chore: import upstream snapshot with attribution
This commit is contained in:
wehub-resource-sync
@@ -0,0 +1,579 @@
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# Server Components and Server Actions
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React 19 Server Components run on server, can be async, enable zero-bundle data fetching. Server Actions handle mutations with progressive enhancement.
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## Async Server Component
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Server Components can be async functions — await data fetching directly.
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```typescript
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// app/users/[id]/page.tsx
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type PageProps = {
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params: { id: string };
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searchParams?: { tab?: string; edit?: string };
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};
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export default async function UserPage({ params, searchParams }: PageProps) {
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// Runs on server - no client bundle
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const user = await fetchUser(params.id);
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const posts = await fetchUserPosts(params.id);
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return (
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<div>
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<header>
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<h1>{user.name}</h1>
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<p>{user.email}</p>
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</header>
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<UserTabs user={user} posts={posts} activeTab={searchParams?.tab} />
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{searchParams?.edit === 'true' && (
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<UserEditForm user={user} />
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)}
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</div>
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);
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}
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async function fetchUser(id: string): Promise<User> {
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const res = await fetch(`https://api.example.com/users/${id}`, {
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cache: 'no-store', // Or 'force-cache', 'revalidate'
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});
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if (!res.ok) throw new Error('Failed to fetch user');
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return res.json();
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}
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```
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## Parallel Data Fetching
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Fetch multiple resources in parallel with Promise.all.
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```typescript
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type DashboardProps = {
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params: { userId: string };
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};
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export default async function Dashboard({ params }: DashboardProps) {
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// Parallel fetching
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const [user, stats, activity] = await Promise.all([
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fetchUser(params.userId),
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fetchUserStats(params.userId),
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fetchRecentActivity(params.userId),
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]);
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return (
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<div>
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<UserHeader user={user} />
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<StatsGrid stats={stats} />
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<ActivityFeed items={activity} />
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</div>
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);
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}
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```
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## Sequential vs Waterfall Fetching
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```typescript
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// ❌ Waterfall - slow
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async function SlowPage() {
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const user = await fetchUser('123');
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const posts = await fetchUserPosts(user.id); // Waits for user
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const comments = await fetchPostComments(posts[0].id); // Waits for posts
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return <div>...</div>;
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}
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// ✅ Parallel - fast
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async function FastPage() {
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const userPromise = fetchUser('123');
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const postsPromise = fetchUserPosts('123');
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const [user, posts] = await Promise.all([userPromise, postsPromise]);
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// If comments depend on posts, fetch after
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const comments = await fetchPostComments(posts[0].id);
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return <div>...</div>;
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}
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```
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## Server Actions - Form Mutations
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Server Actions marked with 'use server' — run on server, callable from client.
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```typescript
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// actions/user.ts
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'use server';
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import { revalidatePath, revalidateTag } from 'next/cache';
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import { redirect } from 'next/navigation';
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import { z } from 'zod';
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const updateUserSchema = z.object({
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name: z.string().min(2, 'Name must be at least 2 characters'),
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email: z.string().email('Invalid email address'),
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bio: z.string().max(500, 'Bio must be less than 500 characters').optional(),
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});
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type FormState = {
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success?: boolean;
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errors?: Record<string, string[]>;
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message?: string;
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};
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export async function updateUser(
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userId: string,
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prevState: FormState,
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formData: FormData
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): Promise<FormState> {
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// Validate
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const parsed = updateUserSchema.safeParse({
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name: formData.get('name'),
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email: formData.get('email'),
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bio: formData.get('bio'),
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});
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if (!parsed.success) {
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return {
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success: false,
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errors: parsed.error.flatten().fieldErrors,
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};
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}
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try {
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// Mutate database
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await db.user.update({
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where: { id: userId },
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data: parsed.data,
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});
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// Revalidate cached data
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revalidatePath(`/users/${userId}`);
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revalidateTag(`user-${userId}`);
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return { success: true, message: 'Profile updated successfully' };
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} catch (error) {
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return {
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success: false,
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message: 'Failed to update profile. Please try again.',
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};
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}
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}
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export async function deleteUser(userId: string) {
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await db.user.delete({ where: { id: userId } });
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revalidatePath('/users');
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redirect('/users'); // Navigate after mutation
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}
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```
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## Client Component Using Server Action
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```typescript
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// components/UserForm.tsx
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'use client';
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import { useActionState } from 'react';
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import { updateUser } from '@/actions/user';
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type FormState = {
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success?: boolean;
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errors?: Record<string, string[]>;
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message?: string;
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};
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export function UserEditForm({ userId, initialData }: Props) {
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const [state, formAction, isPending] = useActionState<FormState, FormData>(
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(prevState, formData) => updateUser(userId, prevState, formData),
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{}
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);
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return (
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<form action={formAction}>
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<div>
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<label htmlFor="name">Name</label>
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<input
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id="name"
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name="name"
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defaultValue={initialData.name}
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required
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aria-invalid={!!state.errors?.name}
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/>
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{state.errors?.name?.map((error) => (
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<p key={error} className="error">
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{error}
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</p>
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))}
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</div>
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<div>
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<label htmlFor="email">Email</label>
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<input
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id="email"
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name="email"
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type="email"
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defaultValue={initialData.email}
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required
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aria-invalid={!!state.errors?.email}
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/>
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{state.errors?.email?.map((error) => (
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<p key={error} className="error">
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{error}
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</p>
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))}
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</div>
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<div>
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<label htmlFor="bio">Bio</label>
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<textarea
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id="bio"
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name="bio"
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defaultValue={initialData.bio}
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aria-invalid={!!state.errors?.bio}
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/>
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{state.errors?.bio?.map((error) => (
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<p key={error} className="error">
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{error}
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</p>
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))}
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</div>
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{state.message && (
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<div className={state.success ? 'success' : 'error'}>{state.message}</div>
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)}
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<button type="submit" disabled={isPending}>
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{isPending ? 'Saving...' : 'Save Changes'}
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</button>
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</form>
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);
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}
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```
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## Programmatic Server Action
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Call Server Actions directly from client code, not just forms.
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```typescript
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'use client';
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import { deleteUser } from '@/actions/user';
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import { useTransition } from 'react';
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export function DeleteButton({ userId }: { userId: string }) {
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const [isPending, startTransition] = useTransition();
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const handleDelete = () => {
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if (!confirm('Are you sure you want to delete this user?')) return;
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startTransition(async () => {
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try {
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await deleteUser(userId);
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// deleteUser calls redirect(), navigation happens automatically
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} catch (error) {
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console.error('Failed to delete user:', error);
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}
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});
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};
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return (
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<button onClick={handleDelete} disabled={isPending}>
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{isPending ? 'Deleting...' : 'Delete User'}
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</button>
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);
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}
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```
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## use() Hook - Unwrapping Promises
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Pass promises from Server to Client components, unwrap with use().
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```typescript
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// Server Component
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async function UserPage({ params }: { params: { id: string } }) {
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// Don't await - pass promise to client
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const userPromise = fetchUser(params.id);
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return (
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<Suspense fallback={<UserSkeleton />}>
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<UserProfile userPromise={userPromise} />
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</Suspense>
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);
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}
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// Client Component
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'use client';
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import { use } from 'react';
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type Props = {
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userPromise: Promise<User>;
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};
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export function UserProfile({ userPromise }: Props) {
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// Suspends until resolved
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const user = use(userPromise);
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return (
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<div>
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<h1>{user.name}</h1>
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<p>{user.email}</p>
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</div>
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);
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}
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```
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## use() with Context
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use() also unwraps context — alternative to useContext.
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```typescript
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'use client';
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import { use } from 'react';
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import { ThemeContext } from './ThemeProvider';
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export function ThemedButton() {
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const theme = use(ThemeContext); // Same as useContext(ThemeContext)
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return <button className={theme.mode}>{theme.primaryColor}</button>;
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}
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```
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## Streaming with Suspense
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Stream components as they resolve — faster initial page load.
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```typescript
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// Server Component
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export default async function Page() {
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return (
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<div>
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<h1>Dashboard</h1>
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{/* Renders immediately */}
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<StaticContent />
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{/* Streams when ready */}
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<Suspense fallback={<Spinner />}>
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<SlowComponent />
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</Suspense>
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{/* Independent stream */}
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<Suspense fallback={<Skeleton />}>
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<AnotherSlowComponent />
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</Suspense>
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</div>
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);
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}
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async function SlowComponent() {
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const data = await slowFetch(); // Takes 2s
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return <div>{data}</div>;
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}
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async function AnotherSlowComponent() {
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const data = await anotherSlowFetch(); // Takes 1s
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return <div>{data}</div>;
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}
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```
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## Error Handling in Server Components
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Use error.tsx for error boundaries.
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```typescript
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// app/users/[id]/error.tsx
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'use client';
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export default function Error({
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error,
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reset,
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}: {
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error: Error & { digest?: string };
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reset: () => void;
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}) {
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return (
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<div>
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<h2>Something went wrong!</h2>
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<p>{error.message}</p>
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<button onClick={reset}>Try again</button>
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</div>
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);
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}
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// Server Component throws error
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export default async function UserPage({ params }: Props) {
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const user = await fetchUser(params.id);
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if (!user) {
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throw new Error('User not found'); // Caught by error.tsx
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}
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return <div>{user.name}</div>;
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}
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```
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## Loading States with loading.tsx
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```typescript
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// app/users/[id]/loading.tsx
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export default function Loading() {
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return <UserSkeleton />;
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}
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// Automatically wraps page in Suspense
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// No need for manual Suspense boundary
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```
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## Server-Only Code
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Ensure code never runs on client.
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```typescript
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// lib/server-only-utils.ts
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import 'server-only'; // Throws if imported in client component
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export async function getSecretKey() {
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return process.env.SECRET_KEY; // Safe - never in client bundle
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}
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export async function hashPassword(password: string) {
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const bcrypt = await import('bcrypt');
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return bcrypt.hash(password, 10);
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}
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```
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## Client-Only Code
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Ensure code never runs on server.
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```typescript
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// lib/client-only-utils.ts
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import 'client-only';
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export function useLocalStorage(key: string) {
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// localStorage only available in browser
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const [value, setValue] = useState(() => localStorage.getItem(key));
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useEffect(() => {
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localStorage.setItem(key, value || '');
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}, [key, value]);
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return [value, setValue] as const;
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}
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```
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## Mixing Server and Client Components
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```typescript
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// app/page.tsx (Server Component)
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export default async function Page() {
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const data = await fetchData();
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return (
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<div>
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{/* Server Component - can be async */}
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<ServerComponent data={data} />
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{/* Client Component - interactive */}
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<ClientComponent initialData={data} />
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</div>
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);
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}
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// ServerComponent.tsx (Server Component - default)
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export function ServerComponent({ data }: { data: Data }) {
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return <div>{data.title}</div>;
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}
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// ClientComponent.tsx (Client Component)
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'use client';
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export function ClientComponent({ initialData }: { initialData: Data }) {
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const [data, setData] = useState(initialData);
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return (
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<button onClick={() => setData({ ...data, count: data.count + 1 })}>
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{data.count}
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</button>
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);
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}
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```
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## Server Component Patterns
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```typescript
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// ✅ Server Component can:
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// - Be async
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// - Fetch data directly
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// - Access backend resources (DB, filesystem)
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// - Use server-only packages
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// - Pass serializable props to client components
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export default async function Page() {
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const db = await connectDB(); // Direct DB access
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const users = await db.user.findMany();
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return <UserList users={users} />; // Pass serializable data
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}
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// ❌ Server Component cannot:
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// - Use hooks (useState, useEffect, etc)
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// - Use browser APIs (localStorage, window, etc)
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// - Add event listeners (onClick, onChange, etc)
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// - Use React Context
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// ✅ Client Component can:
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// - Use hooks
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// - Use browser APIs
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// - Add event listeners
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// - Use React Context
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// - Import Server Components as children
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'use client';
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export function Layout({ children }: { children: React.ReactNode }) {
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const [theme, setTheme] = useState('light');
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return (
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<div className={theme}>
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<button onClick={() => setTheme('dark')}>Toggle</button>
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{children} {/* Server Component can be child */}
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</div>
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);
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}
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// ❌ Client Component cannot:
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// - Be async
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// - Directly access backend resources
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// - Import server-only packages
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```
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## Progressive Enhancement with Server Actions
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Forms work without JavaScript when using Server Actions.
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```typescript
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// components/AddTodoForm.tsx
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import { addTodo } from '@/actions/todos';
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export function AddTodoForm() {
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return (
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<form action={addTodo}>
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<input name="title" required />
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<button type="submit">Add Todo</button>
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{/* Works without JS - progressive enhancement */}
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</form>
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);
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}
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// actions/todos.ts
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'use server';
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export async function addTodo(formData: FormData) {
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const title = formData.get('title');
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if (typeof title !== 'string') return;
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await db.todo.create({ data: { title } });
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revalidatePath('/todos');
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}
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```
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||||
Reference in New Issue
Block a user