In order to decide how to run JavaScript code, the Scala.js sbt plugin uses the following two setting keys:

• preLinkJSEnv: the JavaScript Environment (i.e. virtual machine) used to run unlinked .sjsir files (defaults to Rhino)
• postLinkJSEnv: the JavaScript Environment used to run linked JavaScript (defaults to Node.js if DOM is not required, otherwise PhantomJS)

You may change these environments at your discretion. However, note that running Rhino on linked JavaScript and Node.js or PhantomJS on unlinked JavaScript is unlikely to work or at least slow.

For example, to switch to PhantomJS, you can set:

postLinkJSEnv := PhantomJSEnv().value

We’d like to stress here again, that you need to separately install Node.js and PhantomJS if you would like to use these environments.

Disabling auto-termination of PhantomJS

By default, the PhantomJS interpreter terminates itself as soon as the main() method returns. This may not be what you want, if for example you register time-outs or use WebSockets. You can disable this behavior with the following setting:

postLinkJSEnv := PhantomJSEnv(autoExit = false).value

You can terminate the interpreter from your Scala code with

System.exit(0)

Passing arguments to PhantomJS

You can pass command-line arguments to the PhantomJS interpreter like this:

postLinkJSEnv := PhantomJSEnv(args = Seq("arg1", "arg2")).value

For more options of the PhantomJS environment, see the ScalaDoc of PhantomJSEnv.

Node.js on Ubuntu

On Ubuntu, the Node.js command from the nodejs package is called nodejs instead of node (when installed through the package manager). This will make the Node.js environment fail (since it simply calls node).

You have two options to solve this:

1. Install nodejs-legacy which will add an alias called node
2. Explicitly tell the Node.js environment the name of the command:

postLinkJSEnv := NodeJSEnv(executable = "nodejs").value

For more options of the Node.js environment, see the ScalaDoc of NodeJSEnv.