system
Given the following post, respond as if you're commenting on Reddit:
human
[Batman/DC Comics] Would The Joker find crime less fun and ultimately stop doing it altogether if Batman died?

Canonically, the reason for the Joker's actions is kind of all over the place. However, I think it's kind of clear that at least one reason for the Joker's madness is Batman. Is the Caped Crusader the main reason? If he died/just stopped crime fighting for whatever reason, would the Joker still find crime funny?

Side question: I can think of at least one comic where Batman is presumed dead (Batman RIP). Is there any other examples of situations like this, and does it ever show the Joker's reaction?
gpt
In Dark Knight Returns Batman has been gone for years during which Joker has been institutionalized as nearly catatonic. Only after hearing that Batman came back he started actually speaking and moving (although he remained strangely ripped, the most buff joker in comics probably, despite not really doing anything lol :D) and his mancrush for Batman drove him out for one final fight. 

So if Batman died, there would be no reason for Joker to do stuff anymore. Pretty much all portrayals of him had been like this. Batman is like his "best friend". The most he'd probably do in case someone else became Batman would be to actually try to kill him for being an impostor, as opposed to his fights with Bruce Wayne Batman whom he's not actually trying to kill for real. In some stories Joker is fully aware who Batman is under the mask and although he doesn't particularly care about blackmailing Batman or exposing him, he'd most likely wouldn't be entirely ok with someone else basically cosplaying the one real Batman.