Espruino is an open source Github hosted project that provides an implementation of the JavaScript programming language on a variety of embedded systems. In 2015, this was ported to work on the ESP8266. Espruino has its own JavaScript IDE and a thriving community of users. For details on the Espruino project, see the Espruino home page.
As of October 2015, the port to ESP8266 is in beta but appears to be fully functional. Downloadable firmware images that can be installed on an ESP8266 can be found here.
The community forum for discussing all things Espruino can be found here and this includes discussion on anything ESP8266 as it relates to Espruino and JavaScript programming.
A live gitter stream for chatting with Espruino developers and other users can be found here.