Duktape
http://duktape.org/
Duktape is an embeddable Javascript engine, with a focus on portability and compact footprint.
Duktape is easy to integrate into a C/C++ project: add duktape.c, duktape.h, and duk_config.h to your build, and use the Duktape API to call Ecmascript functions from C code and vice versa.