To use sbt-npm-dependencies in an existing SBT project with Scala 2.12 or a later version, add the following dependencies to your project/plugins.sbt depending on your needs:

addSbtPlugin("io.chrisdavenport" %% "sbt-npm-dependencies" % "<version>")

In your build.sbt, enable it with enablePlugins(NpmDependenciesPlugin) and declare your dependencies with

Compile / npmDependencies ++= Seq(
  "npmPackageName" -> "version",
  "secondNpmPackageName" -> "version",
  ...
)

(For integration with other build systems)

sbt-npm-dependencies will export a file called NPM_DEPENDENCIES to the jar containing the dependencies in the following format:

{
  "compile-dependencies": [
    { "npmPackageName": "version" },
    { "secondNpmPackageName": "version" },
    ...
  ],
  "test-dependencies": [
    { "npmPackageName": "version" },
    { "secondNpmPackageName": "version" },
    ...
  ],
  "compile-devDependencies": [
    { "npmPackageName": "version" },
    { "secondNpmPackageName": "version" },
    ...
  ],
  "test-devDependencies": [
    { "npmPackageName": "version" },
    { "secondNpmPackageName": "version" },
    ...
  ]
}

You can access dependency data from upstream packages in your downstream build through Compile / npmTransitiveDependencies and Compile / npmTransitiveDevDependencies, or by using a bundler plugin like https://github.com/fiatjaf/sbt-esbuild.