Getting started

Basic setup

You need to have npm installed on your system.

Add the sbt-scalajs-bundler plugin to your Scala.js project, in your project/plugins.sbt file:

// For Scala.js 1.x
addSbtPlugin("ch.epfl.scala" % "sbt-scalajs-bundler" % "0.21.1+36-2d9cbce2-SNAPSHOT")
// Or, for Scala.js 0.6.x
addSbtPlugin("ch.epfl.scala" % "sbt-scalajs-bundler-sjs06" % "0.21.1+36-2d9cbce2-SNAPSHOT")

The plugin requires Scala.js 0.6.26+ or 1.0.0-RC1 and either sbt 0.13.17+ or 1.2.1+.

Enable the ScalaJSBundlerPlugin, in your build.sbt file:


If you have a main method, make sure that you enable the Scala.js main module initializer with the following setting:

scalaJSUseMainModuleInitializer := true

Add dependencies to the npm packages your application requires, in your build.sbt file, e.g.:

npmDependencies in Compile += "snabbdom" -> "0.5.3"

You will most probably want to write a Scala.js facade for the JavaScript module. You can find information on how to do that in the cookbook, or draw inspiration from this example.

Then, use the fastOptJS::webpack sbt command to download the npm packages and bundle your Scala.js application and its dependencies into a single JavaScript file executable by a web browser.

In this example, the webpack sbt task produces a single file located at target/scala-2.12/scalajs-bundler/main/<project-id>-fastopt-bundle.js.

See complete examples in the tests.

Integrating with sbt-web

For sbt-web integration use the sbt-web-scalajs-bundler plugin instead of sbt-scalajs-bundler:

// For Scala.js 1.x
addSbtPlugin("ch.epfl.scala" % "sbt-web-scalajs-bundler" % "0.21.1+36-2d9cbce2-SNAPSHOT")
// Or, for Scala.js 0.6.x
addSbtPlugin("ch.epfl.scala" % "sbt-web-scalajs-bundler-sjs06" % "0.21.1+36-2d9cbce2-SNAPSHOT")

Then, enable the WebScalaJSBundlerPlugin on the project that uses sbt-web:

lazy val server = project
    scalaJSProjects := Seq(client),
    pipelineStages in Assets := Seq(scalaJSPipeline)

lazy val client = project.enablePlugins(ScalaJSBundlerPlugin)

You also need to setup the ScalaJSBundlerPlugin on the Scala.js project, as described in the preceding section, and the sbt-web-scalajs plugins as described in their documentation. Note that sbt-web-scalajs's ScalaJSWeb plugin must not be enabled, because ScalaJSWeb will create source mappings to source files copied to a hash path, which conflict with ScalaJSBundlerPlugin's webpack-based source mappings.

The WebScalaJSBundlerPlugin plugin automatically configures the scalaJSPipeline task to use the bundles rather than the output of the Scala.js compilation.

You can see a complete example here.