According to a stackoverflow post https://stackoverflow.com/questions/6449733/how-can-i-add-javascript-inside-blogger it's possible to embedded Javascript code into a blogger.com blogpost. I have tried it out, and it works great.
https://trollheaven.blogspot.com/2020/01/javascript-test.html
What is shown in the blogpost is a canvas element for drawing pictures, plus a simple form to enter text. I'm not sure, what the limits are but it seems, that basic Javascript programs are running great in the blogging software.