Example i18n Express Ap :app/categories/:category/keys/:key

i18n-api.js

const express = require('express');
const _ = require('lodash');
const bodyParser = require('body-parser');


const i18nApp = express.Router();


// parse application/x-www-form-urlencoded
// for easier testing with Postman or plain HTML forms
i18nApp.use(bodyParser.urlencoded({
    extended: true,
}));

// parse application/json
i18nApp.use(bodyParser.json());


// real persistence left as a reader exercise
const data = {
    'en-us': {
        'wca': {
            'login': {
                'username': 'Username is case sensitive.',
                'password': 'Password is case insensitive.'
            }
        },
        'wsp': {
            'start': {
                'header': 'Get your quote in four easy steps.'
            }
        }
    },
    'es-mx': {
        'wca': {
            'login': {
                'username': 'El nombre de usuario es sensible a mayúsculas.',
                'password': 'La contraseña no distingue entre mayúsculas y minúsculas.'
            }
        },
        'wsp': {
            'start': {
                'header': 'Obtenga su presupuesto en cuatro sencillos pasos.'
            }
        }
    }
};


i18nApp.get('/', (req, res) => {
    res.json(data);
});


// check `Accept-Language` header for requested locale
i18nApp.use((req, res, next) => {
    const localeHeader = (req.header('accept-language') || '').toLowerCase();
    const locales = localeHeader.split(',').map(s => s.trim());
    const supportedLocales = _.keys(data);
    const matchingLocales = _.intersection(locales, supportedLocales);
    const locale = _.head(matchingLocales);

    if (data[locale]) {
        req.locale = locale;
        next();
    } else {
        res.status(400).json({ message: `Missing or unrecognized header: 'accept-language'. Provided: "${localeHeader}". Expected one of: ${JSON.stringify(supportedLocales)}` });
    }
});

i18nApp.get('/:app', (req, res) => {
    const p = req.params;
    const match = _.get(data, `${req.locale}.${p.app}`);

    if (_.isEmpty(match)) {
        res.status(404).json({ message: 'no matches' });
    } else {
        res.json(match);
    }
});

i18nApp.get('/:app/categories', (req, res) => {
    const p = req.params;
    const match = _.keys(_.get(data, `${req.locale}.${p.app}`));

    if (_.isEmpty(match)) {
        res.status(404).json({ message: 'no matches' });
    } else {
        res.json(match);
    }
});

i18nApp.get('/:app/categories/:category', (req, res) => {
    const p = req.params;
    const match = _.get(data, `${req.locale}.${p.app}.${p.category}`);

    if (_.isEmpty(match)) {
        res.status(404).json({ message: 'no matches' });
    } else {
        res.json(match);
    }
});

i18nApp.get('/:app/categories/:category/keys', (req, res) => {
    const p = req.params;
    const match = _.keys(_.get(data, `${req.locale}.${p.app}.${p.category}`));

    if (_.isEmpty(match)) {
        res.status(404).json({ message: 'no matches' });
    } else {
        res.json(match);
    }
});

i18nApp.get('/:app/categories/:category/keys/:key', (req, res) => {
    const p = req.params;
    const match = _.get(data, `${req.locale}.${p.app}.${p.category}.${p.key}`);

    if (_.isEmpty(match)) {
        res.status(404).json({ message: 'no matches' });
    } else {
        res.json(match);
    }
});

i18nApp.post('/:app/categories/:category/keys/:key', (req, res) => {
    const p = req.params;
    const value = (req.body.value || '').toString().trim();

    if (value) {
        _.set(data, `${req.locale}.${p.app}.${p.category}.${p.key}`, value);
        res.json({
            key: `${req.locale}.${p.app}.${p.category}.${p.key}`,
            value,
        });
    } else {
        res.status(400).json({ message: `missing request param 'value'.`});
    }
});

i18nApp.use((req, res) => {
    res.status(404).json({ message: 'did not find endpoint' });
});


module.exports = i18nApp;