# Getting Started With Compose for Web In this tutorial, we will create a simple web UI application using the Compose UI framework. ## Prerequisites You need to have the following software installed before you begin: * JDK 11 or later * IntelliJ IDEA Community Edition or Ultimate Edition 2020.2 or later (you can use other editors, but for this tutorial we assume you are using IntelliJ IDEA) ## Creating a new project If you don't want to create the project manually, you can [download the template here](https://github.com/JetBrains/compose-jb/tree/master/templates/web-template) The project wizard doesn't support Compose for web projects yet, so we need to perform the following steps: #### 1. Create a Kotlin Multiplatform project: - Select `Gradle` on the left menu - Tick `Kotlin DSL build script` - Tick `Kotlin/Multiplatform` #### 2. Update `settings.gradle.kts`: ``` kotlin pluginManagement { repositories { gradlePluginPortal() maven("https://maven.pkg.jetbrains.space/public/p/compose/dev") } } ``` #### 3. Update `build.gradle.kts`: ``` kotlin // Add compose gradle plugin plugins { kotlin("multiplatform") version "1.7.20" id("org.jetbrains.compose") version "1.2.1-rc03" } // Add maven repositories repositories { mavenCentral() maven("https://maven.pkg.jetbrains.space/public/p/compose/dev") google() } // Enable JS(IR) target and add dependencies kotlin { js(IR) { browser() binaries.executable() } sourceSets { val jsMain by getting { dependencies { implementation(compose.web.core) implementation(compose.runtime) } } } } ``` #### 5. Add the following directories to the project: - src/jsMain/kotlin - src/jsMain/resources #### 6. Add the `index.html` file to the `resources`: ```html Sample
``` #### 7. Add the `Main.kt` file to the `kotlin`: ```kotlin import androidx.compose.runtime.mutableStateOf import androidx.compose.runtime.getValue import androidx.compose.runtime.setValue import androidx.compose.runtime.Composable import org.jetbrains.compose.web.attributes.* import org.jetbrains.compose.web.css.* import org.jetbrains.compose.web.dom.* import org.jetbrains.compose.web.renderComposable fun main() { var count: Int by mutableStateOf(0) renderComposable(rootElementId = "root") { Div({ style { padding(25.px) } }) { Button(attrs = { onClick { count -= 1 } }) { Text("-") } Span({ style { padding(15.px) } }) { Text("$count") } Button(attrs = { onClick { count += 1 } }) { Text("+") } } } } ``` ## Running the project Use the command line to run: ```shell ./gradlew jsBrowserRun ``` Instead of manually compiling and executing a Kotlin/JS project every time you want to see the changes you made, you can use the continuous compilation mode: ```shell ./gradlew jsBrowserRun --continuous ``` Or run it from the IDE: The browser will open `localhost:8080`: ## Common issues when running the project #### [webpack-cli] Unable to load '@webpack-cli/serve' command https://youtrack.jetbrains.com/issue/KT-49124 ``` [webpack-cli] Unable to load '@webpack-cli/serve' command [webpack-cli] TypeError: options.forEach is not a function ... ``` There is a temporary workaround: ``` In build.gradle.kts: // a temporary workaround for a bug in jsRun invocation - see https://youtrack.jetbrains.com/issue/KT-48273 afterEvaluate { rootProject.extensions.configure { versions.webpackDevServer.version = "4.0.0" versions.webpackCli.version = "4.9.0" } } ```