Function spawn_js_thread 

pub fn spawn_js_thread(
    vendor_path: PathBuf,
    app_path: PathBuf,
    ops_tx: Sender<Vec<Op>>,
    emit_tx: Sender<ReactMessage>,
    request_tx: Sender<RawRequest>,
    anim_tx: Sender<AnimationCommand>,
    outbound_rx: UnboundedReceiver<Outbound>,
    reload_rx: UnboundedReceiver<()>,
)

Available on non-WebAssembly only.

Spawn the JS thread. Builds the isolate once and keeps it alive across hot reloads (re-executing only the app bundle); runs until shutdown.