Language switching UI in NextJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the Next.js router hook for navigation.

NextJS

import { [1] } from 'next/navigation';

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

AuseRouter

BuseState

CuseEffect

DuseContext

Attempts:

3 left

💡 Hint

Common Mistakes

Importing hooks from React instead of Next.js

Using useState for routing

The useRouter hook from next/navigation is used to access routing functions in Next.js.

2fill in blank

medium

Complete the code to get the router object inside the component.

NextJS

const router = [1]();

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

AuseEffect

BuseState

CuseRouter

DuseContext

Attempts:

3 left

💡 Hint

Common Mistakes

Calling useState instead of useRouter

Not calling the hook as a function

Calling useRouter() inside a component returns the router object for navigation.

3fill in blank

hard

Fix the error in the code to change the locale to 'fr' using the router.

NextJS

router.[1]({ locale: 'fr' });

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

Areload

Breplace

Cprefetch

Dpush

Attempts:

3 left

💡 Hint

Common Mistakes

Using reload which reloads the page

Using prefetch which only preloads data

The push method navigates to a new URL or changes locale without reloading the page.

4fill in blank

hard

Fill both blanks to create a button that switches language to Spanish ('es') on click.

NextJS

const switchToSpanish = () => {
  router.[1]({ locale: '[2]' });
};

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

Apush

Bes

Creload

Dprefetch

Attempts:

3 left

💡 Hint

Common Mistakes

Using replace which replaces history entry

Using wrong locale code

Use router.push to change the locale. The locale code for Spanish is 'es'.

5fill in blank

hard

Fill all three blanks to create a language switcher component that updates locale and shows current language.

NextJS

import { useState } from 'react';
import { [1] } from 'next/navigation';

export default function LanguageSwitcher() {
  const router = [2]();
  const [lang, setLang] = useState('en');

  const changeLanguage = (newLang) => {
    router.[3]({ locale: newLang });
    setLang(newLang);
  };

  return (
    <button onClick={() => changeLanguage(lang === 'en' ? 'fr' : 'en')} aria-label="Switch language">
      Current: {lang.toUpperCase()}
    </button>
  );
}

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

AuseRouter

Cpush

Dreplace

Attempts:

3 left

💡 Hint

Common Mistakes

Using replace instead of push

Not updating the state after changing locale

Import and call useRouter to get the router. Use router.push to change locale. This updates the language and UI.

Practice

1. What is the main purpose of a language switching UI in a Next.js app?

easy

A. To let users choose their preferred language for the app content

B. To change the app's theme colors

C. To update the user's profile picture

D. To log out the user automatically

Solution

1. Step 1: Understand the UI purpose

   A language switching UI is designed to let users pick their language preference.

2. Step 2: Match purpose to options

   Only To let users choose their preferred language for the app content describes changing language, others are unrelated to language switching.

3. Final Answer:

   To let users choose their preferred language for the app content -> Option A

4. Quick Check:

   Language switching UI = Choose language [OK]

Hint: Language switch changes content language, not appearance [OK]

Common Mistakes:

• Confusing language switch with theme or profile settings
• Thinking it logs out users automatically

2. Which of the following is the correct way to declare a React state hook for language selection in Next.js?

easy

A. const [language, setLanguage] = useState('en')

B. const language = useState('en')

C. useState = const [language, setLanguage]('en')

D. const [language, setLanguage] = useState()

Solution

1. Step 1: Recall React useState syntax

   The correct syntax is: const [state, setState] = useState(initialValue).

2. Step 2: Check each option

   const [language, setLanguage] = useState('en') matches correct syntax with initial value 'en'. Others have syntax errors or missing initial value.

3. Final Answer:

   const [language, setLanguage] = useState('en') -> Option A

4. Quick Check:

   useState syntax = const [var, setVar] = useState(value) [OK]

Hint: useState returns array destructured into state and setter [OK]

Common Mistakes:

• Not destructuring the array returned by useState
• Missing initial state value
• Incorrect assignment order

3. Given this Next.js component snippet:
<pre>const LanguageSwitcher = () => { const [lang, setLang] = useState('en'); return ( <button onClick={() => setLang('fr')} aria-label="Switch to French">FR</button> ); }; What will be the value of lang after clicking the button once?

medium

A. null

B. 'en'

C. undefined

D. 'fr'

Solution

1. Step 1: Understand initial state

   The state variable lang starts as 'en'.

2. Step 2: Analyze button click effect

   Clicking the button calls setLang('fr'), updating lang to 'fr'.

3. Final Answer:

   'fr' -> Option D

4. Quick Check:

   Click sets lang to 'fr' [OK]

Hint: Click triggers setLang with new language [OK]

Common Mistakes:

• Thinking state stays the same after click
• Confusing initial value with updated value

4. Consider this Next.js language switcher code:
<pre>const LanguageSwitcher = () => { const [lang, setLang] = useState('en'); return ( <button onClick={() => setLang('es')}>Switch to Spanish</button> ); }; Why might this code cause an accessibility issue?

medium

A. The state variable is not initialized

B. The button lacks an aria-label describing its purpose

C. The onClick handler syntax is incorrect

D. The component does not import React

Solution

1. Step 1: Check accessibility features

   The button has no aria-label or descriptive text for screen readers.

2. Step 2: Evaluate other options

   State is initialized, onClick syntax is correct, React import is assumed; only missing aria-label is an accessibility issue.

3. Final Answer:

   The button lacks an aria-label describing its purpose -> Option B

4. Quick Check:

   Missing aria-label = accessibility problem [OK]

Hint: Always add aria-label for buttons with unclear text [OK]

Common Mistakes:

• Ignoring accessibility attributes
• Assuming syntax errors without checking
• Overlooking React import necessity

5. You want to build a language switcher in Next.js that updates the URL locale and changes the displayed language without a full page reload. Which approach is best?

hard

A. Reload the page manually after setting a cookie for language

B. Use window.location.href to change URL and reload page

C. Use Next.js <Link> with locale prop and React state to track language

D. Store language in localStorage and ignore URL changes

Solution

1. Step 1: Understand Next.js locale routing

   Next.js supports locale routing with to change language without full reload.

2. Step 2: Combine URL update and React state

   Using <Link> with locale prop updates URL and React state tracks current language for UI updates.

3. Step 3: Evaluate other options

   Reloading page or using window.location causes full reload, losing SPA benefits. Ignoring URL breaks routing consistency.

4. Final Answer:

   Use Next.js <Link> with locale prop and React state to track language -> Option C

5. Quick Check:

   Next.js locale routing + state = smooth language switch [OK]

Hint: Use Next.js for smooth language changes [OK]

Common Mistakes:

• Reloading page loses SPA benefits
• Ignoring URL locale causes routing issues
• Using localStorage alone misses URL sync