next-fbt

Easily integrate FBT with Next.js apps.

Useful links

• facebook/fbt - a JavaScript internationalization framework
• import.meta - metadata of a JavaScript module

Setup

1. Install.

   npm install next-fbt
   npm install -D next-fbt-cli next-fbt-babel

2. Create next-fbt.config.js.

   /** @type {import('next-fbt').Config} */
   module.exports = {
     // Regular configuration for `i18n` key for Next's config.
     i18n: {
       // These are all the locales you want to support in
       // your application.
       locales: ['en-US', 'pl-PL', 'es-ES'],
       // This is the default locale you want to be used when visiting
       // a non-locale prefixed path e.g. `/hello`.
       defaultLocale: 'en-US',
       // Always use the locale that is specified in url
       // without redirecting to the one detected by the browser.
       localeDetection: false,
     },
   
     // Configuration for 'next-fbt' and 'next-fbt-cli'.
     nextFbt: {
       // The root url your want your translation
       // files to be served from.
       // The pathname of `publicUrl` (here `i18n`) determines
       // the directory name (inside ./public) where files with translations
       // will be put.
       publicUrl: 'http://localhost:3000/i18n',
       // Split translations by file path (relative to the CWD).
       // Must be array of [string, string[]].
       groups: [
         // Example:
         ['components', ['src/components/*']],
         ['home-page', ['pages/index.tsx']],
         ['other-pages', ['pages/*', 'src/pages/*']],
   
         // Above configuration will result in:
         // - all translations under "src/components" directory will land
         //   in 'public/i18n/<locale>/components.json
         // - all translations from "pages/index.tsx" file will land
         //   in 'public/i18n/<locale>/home-page.json
         // - all translations from "pages" directory (but not from "pages/index.tsx" file)
         //   will land in 'public/i18n/<locale>/other-pages.json
         // - translations from files that don't match any of above
         //   patterns will be extracted to 'public/i18n/<locale>/main.json'
       ],
     },
   };

3. Update Babel config.

module.exports = {
-  presets: ['next/babel'],
+  presets: ['next-fbt-babel/preset'],
+  plugins: ['next-fbt-babel/plugin'],
};

4. Wrap next config and pass options.

   // next-config.js
   const { withNextFbtConfig } = require('next-fbt/config');
   const nextFbtConfig = require('./next-fbt.config');
   
   module.exports = withNextFbtConfig({
     i18n: nextFbtConfig.i18n,
     nextFbt: nextFbtConfig.nextFbt,
   
     // ^ you can also just `...nextFbtConfig`
   
     /* the rest of the config */
   });

   I prefer `next.config` as ESM (native ES Module)

   next-fbt.config still has to be a CommonJS

   // next-config.mjs
   import { withNextFbtConfig } from 'next-fbt/config';
   import nextFbtConfig from './next-fbt.config.js';
   
   export default withNextFbtConfig({
     i18n: nextFbtConfig.i18n,
     nextFbt: nextFbtConfig.nextFbt,
   
     /* the rest of the config */
   });

5. Wrap app with provider.

   // pages/_app.tsx
   import { appWithNextFbt } from 'next-fbt';
   
   function App({ Component, pageProps }) {
     return <Component {...pageProps} />;
   }
   
   export default appWithNextFbt(App);

   I don't have a custom app

   // pages/_app.tsx
   import NextApp from 'next/app';
   
   export default appWithNextFbt(NextApp);

   I don't want to use higher-order component

   // pages/_app.tsx
   import { NextFbtProvider } from 'next-fbt';
   
   function App({ Component, pageProps }) {
     // This is basically the same what `appWithNextFbt` does.
     return (
       <NextFbtProvider __NEXT_FBT_PROPS__={pageProps.__NEXT_FBT_PROPS__}>
         <Component {...pageProps} />
       </NextFbtProvider>
     );
   }
   
   export default App;

6. Fetch translations for your page.

   Notice, that for the translations to be fetched, the file you declare the fetching logic has to match any group from the config file.

   import { getPropsFetcher } from 'next-fbt';
   
   export default function Page() {
     // your regular page component
   }
   
   export const { getServerSideProps } = getPropsFetcher(import.meta.url);

   I don't want to use `getServerSideProps`

   // same as above
   
   - export const { getServerSideProps } = getPropsFetcher(import.meta.url);
   + export const { getStaticProps } = getPropsFetcher(import.meta.url);

   I already have my own `getServerSideProps` defined

   import { getProps } from 'next-fbt';
   
   export function getServerSideProps(ctx) {
     // your logic for `yourProps`...
   
     const fbtProps = await getProps(ctx, import.meta.url);
   
     return {
       props: {
         ...fbtProps,
         ...yourProps,
       },
     };
   }

Lazy-loading for dynamic components

The library has first-class support for lazy loading of translations for dynamic components (via next/dynamic).

1. Replace next/dynamic with next-fbt/dynamic.

   This is a little wrapper around next/dynamic that fetches required translations for components that is going to be rendered.

   // Notice that difference in the import source (`next/dynamic` => `next-fbt/dynamic`).
   import dynamic from 'next-fbt/dynamic';
   
   // Limitation: the wrapper can be used only with components that are rendered on the client.
   // If you wish to have SSR-rendered component, use regular `next/dynamic` and fetch translations
   // via `getServerSideProps` / `getStaticProps`.
   const Component = dynamic(() => import('/path/to/component'), { ssr: false });
   
   export function Page() {
     return (
       // The component will be rendered after translations are fetched.
       <Component />
     );
   }

2. Add a property on a component so next-fbt/dynamic knows what to fetch.

   If you use memo or forwardRef the assignTranslations has to wrap the memoized/ forwarded component, since memo and forwadRef loose non-React properties on a component.

   import { assignTranslations } from 'next-fbt';
   
   export default function DynamicComponent() {
     return (/* some jsx */)
   }
   
   assignTranslations(DynamicComponent, import.meta.url);

Collecting FBT's for translations

npx next-fbt-collect

This will output .cache/next-fbt/source-strings.json file which you can upload to translations service that supports translating FBT's (like Crowdin).

Creating translation files

After you translate the source string to other languages, download the translations to /path/to/downloaded and run

npx next-fbt-translate /path/to/downloaded

This will create public/i18n directory with translation files.