js1# is a browser-based implementation of the 1# text register machine used in Larry Moss's recursion theory classes. The 1# interpreter is written in Javascript (with jQuery/Bootstrap) and runs locally, so the whole package can work without connectivity. The goal is simply to build an accessible and easy-to-use tool for students working on the exercises that involve writing 1# programs.
You can try the build here.
Anyone is encouraged to contribute and improve this thing. (Especially students in the recursion theory course...maybe look at it as giving something back.) Even if you're not inclined to work on the code, please feel free to write about bugs, areas for improvement and desirable new features in the issue tracker.