Getting Started with Kotlin/JS


Kotlin/JS allows you to build frontend web applications using the Kotlin programming language. In this guide, we'll walk you through the steps to get started with Kotlin/JS and create a simple web application.


Setting Up Your Environment

Before you start, make sure you have Kotlin and an integrated development environment (IDE) like IntelliJ IDEA installed on your system. You'll also need a web browser to run and test your Kotlin/JS application.


Creating a Simple Kotlin/JS Application

Let's create a basic Kotlin/JS application that displays a "Hello, Kotlin/JS!" message in the web browser:


1. Create a new Kotlin/JS project or module within your IDE. Kotlin/JS projects are typically structured as Gradle or Maven projects with the Kotlin/JS Gradle plugin.


2. Define an HTML file for your web application, for example, `index.html`:

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Kotlin/JS Example</title>
</head>
<body>
    <h1 id="output">Loading...</h1>
    <script src="kotlin.js"></script>
    <script src="app.js"></script>
</body>
</html>

This HTML file includes placeholders for your application's output and references two JavaScript files, one for the Kotlin/JS standard library (`kotlin.js`) and another for your Kotlin/JS application (`app.js`).


3. Create a Kotlin file, for example, `App.kt`, to define your application logic:

fun main() {
    val output = document.getElementById("output")
    output?.textContent = "Hello, Kotlin/JS!"
}

This Kotlin code uses the Kotlin/JS standard library to interact with the HTML DOM and update the content of the "output" element.


4. Build your Kotlin/JS application to generate the `app.js` JavaScript file. You can do this using Gradle or the build tool you're using for your project.


Running Your Kotlin/JS Application

Now, you can run your Kotlin/JS application:


1. Open the `index.html` file in a web browser. You should see the "Hello, Kotlin/JS!" message displayed on the page.


Conclusion

Getting started with Kotlin/JS is the first step to building web applications using Kotlin. This example demonstrates the basics, but you can expand it to include more complex interactions, external libraries, and frontend frameworks.


Happy coding with Kotlin/JS!