client.js

function mountReact(router, useHydrate = true) {
    let renderFunction = useHydrate ? hydrate : render;

    renderFunction(
        <RouterProvider router={router}>
            <App />
        </RouterProvider>,
        document.getElementById('root'),
    );
}

async function initRouter() {
    let router = routerFactory();

    if (state.r.noSsr) {
        router.start(err => {
            if (err) {
                console.error(err);
            }

            mountReact(router, false);
        });
    } else {
        let routerState = await rehydrateState(router, state.r);

        router.start(routerState, err => {
            if (err) {
                console.error(err);
                return;
            }

            mountReact(router);
        });
    }
}