@iwalker ... @Erni is bang on
The port of Espruino (JavaScript engine) to the ESP8266 had a goal to make the ESP8266 "just another" board on which Espruino runs. What this means is that whole story (instructions, tooling, libraries, documentation etc etc) that apply to Espruino are just as applicable to Espruino running on the ESP8266.
For those wanting to play with this new project, the Espruino web site can be found here:
http://www.espruino.com/There is a "Quick Start" page here"
http://www.espruino.com/Quick+StartFor development, there is a Chrome App that provides everything one needs ... see:
https://chrome.google.com/webstore/deta ... difdneehpoWhen you have written some JS script, you can connect to the Serial port that connects to the ESP8266 and simply run.
Alternatively, you can connect your favorite serial terminal and reboot the ESP and you should then see the interactive JavaScript command line for manually entering (or pasting) JS statements and code.
Neil