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:

1import i18next from 'i18next';
2import Backend from 'i18next-chained-backend';
3
4i18next
5  .use(Backend)
6  .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

1{
2  // array of existing i18next backends from https://www.i18next.com/overview/plugins-and-utils#backends
3  backends: [],
4
5  // array of options in order of backends above
6  backendOptions: []
7}

Options can be passed in:

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

1import i18next from 'i18next';
2import Backend from 'i18next-chained-backend';
3
4i18next
5  .use(Backend)
6  .init({
7    backend: options
8  });

on construction:

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

via calling init:

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

caching example

1import i18next from 'i18next';
2import Backend from 'i18next-chained-backend';
3import LocalStorageBackend from 'i18next-localstorage-backend'; // load from local storage
4import HttpApi from 'i18next-http-backend'; // have a own http fallback
5
6i18next
7  .use(Backend)
8  .init({
9    backend: {
10      backends: [
11        LocalStorageBackend,  // primary
12        HttpApi  // fallback
13      ],
14      backendOptions: [{
15        projectId: 'myLocizeProjectId'
16      }, {
17        loadPath: '/locales/{{lng}}/{{ns}}.json' // http api load path for my own fallback
18      }],
19      // cacheHitMode: 'none' // (default)
20      // cacheHitMode: 'refresh' // tries to refresh the cache by loading from the next backend and updates the cache
21      // cacheHitMode: 'refreshAndUpdateStore' // tries to refresh the cache by loading from the next backend, updates the cache and also update the i18next resource store
22      // reloadInterval: 60 * 60 * 1000 // can be used to reload resources in a specific interval (useful in server environments)
23      // 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
24    }
25  });

more complete sample

1import i18next from 'i18next';
2import Backend from 'i18next-chained-backend';
3import Locize from 'i18next-locize-backend'; // load from service
4import HttpApi from 'i18next-http-backend'; // have a own http fallback
5
6i18next
7  .use(Backend)
8  .init({
9    backend: {
10      backends: [
11        Locize,  // primary
12        HttpApi  // fallback
13      ],
14      backendOptions: [{
15        projectId: 'myLocizeProjectId'
16      }, {
17        loadPath: '/locales/{{lng}}/{{ns}}.json' // http api load path for my own fallback
18      }]
19    }
20  });

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.:

1import i18n from 'i18next'
2import ChainedBackend, { ChainedBackendOptions } from 'i18next-chained-backend'
3
4i18n
5  .use(ChainedBackend)
6  .init<ChainedBackendOptions>({
7    backend: {
8      backends: [
9        Locize,  // primary
10        HttpApi  // fallback
11      ],
12      backendOptions: [{
13        projectId: 'myLocizeProjectId'
14      }, {
15        loadPath: '/locales/{{lng}}/{{ns}}.json' // http api load path for my own fallback
16      }]
17    }
18
19    // other i18next options
20  })

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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