kotlin-jskotlinc

How to compile a Kotlin file to JavaScript?

Hi I am getting started with KotlinJS on Node and I've put a very simple kotlin file and I want to compile it using the raw kotlinc-js compiler. Without using gradle

package main

fun heavy() {
    (1..10_000_000).forEach { it*it }
}

fun main() {
    heavy()
    println("Bye JS")
}

Here's the make command I've tried yet without success:

build-js:
    kotlinc-js main.kt -output main.kt.js

It compiles fine, but when I attempt to run node main.kt.js:

throw new Error("Error loading module 'main.kt'. Its dependency 'kotlin' was not found. Please, check whether 'kotlin' is loaded prior to 'main.kt'."); ^

Error: Error loading module 'main.kt'. Its dependency 'kotlin' was not found. Please, check whether 'kotlin' is loaded prior to 'main.kt'. at Object. (/home/nanospicer/KotlinProjects/KotlinScripting/main.kt.js:2:9) at Module._compile (node:internal/modules/cjs/loader:1101:14) at Object.Module._extensions..js (node:internal/modules/cjs/loader:1153:10) at Module.load (node:internal/modules/cjs/loader:981:32) at Function.Module._load (node:internal/modules/cjs/loader:822:12) at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:79:12) at node:internal/main/run_main_module:17:47

Ok, so I figured it's missing the kotlin runtime. I'll try same argument as the JVM compiler: -include-runtime which leads to the error:

error: invalid argument: -include-runtime info: use -help for more information

Then I tried:

build-js:
    kotlinc-js main.kt -kotlin-home "/mnt/c/Program Files/JetBrains/IntelliJ IDEA Community Edition 2021.2.1/plugins/Kotlin/kotlinc/" -libraries "/mnt/c/Program Files/JetBrains/IntelliJ IDEA Community Edition 2021.2.1/plugins/Kotlin/kotlinc/lib/kotlin-stdlib-js.jar" -module-kind commonjs -main call -output main.kt.js

But it still leads to the same error. I also tried removing the libraries flag and it didnt work either

Solution

  • I've found the culprits.

    I basically created a nodejs project from IntelliJ IDEA and took a quick read through the gradle tasks which hinted me that it was preparing a node environment for me under the hood.

    I took a quick glance at npm.js and found that in fact there's a package called kotlin which is the javascript's stdlib for the compiler.

    I finally tweaked the build command on my Makefile to use a module-kind of common-js and it worked out!

    //Definitive main.kt I ended up using
fun heavy() {
    (1..100_000_000).forEach { it*it }
}

fun main() {
    heavy()
    println("Bye JS")
}

    Install kotlin's stdlib using npm:

    $ npm i kotlin --save

    And my Makefile build command looks like:

    $ kotlinc-js main.kt -module-kind commonjs -main call -output main.kt.js

    A small breakdown of the arguments: