This please. It doesn't have to be JS, if I can just POST my form to their server, and have the user redirected back with a token that'll work just as well.
Braintree does this, but they're rather pricey.
I've wanted this feature bad enough I've considered launching my own service to do it. Surely there are a decent number of sites out there that want to retain control of their payment form, but want to seriously reduce PCI scope.