lup-language

Node express middleware for detecting requested language based on:

1. URI prefix e.g. /en/home/
2. Cookie value e.g. lang=en
3. HTTP header e.g. Accept-Language=en-US,en;q=0.5
4. Default language code Request will be modified such that URI does not start with language code and new attribute lang gets added to the request object.

Express Example

server.js

const express = require('express');
const {LanguageRouter} = require('lup-language');

const app = express();

// Add LanguageRouter as middleware that modifies request object 
// based on given options (see documentation).
// Here parameter 'languages' is a list of language codes that 
// your app will accept.
app.use(LanguageRouter({
    languages: ['en', 'de']
}));

// Create your custom routes and retriev request language code 
// by reading it from req.lang
app.get('/', function(req, res){
    res.send("Your requested language is: "+req.lang.toUpperCase()+"<br>"+
             "You can access translations from the translations dir using: "+req.TEXT['TranslationKey']);
});

app.listen(80, function(){
    console.log("Server running");
});

Next.js with Express Example

server.ts

import express from 'express';
import next from 'next';

const dev = Config.isDevMode();
const HTTP_BIND = process.env.HTTP_BIND || "0.0.0.0";
const HTTP_PORT = parseInt(process.env.HTTP_PORT || "80") || 80;

const nextApp = next({dev: dev});
const nextHandler = nextApp.getRequestHandler();

nextApp.prepare().then(async () => {
    const app = express();

    // language middleware
    app.use(await LanguageRouter({
        useNextLanguages: false, /* true if Next ≤12 and i18n */
        languagesFromTranslations: true,
        redirectRoot: true, 
    }));

    // TODO add here your custom routes ...

    // all frontend routes
    app.all('*', (req: Request | any, res: Response) => {
        
        // add language prefix back to url (got removed by LanguageRouter)
        const idx1 = req.originalUrl.lastIndexOf("."), idx2 = req.originalUrl.lastIndexOf("/");
        req.url = (idx1 > idx2 || req.originalUrl.startsWith("/"+req.lang) || req.originalUrl.startsWith("/_next")) ? 
                    req.originalUrl : "/"+req.lang+req.originalUrl;

        return nextHandler(req, res);
    });

    // start server
    app.listen(HTTP_PORT, HTTP_BIND, function(){
        console.log("Server running at "+HTTP_BIND+":"+HTTP_PORT+" in "+(dev ? "development" : "production")+" mode");
    });
});

Next.js ≤12 Page Example

index.tsx

// Next.js page
export default function Home({LANGUAGE_NAMES, TEXT}){

    let components = [];
    for(let lang in LANGUAGE_NAMES){
        let name = LANGUAGE_NAMES[lang];
        components.push(<a href="/{lang}">{name}</a>);
    }

    return (
        <>
            <h1>{TEXT['TranslationKey']}</h1>
            <h2>{TEXT['HelloWorld']}</h2>
            {components}
        </>
    );
}

export async function getStaticProps(context){
    const TEXT = await getTranslations(context.locale, context.defaultLocale, [
        'TranslationKey', 'HelloWorld' 
    ]);

    return {
        props: {
            LANGUAGE_NAMES: await getLanguageNames(),
            TEXT: TEXT
        }
    };
}

Next.js ≥13 Page Example

app/[locale]/translations.ts

'use server';
import "server-only";
import { getTranslations } from "lup-language";

export default async function loadTranslations(locale: string, translationKeys: string[]): Promise<{[key: string]: string}> {
    return await getTranslations(locale, 'en', translationKeys); // second argument is default locale
};

app/[locale]/layout.tsx

app/[locale]/page.tsx

import React from "react";
import styles from './page.module.css';
import loadTranslations from "../translations";
import { StaticParamsContext } from "../../../services/Types.service";

export default async function Home({ params }: StaticParamsContext) {
  const locale = params.locale;
  const TEXT = await loadTranslations(locale, ['HelloWorld']);

  return <>
    <b>Content</b>
  </>
}

export async function generateStaticParams(context: StaticParamsContext) {
  return [];
}