vmunier / scalajs-scripts   1.3.0

Apache License 2.0 GitHub

Twirl templates to link Scala.js output scripts into a HTML page.

Scala versions: 3.x 2.13 2.12 2.11 2.10

Scala.js Scripts

Latest Version License

Small library which provides a way to link Scala.js output to HTML templating engines, such as twirl, scalatags or even standard scala string interpolation.


Add the library to build.sbt:

libraryDependencies += "com.vmunier" %% "scalajs-scripts" % "1.3.0"

Integration with Twirl

Available Twirl Templates

There are four Twirl templates: scripts.scala.html, selectScript.scala.html, jsdeps.scala.html, launcher.scala.html.

  • scripts.scala.html is the main template, it includes the three other templates.
  • selectScript.scala.html selects the full-optimized javascript file (-opt.js) if it exists, selects the fast-optimized javascript file (-fastopt.js) otherwise.
  • jsdeps.scala.html includes the javascript dependencies if they exist.
  • launcher.scala.html includes the Scala.js launcher if it exists.


The templates have the same parameters, and can be called similarly. The parameters are described below:

@(projectName:    String,
  assets:         String => String,
  resourceExists: String => Boolean
  1. projectName, name of the Scala.js project, which is used to compute the Scala.js file names, projectName-fastopt.js, projectName-launcher.js, etc.
  2. assets, function, which given a Scala.js file name, returns the HTTP route from which the file can be fetched.
  3. resourceExists, function, which given a Scala.js file name, returns true when the resource exists, false otherwise.

Generic usage for any HTTP-based application (e.g. Akka HTTP, Spray):

  projectName = "client",
  name => s"/assets/$name",
  name => getClass.getResource(s"/public/$name") != null)

Usage for the Play Framework specifically:

  name => routes.Assets.at(name).toString,
  name => getClass.getResource(s"/public/$name") != null)

Usage for the Play Framework with fingerprinting for public assets:

  name => routes.Assets.versioned(name).toString,
  name => getClass.getResource(s"/public/$name") != null)

Additional HTML attributes can be added to the generated <script> tags:

  projectName = "client",
  name => s"/assets/$name",
  name => getClass.getResource(s"/public/$name") != null,
  Html("""charset="UTF-8" defer""")

Note: The Twirl templates require a resourceExists function because the application classpath may not be accessible from the library. Play for instance, puts libraries in a parent classpath of the application, meaning they can't see the classes provided by the application. Since the classloaders are split, libraries can never make any assumptions about their classloader with regards to the applications classloader. More info about Play classloader can be found in this issue.

Integration with ScalaTags

Integration with ScalaTags is as simple as calling one of the scalajs-scripts function inside a tag. Here is a template showing how to use scalajs.html.scripts to render a basic index.html:

import scalatags.Text._
import scalatags.Text.all._

object Application {
  def index(title: String): TypedTag[String] = {
          .scripts("client", name => s"/assets/$name", name => getClass.getResource(s"/public/$name") != null)

The raw function in ScalaTags allows you to embed raw HTML in the tag and calling .body on the scripts method outputs the raw html.

Publish a new version of the library

New versions are automatically published to Sonatype when creating a git tag, thanks to sbt-ci-release.