Depending what you want to do, there is also the OR1K Emulator running Linux - http://jor1k.com and a generic x86 emulator - v86 - https://github.com/copy/v86

you can check a small benchmark here: https://github.com/s-macke/jor1k/wiki/Benchmark-with-other-e...

via https://news.ycombinator.com/item?id=10498305

a test / development environment inside the browser where a server is emulated for testing purposes too, accompanied with a code editor.

I d like to describe the vm configuration similar to chef or ansible in js and run some dev/test code.