This reminded me of http://engineerjs.com/, a hobby project we did with some friends many years ago. One can write a JS code extended with unit support, linear algebra, complex numbers, create plots, share scripts, create libraries with interactive documentation support (this one never went public), etc. Everything runs in the browser on the user side. The test version (test.engineerjs.com) even has google drive support and can read/write files on it (although Google changed something in the meantime, and it started complaining about not being a verified application). The idea was that everyone could create libraries that others can import use directly. It doesn't have this nice GUI though.