First of all, if you watched the slides, you just ran the first `hello world` Scala-js app in your browser. The slides use the scala-js runtime. Developer tools have scalajs-runtime.js at 1.7MB compressed and about 4s to download/execute, then about 1.5s on subsequent refreshes.<p>Now, having seen the talk at Scala days here are a few notes/thoughts:<p>This is currently the result of 4 months worth of work, and Sébastien Doeraene, the author of the slides and the code there-in, is going to be working on it at EPFL for the next 4 years or so for his doctorate.<p>This is being done by replacing the backend portions of the Scala compiler that emit java bytecode with ones that emit javascript.<p>When the slide showing that it is 16MB came up everyone laughed and the author acknowledged how large a number this is. It is the result of having to bring in the entire the Scala standard lib. He is planning to work on ways of cutting this number down.<p>At the end of talk Martin Odersky commented from the audience that this is an attempt by the EPFL at making Scala useable for large webapp development. If it proves successful more resources will put towards supporting it.<p>I plan to try this out for internal sites used by my company. Currently we split and then have to duplicate a lot of our code between Scala / Javascript. Scala for the server software, Javascript for frontends which are webapps. I haven't had time since I got back to do much more than clone the git repo.