Are unsigned types fully supported on JS? I was trying to use them but I ran into a strange error:

fun main() {
    ubyteArrayOf(
        *listOf(ubyteArrayOf())[0]
    )
}

results in:

Unhandled JavaScript exception: listOf(...).get_c1px32_k$(...).slice is not a function

https://pl.kotl.in/nEyBqjkBZ The same code works just fine when replacing

ubyteArrayOf

with

byteArrayOf

or running it on JVM instead.

Worried about bundle size? Here are two options that can help decrease it: • Using ESM modules • Using ES2015 language features Both of these articles give examples of how the options affect the generated code.

Anybody else ran into this issue before? IDE isn’t able to resolve KotlinJsTargetDsl and it makes dev very annoying bc all the JsExport stuff shows red in the editor https://youtrack.jetbrains.com/issue/KT-81089/

Anyone else run into an issue where changing the version of an npm dependency (via the Gradle DSL, i.e.

implementation(npm(package, version))

does not invalidate build cache? Kotlin 2.2.0, Gradle 8.12 Running build before and after changing the NPM dependency shows the same build cache key for

compileKotlinJs

. I would expect this to trigger a failed build and prompt the user to run

kotlinUpgradeYarnLock

like normal.

While waiting for AWS SDK Multiplatform I wonder why there a no Kotlin-wrappers available for the official AWS S3 JS lib… isn’t that thing popular?

I'm writing type defs and came across

{GridCoordinates2D|HexagonalGridCube2D|Point} HexagonalGridCoordinates2D

and wondered, if there was a way to model that in Kotlin. Couldn't you use a marker interface for that? As in: an empty interface that all of these types extend?

Hello everybody, how can i instruct gradle to get a npm dependency directly from a github repo instead of npmjs.com?

How can I pass a parameter from the Gradle command line to my JS tests (Node, browser, Wasm)? Example: Indicate if tests run on CI.

Hi all, today I noticed that there are no null checks for non nullable fields for generated JS code in KMP. I was assuming that the behaviour might have been similar to JVM where generated bytecode has null checks and code fails fast but it is not. How do people overcome this usually ? I can manually add null checks in

init {}

block but not only kotlin gives warning for that, it's cumbersome process to add to all exposed classes and would pollute the code as well.

Just decided to open source this investment tracker I've been working on as a personal passion project: https://github.com/TENET-THEORY/knance. It is probably the only sample out there that shares code between ktor and next js. Inspired by https://github.com/Kotlin/kmp-fullstack-conference-cms. If you like it, give it a star!

[kotlin - Why can't I use @JsExport in commonMain? Workaround with expect/actual seems to work fine - Stack Overflow](https://stackoverflow.com/questions/79782181/why-cant-i-use-jsexport-in-commonmain-workaround-with-expect-actual-seems-to)

Good morning everyone ☀️ I need your input so much in the following question. In the thread, please share how you publish Kotlin/JS artifacts (not KLIB, but the executable) to a registry (e.g., NPM, JSR, Maven) and any pain points you've encountered with the approach. Thank you for the help 🙏 Artem, Kotlin/JS Lead

Kotlin 2.2.21-RC is out with a couple of fixes for K/JS. https://github.com/JetBrains/kotlin/releases/tag/v2.2.21-RC

[kotlin - Can we expose interfaces from

commonMain

to JS that can be implemented in Typescript? - Stack Overflow](https://stackoverflow.com/questions/79786639/can-we-expose-interfaces-from-commonmain-to-js-that-can-be-implemented-in-type)

How can you create Web Components using Kotlin/JS? I did try to follow this guide and, while it did work in the past, it seems that the

kotlin-browser

bindings for Web Components have changed quite a bit, and now I'm not able to get a custom element to work

Major bottleneck for me right now with kotlin/js is the compilation speed. It slows down the dev loop dramatically vs just using javascript. This is while building backends on nodejs Everything else is fantastic

Edit: https://kotlinlang.slack.com/archives/CDFP59223/p1759383119112699 What's up with this warning in 2.2.20? I suppose it's an IDE bug, and I don't have to worry about anything.

Is there a way for generated typescript files

d.ts

to have KDoc comments transferred over to

d.ts

from the Kotlin files?

I've noticed that the

js(...)

intrinsic only supports ES5 syntax. The version of GWT used by the Kotlin/JS compiler also predates the release of the ES6 standard. I couldn't find any official documentation describing the exact behavior of the intrinsic, but is enforcing ES5 kind of a spec of Kotlin/JS?

I'm testing Kotlin

2.3.0-Beta1

and trying to

@JsExport

a class with suspending method. I'm getting

Declaration of such kind (suspend function) cannot be exported to JavaScript.

error. I thought it had been fixed as https://youtrack.jetbrains.com/projects/KT/issues/KT-56281. Was I wrong?

What are some tips and tricks to reduce the Kotlin/JS production bundle size? There is a lot of scattered tips across the web (and here too) but some of them aren't applicable anymore so I'm wondering what actually works on recent Kotlin versions kodee loving

I think I’ve stumbled upon a fairly serious compiler bug in 2.2.21. https://youtrack.jetbrains.com/issue/KT-81971/Kotlin-JS-incorrectly-compiles-get-to-kotlin.js.get It seems that an inlined/reified function with Any as its type param (inside of a constructor) always gets compiled to

kotlin.js.get

. This is breaking our

koin

integration.

It seems that using

eval

on a project still causes the project's bundle size to shoot up for some unknown reason I did talk about that bug 1+ year ago here on this channel, but that time I could fix the bug by creating proper typings, but sadly this time I really needed to use

eval

(executing scripts sent in HTML fragments by the server) https://kotlinlang.slack.com/archives/C0B8L3U69/p1715660256035359 So here's a workaround: Instead of using

eval

directly, use

window.asDynamic().eval(element.innerHTML)

Bundle sizes: • With

eval(element.innerHTML)

(from

kotlin.js

): 1.788KB • With `window.asDynamic().eval(element.innerHTML)`: 1.030KB

Hello! 👋🏻 Let say I have a KotlinJS module in my project, named

moduleA

. I want to have another module that would be able to showcase how to use that

moduleA

. I have this right now:

plugins {
    kotlin("multiplatform")
}

kotlin {
  js {
    browser()
  }

  sourceSets.jsMain.dependencies {
    implementation(project(":moduleA"))
  }
}

Inside my sample app, I have that

index.html

where it auto import

<script type="application/javascript" src="sampleApp.js"></script>

that is server by webpack. How can I access that

moduleA

from a

<script>

tag inside the index.html ? Thanks!

Hey folks, has anyone manage to access static resources from the

jsTest

resources directory? No matter what I do I seem to just get a 404 It's a service worker so it needs to be accessible as a static file off the root path I've tried the following (with absolute path) but still getting a 404

val devServer = (webpackConfig.devServer ?: KotlinWebpackConfig.DevServer())
                    webpackConfig.devServer = devServer.copy(
                        static = (devServer.static ?: mutableListOf()).apply {
                            add("<ABSOLUTE PATH>/>/src/jsTest/resources/")
                        }
                    )

Hey all, does anyone have more context on this error? Couldn't find anything by googling: "Dependency to project with multiple js/wasm compilations is not supported yet" The error is clear enough. I have a module in my project that declares two js targets (with a gradle attribute to distinguish them), and another module with those two same js projects that I want to depend on the other module. I know this is a bit of an unusual use-case, but basically we have two separate products that are both JS, but we need different actual implementations for both (and both are browser targets as well). Any potential work-arounds, and any clue when this will be supported in the future?

Anyone know if there is a gradle plugin to use with something like this: https://github.com/adamko-dev/kotlinx-serialization-typescript-generator. Was thinking about using it to generate my response models from my ktor backend and possible functions to wrap the rest api

@Artem Kobzar regarding the

export default

of plain objects, I've seen that exporting something like

val obj = js("{}")

Generates something on the line of

var obj = {};
var x = { get: obj };
export default x;

I don't understand the

get:

part to be honest. I understand

getInstance

for instances of Kotlin classes/objects, since they can be lazy, but not for JS objects or externals.

In latest KFC plugins

16.0.0

we use Rolldown by default. It creates production build 3 times faster in our Kotlin/JS cases (2 min -> 40 sec) 😜 2% bundle reducing - additional bonus. Both JS and WasmJS targets supported. Special thanks to @Michael Porotkin

For years now, I've suffered the constant warning that "you're not supposed to have multiple js targets in a single module". So, now that I'm migrating to Java 25, I figured I'd migrate this as well. I've extracted all the different js targets from my

build.gradle

into differnet submodules, but now I have a problem: How do I run this in development mode? In short: I have a main JS file that runs the single-page application, and then I have two more JS files that now has to come from other modules: One is a webworker that runs as part of the application, and the second is a separate js file that is very large and is loaded on-demand when its functionality is needed. Is it not possible to bring all of these js files into the main client application so they're available in developer mode? This was pretty easy when having multiple js targets.