JS target

Learn the JavaScript target with KMP.

JS target

In KMP the JavaScript target compiles Kotlin code into a JavaScript module that runs in the browser or in Node.js.

The target is added in Gradle with the js() block. Inside it you choose the nodejs() (Node) or browser() (browser) environment. The output is a .js file; it can also be published as an npm package. The Kotlin stdlib is embedded into this file automatically. The jsTarget function in this lesson models the concept.

Using the JS module

The module produced by the JS target can be added to an HTML page with a <script> tag or called from Node.js with require.

In Gradle the js { browser { webpackTask { } } } block manages packaging. Kotlin functions marked with @JsExport become visible to JavaScript. This way shared logic runs both in the browser and in Node. Type mapping is automatic: Kotlin String maps to JS string.

Exercise Write jsTarget

Define fun jsTarget(): String. It should return "JS". In main, write println(jsTarget()).

Show example solution

fun jsTarget(): String = "JS"
fun main() {
    println(jsTarget())
}

Test yourself

Complete the js block

____ {
    nodejs()
}

Show answer

js {
    nodejs()
}

What does the js() block produce?
```
The JS output has a .js extension.
```
- .jar
- .framework
- .js file
- .dylib
Show answer

.js file — The js() block produces a JavaScript file.
Match the JS parts

js()

Browser/Node target
nodejs()

Node environment
browser()

Browser environment
.js

Output file

Next lesson: Summary - KMP

We Are Enhancing Your Experience

Cookie Preferences

Strictly Necessary Cookies

Analytical Cookies