[feeley]

If you want full Scheme running on top of JS in the browser: https://try.gambitscheme.org

It has tail calls, continuations and even green threads (SRFI 18 compliant), and a decentralized module system that can load libraries directly from github and a JS FFI! See this paper for advanced examples that you can copy-paste to the REPL: http://www.iro.umontreal.ca/~feeley/papers/BelangerFeeleyELS...