Espruino's functions are tagged such that documentation can be built from them:
/// Comment before
void function();
/** Big comment before */
void function();
void function(); ///< Comment after
To build. go to the root of the Espruino project, install Doxygen, then run:@
doxygen Doxyfile
Most functions you care about will be in doxygen/html/globals_0x6a.html