web-spawn

This crate provides a std::thread shim for WASM builds targeting web browsers.

It borrows from and is heavily inspired by both wasm-bindgen-rayon and wasm_thread but makes a couple different design choices.

Most notably, spawning is explicitly delegated to run in a background task and must be initialized at the start of the program. This task can either run on the main browser thread, or be moved to a dedicated worker to avoid potential interference from other loads.

Usage

Add web-spawn as a dependency in your Cargo.toml:

[target.'cfg(target_arch = "wasm32")'.dependencies]
web-spawn = { version = "0.2" }

Then you must ensure that spawning is initialized. One way to do this is to re-export the following function:

pub use web_spawn::start_spawner;

On the javascript side this can be awaited:

import init, { startSpawner } from /* your package */;

await init();

// Runs the spawner on a dedicated web worker.
await startSpawner();

Now, in the rest of your Rust code you can conditionally use web-spawn anywhere you would otherwise use std::thread::spawn:

#[cfg(target_arch = "wasm32")]
use web_spawn as thread;
#[cfg(not(target_arch = "wasm32"))]
use std::thread;