libmozjs-68-dev 68.5.0-1~fakesyncbuild2 (amd64 binary) in ubuntu focal

 SpiderMonkey is the code-name for Mozilla Firefox's C++ implementation of
 JavaScript. It is intended to be embedded in other applications
 that provide host environments for JavaScript.
 .
 This package contains the header files which are
 needed for developing SpiderMonkey embedders.