Server component translations in NextJS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the rendered output of this server component using next-intl?

Given this Next.js server component using next-intl for translations, what will be rendered when the locale is set to en?

NextJS

import {useTranslations} from 'next-intl/server';

export default function Greeting() {
  const t = useTranslations('Greeting');
  return <h1>{t('hello')}</h1>;
}

// Assume messages for 'en': { "Greeting": { "hello": "Hello, friend!" } }

A <h1>Hello, friend!</h1>

B <h1>Greeting.hello</h1>

C <h1>hello</h1>

D <h1>undefined</h1>

💡 Hint

Remember that useTranslations returns a function to get the translated string by key.

The useTranslations('Greeting') hook returns a function t that looks up keys inside the Greeting namespace. Calling t('hello') returns the translated string Hello, friend! for the en locale.

📝 Syntax

intermediate

Which option correctly loads translations in a Next.js server component?

In Next.js 14 server components, which code snippet correctly loads locale messages for translations?

A

import {readFileSync} from 'fs';

export default function Page({params}) {
  const messages = JSON.parse(readFileSync(`./locales/${params.locale}.json`, 'utf-8'));
  return <div>{messages.title}</div>;
}

B

import {readFile} from 'fs/promises';

export default function Page({params}) {
  const messages = JSON.parse(readFile(`./locales/${params.locale}.json`));
  return <div>{messages.title}</div>;
}

C

import {readFileSync} from 'fs';

export default async function Page({params}) {
  const messages = JSON.parse(readFileSync(`./locales/${params.locale}.json`, 'utf-8'));
  return <div>{messages.title}</div>;
}

D

import {readFileSync} from 'fs';

export default async function Page({params}) {
  const messages = await JSON.parse(readFileSync(`./locales/${params.locale}.json`, 'utf-8'));
  return <div>{messages.title}</div>;
}

💡 Hint

Consider synchronous vs asynchronous file reading in server components.

Server components can use synchronous APIs like readFileSync to load files. Option C correctly uses readFileSync inside an async function and parses JSON synchronously. Option C uses readFile without awaiting, causing an error. Option C is not async but uses synchronous read, which is allowed but less recommended. Option C incorrectly awaits a synchronous function.

❓ state_output

advanced

What is the output when switching locales in a server component with next-intl?

Consider this server component that switches locale based on params. What will be the output if params.locale is fr?

NextJS

import {useTranslations} from 'next-intl/server';

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

// Messages:
// en: { Home: { welcome: 'Welcome!' } }
// fr: { Home: { welcome: 'Bienvenue!' } }

A <p>Bienvenue!</p>

B <p>Welcome!</p>

C <p>Home.welcome</p>

D <p>undefined</p>

💡 Hint

The locale is passed via params and affects which messages are loaded.

The useTranslations hook uses the current locale from the server context, which is set by params.locale. For fr, it loads French messages, so t('welcome') returns Bienvenue!.

🔧 Debug

advanced

Why does this server component throw an error when using useTranslations?

Given this server component code, why does it throw an error?

NextJS

import {useTranslations} from 'next-intl';

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

A useTranslations cannot be used in async server components because it relies on React hooks.

B The component must import 'useTranslations' from 'next-intl/server' in server components.

C The component is missing a 'use client' directive, so hooks cannot run.

D The 'Common' namespace is missing from the messages, causing a runtime error.

💡 Hint

Check the import source for useTranslations in server components.

In Next.js server components, you must import useTranslations from next-intl/server instead of next-intl. Importing from next-intl is for client components and causes errors in server components.

🧠 Conceptual

expert

How does Next.js server component translations improve performance compared to client-side translations?

Which statement best explains the performance benefit of using server component translations in Next.js?

A Server components cache translations in the browser, improving client-side rendering speed.

B Translations are fetched on the client after page load, allowing faster initial server response.

C Using server component translations disables React hydration, making the page static.

D Translations are loaded and rendered on the server, reducing client bundle size and avoiding runtime translation loading on the client.

💡 Hint

Think about where translation data is loaded and how it affects client code size.

Server component translations load and render translated text on the server. This reduces the JavaScript sent to the client because translation logic and data do not need to be included in client bundles. It also avoids client runtime translation loading, improving performance and reducing flicker.