This is JScreme, a self-hosting Scheme subset to JavaScript compiler. I've blogged about JScreme here, the sources are hosted on GitHub.
Below is the REPL. Stuff you might want to try out:
(+ 1 2)
(map (lambda (x) (+ x 1)) '(1 2 3))
(reduce (lambda (x y) (string-append x " and " y)) '("spam" "sausage" "bacon" "spam"))
(compile '(lambda (spam) (list spam spam spam)) *toplevel-bindings*)