Client component boundaries in NextJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to mark a React component as a client component in Next.js.

NextJS

"use client";

export default function [1]() {
  return <div>Hello from client!</div>;
}

Drag options to blanks, or click blank then click option'

AClientComponent

BServerComponent

CApp

DPage

Attempts:

3 left

💡 Hint

Common Mistakes

Using a lowercase component name.

Forgetting the "use client" directive.

Naming the component ServerComponent which implies server rendering.

In Next.js, to create a client component, you add the directive "use client"; at the top and export a React function component. The component name can be anything, but here ClientComponent is a clear choice.

2fill in blank

medium

Complete the code to import a client component correctly in a server component.

NextJS

import [1] from './ClientComponent';

export default function ServerComponent() {
  return <div><[1] /></div>;
}

Drag options to blanks, or click blank then click option'

AserverComponent

BClientComponent

Cclientcomponent

DClientcomponent

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase or incorrect capitalization in import names.

Trying to import a client component with a different name.

When importing a client component, use the exact exported name with correct capitalization. React components must start with a capital letter, so ClientComponent is correct.

3fill in blank

hard

Fix the error in the client component declaration by completing the missing directive.

NextJS

[1]

export default function ClientWidget() {
  return <button>Click me</button>;
}

Drag options to blanks, or click blank then click option'

Ause client;

B"use server";

CuseClient();

D"use client";

Attempts:

3 left

💡 Hint

Common Mistakes

Using "use server" instead of "use client".

Missing quotes around the directive.

Writing the directive as a function call.

The directive "use client"; must be a string literal at the top of the file to mark it as a client component in Next.js.

4fill in blank

hard

Fill both blanks to create a client component that uses a React hook.

NextJS

"[1]";

import { useState } from 'react';

export default function Counter() {
  const [count, setCount] = useState(0);
  return <button onClick={() => setCount(count [2] 1)}>{count}</button>;
}

Drag options to blanks, or click blank then click option'

Ause client

B+

C-

Duse server

Attempts:

3 left

💡 Hint

Common Mistakes

Using "use server" directive in a client component.

Using the minus operator instead of plus to increment.

Client components must start with the directive "use client";. To increase the count, use the + operator inside the setCount callback.

5fill in blank

hard

Fill all three blanks to create a client component that imports a child component and uses it inside JSX.

NextJS

"[1]";

import Child from './Child';

export default function ClientWrapper() {
  return (
    <div>
      <Child [2]="value" />
      <button onClick={() => alert([3])}>Click</button>
    </div>
  );
}

Drag options to blanks, or click blank then click option'

Ause client

Bdata-prop

C"Hello"

Duse server

Attempts:

3 left

💡 Hint

Common Mistakes

Using "use server" directive in a client component.

Passing props without quotes for string values.

Using invalid attribute names for props.

The client component must start with "use client";. The child component can receive props like data-prop. The alert shows a string, so use "Hello" with quotes.

Practice

1. What is the purpose of marking a component with "use client"; in Next.js?

easy

A. To optimize the component for server-side rendering.

B. To make the component run only on the server.

C. To disable the component from rendering.

D. To tell Next.js this component should run in the browser.

Solution

1. Step 1: Understand client component marking

   Adding "use client"; at the top of a file tells Next.js this component runs in the browser, enabling interactivity.

2. Step 2: Differentiate from server components

   Server components run on the server and do not have this directive. Marking a component as client enables browser-only features.

3. Final Answer:

   To tell Next.js this component should run in the browser. -> Option D

4. Quick Check:

   Client components = "use client" [OK]

Hint: Look for "use client" to identify browser-run components [OK]

Common Mistakes:

• Thinking "use client" makes component server-only
• Confusing client components with disabling rendering
• Assuming it optimizes server rendering

2. Which of the following is the correct way to mark a React component as a client component in Next.js?

easy

A. Add "use client"; at the top of the component file.

B. Wrap the component in <Client></Client> tags.

C. Add client: true in the component props.

D. Import the component from a special client folder.

Solution

1. Step 1: Recall client component syntax

   Next.js requires "use client"; at the very top of the file to mark it as a client component.

2. Step 2: Evaluate other options

   Wrapping in tags, adding props, or importing from folders are not valid Next.js client component patterns.

3. Final Answer:

   Add "use client"; at the top of the component file. -> Option A

4. Quick Check:

   Client component syntax = "use client" [OK]

Hint: Always place "use client" as the first line in the file [OK]

Common Mistakes:

• Trying to mark client components via props or wrappers
• Placing "use client" inside the component function
• Assuming folder structure controls client behavior

3. Given this Next.js component file content:

"use client";
import { useState } from 'react';

export default function Counter() {
  const [count, setCount] = useState(0);
  return (
    <button onClick={() => setCount(count + 1)}>Clicked {count} times</button>
  );
}

What will happen when this component is rendered in a Next.js app?

medium

A. The component will throw an error because useState is not allowed.

B. The button will display and update the count on clicks in the browser.

C. The button will render but clicks will not update the count.

D. The component will only render on the server and not be interactive.

Solution

1. Step 1: Identify client component usage

   The file starts with "use client" so it runs in the browser and can use hooks like useState.

2. Step 2: Understand interactivity

   The button uses onClick to update state, so clicks will increase the count and re-render the button text.

3. Final Answer:

   The button will display and update the count on clicks in the browser. -> Option B

4. Quick Check:

   Client component + useState = interactive button [OK]

Hint: Client components can use useState and handle events [OK]

Common Mistakes:

• Thinking useState is disallowed in client components
• Assuming server components handle clicks
• Believing the button won't update without extra code

4. Consider this Next.js component file:

import { useState } from 'react';

export default function Clicker() {
  const [count, setCount] = useState(0);
  return (
    <button onClick={() => setCount(count + 1)}>Clicked {count} times</button>
  );
}

What is the problem with this component regarding client boundaries?

medium

A. It lacks the "use client"; directive, so useState will cause an error.

B. It uses useState incorrectly inside a server component.

C. The onClick handler syntax is invalid in Next.js.

D. The component should be wrapped in a <Client> tag.

Solution

1. Step 1: Check for client directive

   The component uses useState, which requires the component to be a client component marked by "use client".

2. Step 2: Identify missing directive effect

   Without "use client", Next.js treats this as a server component, causing an error when using useState.

3. Final Answer:

   It lacks the "use client"; directive, so useState will cause an error. -> Option A

4. Quick Check:

   useState needs "use client" [OK]

Hint: useState requires "use client" at file top [OK]

Common Mistakes:

• Assuming useState works without "use client"
• Thinking onClick syntax is invalid
• Trying to wrap component in tags for client behavior

5. You have a Next.js app with a server component Profile that fetches user data and a client component EditButton that allows editing the profile. How should you correctly use these components together?

hard

A. Import Profile inside EditButton and mark both with "use client";.

B. Mark Profile with "use client"; and import EditButton without any directive.

C. Import EditButton inside Profile and mark EditButton with "use client"; at its top.

D. Wrap EditButton inside Profile without marking either as client.

Solution

1. Step 1: Understand component boundaries

   Server components can import client components, but client components cannot import server components.

2. Step 2: Apply correct marking

   The EditButton must have "use client" at the top to run in the browser, while Profile remains a server component.

3. Step 3: Correct usage

   Import EditButton inside Profile and mark EditButton with "use client"; this keeps boundaries correct and enables interactivity.

4. Final Answer:

   Import EditButton inside Profile and mark EditButton with "use client"; at its top. -> Option C

5. Quick Check:

   Server imports client; client marked "use client" [OK]

Hint: Server components import client components marked "use client" [OK]

Common Mistakes:

• Marking server components as client unnecessarily
• Trying to import server components inside client components
• Not marking client components with "use client"