foo.js

function asyncReaction<T: ActionTypes>(detector: Detector<T>, handler: Handler<T>): AppMiddleware {
	return store => next => action => {
		const detected = detector(action);
		if (detected !== null) {
			handler(detected, store.getState()).then(store.dispatch);
		}
		return next(action);
	}
}

const middleware = asyncReaction(isProjectsCreate, createProjectHTTP);