SvelteKit data flow guidance. Use for load functions, form actions, server/client data, and invalidation. Covers +page.server.ts vs +page.ts, serialization, fail(), redirect(), error(), invalidateAll().
Which file? Server-only (DB/secrets): +page.server.ts |
Universal (runs both): +page.ts | API: +server.ts
Load decision: Need server resources? → server load | Need client APIs? → universal load
Form actions: Always +page.server.ts. Return fail() for
errors, throw redirect() to navigate, throw error() for failures.
// +page.server.ts
import { fail, redirect } from "@sveltejs/kit";
export const load = async ({ locals }) => {
const user = await db.users.get(locals.userId);
return { user }; // Must be JSON-serializable
};
export const actions = {
default: async ({ request }) => {
const data = await request.formData();
const email = data.get("email");
if (!email) return fail(400, { email, missing: true });
await updateEmail(email);
throw redirect(303, "/success");
},
};
<!--
PROGRESSIVE DISCLOSURE GUIDELINES:
- Keep this file ~50 lines total (max ~150 lines)
- Use 1-2 code blocks only (recommend 1)
- Keep description <200 chars for Level 1 efficiency
- Move detailed docs to references/ for Level 3 loading
- This is Level 2 - quick reference ONLY, not a manual
LLM WORKFLOW (when editing this file):
1. Write/edit SKILL.md
2. Format (if formatter available)
3. Run: claude-skills-cli validate <path>
4. If multi-line description warning: run claude-skills-cli doctor <path>
5. Validate again to confirm
-->data param | ALWAYS
throw redirect()/error()