The Joker first appeared in Batman #1 and he was not a humor character.

Growing up watching the old Adam West TV series, a lot of us got the idea that the Joker was just some wacky guy with a twisted sense of humor that lived to play practical jokes on the dynamic duo. The Batman cartoons from the 70s didn’t do much to change that image, either. What surprises me is that the character was much darker and malevolent in his first appearance.
Think I’m kidding? This story has four murders in it.

Read the original story, scanned from THE GREATEST JOKER STORIES EVER TOLD (ISBN: 0930289-36-6) 1988
originally from BATMAN #1, Spring 1940

What always sticks out to me is that Batman wears a bulletproof vest here, about five decades before the idea that the Caped Crusader wears always wears a thick armor.

In the 1970s it seems like his tunic is just a grey shirt and it all fits under his normal clothes, including his giant cape and thick, everything-included utility belt.