Sveltekit

npm create svelte@latest my-app
cd my-app
npm install
npm run dev

src/
  routes/
    +page.svelte        ← Root page component
    +layout.svelte      ← Root layout (wraps all pages)
    +error.svelte       ← Error boundary
  lib/
    server/             ← Server-only code (never bundled to client)
    components/         ← Shared components
  app.html              ← HTML shell
static/                 ← Static assets

src/routes/+page.svelte          → /
src/routes/about/+page.svelte    → /about
src/routes/blog/[slug]/+page.svelte  → /blog/:slug
src/routes/shop/[...path]/+page.svelte → /shop/* (catch-all)

// src/routes/blog/[slug]/+page.server.ts
import { error } from '@sveltejs/kit';
import type { PageServerLoad } from './$types';

export const load: PageServerLoad = async ({ params, fetch }) => {
  const post = await fetch(`/api/posts/${params.slug}`).then(r => r.json());

  if (!post) {
    error(404, 'Post not found');
  }

  return { post };
};

<!-- src/routes/blog/[slug]/+page.svelte -->
<script lang="ts">
  import type { PageData } from './$types';
  export let data: PageData;
</script>

<h1>{data.post.title}</h1>
<article>{@html data.post.content}</article>

// src/routes/api/posts/+server.ts
import { json } from '@sveltejs/kit';
import type { RequestHandler } from './$types';

export const GET: RequestHandler = async ({ url }) => {
  const limit = Number(url.searchParams.get('limit') ?? 10);
  const posts = await db.post.findMany({ take: limit });
  return json(posts);
};

export const POST: RequestHandler = async ({ request }) => {
  const body = await request.json();
  const post = await db.post.create({ data: body });
  return json(post, { status: 201 });
};

// src/routes/contact/+page.server.ts
import { fail, redirect } from '@sveltejs/kit';
import type { Actions } from './$types';

export const actions: Actions = {
  default: async ({ request }) => {
    const data = await request.formData();
    const email = data.get('email');

    if (!email) {
      return fail(400, { email, missing: true });
    }

    await sendEmail(String(email));
    redirect(303, '/thank-you');
  }
};

<!-- src/routes/contact/+page.svelte -->
<script lang="ts">
  import { enhance } from '$app/forms';
  import type { ActionData } from './$types';
  export let form: ActionData;
</script>

<form method="POST" use:enhance>
  <input name="email" type="email" />
  {#if form?.missing}<p class="error">Email is required</p>{/if}
  <button type="submit">Subscribe</button>
</form>

<!-- src/routes/+layout.svelte -->
<script lang="ts">
  import type { LayoutData } from './$types';
  export let data: LayoutData;
</script>

<nav>
  <a href="/">Home</a>
  <a href="/blog">Blog</a>
  {#if data.user}
    <a href="/dashboard">Dashboard</a>
  {/if}
</nav>

<slot />  <!-- child page renders here -->

// src/routes/+layout.server.ts
import type { LayoutServerLoad } from './$types';

export const load: LayoutServerLoad = async ({ locals }) => {
  return { user: locals.user ?? null };
};

// src/routes/docs/+page.ts
export const prerender = true;   // Static — generated at build time
export const ssr = true;         // Default — rendered on server per request
export const csr = false;        // Disable client-side hydration entirely

// src/routes/dashboard/+layout.server.ts
import { redirect } from '@sveltejs/kit';
import type { LayoutServerLoad } from './$types';

export const load: LayoutServerLoad = async ({ locals }) => {
  if (!locals.user) {
    redirect(303, '/login');
  }
  return { user: locals.user };
};

// src/hooks.server.ts
import type { Handle } from '@sveltejs/kit';
import { verifyToken } from '$lib/server/auth';

export const handle: Handle = async ({ event, resolve }) => {
  const token = event.cookies.get('session');
  if (token) {
    event.locals.user = await verifyToken(token);
  }
  return resolve(event);
};

<script lang="ts">
  import { invalidateAll } from '$app/navigation';

  async function refresh() {
    await invalidateAll(); // re-runs all load functions on the page
  }
</script>

<button on:click={refresh}>Refresh</button>