What on earth would you expect BTN to refer to? The ESP8266 module doesn't have a button on it!
Dev boards like NodeMCU and D1 Mini do. They don't respond as BTN but...
@Ollie 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.
What on earth would you expect BTN to refer to? The ESP8266 module doesn't have a button on it!