When to use client components 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 <button>Click me</button>;
}

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

AButtonStatic

BServerButton

CButtonServer

DClientButton

Attempts:

3 left

💡 Hint

Common Mistakes

Using a name that suggests server-side rendering instead of client-side.

Forgetting to add "use client" at the top of the file.

In Next.js, to make a component a client component, you add "use client" at the top and export a React component. Naming it clearly like ClientButton helps understand its role.

2fill in blank

medium

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

NextJS

import [1] from './ClientButton';

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

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

AServerButton

BButtonStatic

CClientButton

DStaticButton

Attempts:

3 left

💡 Hint

Common Mistakes

Importing a server component name instead of the client component.

Using a name that does not match the exported component.

You import the client component by its exact exported name. Here, ClientButton is the client component imported into a server component.

3fill in blank

hard

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

NextJS

[1]

import React from 'react';

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

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

A"use client";

B"use server";

Cimport React from 'react';

Dexport const client = true;

Attempts:

3 left

💡 Hint

Common Mistakes

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

Forgetting to add the directive at the top of the component.

Client components in Next.js must start with the directive "use client"; to enable client-side features like state and events.

4fill in blank

hard

Fill both blanks to correctly use a client component with state and event in Next.js.

NextJS

"use client";

import React, { [1] } from 'react';

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

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

AuseState

BuseEffect

CuseRef

DuseContext

Attempts:

3 left

💡 Hint

Common Mistakes

Using hooks like useEffect or useRef instead of useState for state.

Importing the wrong hook or forgetting to import useState.

The useState hook is imported and used to create state in a client component for interactive behavior.

5fill in blank

hard

Fill all three blanks to create a client component that uses state and effect.

NextJS

"use client";

import React, { [1], [2] } from 'react';

export default function Timer() {
  const [seconds, setSeconds] = [3](0);

  React.useEffect(() => {
    const interval = setInterval(() => {
      setSeconds(s => s + 1);
    }, 1000);
    return () => clearInterval(interval);
  }, []);

  return <button>Seconds: {seconds}</button>;
}

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

AuseState

BuseEffect

CuseRef

DuseCallback

Attempts:

3 left

💡 Hint

Common Mistakes

Importing or using the wrong hooks like useRef or useCallback.

Not matching the hook usage with the import.

The component imports useState and useEffect. It uses useState to hold seconds and useEffect to update seconds every second.

Practice

1. Which of the following is the main reason to use a client component in Next.js?

easy

A. To make parts of the app interactive and respond to user actions

B. To improve server-side rendering speed

C. To reduce the size of the JavaScript bundle sent to the browser

D. To fetch data from the database on the server

Solution

1. Step 1: Understand client components purpose

   Client components run in the browser and handle interactivity like clicks and animations.

2. Step 2: Compare options with this purpose

   Only To make parts of the app interactive and respond to user actions matches making the app interactive and responding to user actions.

3. Final Answer:

   To make parts of the app interactive and respond to user actions -> Option A

4. Quick Check:

   Client components = interactivity [OK]

Hint: Client components run in browser for interactivity [OK]

Common Mistakes:

• Thinking client components improve server rendering
• Confusing client components with server data fetching
• Believing client components reduce bundle size

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

easy

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

B. Name the file with a .client.js extension

C. Add "use client"; at the top of the file

D. Add client: true in the component props

Solution

1. Step 1: Recall Next.js client component syntax

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

2. Step 2: Check other options

   Options A, C, and D are not valid Next.js syntax for client components.

3. Final Answer:

   Add "use client"; at the top of the file -> Option C

4. Quick Check:

   Client component marker = "use client"; [OK]

Hint: Remember: "use client"; at file top marks client component [OK]

Common Mistakes:

• Trying to use special tags to mark client components
• Using file extensions to indicate client components
• Passing props to mark client components

3. What will happen if you try to use useState in a Next.js server component without marking it as a client component?

medium

A. You will get a runtime error because hooks like useState only work in client components

B. The state will be shared across all users

C. The app will render normally without errors

D. The component will automatically become a client component

Solution

1. Step 1: Understand hook usage rules

   Hooks like useState only work in client components because they run in the browser.

2. Step 2: Check behavior in server components

   If you use useState in a server component without "use client" directive, Next.js throws a runtime error.

3. Final Answer:

   You will get a runtime error because hooks like useState only work in client components -> Option A

4. Quick Check:

   useState in server component = runtime error [OK]

Hint: Hooks need client components or error occurs [OK]

Common Mistakes:

• Assuming hooks work in server components
• Thinking state is shared globally without errors
• Believing components auto-switch to client

4. You wrote a Next.js component with "use client"; but forgot to import useState from React. What will happen?

medium

A. The component will render but state updates won't work

B. The component will work fine without errors

C. Next.js will automatically import useState for you

D. You will get a ReferenceError because useState is not defined

Solution

1. Step 1: Check import requirements for hooks

   Hooks like useState must be explicitly imported from React to be used.

2. Step 2: Analyze missing import effect

   Without importing, JavaScript throws a ReferenceError because useState is undefined.

3. Final Answer:

   You will get a ReferenceError because useState is not defined -> Option D

4. Quick Check:

   Missing import useState = ReferenceError [OK]

Hint: Always import hooks before using them [OK]

Common Mistakes:

• Assuming Next.js auto-imports React hooks
• Ignoring import errors thinking component still works
• Confusing runtime errors with silent failures

5. You have a Next.js app with a server component that fetches data and a button that updates UI state on click. How should you organize components?

hard

A. Make the whole component a client component to handle data fetching and button state

B. Keep data fetching in a server component and create a separate client component for the button with state

C. Use only server components and handle button clicks with server actions

D. Fetch data in the client component and handle button state in the server component

Solution

1. Step 1: Separate concerns for performance and interactivity

   Server components are best for data fetching; client components handle interactivity like button clicks.

2. Step 2: Organize components accordingly

   Keep data fetching in server component and create a small client component for the button with state and event handlers.

3. Final Answer:

   Keep data fetching in a server component and create a separate client component for the button with state -> Option B

4. Quick Check:

   Server fetch + client interactivity = separate components [OK]

Hint: Use server for data, client for interactivity [OK]

Common Mistakes:

• Making entire component client causing slower loads
• Trying to handle UI state in server components
• Fetching data in client causing unnecessary delays