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express-rest-i18n

library1.0.1jsnpmunverified

Dead simple i18n middleware for Express REST APIs. Version 1.0.1 provides lightweight, dependency-free internationalization with nested message support and automatic locale detection via query, header, or cookie. No build tools, no extra dependencies; simply define messages in JSON and use the `t()` method on `req` or `res`. Unlike heavier i18n libraries, it focuses solely on REST APIs with a minimal footprint. Released as stable, with no active development but no known issues.

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npm install express-rest-i18n

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INSTALL

IMPORT

SIG · EXPRESS-REST-I18N

express-rest-i18n

devopsjavascriptv1.0.1

harness data pending

Install & Compatibility

Where this runs

No compatibility data collected yet for this library.

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

default

✓ import i18nCreate from 'express-rest-i18n';

✗ const i18nCreate = require('express-rest-i18n');

ESM import using default export. CommonJS require also works as the package exports a single function.

i18nCreate

✓ const i18nCreate = require('express-rest-i18n');

✗ import { i18nCreate } from 'express-rest-i18n';

CommonJS style - the package exports a single function as default; named import is incorrect.

t() method on res/req

✓ const text = res.i18n.t('key');

✗ const text = req.t('key');

The `t()` method is available on `res.i18n` or `req.i18n`, not directly on `req` or `res`.

Creates an i18n middleware, registers it, and uses the t() method in a route.

import express from 'express'; import i18nCreate from 'express-rest-i18n'; const app = express(); const i18n = i18nCreate({ defaultLocale: 'en', allowFallback: true, messages: { en: { greeting: 'Hello' }, 'pt-br': { greeting: 'Olá' }, }, }); app.use(i18n.middleware); app.get('/', (req, res) => { const msg = res.i18n.t('greeting'); res.send(msg); }); app.listen(3000);

Debug

Known issues

gotchaMiddleware should be added after body-parser to recognize parsed body for locale detection.

fix

Ensure app.use(i18n.middleware) comes after app.use(bodyParser.json()) or similar.

affects: >=1.0.0

breakingThe t() method is attached to res.i18n and req.i18n, not directly on res or req.

fix

Use res.i18n.t('key') or req.i18n.t('key') instead of res.t('key') or req.t('key').

affects: >=1.0.0

gotchaWhen a key is not found, t() returns the key string itself, not an error or undefined.

fix

Check if the returned value equals the key to detect missing translations.

affects: >=1.0.0

gotchaLocale detection order: query param (locale), header (Accept-Language), then cookie (locale). Unknown behavior if multiple sources conflict.

fix

Ensure only one locale source is used or understand the priority: query > header > cookie > defaultLocale.

affects: >=1.0.0

gotchaallowFallback: true (default) means missing keys fall back to defaultLocale, not chain fallback through multiple locales.

fix

Set allowFallback: false if you want strict locale enforcement.

affects: >=1.0.0

Errors

Common errors & fixes

Cannot read properties of undefined (reading 't')

Middleware not added or added before body-parser, so res.i18n or req.i18n is undefined.

fix

Ensure app.use(i18n.middleware) is called after body-parser and before routes.

t is not a function

Attempting to call t() directly on req or res instead of req.i18n or res.i18n.

fix

Use req.i18n.t('key') or res.i18n.t('key').

import i18nCreate from 'express-rest-i18n'; SyntaxError: Cannot use import statement outside a module

Using ESM import in a CommonJS project without proper configuration.

fix

Use const i18nCreate = require('express-rest-i18n'); or add "type": "module" to package.json.

module.exports = function(...) - TypeError: i18nCreate is not a function

Incorrect import: using named import for a default export.

fix

Use default import (import i18nCreate from ...) or const i18nCreate = require(...).

Upgrade

Version history

1.0.1latest on npm

Audit

Dependencies

expressrequiredPeer dependency - middleware requires Express app

Agent activity

2 hits · last 30 days

node

Resources

githubhttps://github.com/felippe-regazio/express-rest-i18n ↗

packageexpress-rest-i18n ↗

homepagehttps://github.com/felippe-regazio/express-rest-i18n#readme ↗