README.md

Kotlin-Js Interop

The Kotlin-Js Interop is a feature of Kotlin/JS that allows the use of JavaScript libraries in Kotlin code and vice versa.

Table of Contents

• Javascript to Kotlin
  • Demonstrations
  • NPM Dependencies
  • Build and Run
• Kotlin to Javascript
  • Demonstration
  • Build and Run
• References

Javascript to Kotlin

Module: js-to-kotlin

Demonstrations

Javascript	Kotlin
src	jsMain jsTest

NPM Dependencies

To use npm dependencies in Kotlin/JS, the dependencies must be added to the dependencies block of the build.gradle.kts file.

dependencies {
    // Install npm dependencies
    implementation(npm("randomstring", "1.3.0"))
}

And then define the exported function according to the JavaScript library's API.

Javascript	Kotlin
var randomstring = require("randomstring"); randomstring.generate(); // >> "XwPp9xazJ0ku5CZnlmgAx2Dld8SHkAeT" randomstring.generate(7); // >> "xqm5wXX"	@JsModule("randomstring") @JsNonModule external object RandomStringFromNpm { fun generate( length: Int = definedExternally, ): String }

Tip

To delegate default parameter value to the imported JavaScript function, use definedExternally.

Build and Run

# from root
cd js-to-kotlin/kotlin-app
./gradlew cleanAllTests allTests --rerun-tasks

Kotlin to Javascript

Module: kotlin-to-js

Demonstration

Kotlin	Javascript
src	js-test

Build and Run

1. Execute the perl script to link local npm packages in this project.
2. Run the tests:

   # from root
   cd kotlin-to-js/js-app
   npm test

References

• Kotlinlang: JS to Kotlin Interop
• Kotlinlang: Kotlin to JS Interop
• Kotlinlang: Dependencies from NPM
• Kt.Academy: JS Interop
• Dev.to: @JsExport guide for exposing Kotlin to JS