it seems like that the interpreter mode only support Python language, if I use javascript develop web site, I can’t use it, isn’t?
it depend on Jupyter extensions ,so I think it only support Python. is right?
Yes, it only has access to a Python notebook.
You can still try it out for javascript development! It uses Python as its “thinking engine” but it can write any language.
Still in beta though so might not be that good 
would love feedback on how it works for you!