Your Scala code in Main.scala, running on Cloudflare Workers
In addition to Wrangler you will need to install the Scala build tool sbt, including a JDK.
To generate using wrangler
wrangler generate projectname https://github.com/cloudflare/scala-worker-hello-world
Further documentation for Wrangler can be found here.
After installing sbt per the linked instructions above,
cd projectname
sbt fullOptJS
That will compile your code and package it into index.js, after which you can run wrangler publish to push it to Cloudflare.
If you just want to check for errors during development without taking the time to package, running sbt ~compile will watch for filesystem changes and recompile. For more information, see the sbt docs
For more information on how Scala translates to Javascript, see the Scala.js docs.