As of this version the implementation lives in js-sys under the futures feature. Depending on this crate automatically activates that feature, which gives js_sys::Promise a first-class IntoFuture implementation — meaning you can .await any Promise directly:

use js_sys::Promise;
use wasm_bindgen::prelude::*;

async fn example(promise: Promise) -> Result<JsValue, JsValue> {
    promise.await
}

All public items from the previous API are re-exported unchanged for backwards compatibility:

JsFuture — convert a Promise into a named Future type
spawn_local — run a Future<Output = ()> on the JS microtask queue
future_to_promise — convert a Future into a JS Promise
future_to_promise_typed — typed variant of future_to_promise

Under the feature flag futures-core-03-stream there is support for AsyncIterator to Stream conversion via JsStream.

See the API documentation for more info.