Do you need to convert your JS to strictly uppercase or lowercase? No problem. This is a web app that converts it for you.
https://arinerron.github.io/case-insensitive-xss/index.html
Basically, it JSF*ck-encodes eval(decodeURIComponent(...)) where ... is your JavaScript, and URL encodes the other uppercase/lowercase characters.
Yes, as long as the target app's CSP whitelists eval.