wasmjs: JavaScript tooling for WebAssembly

wasmjs is a self-contained collection of JavaScript tools which can manipulate WebAssembly. At its core is wasm.json, a JSON decription of the WebAssembly format and other interesting facts about WebAssembly as used by the Webkit project (such as the names of associated JavaScriptCore opcodes).

wasmjs requires modern JavaScript features such as ES6 modules, which is acceptable because WebAssembly is itself contemporary to these other features.

Builder API

The current core API of wasmjs is the Builder API from Builder.js. It is used to build WebAssembly modules.

A simple example:

import Builder from 'Builder.js';

const builder = new Builder();

// Construct the equivalent of: (module (func (nop) (nop)))
builder
    .Code()
        .Function()
            .Nop()
            .Nop()
        .End()
    .End();

// Create an ArrayBuffer which is a valid WebAssembly `.wasm` file.
const binary = builder.WebAssembly();

Code such as the above can then be used with JavaScript's WebAssembly global object.

Testing

Tests can be executed using:

JSSHELL=/path/to/my/js-shell test.sh

They can also be executed by using WebKit's run-javascriptcore-tests tool:

./Tools/Scripts/run-javascriptcore-tests --release --filter wasm -arch x86_64

The self-test folder contains tests for wasmjs itself. Future additions will also test the JavaScript engine's WebAssembly implementation (both JavaScript API and usage of that API to compile and execute WebAssembly modules).