AssemblyScript

AssemblyScript compiles strictly typed TypeScript (basically JavaScript with types) to WebAssembly using Binaryen. It generates lean and mean WebAssembly modules while being just an npm install away.

See the AssemblyScript wiki for instructions and documentation. You can also try it out in WebAssembly Studio!

Motivation

Being able to write C-performance code in TypeScript feels so good – Ari on Slack (Apr 19, 2018)

Perhaps the fundamental issue [to get a small .wasm file] is that JavaScript is the only language for which the Web runtime is a perfect fit. Close relatives that were designed to compile to it, like TypeScript, can be very efficient as well. But languages like C, C++, Rust, and so forth were not originally designed for that purpose. – Alon Zakai, Small WebAssembly Binaries with Rust + Emscripten (Apr 18, 2018)

JavaScript's heyday as the only browser language is over, but most web developers are used to writing JavaScript, and learning a new syntax just to get access to WebAssembly is not (always) ideal. If only there was something in to bridge the gap… – Jani Tarvainen, TypeScript is the bridge between JavaScript and WebAssembly (Feb 20, 2018)

I do think [compiling TypeScript into WASM] is tremendously useful. It allows JavaScript developers to create WASM modules without having to learn C. – Colin Eberhardt, Exploring different approaches to building WebAssembly modules (Oct 17, 2017)

Examples

• Conway's Game of Life [ demo | fiddle ]
  Continuously updates the cellular automaton and visualizes its state on a canvas.

• Mandelbrot Set [ demo ]
  Renders the Mandelbrot set to a canvas.

• i64 polyfill
  Exposes WebAssembly's i64 operations to JavaScript using 32-bit integers (low and high bits).

• PSON decoder
  A simple decoder for the PSON binary format.

• WASM parser
  A WebAssembly binary parser in WebAssembly.

Or browse the compiler tests for a more in-depth overview of what's supported already. One of them is a showcase.

Installation

Note that this version of the compiler is relatively new and that some features a TypeScript programmer might expect are still in the works (see also: Limitations). Therefore, it's not on npm, yet, but you can already try it out today:

$> git clone https://github.com/AssemblyScript/assemblyscript.git
$> cd assemblyscript
$> npm install
$> npm link

Alternatively, it's also possible to point npm to the GitHub repository for now:

$> npm install AssemblyScript/assemblyscript

Afterwards, once your project is configured, it's just a matter of using your existing TypeScript tooling while coding, and running the CLI to build to WebAssembly:

$> asc myModule.ts -o myModule.wasm --optimize --validate --sourceMap

Building

To build an UMD bundle to dist/assemblyscript.js (depends on binaryen.js):

$> npm run build

This also builds a browser version of asc to dist/asc.js (depends on assemblyscript.js).

Running the tests:

$> npm test

Note that freshly cloned copies of the compiler will use the distribution files, but it can also run the sources directly through ts-node after an npm run clean, which is useful in development. This condition can also be checked by running asc -v (it is running the sources if it states -dev).