it is implemented, you find it here http://www.espruino.com/Reference#l__global_isFinite
@MaBe started
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
it is implemented, you find it here http://www.espruino.com/Reference#l__global_isFinite