# web-spawn

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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`](https://crates.io/crates/wasm-bindgen-rayon) and [`wasm_thread`](https://crates.io/crates/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`:

```toml
[target.'cfg(target_arch = "wasm32")'.dependencies]
web-spawn = { version = "0.1" }
```

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

```rust,ignore
pub use web_spawn::start_spawner;
```

On the javascript side this can be awaited:

```javascript
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`:

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