each from different version are being loaded. Since the library do not keep backward compatibility someone code will probably fail, either the code using the first instance or the code using the second.
For graceful degradation I am going to wrap the problematic code in a try { } catch {}
block to have only my code fail instead of the whole page.
The question is really how do I report to the user that there is a problem. logging to console is fine once you need debuging data but it is not user friendly. Lets assume for the sake of this question that we are talking about traditional admin side only.