There's narcissus too (https://github.com/mozilla/narcissus)

Hah, that's definitely not what I meant. It was in reference to the previous time js.js was (prematurely) posted to hacker news

Agreed, it's partially cheating, although a lot of work went into getting it to compile to LLVM and patching it work with Emscripten. That's not where it stops though. The plan is to make the library work just like the SpiderMonkey JS API, which will require wrapper scripts in JS.

Not quite. It will support everything that SpiderMonkey's API supports when embedding the interpreter into a C++ application. Much more powerful than eval().

65MB is our current unoptimized, uncompressed version. I expect the final version to be around 5-10MB. Still large, but not quite as bad.

I'm not super familiar with Narcissus in practice, but on paper your projects sound very similar. Were there any interesting reasons why you opted to make this project instead?

We wanted the full power of the SpiderMonkey JS API and maximum browser compatibility.