Example application written in Scala.js

This is a barebone example of an application written in Scala.js.

Get started

To get started, first make the Scala.js compiler, library and sbt plugin available locally by publishing them locally. This is very easy, just follow the instructions in the Scala.js readme.

Then, copy the Scala.js runtime into the js/ subdirectory of this project. You will find it in the subdirectory target/ of Scala.js, it is named scalajs-runtime.js. Optionally, also copy the source map scalajs-runtime.js.map.

Now, you are good to go. Open sbt in this example project, and issue the task package-js. This creates the file target/example.js. You can now open index-dev.html in your favorite Web browser!

During development, it is useful to use ~package-js in sbt, so that each time you save a source file, a compilation of the project is triggered. Hence only a refresh of your Web page is needed to see the effects of your changes.

Note that Scala.js and sbt do not play well enough together for incremental compilation to work. So package-js will recompile all your source files everytime.

The optimized version

Instead of running package-js, you can also run optimize-js to generate a much more compact version of the JavaScript code. While index-dev.html refers to the JavaScript emitted by package-js, index.html refers to the optimized JavaScript emitted by optimize-js.

The optimization phase is performed by the Advanced Optimizations of the Google Closure Compiler, which make strong assumptions about the code being compiled.

All the code generated by Scala.js respects these assumptions. But if you modify startup.js, make sure that you comply with them if you want to be able to use optimize-js.

In a bigger application, startup.js or an equivalent file will typically export selected APIs from the code generated by Scala.js. The exported symbols can then be used from other JavaScript code that is not being processed by Closure.

Troubleshooting

I don't find `scalajs-runtime.js` Scala.js

You have probably forgotten to execute package-js from the sbt prompt in Scala.js.

I have unresolved dependencies on `scalajs-...`

You have probably forgotten to execute publish-local from the sbt prompt in Scala.js.

gitbm/scala-js-ws-frontend