quickjs/mquickjs are good at embedding but nowhere close to luajit in terms of speed. (i have some experience with quickjs https://github.com/justjake/quickjs-emscripten)
as an aside i’m curious how quickjs/mquickjs compares to mruby in speed and size. something to ponder
Fabrice Bellard! https://github.com/bellard/mquickjs
(I agree with you, just wanted to note this super neat project)