JS target
- Kotlin course
- Expert
- Lesson 29/47
- 5 min
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.
Practice Write jsTarget
Define fun jsTarget(): String. It should return "JS". In main, write println(jsTarget()).
Starter code
// add the jsTarget function
fun main() {
// print the JS target
}Sample solution
fun jsTarget(): String = "JS"
fun main() {
println(jsTarget())
}Expected output
JS
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Complete the js block
____ {
nodejs()
}js {
nodejs()
}Explanation: The js() block adds the JavaScript target.
2 What does the js() block produce?
The JS output has a .js extension.- .jar
- .framework
- .js file Correct answer
- .dylib
Explanation: The js() block produces a JavaScript file.
3 Match the JS parts
| Term | Meaning |
|---|---|
js() |
Browser/Node target |
nodejs() |
Node environment |
browser() |
Browser environment |
.js |
Output file |