class Session extends Map { set(id, value) { if (typeof value === 'object') value = JSON.stringify(value); sessionStorage.setItem(id, value); } get(id) { const value = sessionStorage.getItem(id); try { return JSON.parse(value); } catch (e) { return value; } } }

When Sapper renders a page on the server, it will attempt to serialize the resolved value (using devalue) and include it on the page, so that the client doesn't also need to call preload upon initialization.