Good library for a web-based REPL?

I'm working on a programming language implementation, and I'd like to offer a web-based REPL so people can try it easily. Frontend is not really my area, so maybe I didn't use the right search keywords. But an online search only revealed what seem to be single maintainer, fairly outdated jQuery plugins.

Does every try website out there just implement its own REPL? Seems like a ton of work.