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

Check out the documentation or try it out in WebAssembly Studio!

The core team members and most contributors do this open source work in their free time. If you use AssemblyScript for a serious task or plan to do so, and you'd like us to invest more time on it, please donate to our OpenCollective. By sponsoring this project, your logo will show up above. Thank you so much for your support!

You are now able to write WebAssembly, without learning a new language, and harness all these benefits WebAssembly might offer you. I think that is kind of powerful. [...] It [AssemblyScript] is absolutely usable, and very enjoyable! - Surma, WebAssembly for Web Developers (Google I/O ’19) (May 8th, 2019)

AssemblyScript was frictionless. Not only does it allow you to use TypeScript to write WebAssembly, [...] it also produces glue-free WebAssembly modules that are very small with decent performance. – Surma, Replacing a hot path in your app's JavaScript with WebAssembly (Feb 16, 2019)

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)

For general usage instructions, please refer to the documentation instead. The following sets up a development environment of the compiler, for example if you plan to make a pull request:

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

Note that a fresh clone of the compiler will use the distribution files in dist/, but after an npm clean it will run the sources directly through ts-node, which is useful in development. This condition can also be checked by running asc -v (it is running the sources if it states -dev). Also please see our contribution guidelines before making your first pull request.

To build an UMD bundle to dist/assemblyscript.js (depends on binaryen.js), including a browser version of asc to dist/asc.js (depends on assemblyscript.js):

$> npm run build

Cleaning the distribution files (again):

$> npm run clean

Linting potential changes:

$> npm run check

Running the tests:

$> npm test

Running everything in order (lint, clean, test, build, test):

$> npm run all