One of the reasons I think JS gets a lot of hate is the tooling is a bit of a mess. If you go that route I encourage you to generate or find a barebones project to start from. Getting that very first "Hello World" app to run can be a massive pain in the ass.

I also don't think the requirement to a desktop app and website in the same language is being fair. It's definitely possible but different languages have different strengths. It shouldn't make your brain explode to deal with more than one language and I think you could benefit from a shift in mindset. When I'm in JS world I know l I've gotta let go of performance and security desires (i.e. JS in the browser is a "clear box" and users can fully control it). When I'm in Java I know those things are highly important but also to not stress about "presentation".