I'm trying to do some ajax in completely vanilla javascript — no libraries. And simply nothing happens. Nothing shows up in the network tab. Nothing shows up in the console tab. No errors. No HTTP requests. Nothing. I've created a simple standalone version below.

I am aware that I am not handling the response here. That's okay. I want to fire off a request to the server when a button is clicked (that detail is omitted from the simple example above), and I hope that it gets through, but if something goes wrong that's no tragedy and the error is not worth catching.