We're reusing the stuff we built for the Try iOS course we came out with late last year. I've looked into Emscripten for this and from what I saw it really wouldn't work with this course, although maybe I missed something?

You could always boot the VM with an image that contains the compiler and run there. If it truly does boot faster than the results take otherwise then you could move it all into javascript that way, and not have to worry as much about the infrastructure around it.

Looks like work has started on using emscripten with Objective-C code:

https://github.com/kripken/emscripten/pull/1162/files

Still, a long way to go.

Wow, this is totally awesome. This is my first time hearing about emscripten and I've been a Cocoa and JS programmer for about 9 years.

What are some of the coolest applications of emscripten?

Not sure if this qualifies as 'cool', but I used Emscripten to port parts of OpenSCAD to Javascript http://www.fabfabbers.com/openscad

PDF.js is used by Firefox to render PDFs in the browser.

PDF.js doesn't use emscripten, as far as I can tell.

For a recent example of emscripten, try this one from yesterday: https://news.ycombinator.com/item?id=5673356