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The Wheel of WebAssembly

Build Status

The Wheel of WebAssembly is a project aiming to show the diversity of languages that compile to WebAssembly. My initial idea was to define two functions in each language:

  • name() - returning the name of the language. This is used to render each part of the wheel.
  • feelingLucky() - returning a random integer between 1 and 100. This is used when the wheel is spinned.

In theory, when compiling each language, the output wasm file should be almost identical. In practice, this is not the case. As many of the compilers are still very experimental, these two functions cannot be definen in all the languages. Some have issues with generating a random number, so I import JavaSript's Math.random() to help them. Others cannot handle strings properly. WebAssembly defines only numeric types and strings are suppsed to be put in the linear memory and accessed via a pointer from JavaScript.

Wheel of WebAssembly screenShot

Supported languages

  • C / C++
  • C#
  • AssemblyScript
  • Rust
  • Java
  • Kotlin
  • Go
  • PHP

Getting started

You need Docker to build each wheel part.

$> git clone
$> cd wasm-wheel
$> npm i
$> npm run build
$> npm start

You can then access the site on http://localhost:8080.

You can re-build individual wheel parts by running

$> npm run build -- [lang]

Wheel parts

Each wheel part represents a language that can be compiled to WebAssembly. My initial idea was to use toolchain to compile each source automatically, but this turned out to be a bit more complex. That is why I am putting here how each source can be compiled individually.

C / C++

Compiled by emscripten.


You would either need Mono or Visual Studio 2017+ installed on your machine to compile the source. Although Mono has an example of compiling C# directly to WebAssembly, the set-up is a bit more complicated. That is why I use Steve Sanderson's initial adjustment of DotNetAnywhere to interpret .NET into the browser. You would also need emscripten >= 1.38.12 to compile DotNetAnywhere's interpretter to WebAssembly.


AssemblyScript defines a subset of TypeScript that can be compiled to WebAssembly. Currently using version 0.9.4 of the compiler.


You have to install the Rust toolchain by following these instructions. Afterwards you need to add the wasm32 target.

$> rustup update
$> rustup target add wasm32-unknown-unknown


In order to compile Java into WebAssembly, I use TeaVM. The only thing you need is Maven - it will install its depedencies afterwards. You obviously need Java SDK as well.


Kotlin/Native is used to compile Kotlin to WebAssembly. Compiling Kotlin to native restricts you from importing Java libraries. In order to generate random numbers, one may use C instead (as in the C wheel part), but this requires further configuration using the cinterop tool. I think it is easier just to import the JavaScript one.


Go 1.14 ships experimental WebAssembly support. The communication from JavaScript to Go works with callbacks, which made me change all other calls to use promises. The output file is quite large so far (~ 1.5MB), but this is already being addressed.


The PHP interpreter is compiled to WebAssembly and then using the wrapper function pib_eval we can evaluate PHP code, which gets printed on the console.

Questions & contribution

You can follow me on Twitter with @boyanio and ask me questions you might have. You can also open an issue here on GitHub. Pull requests are welcome, too :-)


Demo project aiming to show the diversity of languages that compile to WebAssembly. See demo at





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