jspawn

A subprocess API for WebAssembly programs.

- Supports WASI and Emscripten binaries
- Works in the browser and Node.js
- Async interface (programs run in worker threads)

Compiling and interfacing with WebAssembly programs can be hard. jspawn provides a unified interface and a collection of pre-built binaries.

WARNING: expect breaking/backwards-incompatible changes for MINOR versions before v1.0.0.

``sh
npm install --save @jspawn/jspawn
`

Examples

$3

index.mjs

`javascript
// Or const { VirtualEnv } = require("@jspawn/jspawn");
import { VirtualEnv } from "@jspawn/jspawn";

const venv = await VirtualEnv.instantiate();

// WASM/binary resolution happens automatically in node when the first argument isn't a path -
// more specifically, it doesn't contain a path-separator and doesn't end with .wasm.
const output = await venv.run(
// Assumes @jspawn/imagemagick-wasm is installed.
// npm install --save @jspawn/imagemagick-wasm
"magick",
// Create a blank PNG.
["-size", "100x100", "xc:blue", "blank.png"]
);
console.log(output); // { exitCode: 0, stdout: "", stderr: "" }
`

Run with:

`sh


Depending on your version of node, you may not need the experimental flags.


node --experimental-wasm-bigint --experimental-wasi-unstable-preview1 index.mjs
`

$3

`javascript
import { VirtualEnv } from "https://unpkg.com/@jspawn/jspawn/esm/jspawn.mjs";

const venv = await VirtualEnv.instantiate();

const output = await venv.run(
// Full path to a WASM file - no automatic resolution in the browser.
"https://unpkg.com/@jspawn/imagemagick-wasm/magick.wasm",
// Create a blank PNG.
["-size", "100x100", "xc:blue", "blank.png"]
);

console.log(output); // { exitCode: 0, stdout: "", stderr: "" }

// The file system lives in memory for browser environments.
// Access it using the fs module.
const png = await venv.fs.readFileToBlob("blank.png");

// Now, do what you will with the Blob.
// Maybe display it.
const img = document.createElement("img");
img.src = URL.createObjectURL(png);
document.body.append(img);
``