Tokio

Real world example (opens in a new tab)

You can also run Tokio futures in Node.js. With the tokio_rt feature, napi-rs will create a tokio runtime so that you can use Env::execute_tokio_future to execute a future and return a JavaScript Promise.

tokio_rt needs ThreadSafeFunction under the hood, so enable tokio_rt feature will enable napi4 by default.

#[js_function(1)]
pub fn readfile(ctx: CallContext) -> Result<JsObject> {
  let js_filepath = ctx.get::<JsString>(0)?;
  let path_str = js_filepath.into_utf8()?.into_owned()?;
  ctx.env.execute_tokio_future(
    tokio::fs::read(path_str).map(|v| {
      v.map_err(|e| {
        Error::new(
          Status::GenericFailure,
          format!("failed to read file, {}", e),
        )
      })
    }),
    |&mut env, data| env.create_buffer_with_data(data).map(|v| v.into_raw()),
  )
}

readfile('./test.txt').then((data) => {
  console.log(data) // Buffer<00 03 ...>
})

Thread safe function Wrap native object