Language switching UI in NextJS

Introduction

A language switching UI lets users pick their preferred language on a website. It helps make your site friendly for people who speak different languages.

You want visitors from different countries to read your site in their own language.

Your website has content available in multiple languages.

You want to improve user experience by letting users choose language easily.

You are building a global app that needs to support many languages.

Syntax

NextJS

import { useState } from 'react';

export default function LanguageSwitcher() {
  const [language, setLanguage] = useState('en');

  function changeLanguage(lang) {
    setLanguage(lang);
    // Add code here to update app language
  }

  return (
    <div>
      <button onClick={() => changeLanguage('en')}>English</button>
      <button onClick={() => changeLanguage('es')}>Spanish</button>
      <p>Current language: {language}</p>
    </div>
  );
}

This example uses React's useState hook to track the selected language.

Buttons call a function to update the language state when clicked.

Examples

Starts with English as the default language.

NextJS

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

Button to switch language to French.

NextJS

<button onClick={() => setLanguage('fr')}>French</button>

Shows which language is currently selected.

NextJS

<p>Current language: {language}</p>

Sample Program

This component shows three buttons for English, Spanish, and French. When you click a button, it updates the language state and shows the selected language in uppercase. It uses aria-pressed for accessibility to indicate which button is active. The selected language text updates live for screen readers using aria-live.

NextJS

import { useState } from 'react';

export default function LanguageSwitcher() {
  const [language, setLanguage] = useState('en');

  function changeLanguage(lang) {
    setLanguage(lang);
  }

  return (
    <main>
      <h1>Choose your language</h1>
      <nav aria-label="Language selection">
        <button onClick={() => changeLanguage('en')} aria-pressed={language === 'en'}>English</button>
        <button onClick={() => changeLanguage('es')} aria-pressed={language === 'es'}>Spanish</button>
        <button onClick={() => changeLanguage('fr')} aria-pressed={language === 'fr'}>French</button>
      </nav>
      <section aria-live="polite">
        <p>You selected: <strong>{language.toUpperCase()}</strong></p>
      </section>
    </main>
  );
}

Important Notes

Use semantic HTML elements like <nav> and <main> for better structure.

Use ARIA attributes like aria-pressed and aria-live to improve accessibility.

Keep the UI simple and clear so users can easily switch languages.

Summary

A language switching UI helps users pick their preferred language easily.

Use React state to track and update the selected language.

Make the UI accessible with proper HTML and ARIA attributes.

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