For anyone else who had no idea what this was, opal[0] is a ruby-to-js transpiler, and AFAIK this is just an example of it being used to make a hello world app.

For anyone else who had no idea what this was, opal[0] is a ruby-to-js transpiler, and AFAIK this is just an example of it being used to make a hello world app. [0] https://github.com/opal/opal https://github.com/opal/opal