JS and Python are slow [see below] and heavyweight. Lua might work, I don't know... but this being header-only makes it pretty nice for simpler situations.
EDIT: Sorry, I wrote this a little too quickly and ended up writing a bit too coarse of a description. I meant JS and Python are both heavyweight to include in a project, and Python is slow both to initialize and to run. I didn't mean JS is slow to run. I don't know how fast it starts up either.
EDIT: Sorry, I wrote this a little too quickly and ended up writing a bit too coarse of a description. I meant JS and Python are both heavyweight to include in a project, and Python is slow both to initialize and to run. I didn't mean JS is slow to run. I don't know how fast it starts up either.