Next-intl library integration in NextJS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the rendered output of this Next.js component using next-intl?

Consider this Next.js functional component using next-intl for translations. What will it display when the locale is set to en and the messages contain { greeting: 'Hello, {name}!' }?

NextJS

import {useTranslations} from 'next-intl';

export default function Greeting({name}) {
  const t = useTranslations();
  return <p>{t('greeting', {name})}</p>;
}

A Hello, {name}!

B Hello, John!

C greeting

D Error: Missing translation

💡 Hint

Think about how useTranslations replaces placeholders in the message.

The useTranslations hook fetches the message for the key greeting and replaces {name} with the passed prop value. So it outputs "Hello, John!".

📝 Syntax

intermediate

Which option correctly initializes next-intl messages in a Next.js page?

You want to load translations for a Next.js page using next-intl. Which code snippet correctly fetches messages for the current locale?

NextJS

export async function getStaticProps({locale}) {
  // Fill in the correct code to load messages
}

A

const messages = JSON.parse(`../messages/${locale}.json`);
return {props: {messages}};

B

const messages = require(`../messages/${locale}.json`);
return {props: {messages}};

C

const messages = fetch(`../messages/${locale}.json`).then(res => res.json());
return {props: {messages}};

D

const messages = await import(`../messages/${locale}.json`);
return {props: {messages: messages.default}};

💡 Hint

Remember that getStaticProps runs on the server and supports dynamic imports.

Using await import() dynamically loads the JSON file and you must access default to get the messages object. Other options either use unsupported syntax or asynchronous code incorrectly.

🔧 Debug

advanced

Why does this Next.js page using next-intl throw a runtime error?

Given this page code, why does it throw TypeError: t is not a function when rendering?

NextJS

import {useTranslations} from 'next-intl';

export default function Page() {
  const t = useTranslations;
  return <p>{t('welcome')}</p>;
}

A Because the component is missing a <IntlProvider> wrapper around it.

B Because the translation key 'welcome' is missing in messages, causing t to be undefined.

C Because useTranslations is assigned without calling it, so t is not a function but a reference to the hook.

D Because useTranslations must be called with a namespace string argument.

💡 Hint

Check how useTranslations is assigned and used.

The code assigns t = useTranslations without parentheses, so t is the hook function itself, not the translation function. Calling t('welcome') causes a TypeError.

❓ state_output

advanced

What is the output after changing locale dynamically with next-intl?

In a Next.js app using next-intl, you have a button that changes the locale from 'en' to 'fr'. What will the component display after clicking the button?

NextJS

import {useTranslations, useLocale, useRouter} from 'next-intl';
import {useState} from 'react';

export default function LocaleSwitcher() {
  const t = useTranslations();
  const locale = useLocale();
  const router = useRouter();
  const [currentLocale, setCurrentLocale] = useState(locale);

  async function switchLocale() {
    const newLocale = currentLocale === 'en' ? 'fr' : 'en';
    setCurrentLocale(newLocale);
    await router.push('/', '/', {locale: newLocale});
  }

  return (
    <>
      <p>{t('greeting')}</p>
      <button onClick={switchLocale}>Switch Locale</button>
    </>
  );
}

A The greeting text updates to French after clicking the button.

B The greeting text stays in English even after clicking the button.

C The page reloads but the greeting text does not change.

D An error occurs because useLocale cannot be updated this way.

💡 Hint

Consider how router.push with a new locale affects the page and translations.

Calling router.push with a new locale reloads the page with that locale, so useTranslations returns messages in French, updating the greeting text.

🧠 Conceptual

expert

Which statement best describes how next-intl handles message loading in Next.js App Router?

In Next.js App Router (app directory), how does next-intl recommend loading locale messages for server components?

A Use async server components to import JSON message files dynamically based on the locale parameter.

B Use a global context provider that fetches messages once on the client side and shares them.

C Load all locale messages statically at build time and pass them as props to client components.

D Use client components with useEffect to fetch messages from an API endpoint at runtime.

💡 Hint

Think about Next.js App Router's server components and static imports.

Next-intl recommends loading messages in async server components by dynamically importing JSON files based on the locale parameter. This leverages server rendering and avoids client fetching.