SSR.js

const StyleSheetServer = {
    async renderStatic(appRenderFunc) {
        reset();
        startBuffering();
        const result = await appRenderFunc();
        const cssContent = flushToString();

        return {
            result,
            css: {
                content: cssContent,
                renderedClassNames: getRenderedClassNames(),
            },
        };
    },
};