using js prompt() instead of a form with create method

I have a new/create method that only has one field, and I'd rather use a
js prompt() to get the data instead of a form.

The trigger for this is not a link, it's a span. Using "onclick" in the
span, how can I call a prompt(), return the single param to the
contoller "create" method, and then call the controller "list" method to
update the page?

Well you can make an Ajax request, and pass the value of the
javascript variable in a query parameter in the url.