In SvelteKit, both +page.js and +server.js are used for data handling, but they serve different purposes and run in different contexts.
+page.js is used to define load functions for a page or layout. It can run on both the server (during SSR) and the client (during client-side navigation). Its main purpose is to fetch or prepare data that will be injected into the corresponding +page.svelte or +layout.svelte as the data prop.
+server.js defines endpoints and handles HTTP requests on the server only. It is not included in the client bundle. You can define handlers for methods like GET, POST, PUT, or DELETE to create API routes. Data from +server.js can then be fetched using fetch in +page.js, load functions, or directly in the browser.
+page.jsis for page-level data fetching;+server.jsis for server-side API endpoints.+page.jsruns on server and client;+server.jsruns only on the server.Data from
+server.jsmust be fetched viafetchin+page.jsor components.+page.jsaffects hydration by preloading data for SSR pages.+server.jsdoes not directly affect hydration; it provides data to be fetched when needed.