> For the complete documentation index, see [llms.txt](https://www.i18next.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://www.i18next.com/translation-function/essentials.md). # Essentials ## Accessing keys resources with 2 keys: ```javascript { "key": "value of key", "look": { "deep": "value of look deep" } } ``` sample {% tabs %} {% tab title="JavaScript" %} ```javascript i18next.t('key'); // -> "value of key" i18next.t('look.deep'); // -> "value of look deep" ``` {% endtab %} {% tab title="TypeScript" %} ```typescript i18next.t($ => $.key); // -> "value of key" i18next.t($ => $.look.deep); // -> "value of look deep" ``` {% endtab %} {% endtabs %} ## Passing a default value You can pass in a default value for cases the key could not be found in translations like: {% tabs %} {% tab title="JavaScript" %} ``` i18next.t('key', 'default value to show'); ``` {% endtab %} {% tab title="TypeScript" %} ```typescript i18next.t($ => $.key, { defaultValue: 'default value to show' }); ``` {% endtab %} {% endtabs %} {% hint style="info" %} In case you're using the [saveMissing functionality](/overview/configuration-options.md#missing-keys), it will also pass the defaultValue to your chosen backend, like shown in [this React.js example](https://github.com/locize/react-tutorial). {% endhint %} ## Accessing keys in different namespaces Namespaces are a feature in i18next internationalization framework which allows you to separate translations that get loaded into multiple files. init ```javascript i18next.init({ ns: ['common', 'moduleA'], defaultNS: 'moduleA' }); ``` moduleA.json ```javascript { "name": "Module A" } ``` common.json ```javascript { "button": { "save": "save" } } ``` sample {% tabs %} {% tab title="JavaScript" %} ```javascript i18next.t('name'); // -> "Module A" // from different namespace (not recommended with namespace prefix when used in combination with natural language keys) i18next.t('common:button.save') // -> "save" // better use the ns option: i18next.t('button.save', { ns: 'common' }) // -> "save" ``` {% endtab %} {% tab title="TypeScript" %} ```typescript i18next.t($ => $.name); // -> "Module A" // use the ns option, if ns is not defaultNS: i18next.t($ => $.button.save, { ns: 'common' }) // -> "save" ``` {% endtab %} {% endtabs %} {% hint style="info" %} **Selector API and namespace prefixes.** When you call `i18next.t(...)` directly with `ns: ['nsA', 'nsB']`, you can also use a namespace-prefixed selector path: `t($ => $.nsB.foo, { ns: ['nsA', 'nsB'] })`. The runtime detects that the first segment matches one of the secondary namespaces and routes the key accordingly. The same convention is supported under react-i18next's `useTranslation(['nsA', 'nsB'])` (since `i18next` v26.0.10 / `react-i18next` v17.0.7). Plain `t('foo')` lookups still stay isolated to the primary namespace by default — only the **selector** path\[0] is checked against the hook's namespace list. The first entry of the array is the primary and is never rewritten: `$.primary.foo` means a literal sub-key inside the primary namespace. {% endhint %} {% hint style="info" %} **Strict selector mode.** If the asymmetry above bites you — `$.primary.foo` typechecks but doesn't resolve under multi-ns hooks — enable `enableSelector: 'strict'` (since v26.1.0). In strict mode, the proxy stops exposing the primary's keys flat on `$`; every namespace (including the primary, and including single-ns hooks) is reached only through `$..key`. The runtime rewrites the leading segment as a namespace prefix uniformly. The trade-off: keys whose names match a sibling namespace stop resolving (see [#2405](https://github.com/i18next/i18next/issues/2405)), so don't enable strict mode if your translations have that shape. {% endhint %} ## Multiple fallback keys Calling the t function with an array of keys enables you to translate dynamic keys providing a non specific fallback value. As a sample think of an error code you get and you like to show a specific warning in some cases: keys ```javascript { "error": { "unspecific": "Something went wrong.", "404": "The page was not found." } } ``` sample {% tabs %} {% tab title="JavaScript" %} ```javascript // const error = '404'; i18next.t([`error.${error}`, 'error.unspecific']); // -> "The page was not found" // const error = '502'; i18next.t([`error.${error}`, 'error.unspecific']); // -> "Something went wrong" ``` {% endtab %} {% tab title="TypeScript" %} ```typescript // const error = '404'; i18next.t($ => $.error[error], { defaultValue: t($ => $.error.unspecific) }); // -> "The page was not found" // const error = '502'; i18next.t($ => $.error[error], { defaultValue: t($ => $.error.unspecific) }); // -> "Something went wrong" ``` {% endtab %} {% endtabs %} ## Overview options `i18next.t(key, options)` | option | description | | ------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | defaultValue | defaultValue to return if a translation was not found, you also can define defaults for plurals by adding defaultValue\_other -> \_suffix depends on same [pluralrules](/translation-function/plurals.md). | | count | count value used for [plurals](/translation-function/plurals.md) | | context | used for [contexts](/translation-function/context.md) (eg. male / female) | | replace | object with vars for [interpolation](/translation-function/interpolation.md) - or put them directly in options | | lng | override language to use | | lngs | override languages to use | | fallbackLng | override language to lookup key if not found see [fallbacks](/principles/fallback.md) for details, passing `false` will not do a fallback to any language | | ns | override namespaces (string or array) | | keySeparator | override char to separate keys | | nsSeparator | override char to split namespace from key | | returnObjects | accessing an object not a translation string (can be set globally too) | | returnDetails | returns an object that includes information about the used language, namespace, key and value | | joinArrays | char, eg. '\n' that arrays will be joined by (can be set globally too) | | postProcess | string or array of postProcessors to apply see [interval plurals](/translation-function/plurals.md) as a sample | | interpolation | override [interpolation options](/translation-function/interpolation.md) | | skipInterpolation | skip interpolation and nesting for this call to t function | | ignoreJSONStructure | if a key is not found as nested key, it will try to lookup as flat key |