i18next-chained-backend

What is i18next-chained-backend?

The i18next-chained-backend package is a backend layer for i18next that allows chaining multiple backends. This is useful for scenarios where you want to load translations from multiple sources, such as a local file system, a remote server, or a database, in a specific order.

What are i18next-chained-backend's main functionalities?

Chaining Multiple Backends

This feature allows you to chain multiple backends together. In this example, the translations are first attempted to be loaded from the local storage. If they are not found there, the HTTP backend is used as a fallback to load the translations from a remote server.

const i18next = require('i18next');
const ChainedBackend = require('i18next-chained-backend').default;
const HttpBackend = require('i18next-http-backend').default;
const LocalStorageBackend = require('i18next-localstorage-backend').default;

i18next.use(ChainedBackend).init({
  backend: {
    backends: [
      LocalStorageBackend, // primary
      HttpBackend // fallback
    ],
    backendOptions: [
      { /* options for local storage */ },
      { loadPath: '/locales/{{lng}}/{{ns}}.json' } // options for http backend
    ]
  }
});

Custom Backend Order

This feature allows you to define a custom order for the backends. In this example, a custom backend is used as the primary source, followed by local storage, and finally the HTTP backend as a fallback.

const i18next = require('i18next');
const ChainedBackend = require('i18next-chained-backend').default;
const HttpBackend = require('i18next-http-backend').default;
const LocalStorageBackend = require('i18next-localstorage-backend').default;
const CustomBackend = require('./myCustomBackend').default;

i18next.use(ChainedBackend).init({
  backend: {
    backends: [
      CustomBackend, // primary
      LocalStorageBackend, // secondary
      HttpBackend // fallback
    ],
    backendOptions: [
      { /* options for custom backend */ },
      { /* options for local storage */ },
      { loadPath: '/locales/{{lng}}/{{ns}}.json' } // options for http backend
    ]
  }
});

Other packages similar to i18next-chained-backend

i18next-http-backend

The i18next-http-backend package is used to load translations from a remote server via HTTP. It is useful for applications that need to fetch translations dynamically from a server. Compared to i18next-chained-backend, it does not support chaining multiple backends but can be used as one of the backends in a chained setup.

i18next-localstorage-backend

The i18next-localstorage-backend package is used to store translations in the browser's local storage. This can improve performance by reducing the need to fetch translations from a remote server on every page load. Similar to i18next-http-backend, it does not support chaining but can be used as part of a chained backend setup.

i18next-fs-backend

The i18next-fs-backend package is used to load translations from the file system. This is particularly useful for server-side applications or during development. It does not support chaining multiple backends but can be used in conjunction with i18next-chained-backend to provide file system-based translations as one of the sources.

README

Introduction

This is a i18next backend to chain multiple other backends and caches. So you can define an additional caching backend or fallback backends.

Usage examples for caching configurations can be found here and for fallback backends can be found here.

How it works

For each backend read call (so for each language and namespace combination), it will try to read from from all backends in order until a backend returns some resources. So if it does not find the resource (language + namespace) in the first backend, it goes to the next, etc.

Getting started

Source can be loaded via npm or downloaded from this repo.

# npm package
$ npm install i18next-chained-backend

Wiring up:

import i18next from 'i18next';
import Backend from 'i18next-chained-backend';

i18next
  .use(Backend)
  .init(i18nextOptions);

• As with all modules you can either pass the constructor function (class) to the i18next.use or a concrete instance.
• If you don't use a module loader it will be added to window.i18nextChainedBackend

Backend Options

{
  // array of existing i18next backends from https://www.i18next.com/overview/plugins-and-utils#backends
  backends: [],

  // array of options in order of backends above
  backendOptions: []
}

Options can be passed in:

preferred - by setting options.backend in i18next.init:

import i18next from 'i18next';
import Backend from 'i18next-chained-backend';

i18next
  .use(Backend)
  .init({
    backend: options
  });

on construction:

  import Backend from 'i18next-chained-backend';
  const Backend = new Backend(null, options);

via calling init:

  import Backend from 'i18next-chained-backend';
  const Backend = new Backend();
  Backend.init(null, options);

caching example

import i18next from 'i18next';
import Backend from 'i18next-chained-backend';
import LocalStorageBackend from 'i18next-localstorage-backend'; // load from local storage
import HttpApi from 'i18next-http-backend'; // have a own http fallback

i18next
  .use(Backend)
  .init({
    backend: {
      backends: [
        LocalStorageBackend,  // primary
        HttpApi  // fallback
      ],
      backendOptions: [{
        projectId: 'myLocizeProjectId'
      }, {
        loadPath: '/locales/{{lng}}/{{ns}}.json' // http api load path for my own fallback
      }],
      // cacheHitMode: 'none' // (default)
      // cacheHitMode: 'refresh' // tries to refresh the cache by loading from the next backend and updates the cache
      // cacheHitMode: 'refreshAndUpdateStore' // tries to refresh the cache by loading from the next backend, updates the cache and also update the i18next resource store
      // reloadInterval: 60 * 60 * 1000 // can be used to reload resources in a specific interval (useful in server environments)
      // refreshExpirationTime: 7 * 24 * 60 * 60 * 1000 // In case of caching with 'refresh' or 'refreshAndUpdateStore', it will only fetch from the next backend if the cached namespace is expired. Only supported if the backend returns the saved timestamp, like i18next-fs-backend, i18next-localstorage-backend
    }
  });

more complete sample

import i18next from 'i18next';
import Backend from 'i18next-chained-backend';
import Locize from 'i18next-locize-backend'; // load from service
import HttpApi from 'i18next-http-backend'; // have a own http fallback

i18next
  .use(Backend)
  .init({
    backend: {
      backends: [
        Locize,  // primary
        HttpApi  // fallback
      ],
      backendOptions: [{
        projectId: 'myLocizeProjectId'
      }, {
        loadPath: '/locales/{{lng}}/{{ns}}.json' // http api load path for my own fallback
      }]
    }
  });

More locize examples can be found here:

• Caching
• Backend Fallback
• Multiple projects in same i18next instance

TypeScript

To properly type the backend options, you can import the ChainedBackendOptions interface and use it as a generic type parameter to the i18next's init method, e.g.:

import i18n from 'i18next'
import ChainedBackend, { ChainedBackendOptions } from 'i18next-chained-backend'

i18n
  .use(ChainedBackend)
  .init<ChainedBackendOptions>({
    backend: {
      backends: [
        Locize,  // primary
        HttpApi  // fallback
      ],
      backendOptions: [{
        projectId: 'myLocizeProjectId'
      }, {
        loadPath: '/locales/{{lng}}/{{ns}}.json' // http api load path for my own fallback
      }]
    }

    // other i18next options
  })

IMPORTANT ADVICE for the usage in combination with saveMissing/updateMissing

We suggest not to use mutliple backends in combination with saveMissing or updateMissing, because it may happen, that the trigger for this is based on stale data.

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Changelog

4.6.2

• fix package exports