Note there’s already (and we sort of compete with that unsuccessfully…):
VS Code for the Web (https://vscode.dev) has been available for some time now and it has always been our goal to support the full edit / compile / debug cycle in the browser. […] It is harder for other languages since we must be able to execute (and therefore debug) the code. For example, to run Python source code in a browser, there needs to be an execution engine that can run the Python interpreter. […] To find out what is possible with WebAssemblies today, we decided to take a Python interpreter written C/C++, compile it to WebAssembly, and run it in VS Code for the Web.
I believe the VS Code is cut-down, and maybe even Python in it too (but not too much).
Julia has already been run in WebAssembly. Julia is huge so it’s slower to start, but it can be cut down a lot, e.g. OpenBLAS left out (was done that way already?).
LinearAlgebra.jl is not longer part of Julia, or its repo, at least. I think cutting out as much as possible, and making it work that way for a start is a good goal, without VS Code, then with.
Even though mthelm85’s demo for Julia on the web, just posted here was cool, it wasn’t really on the web only, since connecting to a server, i.e. using Docker there, and we should just not try, too hard (IMHO), to make such a playground work, to eliminate all the (server) costs.
Running in WebAssembly, i.e. in the browser, mean more development cost, but worth it since it’s work we want to day anyway, make Julia even smaller, for small binaries, already making huge progress there. All web browsers support GC now for WebAssemly, in case we want to adopt it, not provide our own GC, and I see there’s also some work to allow exceeding the 4 GB limit.