This is a JavaScript runtime for the Apoxy Edge Functions. It allows you to write serverless functions in JavaScript that are executed for each in-flight request or as terminating HTTP handler a la Cloudflare Workers.

This runtime is built using these libraries:

• quickjs-wasm-rs - A Rust wrapper around QuickJS that compiles to WebAssembly (aka Javy from Shopify).
• wizer to run user-supplied Javascript code in a WebAssembly sandbox.
• Extism Rust PDK - A Rust library for writing Extism plugins.

It interacts with Apoxy Edge Function runtime via the Extism PDK.

You will want to use a bundler if you want to want to or include modules from NPM, or write the plugin in Typescript, for example.

There are 2 primary constraints to using a bundler:

1. Your compiled output must be CJS format, not ESM.
2. You must target es2020 or lower.

The easiest way to set this up would be to use esbuild. The following is a quickstart guide to setting up a project:

# Make a new JS project npm init -y npm install esbuild @extism/js-pdk --save-dev mkdir src mkdir dist

Optionally add a jsconfig.json or tsconfig.json to improve intellisense:

{ "compilerOptions": { "lib": [], // this ensures unsupported globals aren't suggested "types": ["@extism/js-pdk"], // while this makes the IDE aware of the ones that are "noEmit": true // this is only relevant for tsconfig.json }, "include": ["src/**/*"] }

Add esbuild.js:

const esbuild = require('esbuild'); // include this if you need some node support: // npm i @esbuild-plugins/node-modules-polyfill --save-dev // const { NodeModulesPolyfillPlugin } = require('@esbuild-plugins/node-modules-polyfill') esbuild .build({ // supports other types like js or ts entryPoints: ['src/index.js'], outdir: 'dist', bundle: true, sourcemap: true, //plugins: [NodeModulesPolyfillPlugin()], // include this if you need some node support minify: false, // might want to use true for production build format: 'cjs', // needs to be CJS for now target: ['es2020'] // don't go over es2020 because quickjs doesn't support it })

Add a build script to your package.json:

{ "name": "extism-plugin", // ... "scripts": { // ... "build": "node esbuild.js && extism-js dist/index.js -i src/index.d.ts -o dist/plugin.wasm" }, // ... }

Before compiling the compiler, you need to install prerequisites.

1. Install Rust using rustup
2. Install the WASI target platform via rustup target add --toolchain stable wasm32-wasi
3. Install the wasi sdk using the makefile command: make download-wasi-sdk
4. Install CMake (on macOS with homebrew, brew install cmake)
5. Install Binaryen and add it's install location to your PATH (only wasm-opt is required for build process)
6. Install 7zip(only for Windows)

Run make to compile the core crate (the engine) and the cli:

make 

To test the built compiler (ensure you have Extism installed):

./target/release/extism-js bundle.js -i bundle.d.ts -o out.wasm # => "{\"count\":4}"