Eventually I would want to redirect them to content that is able to work in the absence of JS, but I need this detection as a placeholder to start.
Best Answer:I’d like to add my .02 here. It’s not 100% bulletproof, but I think it’s good enough.
So, what you really want is a “redirection” to a page that says “turn on JS, silly”. But, of course, you can’t reliably do meta redirections. So, here’s the suggestion:
If you have better answer, please add a comment about this, thank you!